Made a battery for my DS1054Z - 20hr batt life - Page 1
Forum section: electronics / testgear

author: okashira
author_rank: Contributor
timestamp: March 04, 2016, 11:46:22 pm
content: I got tired of dealing with ground loops, interference, and already shorting one of my probes across mains...So I made a battery. It's 20 series 2 parallel of cells I pulled from a wrecked 2014 Tesla Model STested it at ~20 hrs run time.I expect them to last 15 years charging to 4.05V/cell (81V DC)I split them into two 10 series packs, so I can charge them with my iCharger in parallel.Will fit nicely on the back once I clean up wiring and get some velcro.

author: uncle_bob
author_rank: Unknown
timestamp: March 05, 2016, 12:00:26 am
content: HiIf you had fun shorting things ... don't short those cell packs !!Also keep in mind that one thing the line cord provides is a case ground. Without that, you can easily have a scope chassis that has enough voltage on it to kill you.Bob

author: okashira
author_rank: Contributor
timestamp: March 05, 2016, 12:04:17 am
content: Quote from: uncle_bob on March 05, 2016, 12:00:26 amHa! shorting these is no biggie.Thanks for the advice. Do you think I should connect the battery negative to ground? Or how else to mitigate this without grounding to mains?We shorted the whole Tesla pack before pulling it apart.

author: TheSteve
author_rank: Unknown
timestamp: March 05, 2016, 12:11:31 am
content: I think I would have stuck to a 12S pack or similar to keep the weight/size down.

author: okashira
author_rank: Contributor
timestamp: March 05, 2016, 12:19:30 am
content: 12s would have been useless for other stuff, furthermore 12s is too low voltage.If I wanted it tiny I would have done 20s1p. This pack is 40 cells. It' barely makes the scope bigger, way more portable then lugging the mains cord.Also nice to have the 1-2 day battery life

author: markone
author_rank: Frequent Contributor
timestamp: March 05, 2016, 02:12:26 am
content: Quote from: okashira on March 04, 2016, 11:46:22 pmWouldn't be easier and safer to use a power line isolation transformer to feed the scope ?If those are unprotected lithium nickel cobalt cells (NCR18650A ?), as allstraighthigh density Li-ion they are quite dangerous.Quote from: okashira on March 04, 2016, 11:46:22 pmWhy ?It wasn't a smart move ....I would say : do not try this at home !

author: okashira
author_rank: Contributor
timestamp: March 05, 2016, 02:35:28 am
content: They are quite safe - I've made dozens of packs from these cells by now and we've conducted a lot of abuse testing.They can handle almost everything without thermal run away or any drama - overcharge, crush, storage at 0v, dead short.The only things that cause thermal run away are penetration (nail, etc) and heating them above 230°C - neither of which will be happening on the back of my scope.On the pack, because we could? It wasn't on accident, and precautions were taken. Used 14awg wire to prevent the cell fuses from blowing (instead - it practically vaporized the 14awg wire)We shorted a single module with 4awg and it killed most of the fuse wires:Didn't want to do that to the whole pack...

author: markone
author_rank: Frequent Contributor
timestamp: March 05, 2016, 02:59:17 am
content: LOL !Beer & Brymen, i agree with bothOK, so you relied on safety wire fuses placed in series with every single cell, without those the result would have been utterly different.It was a battery pack from a defective/wrecked car ?AFAIK those are quite expensive.

author: okashira
author_rank: Contributor
timestamp: March 05, 2016, 03:05:52 am
content: Quote from: markone on March 05, 2016, 02:59:17 amWe didn't "rely" on anything.If the module didn't have fuse wires, it would have hit 3,000 amps or so, which would have fused the 4awg wire. It would just have been a little more dramatic.Yes.

author: markone
author_rank: Frequent Contributor
timestamp: March 05, 2016, 03:18:00 am
content: Quote from: okashira on March 05, 2016, 03:05:52 amI wonder if those have an integrated safety PTC.Are they actually Panasonic NCR18650A ?

author: okashira
author_rank: Contributor
timestamp: March 05, 2016, 03:31:32 am
content: Quote from: markone on March 05, 2016, 03:18:00 amNo to both.

author: digsys
author_rank: Unknown
timestamp: March 05, 2016, 03:40:39 am
content: Do you have any details / links to the batteries? What did the pack cost? If you are able to give any details, it would be appreciated.

author: markone
author_rank: Frequent Contributor
timestamp: March 05, 2016, 03:51:06 am
content: Quote from: okashira on March 05, 2016, 03:31:32 amSo i assume you put a fuse nearby every battery pack.I just took a YouTube toor on DIY battery packs, in some cases straight Li-ion cells hand soldered without any kind of protection/balancing circuit, quite scary things IMHO.

author: okashira
author_rank: Contributor
timestamp: March 05, 2016, 03:57:22 am
content: Quote from: digsys on March 05, 2016, 03:40:39 amNCR18650BE3.2Ah4.2V max2.5V minDCIR @ 25°C approx 45 mOhmDCIR @ 50°C approx 30 mOhm45g

author: okashira
author_rank: Contributor
timestamp: March 05, 2016, 04:35:04 am
content: Velcro I ordered came. worked perfect. 3M heavy duty stuff.Almost too hard to pull it off..Just need to shorten and clean up the wiring.

author: luney
author_rank: Contributor
timestamp: March 05, 2016, 08:51:10 am
content: I'm into RC flying and actually thought about trying Lipo packs to do the same. Very nice work. Very nice indeed. It's funny because the truly nice handheld scopes (by nice I mean of decent quality and feature rich) are dang near that same size anywho. I say, "Good on ya mate!"

author: tautech
author_rank: Super Contributor
timestamp: March 05, 2016, 09:06:39 am
content: Quote from: okashira on March 04, 2016, 11:46:22 pmTrouble is you've made it only half safe.While you have removed the chance of mains ground loops there's still all the BNC shells commoned so there's still potential for Reference (GND) lead loops by way of non-common points of connection for the probes Reference (GND) lead.Furthermore one still has the rated channel 300V inputs and while using one channel you might be able to now exceed that, definately not using 2 channels or more.An Isolated channel DSO or Differential probes are the proper solution.Portability, yep you've accomplished that.

author: Kilrah
author_rank: Unknown
timestamp: March 05, 2016, 09:15:16 am
content: Quote from: okashira on March 05, 2016, 03:05:52 amAnd splattered molten copper all over you, yep...

author: markone
author_rank: Frequent Contributor
timestamp: March 05, 2016, 02:25:10 pm
content: Quote from: okashira on March 05, 2016, 03:57:22 amNCA chemistry as NCR18650BD, but with lower discharge rate and price.@digsys :safe building battery pack starting from single naked cells requires skill and equipment, they must be spot welded together using nickel strip for contacts, sure not iron soldered.As all other Lithium Nickel Cobalt Aluminum Oxide cells are safer than older Li-Ion chemistries but not "intrinsically safe" and there is still risk of explosion or fire.Ideally theyshouldbe fitted with protection circuits to provide charging / discharging voltage cut-offs and overcurrent trip.It's true that sourcing the DS1000Z scope it's a soft task for them but also normal handling requires some care.@okashira :there is additional electronic inside the black plastic wrapping ?Is the white connector wired to the battery pack suited for a balanced charging system connection?

author: bitseeker
author_rank: Super Contributor
timestamp: March 05, 2016, 02:40:45 pm
content: I remember a thread here about battery powering the 1054. Cool to see someone made one. Thanks for sharing.For polish, perhaps put the packs and wiring into a nylon pouch affixed to the rear to look like an accessory pocket for probes, etc.

author: okashira
author_rank: Contributor
timestamp: March 05, 2016, 03:11:56 pm
content: Quote from: markone on March 05, 2016, 02:25:10 pmYes, of course, I put a voltage tap for each cell on each 10 series pack. This way I can balance charge them with my iCharger. Like I said, I expect the packs last 15 years.Upper and lower voltage "protection" are not necessary. I can just use a volt meter display if I want to watch voltage so they are not over-discharged.Either way, they can handle an over discharge just fine if an accident occurs, like I forget to turn it off.The scope will shut off anyhow near 40V, which happens to be high enough so that the pack is not over-discharged too much.There is no risk of fire or explosion here. You base your experiences on Hobby King Lipos and Chinese made 18650's. These cells are in another league in quality and design.

author: okashira
author_rank: Contributor
timestamp: March 05, 2016, 03:17:12 pm
content: Quote from: Kilrah on March 05, 2016, 09:15:16 am

author: markone
author_rank: Frequent Contributor
timestamp: March 05, 2016, 03:53:10 pm
content: Quote from: okashira on March 05, 2016, 03:11:56 pmSure i know, japanese Li-Ion cells are way better than most cheap crap you can find out there, i simply reported the official Panasonic's guidelines for this product category to warn who does not have experience with this stuff, of course not youI know quite well the matter having developed (actually several years ago, when dedicated IC's were not available) a uC based custom Li-ion battery charger used inside a mobile device.I also tinkered for years with high power led flashlights, where Li-Ion cells are inside a robust metal pipe that could easily become a small bomb, so i have always been very conservative using only quality IC protected battery with Sanyo & Panasonic cells inside.For this kind of application (battery operated DS1000Z) could be enough to use a total of 16 cells in series, keeping the overall cost within 60-80 USD (plus charger) of course with reducted lasting respect your pack topology.Just out of curiosity : why that Tesla battery pack was "scrapped" ?

author: markone
author_rank: Frequent Contributor
timestamp: March 05, 2016, 04:00:19 pm
content: Just to have a glimpse about the potential of a single mistreated and/or low quality Li-Ion cell, jump to 00:25 of

author: tsaG
author_rank: Contributor
timestamp: March 05, 2016, 04:20:47 pm
content: Why not just directly supplying 14V to the DSO and regulate it to 12V (as I think they are using as secondary voltage) and just skip the Primary voltage?Did it with my old Rigol once, worked perfect using a 4S Lipo.

author: markone
author_rank: Frequent Contributor
timestamp: March 05, 2016, 05:17:55 pm
content: Quote from: tsaG on March 05, 2016, 04:20:47 pmWhich old Rigol model ?Looking at the older DS1000/DS1000E series PSU schematic you simply cannot do that :"https://www.eevblog.com/forum/blog/rigol-ds1052e-nasty-surprise!/

author: nuno
author_rank: Frequent Contributor
timestamp: March 05, 2016, 05:40:41 pm
content: Nice, I like itWhat is the current consumption on the battery side, have you measured it?

author: Eheran
author_rank: Regular Contributor
timestamp: March 05, 2016, 08:21:08 pm
content: Ive got 2x 18650 LiFePO4 18650M1A 4s1p packs (so very small) and one Li-Ion 18650PD (2900mAh) 8s1p pack. The later one is used to power a 70W small LED light as well as a 24V fan - both very handy items when camping (obviously the LED is only at ~1% in a tent). So i just put them all in series and get 60V, tho the "weak link" is one of the LiFePO4 packs with only 700mAh. That still lasts more then 2h, longer then everything i need off-grid, like cranking current of a car... if i would need it any longer i would just make another 8s1p Li-Ion Pack.QuoteJeah, with a dedicated DC input... that would be the ideal way.

author: okashira
author_rank: Contributor
timestamp: March 06, 2016, 04:31:49 am
content: Quote from: nuno on March 05, 2016, 05:40:41 pmIt was around 220mA IIRC? If I fully charged the packs, they would have ~6200 mAh capacity, so it could be good to more then 24 hours :-D

author: okashira
author_rank: Contributor
timestamp: March 08, 2016, 01:16:42 am
content: Quote from: okashira on March 05, 2016, 12:04:17 amSince my question wasn't answered, I figured I would answer it myself.Here is some of Tek's documentation in regards to using battery powered scopes:http://in.tek.com/dl/3AW_19134_2_MR_Letter.pdfhttp://www.tek.com/dl/51W_10640_1.pdfCliffs are - Stick to 42V P-P measurements when using a battery powered scope. Anything higher, add a ground strap to the case.It's pretty conservative. I think one could keep it to ~80V P-P and be okay. Anything higher, and definitely ground the scope to mains ground.I've built a few 20 series packs at ~80V and touched the leads. You can't even feel it unless you press hard. Danger comes when you hands are sweaty/have cuts on your skin.If anyone wants a pack made, let me know. You could be the 2nd person to have a Tesla powered oscilloscope. :-D I have a few thousand cells sitting around...

author: Emix
author_rank: Newbie
timestamp: March 17, 2020, 03:05:36 pm
content: I've read the two threads about battery powered DS1054Z and want to make my own soon.Li-ion batteries and cells are my specialty, coming from the DIY ebike world. A 20S (72 V nominal) battery is easily done, but would it not be possible to feed the scope with battery power thru diodes (and fuse) straight into the PSU's primary side's capacitors, bypassing the rectifier bridge?If this is feasible I could plug the 230 V power cord in and out as I see fit for the task at hand, making the switch from stationary to portable easy while keeping the power on. No current should run backwards into the battery leads, right?