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Second hand laptop Batterries extra


beserker786
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Hi guys I came across more second hand laptop Batterries  if anyone is interested.

 

I can give them to you for R10-R15 a laptop battery, depending on how many you take. I’m based in midrand. They’re perfect for DIY powerwall and small projects!

 

there is too many for me to add to my power wall.

DEFA663E-D3C9-440C-8071-63E8E9D601D5.jpeg

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Hi Stok. On average , when I tested, I had usually all were good, or 4 were good, or all were bad per pack. Depends on the pack. The average Mah can vary, but I managed to make about 3x 24V packs with about 280 cells, all above 2000mah, some closer to 3000mah. I’d say a definite good yield of about 50% cells made it to my power wall. 

Edited by beserker786
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that's not too bad, considering that laptop (or  any other lithium battery pack) in south africa is as scarce as chicken teeth.

 

the cells that you sell, are the packs already opened and cells sorted and tested? or do you sell the complete battery? 

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9 hours ago, beserker786 said:

 The average Mah can vary, but I managed to make about 3x 24V packs with about 280 cells, all above 2000mah, some closer to 3000mah. I’d say a definite good yield of about 50% cells made it to my power wall. 

How did you build a battery pack?  Did you use a system from someone or from scratch?

 

Edited by Pietpower
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8 hours ago, beserker786 said:

So I 3d printed cell holders for the Batterries, soldered on the fuses, hooked them together 7p, got a 24V cell meter balancer. And connected the terminals to the battery connection on the inverter. I’d say tested the cells and built the battery from scratch.

Please post a pic of the final battery showing the fuses and balancer.

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  • 4 weeks later...

These builds interest me more than the 'second life' batteries you can buy from the local Li battery suppliers. What I understand of these is they are imported from China as 'second life' and you pay good money for them.

At least with the 18650 battery packs one gets them for nothing (or close) and you can sort the good from bad. 

What I need to know from those who have done this and built their power wall battery is what is the important criteria when sorting: capacity, internal resistance etc. ??

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On 2020/12/12 at 7:45 AM, Richard Mackay said:

These builds interest me more than the 'second life' batteries you can buy from the local Li battery suppliers. What I understand of these is they are imported from China as 'second life' and you pay good money for them.

At least with the 18650 battery packs one gets them for nothing (or close) and you can sort the good from bad. 

What I need to know from those who have done this and built their power wall battery is what is the important criteria when sorting: capacity, internal resistance etc. ??

Apologies for the thread hijack. this is a +- 3kw 24v battery I built using these cells( salvaged 18650) 

It consists of 420 cells arranged in a 7s30p configuration paid +- R3500 for the cells (some were new)

used 3x18650 cell holders from bid or buy, paid probably R2.00 each, 280 x R2.00 is  R560

15mm copper water pipe, used about 10m for the busbars. paid R900

10mm2 cable, paid R100 (IIRC I bought 2.5m red and black)

25mm x 2.5mm aluminum used about 2.5m, cost R180

cellmeter7 battery checker and balancer, paid R250

100A watt meter with bluetooth, Paid R450

Lugs and screws +_ R150

man hours, PLENTY!!

total for a 3kw 24v battery R6090

I fused both positive and negative side(should only do neg in the future to save time and frustration) this was by far the worst part of the build,

during assembly on the plywood board I managed to short out 2 packs and blow about 110 cell fuses, now i use cardboard cutoffs between the packs.

overall this was a very satisfying project to build.

this battery have been in operation since august 2019, and is cycled daily (max volt is 27.4v equals cell voltage of 3.91v, low volt disconnect is 24.8v, 3.54v per cell)

I use this battery in parallel with a 3kw lifepo4 battery, and the charging profile i use is very gentle on the cycle life of the cells (liion and lifepo4) 27.4v equals 3.42v per cell and 24.6v equals 3.1v per cell.

 

Regards and keep safe.  

20200402_140813a.jpg

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I reckon these builds sort the serious enthusiasts from the ouks bragging about how big their systems are.. ('my system's bigger than yours..')

The only thing I'm still trying to get my head around is how to maintain the individual cells (or the banks). How do you know their capacity has dropped or cells have died..?

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Hi Sir, i use the cellmeter to tel the individual voltage of all the 60 cells in a pack, when one pack starts to drift out of balance then its time to investigate the specific pack. if a cell died then either the CID(current interrupter device, basiically a internal fuse in all 18650 cells that pop when the cell internal pressure gets to high due to overcharging)  have popped in which case the cell will be open circuit, so the currant will bypass that cell. or the internal resistance became to high due to degradation then that cell will draw a lot of current heat up and hopefully the cell level fuse will do its job. I used a single strand of 1.5mm cable that was untangled into probably 18 or so single wires, i do not have a spec for the wire i used, i tested a lot of different size wires with a 10A buck converter, 35mm length, set the buck conveter to 3.8v and slowly increased the amps, most thin wires i tested get red hot between 4 and 6 amps and burn off at 8a+, the wire i settled on got hot at 1.8A and burned off at 2.6A. That gives me a max AMP rating for the battery of 108A, I still use a 80a fuse between battery neg and inverter. 

IIRC the wire is 0.08mm 

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