APC Smart 1000XL - Lithium Conversion - Page 1
Forum section: electronics / beginners

author: Thor187
author_rank: Newbie
timestamp: December 24, 2022, 07:53:33 am
content: Hello everybody, long-time lurker, decided to get me an account!I live in South Africa and for these of you who don't know we have "loadshedding" basically, government-imposed blackouts 12 hours a day split into chunks. In other words our grid is fcked and we sit without power for 2 to 4 hours at a time, multiple times a day.^quick context, now the question;I have a couple of APC UPSes, 1000XL, and 2200XL, APC charges ( in Rands now ) R11k for a PRC7 replacement battery which is just 2 x 18Ah lead acids, which costs no more than R500 each, so needless to say one option I have would be to just replace all the batteries, BUT, lead-acid with its low cycle count and inability to DoD it properly, makes it not suitable for loadshedding. I thus want to convert it to lithium, so I bought 2 7Ah lithium batteries which are "drop-in replacements" to their SLA counter parts because of their built-in BMS.But... seems it wasn't that straightforward, as the runtime is only minutes on a 80 watt load, it's as if the Life4Po batteries drop their voltage VERY quickly. ( odd chance that it might just be bad quality batteries although this is the "premier" brand in SA )That got me thinking, why not build a 7S7P or bigger battery pack from scratch?The problem is I cannot seem to find information anywhere on what the Charge voltage is of the unit and what the cut off voltage is and the float etc. ( the parameters I need to program a custom BMS )Is there software for this unit that would allow me to set the float voltage and charge etc?( I am failing to understand what the "smart" stands for. )The point is I have a couple of APC UPSes and would love to breathe new life into them by putting Lithium batteries inside them, but I need a bit finer control in terms of cut-off voltages.Hope someone else endeavored down this path of converting these APC UPSes and would be willing to share some information.I also have a few Tripp Lite 24V battery banks with busted lead acid batteries so was also thinking of replacing them with Lithium, but the individual BMSes might conflict with each other, so I am also leaning towards a single BMS 24V50Ah battery pack maybe?

author: mvs
author_rank: Frequent Contributor
timestamp: December 24, 2022, 06:30:28 pm
content: APC Smart UPSes have a register for a battery capacity. You need to use a service tool (like 3rd party apcfix) or a terminal to reset it to max value (0xFF) and then recallibrate your battery.Floating voltage can also be set in a small range (default setting is aprox. 27.7V , which is kind of ok for 8S LiFePO4 battery).

author: Thor187
author_rank: Newbie
timestamp: December 24, 2022, 10:23:22 pm
content: The only thing I understood of that whole post was that the floating voltage is give or take 27.7VHehe, I'm a such amateur.( I know what a resister is just unsure how it works in this context )

author: SeanB
author_rank: Super Contributor
timestamp: December 25, 2022, 06:41:49 am
content: The problem with the 7Ah lithium batteries you tried is they have an overcurrent shut off, which is around 20A, so it will be triggered after a few minutes running. I simply went and put external 519 car batteries on, though they are now, after 2 years, just out of warranty and have degraded down to not lasting 2 hours. 15 minutes short, so looking to get 2 scrap batteries from the scrappie ( got to be cheaper than R300 core charge for new batteries) and get another 2 619 batteries to parallel with the existing ones, and get higher capacity and longer run time. Otherwise R1700 for the 100Ah deep discharge batteries by me in Durban, so you would need to buy 2 to get decent runtime over the R1000 plus R600 for putting 2 619 in parallel.If you want to buy the 7Ah SLA they are only R200 each if you know where to shop for them. Hint it is not Builders or Security superstore.....

author: Thor187
author_rank: Newbie
timestamp: December 25, 2022, 08:02:37 am
content: Hey SeanB.I get you.Just the 20A cut off part, would that APC on a load less than 200 watt ( 80 watt at the moment ) really pull >20A?Is there a formula perhaps that I can use to calculate per use case, because then I'll need to take that into account if I am going to build my own battery pack.I kind of did take it into account and figured a 20A BMS should be plenty.

author: Thor187
author_rank: Newbie
timestamp: January 01, 2023, 08:20:41 am
content: I think I am going to take the plunge and buy some 18650 cells and a BMS.

author: Vovk_Z
author_rank: Super Contributor
timestamp: January 01, 2023, 07:00:47 pm
content: IDK what to sayto TS, but I have similar situation, and I want to share my humble experience with Smart-UPS and LiFePo4 24V battery.8s LiFePo4 with Dali 250A! Smart-BMS and APC SC1000i work strange together: it seems that Dali Smart-BMS have some transition time from charging mode to load mode, so when Smart-UPS loose mains it can't work from 105 Ah battery, because Smart-BMS can't switch instantaneously from 'charge' to 'load'. BMS turns off, and then on (but Smart-UPS loose battery). Switching it in slow manual mode - it works ok.I wasn't prepared for it, I thougt LiFePo4 is a good replace for a Lead/Plumbum battery. But BMS makes things worse.

author: Thor187
author_rank: Newbie
timestamp: January 03, 2023, 08:24:59 am
content: Very interesting comment regarding the BMS.I suppose I will need to check a couple of BMSes, but that can get expensive unless there is a "defined" name for this behavior like "switch time" or something, then one can ask the BMS manufacturer before buying it.

author: Thor187
author_rank: Newbie
timestamp: January 05, 2023, 02:42:07 pm
content: Running to spec so far, I created a calculator to help me estimate runtime:Battery Runtime CalculatorAccording to the calculator, 24V 6Ah should give me 33 Minutes on my load, I managed to get 32 Minutes, not bad.Which means the lithium battery works.Now to find the most affordable way to build a 24V 60Ah lithium battery...The charging voltage of the UPS appears to be 27.6V and the cut-off voltage seems to be 22V

author: SeanB
author_rank: Super Contributor
timestamp: January 06, 2023, 12:28:10 pm
content: Do what I did as well, and put a big capacitor across the battery terminals in the case. I went external battery, and used the internal battery leads to put in some good used 22000uF 63V can electrolytics inside the case, which help as well with the switch over time, and also average the current spikes.Mantech has 72M3403-X at R190 Xcl VAT, which is 47000uF 50V, and has an ESR about that of the leads to the battery anyway, and which has 17A ripple current, more than enough for your application, as it should be running a lot cooler than 85C anyway in the case.

author: Thor187
author_rank: Newbie
timestamp: January 06, 2023, 05:24:33 pm
content: I just want to make sure I understand correctly,Internally, you have Capacitors instead of a batteryExternally, you added a batteryIs that correct?I am going to be honest, I do not always understand the effect of capacitors in circuits, 22 000uF, is less than 0.1Ah correct?So what value does that add, versus throwing in a >20Ah battery internally instead of a capacitor?Quote from: SeanB on January 06, 2023, 12:28:10 pm

author: SeanB
author_rank: Super Contributor
timestamp: January 06, 2023, 08:37:14 pm
content: No, I put in the external battery, but with the massive capacitor in parallel with the battery, inside the case, to handle the ripple current out of the battery.