# Technical Analysis Supporting the NPRM to Update Electrical Safety Requirements in FMVSS No. 305, uElectric-powered vehicles; electrolyte spillage and electrical shock protection" Februar y 2 016

### Table of Contents I. Executi ve Summary . . ... . .......... . ............. . .............................. . ................................. . .... . ............ 1 fl
. Background . . ... . ...................... . .. . . ... . ........ . ............... . ................... . .... .. .... . ........ . ........ . ....... . . . ..... 3 lll. NHTSA' s evaluation of the physical barrier option for electrica l safety in GTR No. 13 .... . .. 5 IV . Petition for Ru l emaking from Alliance ... . .......... . ... . ... . ............... . .......... . .... . ........ . ... . ... . ....... . . 14 V. NHTSA's Analys i s ofthe Petition For Rulemaking from Alliance .. . . . . .. . .... . ... . . . .. . ............... 1 7 VI. Discussion .... . ......................... .. .. . ... . . ........................ . ... . .................................................... ... .. 21

### I. 

### Executive Summary This document provide s technical detail s in support of the Not ice of Proposed Rul emaking (NPRM) to update FMVSS No. 305 , "Electric-powered veh icl es; e lectrolyte sp illage and electr ical s hock protection." 1 The NPRM proposes an addit iona l method of meeting post-cra s h electrical safety requirements in FMVSS No. 305 that invol ves physical barriers of hi gh vo ltage sources to prevent electric shock due to direct and indirect contact of high vo ltage sources. The NPRM also incorporate s into FMVSS No. 305 electrical safety r equirements in the Global Technical Regulation (GTR) No. 13 , "Hydroge n and fuel ce ll vehicles," that involves electrical isolation and direct and indirect contact of high voltage sources to prevent electric shock during normal operation of e lectric-powered vehicles. This proposal responds to petition s for rulemaking from Toyota Motor Company and Auto Alliance (A lliance) 2 to facilitate the introduction of fuel cell vehicles and 48 vo lt mild hybrid technologies and aligns FMVSS No. 305 electrical safety requirement s with tho se in GTR No. 13. This document provide s a technical analysis of direct and indirect contact protection for hi gh vo ltage so urces specified in GTR No. 13 and those requested by Alliance in it s petition for rulemaking. GTR No. 1 3 requires preventing direct contact of high vo ltage so urce s by way of enclosures (electrical protection barriers) that do not permit entrance of a finger probe and r eq uire s these electrical protection barriers to have a conductive connectio n to the electrical chassis with re sistance le ss than 0.1 ohms to prevent indirect contact. The Alliance reque sted that direct a nd indirect contact protection requirements in th e January 2014 version ofSAE 11766 3 be included as an additional compliance option for meetin g p ost- crash electrical safety. SAE 11766 (January 2014) provides two optional methods of meeting direct and indirect contact protecti o n . The first optional method for direct and indirect contact protection (Option 1) includes the requirement in GTR No 13 and an additional

1 Docket No. NHTSA-20 16-00 29 ; RfN 2127 -AL68. 2 Auto Alliance is a trade association w ho se members at th e time of s ubmitting it s petition were, BMW Group, Chrys ler Group LLC , Ford Motor Company , General Motors LL C , Jag uar Land Rover, Mazda , Mercedes-Benz USA , Mitsubishi Motors , Porsche , Toyota, and Volk s wagen. 3 SAE J 1766 , " Recommended practice for electric , fuel cell , and hybrid electric vehicle crash integrity testing, " January 20 14 , SAE International , http : www .s ae .o rg .requirem e nt that the e lectri ca l i so lati o n be tween a hi g h vo ltage so urce and it s electrical protecti o n barri e r be a minimum of 0.01 ohm s/vo lts for direct current (DC) hi gh voltage s ourc es or 0.05 o hms /vo lts for alternating current (AC) hi gh vo ltage so urc es. Th e seco nd optional method for dire ct and indir ec t contact protection (Option 2) requires preventin g direct contact of hi g h vo lt age so urces by way of e lectric a l protect ion barri ers and requires the voltage between these electrical protection b a rriers and other exposed conductive p art s be at leve l s considered low vo ltage (30 vo lt AC or 60 vo lt DC). The agency's anal ysi s of th e direct and indirect co ntact protec tion r equirement in GTR No . 1 3 d e mon s trated that it is possible to ge t electric s hock throu g h indire ct contact of hi g h voltage so urces for a vehicle that complie s with GT R No. 13 electric a l safety requireme nts; however, the proba bilit y of e lectri c s hock i s very low because multiple system failure s would have t o occ ur along with a p erson to uching spec ific areas of the ve hicle for the per so n t o experi e nc e e lectri c s hock . T he age ncy ' s anal ys i s of the direct and indirect co ntact protecti o n r e quirement s in the A lliance ' s petition s h owed that the fir s t op ti o n (Op ti o n 1 ) wou ld prevent electric s h ock even w hen there were multiple syste m failures. The seco nd o pti o n (O pti o n 2) would also protec t aga in s t e lec tri c s hock because the co ntac tabl e s urf aces would be low vo ltage and con s idered safe . T h e agency 's a nal ysis showe d that vehicl e sys tem s that meet direct and indirect co nt act protection by Option 1 would a lso me et the low vo ltage requirement of Option 2. Because it i s difficult to meas ure resistance betwe e n a hi gh vo ltage so urce and th e e lec tri ca l protection barrier enclo s in g it that is nee ded to eva lu ate Option 1 in the A llian ce petition , the agenc y is propos in g to co mbine the two op tiona l methods for direct and indirect contac t protection s uggested by Alliance. Specifically , the indirec t co ntact protection requirement prop o s e d in the N PRM include s the indirec t co ntact protec ti o n in GTR No. 1 3 (e lectri ca l protection barri e rs are conductively connected t o the e lec trical chassis with maximum resistance of 0.1 ohm s) and th e low vo ltage r equirem en t of e lectrica l protection barriers in Option 2 in the Alliance p etiti o n (voltage betwee n an e lec tri ca l protec tion barrier and ex po se d cond ucti ve parts i s not gr eater than 60 vo lt s for DC so urces and 30 vo lts for AC sources).

2The technical analysis presented in this document demonstrates that the proposed po s tcrash physical barrier protection option (with the first two requirements in GTR No. 13 and an additional third requirement that the electrical protection barriers be low voltage) affords the same level of safety as the post-crash electrical iso lation option currently in FMVSS No. 305. That is , the current through the body would not exceed I 0 milliamperes (rnA) DC and 2 rnA AC, which are con s idered to be safe levels for electric shock. 

### II. Background In a final rule publi s hed on June 14 , 20 l 0, 4 NHTSA updated the electrical safety requirements in FMVSS No . 305 to facilitate the development and introduction of h yd ro gen fuel cell vehicles (HFCVs). The post-cra s h electrical safety requirements in FMVSS No. 305 currentl y , which are based on this final rule , specify that high voltage sources (electrical components contained or connected to the electric powertrain that have a working voltage greater than 30 volts AC (VAC) or 60 volts DC (VDC)) are either electrically i solated from the chassis at a leve l gre ater than or equal to minimum spec ifi ed levels or their vo ltage is less than or equal to s pecified level s that is considered as low voltage. Voltage leve l s less than or eq ual to 30 VAC and 60 VDC are con s idered as low vo ltage and safe from e lectri c s hock hazards . The specified minimum level s of electrical isol ation is 500 ohms/volt for AC and D C high vo ltage so urc es but a l ower elec trical i so lation lev e l of l 00 ohms/vo lt is permitted for DC source s with an e lectrical isolation monitoring system. These limit s on minimum e le ctrical isolation ensures that the current throu gh a body co ntactin g the ve hicle s tructure i s no more than 2 mA AC or 10 rnA DC , which would not cause any tissue damage or fibrillation , and is considered to be safe . FMVSS No. 305 doe s not specify any electrical safety requireme nt s during normal ve hicle op eratio n s . The GTR No . 1 3 for HFCVs was es tabli s hed on June 27 , 20 13. It specifies electrica l safety requirements during normal vehicle operation and afte r a crash test (post-crash) to protect against e lect ric s hock in the event of a failure in the hi gh voltage propulsion system . The followin g is a li s tin g of requirement s durin g normal vehicle operation and post-crash e lectrical safety requirement s in GTR No. 1 3 .

4 75 FR 335 15 (Docket No. NHTSA-20 I0-002 1 ). 3Electrical safety requirements during normal vehicle operation in GTR No. 13: High voltage sources of HFCV s connected to the electric power train are required to meet the following conditions during normal vehicle operation. 1 . Prot ec tion from dire ct co ntact : High voltage sources inside the passenger compartment or luggage compartment are required to be enclosed in electrica l protection barriers 5 with protection degree IPXXD . 6 High vo ltage sources in areas other than the passenger compartment or the lu ggage compartment are required to be enclosed in electrical protection barriers with protection degree IPXXB. 7 This requirement mitigates direct contact of high voltage s ources. Additional requirement s to mitigate direct contact of high voltage sources include markings and co lo r coding for cables. 2. Protectionfrom indir ec t contact: Exposed conductive parts , (parts which may become electrica ll y energized under electrical isolation failure and which can be contacted by a human) , such as electrical protection barriers, are required to be conductively connected to the electrical chassis such that the resistance between all exposed conductive parts and the e l

ectrica l cha ss is i s less than 0.1 ohms when there is current flow of at least 0.2 amperes (A) . This requirement ensures that in the event of loss in electrical isolation , no dangerou s vo ltage potentials are produced between exposed conductive parts and the electrica l chassis , and therefore very low levels of current would flow throu g h the human bod y contacting different parts of the vehicle. To prevent e lectric shock during charging of vehicles with rechargeable energy sources, the electrical chassis is required to be grounded to earth during charging. 3. Prot ec tion from electric shock by electrical iso lation : a. AC and DC high vo lt age sources that are electrically isolated are required to have minimum electric a l isolation of 500 

### ohmsN AC and 1 00 

### ohm sNDC.

5 An electrica l protection barrier is defined in GTR No. 13 as the part providing protection from direct contact with high voltage so urce s ftom any direction of access. These may be phys ical barriers or in s ulators that enc l ose high voltage so urce s. 6 The International Electrotechnica l Commission (IEC) 605 29 , " Degrees of protect ion provided by e nclo s ures,'· provide s s pecification for protection ftom direct co nt act of high vo ltage sou r ces . Protection degree IPXXD is ve rifi ed when a I 00 mm long and I mm diameter ri gi d test wire sta ndard probe does not contact hi g h voltage components whe n prob ed to enter an electrical protection b a rrier . 7 Protection de g ree IPXXB i s verified (per IEC 60529) when an 80 mm long a nd 12 mm diameter jointed s tandard fin ge r probe doe s not contact hi g h voltage components when probed to enter an electrical protection barri er . 4b. AC and DC high voltage sources that are conductively connected are required to either have minimum electrical isolation of 500 ohms/volt or have electrical isolation of l 00 ohms/volt provided that the AC high voltage sources have direct and indirect contact protection as s pecified in I and 2 (above). c. For electric vehicles with rechargeable energy s torage systems, the isolation resistance between the high voltage source (that is conductively connected to the vehicle inlet which connects to the external power supply) and the electrical chassis i s required to be at least I million (M) ohms when the charge coupler is disconnected. 4. Electrical isolation monitoring system: DC high voltage so urce s of an HFCV, such as fuel cell s tack s, are required to be equipped with an on-board electrical isolation monitoring sys tem that warns the driver in the event that isolation resistance drops below I 00 ohmsNDC. Po st-crash electrical safety requirements in GTR No. 13: After a crash test , each high voltage source in the vehicle mu s t meet at least one of the three requirem ents listed below. 1 . Absence of hi

gh voltage: The voltage of high voltage sources must be tess than or equal to 30 VAC or 60 VDC. 2. Electrical isolation: These requirements are the same as the electrical isolation requirement s for normal vehicle operation for AC and DC high voltage sources that are electrically isolated or conductively connected as discussed above. 3. Physical barrier protection : This is an optional requirement for each contracting part y to adopt. These requirements are the same as the direct and indirect contact protection for normal vehicle operation presented above except that the protection degree IPXXB applies in the pa ssenger and luggage compartments. 

### Ill. NHTSA ' s evaluation of the physical barrier option for electrical safety in GTR No. 13 NHTSA initiated a research program in 20 I 0 with Battelle Memoriallnstitute (Battelle) to better understand and evaluate the s uitability of including physical barrier protection as an option for providing electrical safety in FMVSS No. 305. The objectives of the research were to : 5( 1) determine failure modes associated with electri ca l protection barrier s that co uld potentially result in electric shock to occupant s in the veh icl e or t o rescue workers due to direct or indirect contact, (2) evaluate the practicability and feasibilit y of test procedure s proposed in the draft 8 GTR fo r HFCV s (GT R No. 13 draft) , for direct and indirect contact protection. The Battelle study 9 identified var ious scenarios of e lectr i cal safety sys tem fa il ures , including direct contact of high voltage so urce , indirect contact of live parts of high vo ltage sources , loss in conductive connection between electrical protection barrier and chassis, and a combination of these failures. Direct contact of a hi g h vo ltage so urce could occur in the event of a crash that result s in mechanical failure of protection barriers or penetration of e l ectr i cal insulation that wou ld allo w fingers or conductive tool s to enter protection barriers and contact the high vo ltage so urces within the barrier. Indirect contact of high voltage sources could occur in the event of a crash in which an e lec tri ca l protection barrier i s energized due to loss in e lectrica l i so lation of the high voltage so urce w ithin the barrier. To illustrate failure modes assoc iated wi th e lectric protection barriers, Battelle used the sc hematic s hown in Figure 1 below in which a high vo ltage source (shown on the left side of the figure) i s i so lated from the vehic le c ha ss is by resi s tances RiH and R iL on the positive and negative side , re spectively, and enclosed in an e le ctrical protection barrier (EPB 1) . The high vo ltage so urce may be either DC or AC and may represent a variety of components s uch as a fuel cell , battery , motor , or capacitor. Also s hown in Figur e l are electrical wirings from the po si ti ve s ide ofthe high voltage source to it s negative side to complete the circuit. The sc hematic s how s two electric protection barriers (EPB 2 and EPB 3 ) enclosing the wirings on the positive and negative side , re spect ively , and a body with resistance Rb contacting these two protection barriers. All three electrical protection barriers in the figure are conductively connec ted to the electrical chassis with resis tances Rc h , R c hH , and RchL·

8 The electrica l safety requirements in the 20 I0 draft vers ion of GTR No. 1 3 are the s ame as those in the GTR No. 13 that was estab li shed on June 27, 2013. Henceforth , w e refer to th e draft version as th e adopted GTR. 9 H yd rogen Fuel Ce ll Vehicle- Electrica l Protective Barri er Option , Fina l Report , DOT H S 812134 , May 20 15. Available at hnp : www.nhtsa.gov Re sea rch C ra s hw o rthiness Alternative 0 o20Energv%20Vehicle 0 o20Sys tem s 0 o20SafctvC! o20Re sea rch and in Docket No. NHTSA-20 1 6-0029. 6For nonnal vehicle operation , GTR No. 13 require s RiH and R i L re s i s tances to provide electrical iso lation of at lea s t 500 

### ohmsN AC or 1 00 ohm s/VDC . 

### It also requ ires the electrical wiring to be in sulated . Further , it requires the three electrical protection barriers (EPB 1 , E PB 2, and EPB3) to have protection degree IPXXD or IPXXB and be conductively connected to th e chas s i s s uch that the resistances RCh , R c hH , and Rc hL are less than 0.1 ohms. The lo wes t po ssi ble value of body re s i s tance Rb is 500 ohms.

_----- l so lal ion R esislance 

### ...- R ;H Wiring [p osi tive side] _.-- EPB , High Voltage Source Wiring [ negative side]

Isolation Res istance - Insu lated Hogh Vol tage Pans Love Htg h Voltage P ans

- Enclosure I Protective Barne r

Figure 

### 1. Schematic of body c o ntact with electrical protection barrier s

Battelle ' s analysis of the sc h ematic in Figure 1 identified s cenarios of direct contact an d indirect co ntact of hi gh voltag e so urc es. Direct contact occurs when the e lectrical prot ec tion barri ers E PB 2 and/or E PB 3 are breached or penetrated and the bod y contacts the wiring enclos ed w ithin . Indire ct contact occurs when EPB2 and/or EPB3 are e ne rgi ze d du e to 

### los s of e lectrical i s olation of the high vo ltage so urce within the barrier and the body contact s th e e lectrical protection barriers as shown in Figure 1 . Examples of direct and indirect contact scenarios are pre s ented below:
• Case I

- Dir ec t contact of hi g h voltage so urce without electric shock ha z ard . Protection barrier EPB 2 i s comprom is ed and the bod y directl y co ntact s the e le c trical w irin g from the p os iti ve s id e , and al s o contacts the el ect ri cal protec tion barri e r EPB 3 e nclo s in g the wirin g

7on the negative side of the high voltage so urce (F igure 2) . In this ca s e , as long as the re s istance Ri L or RiH is greater than or equal to 500 

### ohmsN AC or I 00 

### ohmsNDC, the current through the body (shown b y das hed lines ) will be within safe limits.

- ----- EPB , +

- lnsulaled Hogh Vollage Pans Live**H~gh** Voltage Part s

- Endosure I Protec l 1 '1 e Barne r Shock Hazard Clfcu•l 

### Figure 2. Case 1

- Direct contact of wiring on positive s ide of hi g h voltage s ourc e and contact with e lectr ical prote ction barrier (EPB 3 ) of th e wiring on the negative side. • Case 2 - Direct contact of a high voltage so urc e with e lectric s hock hazard . E lectrical protection barriers EPB 2 and EP B 3 of the wiring on the positive and negati ve s ide of th e hi g h voltage so urce are compromised and the body contacts the po s itive and negative wiring (F i g ure 3) . For the worst Case 2 condition , a body resistance Rb equal to 500 o hm s (lowest po ssib le) is used. For a DC high vo ltage s ource of350V , the minimum resistance value for Ri L and RiH is 35 , 000 ohms . Since the body resi s tance R b i s s ignificantly lower than the e l ectrical isolation RiL and Ri H, c urre nt t hrou gh the body ( s hown by dashed line s) is not limited and the bod y would experience electric s hock.

8- Insulated H ogh Voltage Pans love H ogh Vo ltage P ans

- Enclosure I P ro 1ect1ve Barne r Shock H .uar<!**C~rcu•\** Figure 3. Case 2

- Direct contact of wiring on positi ve and negative s ide of high voltage source due to compromise (breaching or penetration) of electrical protection barriers 

### EPB 2 and 

### EPB 3. • Case 3

- Indirect contact of high voltage so urce without electric s hock hazard . The wiring on the positi ve side of the high voltage source loses electrical iso lation to the**l~ctrical** protection barrier, 

### EPB 2 , and th e body contacts the electrical protecti o n barri er s E PB 2 and 

### EPB 3 of the po s iti ve and negative wiring ( Fi g ure 4). Simil ar to Case I , a s lon g as the isolation resi s tance R iL or RiH is greater th an or equal to 500 

### ohmsN A C o r 100 ohmsNDC , the current throu g h the b ody (s hown by dashed line s) will be within safe limit s.

9- lnsulale<l Hogh Voltage Parts Love Hogh Vol tage Pans

- Enclosure I P ro l ec h vo B arner Shoek H azard Orcu t t
Figure 4 . Case 3

- Wiring on positive side of the high vo ltage source lo ses electrical isolation to th e protective barri er 

### E PB2 and the bod y contacts protecti ve barriers 

### EPB 2 and 

### EPB 3 . • Case 4

- Indirect contact of high vo ltage so urce w ith possibility of electric s hock. The e lectri c wiring of th e po s itive and n egati ve s ide s of the hi gh voltage so ur ce l ose e lectrica l isolation to the protective barriers EPB 2 and 

### EPB 3, respectively , and the body contacts th e two protec tiv e barriers EPB 2 an d 

### EPB 3 (Figure 5). Since Rc h, Rc11H and R c hL are all very low va lu es (less than 0.1 ohms accordi ng to GTR No .l 3), thi s condition wo uld re sult in a sh ort circ uit of th e hi gh vo ltage s ource that could activate and open a short c ir cu it fuse that is genera ll y eq uipp ed in e lec tri c p ropu l s i on vehicl e s . If a fu s e ac ti vate s, then no current wi ll flow and so no e lectrical shock wou ld occur. Howe ver, if the fuse does not activate , and if th e e lectr i cal isolation RiL an d RiH are reduced to low levels and the chassi s r e sistance i s not signifi can tl y low compared to th e body re s istance , then th e current thro ug h th e body contacting the protective barriers (s h own by dashed line) may not be within safe lim its and the body cou ld ex per ienc e e lec tri c s ho ck.

10**~** Is o l ati o n Re s istance 

## .. R ltf High •voltage

Source

Isolati o n Resi s tan ce Human body

- Insu l a t ed H igh Voltage P arts L1ve H igh Voltage Pa rt s

- E ndosu re I Protect ive B arner Shock H azard Ci rcuit

Figure 5. Case 4- Wiring on positive and negative side of the high vo ltage source lose e lectrica l isolation to the protective barriers EPB 2 and EPB 3, respectively , and the bod y contacts protecti ve barriers EPB 2 and EPB 3. Battelle identified additional scenarios , including those regarding loss in e lectrical i s o l ation R i L and/or RiH and lo ss of electrica l bonding of the protective barriers with th e chassi s . 1 0 These scenarios showed that , for vehicle s that meet the e lectrical i s olation and physical barrier protection requirement in GTR No. 13 during normal vehic le operation , e lectric shock is not po ss ible when there is on ly a s ingle point of fai lure in the electrical s afety s y s tems. However , elec tric sh ock is possible when at le ast two or three failures of electrical safety systems occur a nd a human bod y come s into contact with two compromised protective barriers on oppo s ite sides of the high voltage source to complete the c ircuit. For example , in Case 2 , e l ectric shock could occur if two e lectrical protection barriers on the po s itive and negative s ide of the hi g h vo lt age s ource are compromised and a body contacts the positive and negative s ide o f a high voltage source by entering the two compromised protection barri er s. In Ca se 4 , electric shock could occur onl y if at lea s t four electric safet y feature s ( los s in electrical is olation of e lectrical protection barriers EPB 2 and EPB 3 which are on the po s itive and negative s ide of the hi gh

10 Detail s of the s e s cenar io s a re pre s ented in the Batte ll e final r eport, DOT HS81 2 1 34 , May 2 01 5. which i s a va ilable in Docket No . NHTSA- 2 0 I 6-00 2 9 . IIvoltage so urce and lo ss in electrica l iso lation RiH and RiL of the hi gh vo ltage so urce) are compromised and the body contacts both compromised barriers , EPB 2 and EPB 3 . To address the concern of electric sho ck from indirect contact , GTR No. 13 specifie s that the phy s ical barriers enclosing high vo ltage so urces shou ld be conductively connected wit h low re s istanc e (less than 0.1 ohm s) to th e electrica l chassis , so that if o ne segment ofthe hi g h voltage source s hould lose e lectri cal is olation , all contactab le surfaces of the vehicle c hassis and protecti ve barriers w ill be at the s ame voltage and thereb y prevent e lectric shock to a pers on touching two diff e rent protective barriers or parts of the electrical chassis. Batte ll e a lso evaluated the maximum re s istance (O. l ohms) of the electric bonds between e lectri ca l protection barriers and th e e lectrica l chassis that is specified in GTR No. 13 . Battelle prepared a s implifi ed circuit diagram (Figure 6) to analy ze the indirect contact scen a rio s s hown in Figur e 5 (for the condition where i so lation re s i s tance RiH and Ri Lare equal to zero).

High Voltage Source#1

Power Source

High Voltage

Source#2 Rs= 0.04ohms

Figure 6. Battelle 's model of the indirect contact scenario (Case 4) with RiL = RiH''= O The "V s" e le ment in thi s circuit repre sent s an y hi g h voltage potential that i s prese nt in the vehicle , such as a battery or fuel ce ll. The " R s " e l ement re pre sent s the internal so urc e res i s tanc e. The " R:h " e le ment repre sent s the chass is re s i s tanc e between the point s at which the pers on is

1 2touchin g the chass i s. The " Rb" el ement i s th e res i stance of the b ody. " Ic" a nd " lb " represe nt the c urrent thro u gh the chassis and body , re spective l y. Us in g the circuit diagram in Figure 6, Battelle derived the value of current through the bod y contacting th e protective barrier as shown b e l ow.

For illus tr ation purpo ses, Batt e lle assumed Vs=3 00 V and R s= 0 .04 ohms, which 

### it believed were reasonab le estimates for e lectri c propul sio n batteri es . Body cun·ent (Ib) for bod y re s i s tan ce (Rb) of 5 00 ohms (0. 5kQ ) , 5000 ohms (5 kQ ), 50, 000 o hm s (50 kQ) , and 500,000 ohms (500 kO) , and chassi s resistance (Rch) ran g ing from 0.00 1 o hms to 10 ohms was determined and p l otte d in Figu re 7.

"' c. E 

## ;a

. E


# .. c: Cll 1:**~** u > "C 0 CD 1000

100

10

1

0 . 1

0 .01 0.001 Body Current vs. Chassis Resistance

- Rb 

### = O

. SkO

- R b 

### = SkO Rb = SOkO

- Rb = SOOkO

0 .01 0.1 1 10 Chassis Re sistance (Ohms) Figure 7. Body Cu rre nt (Ib) vs. C hassis Re s i s tan ce (Rch) fro m th e circ uit di agram in F igure 6 for

V 5 =3 00 V and Rs= 0.04 ohms. Note th at th e m ax imum bo dy c urre nt limit cons idered s afe is 2 rnA for AC and I 0 rnA for DC hi g h vo ltage so urce s .

13Figure 7 indicates that, for the model and parameters selected, low body re s i s tance s may result in body currents well above that considered safe (les s than 2 rnA AC and 10 rnA DC) . For the values chosen in this model , the body current for a conservative 500 ohms body resistance (O.S kO ) is full y outside the "sa fe zone .' · However, as noted earlier , for vehicles that comply with the requirements during normal vehicle operation in GTR No. 13, a number of system failures (los s in electrical isolation of both the positive and negative sides of the high voltage source , loss of electrical isolation to two electrical protection barriers on opposite sides of the high voltage source, and body contact with these two electrical protection barriers) need to occur for the condition represented by Figure 6 to occur. 

### IV. Petition for Rulemaking from Alliance On November 10 , 2014 , Alliance submitted a petition for rulemaking to update and upgrad e FMVSS No. 305 to incorporate an electrical protection barrier compliance option to provide protection against electric shock. Alliance s tated that the implementation of an electrical protection barrier compliance option is especially critical to facilitate both the introduction of HFCV s as well as 48 volt mild hybrid technologies 11 in the United States. Alliance stated that the electrical protection barrier compliance option was essential for FMVSS No. 305 certification ofHFCVs in low speed crashes where the automatic disconnect is not designed to operate. Alliance stated that when AC and DC high voltage so urces of HFCVs are conductively connected, DC high voltage sources can impinge on AC high voltage sources making it impractical to achieve 500 ohms/volt el ectrical isolation for AC high voltage sources. Alliance also explained that while 48 volt systems would see m to be outside scope of FMVSS No. 305 , the se systems ty pically convert DC voltage into three-phase AC voltage that can exceed the 30 V AC voltage thresholds and would be considered a high voltage so urce according to FMVSS No. 305. Since 48 volt sys tems are typicall y conductively connected to the electrical

1 1 48 vo lt mild hybrid sys tem s are generally internal combustion engines and a 48 volt battery equipped with an e lec tric machine (one motor /generator in a parallel configuration) allowing the engine to be turned off whenever the car is coasting , braking , or stopped , ye t restart quickl y. These mild hybrids may employ regenerative braking and s ome leve l of pow e r assist to th e internal combustion e n g ine , but d o not have an exclusive electric-only mode of propul s ion . 14chassis, AC hi g h vo ltage so urc es of th ese sys tems would not b e abl e to comply w ith the e lec tri ca l iso latio n requirem e nt in FMVSS No. 305. For the se rea sons, A llianc e requested that an additional e l ect rical safety option through e l ec tri ca l protection barriers be adde d to FMVSS No. 305. A lliance stated that the age nc y's researc h on the protecti ve barrier o pti on ( re searc h program with Batte ll e) s howed that e l ectric shock from indirect co nt act in a cras h (suc h as that shown in Figure 5) could o nl y be possible , if the following conditions wer e met: 1. a l oss of e lectri ca l isolation within th e enclos ure of a high vo lt age source (EPB 2 or E P8 3 ), 2. a l oss of electrical i so l ation with in a second (diffe rent) hi g h vo ltage so urc e e ncl os ure (EPB 2 o r EPB 3), 3 . the se two di s tinct l osse s in i so lation (s p ec ifi ed in ( l ) and (2)) occur o n opposite rail s ( p osi ti ve a nd negati ve) ofthe high vo ltage so urce , 4 . th e over current devic es do not automatica ll y o pen the c ircuit as a res ul t of the s imultaneo us loss of isol a tion o n the p osi ti ve and ne gative rail s to g round (A lli a nc e s tated that t he no nn a l des ig n practice is fo r t he overcurrent devices to automatically open un der the circumstances o utlined in (3)) , 5 . a p e rso n has access to these two enclosures in th e crashed vehicle , a nd 6. a p erso n touche s the se two enclosures s imultaneo u s ly. Alliance no ted that the indirect contact sce n ar io de picted b y the circuit diagram in Fig ure 6 ha s a ve ry l ow li kelihood of occ urrence. A llianc e s tated that despite the extreme l y low likel ih ood of a safet y issue from any of the scenarios in the final Batte ll e r eport , the updated version of SAE J 1766 ( Janu ary 20 14 ) includes po s t -cras h perf ormance req uirement s t h at safegu ard again st all sa fety c ritic a l direct and indirect co ntact scenarios ide ntifie d in the Battelle report. All iance requested that FMVSS No. 305 be upd a ted in acco rdan ce w ith the fo ll owi n g in the Janu ary 20 14 vers ion of SAE 

### 1 ! 766. 

### 5.3.4 Electrical Protection Barrier ( Reprinted with P e rmi ss ion from SAE Jl766 J an20 1 4 

### © 20 14 SAE Inte rnatio nal) Protec ti on aga in st e lectric s ho ck s h a ll b e demon s trated by me eting either I tems 1 , 2, and 

### 3 or Item s I and 4 of the fo ll ow in g requ irements:
151. Acce ss to live parts is preve nted by protection degree IPXXB. See Appendix C. I for the app li cable te s t procedure . 2. The r esis tance between ex po sed conducti ve pru1 s of the e lec trical protection barrier(s) and the e lectricall y -c on du ctive chassis is less than 0.1 o hm s w he n th e re i s a current flow of a t least 0.2 amp e res. This require me nt is de emed sa ti s fied if the galvanic connectio n has been made by welding , and the weld is intact after eac h of the s pecified crash t est s. See Appendi x C.2. 1 for the applicab le test procedur e. 3. The res is tanc e betwee n the c ircuit and ex p ose d conductive part s o f the electri ca l prot ec ti o n barrier s hall**~** O.O I ohmsNDC or 0.05 ohm sNAC. This require m e nt i s de e med sati sfie d if the sys tem meet s iso l ation requ irement s in 5.3.2. See C.2 . 2 for the app li cab le test procedur e for o ther situations. 4. T he vo ltages between th e e lectrica l protection barrier and other expose d conductive parts (that are not pro tected by IPXXB ) s ha ll be e qual to or less than 3 0 V AC or 60 VDC within the time period specified in 5.3 . See C.2.3 for th e applicable te st proc edure. " SAE JI 766 (January 2 0I4 ) provides two option s for post -c rash e lectric a l safet y by m ean s o f physical barri ers . The first option (O ption I for e lec tri ca l protec tion barriers) requires that conditions I , 2, and 3 ofthe e lectrica l prot ection barri e r re quirement s in 5.3.4 be met. Option I i s s imilar t o th e po s t-crash electrica l prot ection barri e r opt io n for e lectrica l saf e ty in GTR No. 13 , 1 3 but includ es an a dditiona l require ment that th e res i s tan ce between th e hi g h vo ltage so urce e nclo sed by th e ph ys ical barrier a nd the ex p ose d conduct i ve part s of th e e lec trical protection barrier be greater than 0.0 1 o hm s/ vo lt for DC hi g h voltage so urc es and 0.05 ohms/ vo lt for AC hi g h voltage s ources. T he second o ption for e lec trical s afety through e l ec trical protection b arriers (O pti o n 2 for e lec trical pro tec tion barriers) in SAE 11776 (Janu ary 20 14 ve r s ion) require s that conditions 1 and 4 of 5.3 .4 b e me t (protect io n from direc t contact b y protection de gre e IPXXB and that the vo ltage b e tw ee n th e e lec tric a l protection barrier and other exp o s ed cond u ctive parts and the e lectrica l chassis is less than or equal to 30 V AC for AC hi g h voltage

1 3 Protect ion again s t direct co nt act wi th h ig h vo ltage so urc es is provided by protection degree IPXXB a nd protect ion aga in s t indirec t co nt ac t of hi g h vo l tage s o urce s is provided by re quirin g th e r e s is t a nce betwee n ex po s ed co ndu ctive parts and the e l ectrica l c h ass i s to b e lowe r th an 0 . 1 o hm wh e n th ere is a c u rre nt fl ow of a t least 0. 2 a mp eres . 1 6sources and 60 VDC for DC high voltage sources). Alliance stated that option 2 i s similar to the low voltage option already in FMVSS No. 305. 

### V. NHTSA's Analysis of the Petition for Rulemaking from Alliance NHTSA conducted an analysis to evaluate the SAE 

### J 1766 (January 2014) physical barrier option using the circuit diagram in Figure 8. 14 In this diagram (Figure 8), a human body with re s i s tance Rb is in contact with two electrical protection barriers (EPB2 and EPB 3) e nclo sing high voltage so urces that have lost electrical isolation to these barriers. The resistance R 1 is the resistance between the positive side of the high voltage so urce # 1 and the exposed conductive part of the electrical protection barrier EPB2. The re s istance R 2 is the resistance between the negative side of the high voltage source #2 and the exposed conductive part ofthe electrical protection barrier EPB 3 . R ch H is the resistance between electrical protection barrier EPB2 and the chassis. RchL i s the resistance between electrical protection barrier EPB 3 and the chassis. High Voltage Source #1

Power Source

High Voltage

Source#2 EPB 1



### Vs Chassis

Figure 8. Circuit diagram to evaluate electrical protection barriers proposed by Alliance (based on circuit diagram in SAE Jl766 (January 2014)). Anal ys is of the circuit in Figure 8 is as follow s:**~** The circuit diagram in Figure 8 was d erived from the circuit diagram in SAE J 1766 (January 20 14 ). 17• Total chassis resistance (Rc h): Rch == RchH + Rc hL • Equivalent combined resistance of chassis and body contacting electrical protection barriers EPB z and EPB 3 (Rcq): R eq 

### = Rch* Rb R ch +Rb • Measured resistance between high vo ltage so urce and conductive part of electrica l protection barriers (Rmeas): As shown in Figure 8 , the resistance measured is not R 1 or R2 but the combined resistance ofthe chassis and R 1 and R 2 in parallel which results in



## • • • • 

## • • • • R _ ( R1 +RchH ) (Rz+Rchd mea s - R1 +RchH+R2 +RchL The total resi s tance to current (RT): RT = R 1 + Req + Rz The total current in the circuit (I 

### r): I 

### r = 

### v 5 Rr The vol tage drop through resistance R1 (VRJ): VR 1 

### = l r(R 1 ) The voltage drop through resistance R2 (VR2): VRz = lr(R 2 ) The voltage between EPB2 and chassis (VH): VH 

### = V s(Rt+ RchH )

- VR 1 R1+RchH+R2 +R c hL 

### h I . Vs(R2+RchL) T e vo tage between EPB 3 and chassis (V L): VL 

### = VRz
- 

### -...::;....;.-"---==-- Rt +R chH+R2 +R c hL The voltage between EPB 2 and EPB 3 (V HL): V I-lL = V H - (V L ) The current through the body (Ib): Ib == V HL/Rb According to the Alliance proposal for post-crash e lectrical protection barriers, Option 1 method of comp li ance requires condition s 1 , 2, and 3 li sted below be met and Option 2 method of compliance requires condition s 1 and 4 li sted below be met. condition I. Direct contact protection of high voltage sources (IPXXB) , condition 

### 2. RchH < O . l ohms and Rc hL< 0 . 1 ohms , condition 3. Rmeas > 0.01 

### ohmsNDC or 0.05 

### ohmsN AC . For V ,= lOOO VDC , Rmcas> lO ohms , condition 4 . VH , VL , and VHL < 30 VAC orV1-1 , VL , and VHL < 60 VDC. Tables I to 3 show the ca lculations of body current and vo ltage between EPBz and EPB 3 for different values of R 1 , R2 , RehH and RchL· For i llu stration purposes , V s= 1000 VDC and the minimum body resistance Rb = 500 ohms is used. S imil ar analysi s for AC high voltage sources would result in similar conclusions. In all the scenarios presented in Tables 1 to 3, the electrical protection barriers prevent direct contact of the high voltage sources.

18Table l pre sents the scenario where the first three conditions of the electrical protection barrier requirements in SAE 

### J 1766 are met (Option 1 for electrical protection barriers) at their threshold levels: (1) No direct contact of high voltage sourc es, (2) resistance b etween e lectric a l protection barriers and chassis is le ss than 0.1 ohms (RchH = O.l ohms , Rch L = 0.1 ohms) , and (3) mea s ured re sis tanc e between the high vo ltage so urce to the conductive part of the protective barrier is greate r th an 0.01 o hm s (Rm eas=O.O 1 ohms/vo lt) . The analysis s how s that electrical protection barriers meeting all thre e conditions in Option I result in body current that i s wit hin safe level s (less than l 0 rnA DC). Additionally, when all three conditions in Option I are met , the electrical protection barri ers also meet condition 4 for electrica l protection barri ers an d so also sa ti sfy Option 2 requirements. 

### Tab l e 1. Scenario w h ere Option 1 (conditions 1, 2, and 3) of SAE J1766 e lectrical f b 

### protec ton arner reqmrements are met Parameten. Values Comments Voltage Source CVs ) 1000 volts Body Re s istance**(~)** 500 o hms Minimm1 body re sistance Resistance between EPB 2 and chassis (R
. hu) 0.1 ohms Thre s hold valu e ofc hass is resistance permited Resistance between EPB 3 and chassis (RchL) 0.1**ohm~** by SAE J 1766 (condition2) Total c h assis r esis tance (R.h) 0.2 ohms Equivalent co mbin ed r esistance of chassis and body (R.,q) 0 . 1 999 ohms Re sistance between high voltage source # I and**EP~** (R 1 ) 20 ohms Re sistance between hi gh vo ltage so urce #2 and EPB 3 (R 2 ) 2 0 o hms Measured resistance between hi g h vo l tage source and chassis (Rm
... ) 10.05 ohms Meets SAE J 1 766 requireme nt (condition 3) Total re sistance t o curre nt (Rr) 40. 1999 ohms Total current in c ircuit (l r) 24.8757 amp s Voltag e drop through r esis tance R1 CVRI) 497.51 3 4 vo lts Voltage between EPB 2 and chassis**(Vt~)** 2.4866 volts Meets SAE J 1 766 r equirement (condition 4) Voltage drop through re sistance R 2 (VR2) 497.5134 vo lts Voltage between EPB 3 and chassi s (VL) -2 .4866 volts Meets SAE J 1 766 req uir ement (condition 4) Voltage between EPB2 and EPBJ (VHL) 4.9731 volts Meets SAE J 1 766 r eq uirement (condition 4) C urrent through the body (lb) 0.0099 amps Body current is at sate levels (less than I 0 rnA)

1 9Tab le 2 pre s ents the s cenario w here conditions 1 a nd 3 (no direct contact and R mcas> O.Ol ohms/volt) of the electrical pro t ectio n b a rrier requireme nt s in SA E J 1766 are met but condit i on 2 (R:hH < O.l ohms, R:hL < 0.1 ohms) i s v iolated. The anal ys i s shows that the current through the b ody (lb) is n ot w ithin safe levels( > l 0 rn A D C). Additionall y, the e lectrical protection barriers mee t the fourth condition for e lectrical protec tion barrier s th at the vo ltage between el ec trical protection barriers and ex po sed co nducti ve part s is less than or equal to 30 V AC or 60 VDC. This indicates th a t Option 2 of the Alliance proposal (meeti ng condition 1 and conditi o n 4) does not e n sure that current throug h the b o dy is wi thin safe l eve ls . 

### Table 2. Scenario where Option 2 (conditions 1 and 4) of SAE Jl766 electrical protection barrier requirements are met . Conditions 1 and 3 of Option 1 are also met but not condition 2 . Parameters Values Comments Vo ltage Source (V s ) I 000 volts Bo dy Re sistance (Rt,) 5 00 ohms Minimum body re s istance Resistance between EPBz and chassis (R c hH) 0.2 ohrm C hassis re s ist a n

ce is greater than t hre s hold Resistance between EPB3 and chassis (R chd 0.2 ohrm val ue pennit e d by SAE 11 766 (co ndition2) Total c hassis re sistance (R., 11 ) 0.4 o hm> Equivalent co mbin ed re sistance of c h

assis and b o d y (R.,q) 0.3997 ohms R

esistance b etwee n high vo ltage s o ur ce # I and EPB 2 ( R 1 ) 2 0 o hms R

esistance between high vo ltage so urce #2 and E PB 3 ( R 2 ) 20 o h m> Measured resistance between high voltage so urc e and chassis <Rm eas ) 10. 1 ohrm Meets SAE J 1766 re quirement (conditio n 3) Total resistance to c urr e nt ( R T) 40.3997 o hms Total c urr e n

t in circ uit (IT) 24 . 7527 a!ll> S Voltage dr o p thro ugh re sistance R 1 (V R 1 ) 495.0534 volts Vo ltage between EPB 2 and chassis (VH) 4.9466 volts Meets SAE J 1766 requirement (co nditio n 4) Vo kage drop thro ugh resistance R 2 (VR2) 495 . 0 53 4 volts Voltage between EPBl and chas s is (VL) -4 . 9466 volts Meets SAE 1 1 766 requi rement (con ditio n 4) Voltage between EPBz and EPB3 (VHL) 9.8932 vo lts Mee ts SAE 117 66 requirement (co nd ition 4 ) C urrent through the body (lb) 0 .01 9 8 amps Body current is not at sate levels (> I 0 rnA)

Table 3 pre se nts th e scena ri o whe re condition s 1 and 2 ( no direct contact and R chH < O.l ohms , R:h L < 0.1 ohms Rme as> O.O 1 ohms/vo lt ) of the e lectri cal protecti o n barrier require m e nt s in SAE J 1 766 are met but condition 3 (Rmeas> O.O l ohms/vo lt) is v io la te d . T he analys i s s ho ws th at

20the current through the body current is not within safe le ve ls(> 10 rnA DC) . Additionally, the e lectrical protec tion barriers meet condition 4 for electrical protection barriers that the voltage between e lectrical protection barriers and exposed conductive parts is less than or equal to 60 VDC. This indicate s that Option 2 of the Alliance proposal (meeting condition 1 and condition 4) doe s not ensure that current through the bod y is within safe level s.



### Table 3 . Scenario where Option 2 (conditions 1 and 4) of SAE Jl766 electrical protection barrier requirements are met. Conditions 1 and 2 of Option 1 are also met but not condition 3. Parameters Values Comments Voltage So urce (V5 ) 1000 volts Body Resistance**(~)** 5 00 ohm; Minirrum body re sistance Thres hold value ofchassis resistance pennited Resistance between EPB2 and chassis (Rthu) 0 . 1 ohrm by SAE J 1766 (co ndition2 ) Resistance between EPB3 and chassis (Rchd 0 . 1 ohrm Total chassis re sis tance (Rch) 0 .2 ohm; Equivalent combin ed resistance of chassis and body (Rcq) 0 . I 999 ohms Resistance between high voltage so urce # I and EPB 2 (R 1 ) 1 . 6 ohms Resistance between high voltage so urce # 2 and EPB 3 ( R 2 ) 1 .6 o hms Measured resistance between high voltage source Doe s no t meet co ndit io n 3 ofSAE J I 766 and chassis (Rm us ) 0 . 85 ohms (Rmcas> O.O I o hms/vo lt ) Tota l re sis t a nce to c urr en t ( R r) 3 . 39992 ohm; Total current in c ircuit (l r) 294. 1 246 amp s Voltage dr o p thro ugh resistance R 1 (VRJ) 4 70.5993 volts Vo ltage between EPBz and chassis (Vu) 29.4007 volts Meets SAE J 1766 requirement (condition 4) Voltage dr o p thro ugh resistance R 2 (V R2) 470.599 3 volts Voltage between EPB3 and chassis (Vt) -29.4007 volts Meets SAE J 1766 requirement (co ndition 4) Voltage between EPBz and EP83 CVut) 58 . 80 l 4 volts Meets SAE J 1766 requirement (co ndition 4) Current through the body (lb) 0.1176 amps Body current is not at sate levels(> I0 mA) 

### V I. Di s cu ss ion

The agenc y's ana l ys is of Alliance's propo sal for an e lectrical protect ion barrier option for post-cra sh electrical safety in FMVSS No. 305 confirmed that the electric current through the body is within safe limits (less than or equal to 10 rnA DC or 2 rnA AC) when the electrical protection barriers meet conditions 1 , 2 , and 3 (O pti on 1 ) . Additionally , when all three

21conditions in Option 1 are met , the electrical protection barrier also meets th e conditi o ns 1 and 4 for Option 2. The analysis also showed that mee ting Option 2 requirement s (conditions 1 and 4) alone does not g uarantee that the current throu gh the body is within safe limits . Howe ve r , FMVSS No. 305 and internati o nal standards already recogni ze voltage s le ss th a n o r equal to 30 VAC and 60VDC a s low voltage and co nsidered safe . For vo ltage b e low or equal to 30 VAC and 60 VD C , the potential bod y c urrent i s be low th e let-go limit 1 5 and below the limit for elec tric s hock with non-rever s ible harm. N HTSA is aware that it is diffi cult to meas ure the re s istance b etween hi gh vo ltag e so urc e and the expose d conductive part s of the electrical protection barriers since th e r es istance level is too low to meas ure accurately and becau se some di sassemb l y of the barrier ma y be needed to access th e high voltage source. Additionally , for electric powered vehicles that meet the e lectrical isolation and the direct and indirect contact protect ion r eq uirement s in GTR No . 13 durin g normal vehicle operation , th e sce nario represented by the circuit diagrams in Fi g ure 6 and Figure 8 ha s a very lo w lik el ih oo d of occ urrenc e s inc e s uch a scen ario i s o nl y po ss ibl e w he n multipl e fa ilure s of sa f ety systems occur along with hum an contact t o s pecific part s of the veh icl e. Therefore , the agenc y i s propo sin g a combination of Option 1 and Option 2 of th e Alliance pro po sal for po s t- cras h electrical safety u s in g e le ct rical protection barriers . Specificall y, the age nc y i s propo s in g th e following po s t-cra sh requirement s for e lec trical protection barriers. I . Direct co ntact protection: Electr ical protection barriers have pro tec tion deg r ee IPXXB 2 . Indirec t contact pro te ction : Elec tri ca l protection barriers are conductively connected t o th e cha ssis with re s is t ance less than 0. 1 ohm s and resi s tance betwee n tw o electri cal protec tion barri er s that are access ibl e within 2.5 meter s is les s than 0. 2 ohms , 3. Low Voltage: Voltage between e lectrical protec tion barriers and o th e r exposed conductive part s i s le ss th a n 30 VAC or 60 VDC.

15 M ax imum va lu e of tou c h c urre nt at which a perso n hold in g e l ec trod e s can le t go o f the e l ectrodes. 22The first two co nditions in the agency's proposal are spec ifi ed in GTR No. 13 and the third condit ion is a lready recognized as safe in FMVSS No. 305 an d in international s tandard s. The technical analysi s pre sented in this document demons t rates that the proposed postcrash physical barrier protection option (with the first two requirement s in GTR No. 13 and an additiona l third req uirement that the electrica l protection barriers be low voltage) afford s the s ame level of safety as the post-crash e lec tric a l i so lation option currentl y in FMVSS No. 305. That is , the c urre nt through the bod y would not exceed 1 0 rnA DC and 2 rnA AC, which are considered to be safe levels for electric shock.

23