Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
What to do with 100 4P4S packs
#1
I have been collecting and processing cells for a diy powerwall for a while and I recently scored 100 4p4s 5.6Ah packs - 8kwh!. They have unbranded cells but are in mint condition as they were backup batteries from emergency signage that require replacement every 2years, so barely a cycle on them.

Background: This is a long term project with the intention of finishing it to coincide with renovating my house and finally getting solar hopefully by xmas. So I don't have an inverter yet (or anything else).

So now I have these 4s batteries (and the possibility of getting more of the same) it feels a bit mental to break them all down and process them. Should I:

A. Just harvest the cells
B. Put them all in parallel for a giant 4s battery
C. Build a 12 or 16s battery

My first instinct is C, but would this even work with the existing bms's? B would certainly be the easiest and neatest but that is going to be a huge amount of amps if I end up with 20kwh.

Any suggestions? It's a good problem to have I know Smile

Cheers,
Pete

Reply
#2
Post some pictures. 4s isn't very useful. 8s is probably too much for 24v devices. Same with 12s or 16s. I would think removing the stock BMS and re wiring them would be wise. You are most likely going to have to tear them down to some extent. Even then you may need to be mindful, that while each pack should have very similar capacity cells, you can't really take this for granted.

A possibility would be leaving them in 4p groups and testing them like so. But then, you have the problem of holders for 4p groups, to build your final pack.
Reply
#3
Pics please! I've never seen emergency signs with lithium batteries, always lead acids or NiCd. I'm really curious about these emergency signs! Here in the US, they have to be replaced every 4 years, and most of the time the batteries are fried from being overcharged all the time. Anyway, lithium batteries hate sitting at full charge, so if that's what these were doing, expect some capacity loss. From what I've been seeing, sitting at full charge is worse than cycling. And these are rated at 1.4Ah per cell brand new, almost doesn't make sense to break up the packs. Best thing would be to run these at 12S as is after testing them, of course. What do the BMS's look like?
Reply
#4
Build 14s system. Ie 12s + 2s = you need to break up the end pack to get them to what you need.
Geek likes this post
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
Reply
#5
Thanks for your feedback guys. I tried to add pics in the original post but it didn't seem to work on my phone. So pics here https://photos.app.goo.gl/wbxtPed3DCqzHh8q9

They seem well constructed with a piece of fibreglass and a heatsink plate on the BMS. I take your point about them possibly being overcharged, I guess that depends on how the BMS is configured. I'll break down a couple and test the cells individually and see how consistent they are. I can measure capacity of the whole pack relatively accurately with my RC chargers (albeit slowly - like@20W).

Not that certain of the provenance, I "bought" them for a case of beer per box from a third party so information is at least second hand.

I was going to build my battery to match my inverter, but I guess I could look for an inverter that works with some multiple of 4s if C is an option.
Reply
#6
(02-14-2019, 10:51 AM)askpete Wrote: Thanks for your feedback guys. I tried to add pics in the original post but it didn't seem to work on my phone. So pics here https://photos.app.goo.gl/wbxtPed3DCqzHh8q9






They seem well constructed with a piece of fibreglass and a heatsink plate on the BMS. I take your point about them possibly being overcharged, I guess that depends on how the BMS is configured. I'll break down a couple and test the cells individually and see how consistent they are. I can measure capacity of the whole pack relatively accurately with my RC chargers (albeit slowly - like@20W).

Not that certain of the provenance, I "bought" them for a case of beer per box from a third party so information is at least second hand.

I was going to build my battery to match my inverter, but I guess I could look for an inverter that works with some multiple of 4s if C is an option.

Added the photos to your post, I can take them down if you don't agree. Nice Ego batteries in the background, btw!

I looked up Ronda Batteries, they definitely do emergency lighting. They don't have that specific battery listed and they mostly talk about LiFePo4 cells, so their website probably hasn't been updated in a while. But the specs on the battery cover show 14.8 V, which is a Lithium Ion 4S voltage. The "1710" looks like a date stamp, these might even be less than 2 years old! Did you check any cell voltages? I'm curious if they were at 4.2 all the time or something else. The BMS looks like it has balancing resistors in it, which is a plus for leaving the BMS's attached. 

It's totally up to you, but if I scored this find, I would test each pack with the RC charger and also do some testing on the BMS to see high voltage cutoff voltage, low voltage cutoff voltage, short circuit protection, overload protection, etc. Most likely, I would leave the BMS attached and the packs as is. I would take 1 pack as a sacrifice pack and longevity test the cells (repeatedly charge and discharge the cells at least a hundred times). That's how you know how your pack will behave when you have 1600 of the same cell, but no data sheet. Those cell wraps look thicker than the typical 4x5 cell holder could accommodate. Most 48V inverters cut out around 40-42V where your cells will be around 3.4-3.5V, so 12S will work. You just need a charge controller that you can manually set the top end voltage to something like 48V (4V per cell). It sounds like you already have an inverter? If it is 24V, you can do 8S.
askpete likes this post
Reply
#7
I also have a bunch of those and have tested the cells. They seem to be 1400mA cells although I have had them test as high as 1700mAh.
They come apart rather hard as the cell wrappers are fused to each other.
I have also decided to keep them intact and look forward to see what you will do with them.


Wolf
askpete likes this post
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 6/10/2019
Total Number of Cells                          5940
Cells  >80% of Capacity                      4334
Cells <80% of Capacity                       1605
Cells ≥2200mAh & ≥ 80% & ≤75mΩ    2800 +236
For Info Google Drive
Not your average Wolf       
            Cool



Reply
#8
Thanks dallski I will need to do more investigation/testing. Luckily I'm not in a hurry. I haven't bought anything yet so that is good too. I went through a box and they ranged from 12 to 16v with no apparent pattern. So I guess my first job will be to get them all to storage voltage.

Those ergo batteries are excellent, I have a good source where I get a few every week for free. The BMS in those seems especially fragile - good for me ? I've rewired a few as 7s and sold them to mates for charging racing quad batteries. Making this almost a self funding project.

@wolf yep they look exactly the same as these ones. Will keep you posted, though might be awhile before I get onto it.
Reply
#9
Are those li-ion or lifepo4 cells? You don't see carboard wrapping in li-ion much but it is common on the lifepo4 cells.
Reply
#10
(02-15-2019, 02:32 AM)gpn Wrote: Are those li-ion or lifepo4 cells? You don't see carboard wrapping in li-ion much but it is common on the lifepo4 cells.

Doesn't look like it. 14.8v nominal is 3.7v per cell. They are definitely Li-Ion.
Reply


Who read this thread?
58 User(s) read this thread:
daromer, Korishan, PAF, Mike C, watts-on, Dan Lim, Stefaan De Ridder, BlueSwordM, ivnz, Geek, Grumplestiltskin, ChrisD5710, Oz18650, djuro, gpn, Chablis_m, Headrc, rodagaster, jonyjoe505, Redpacket, Ibiza, Walde, 100fuegos, bukvaahmed@gmail.com, chuckp, hazSolar, Leipi35, deniscroombs, Wolf, Bastler_Ro, camthecam, Dallski, Solardad, ajw22, lloulou11, Lagachette, mart1nn, LEDSchlucker, zoookii, Powersaver, kurt13r, Richard, mskip, Church1182, bournevexed, beserker786, kophi, winny, Edster, Lucan, Havskum, askpete, Dennis, BarryG, aarontyree, kronos, gtgraber, Stuie0

Forum Jump:


Users browsing this thread: 1 Guest(s)