Handheld Computer battery packs

doniel

New member
Joined
Jan 14, 2021
Messages
2
Hello folks,

I am about to create a Power Wall for my 7,2kW photovoltaic system. I am now looking for batteries. And I have the chance to get a big bunch of mobile computer batteries for free which have never been used or only little used. One battery back consists of 2x18650 with in total 5000mAh and the other pack is a flat one from LG with 4040mAh. Both battery pack types have a PCB inside which looks like a BMS. I have attached a picture of the PCB and the battery pack connectors I have 2 questions:

1) Does it make sense to build a battery pack with these batteries and keep the PCB of the batteries? Would it increase safety, can I use it for a BMS?
2) How would you build a pack with these batteries? For the flat batteries I have concerns regarding security because + and - pole are very close to each other. Any idea welcome!

Looking forward to your thoughts guys!

Cheers

doniel
 

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OffGridInTheCity

Well-known member
Joined
Dec 15, 2018
Messages
1,265
Since you have a 7.2kw PV array - you'll likely be building a larger powerwall, maybe 10 - 30kwh? My point being is that it sounds like you'll have literally 1,000(s) of 18650 cells or flat-batteries. If so, then I'd rather have an overall BMS to see what's happening. Not pushing Batrium - but one of the things I love about it is that I can *monitor* both visually and data to a database for long term management.

Here's a Batrium snapshot - each blue line is a separate 'pack' of cells in parallel....
1610640192124.png

So maybe the answer lies in the scale of what you plan :)
 

anton_voltx

New member
Joined
Jan 13, 2021
Messages
14
1) Does it make sense to build a battery pack with these batteries and keep the PCB of the batteries? Would it increase safety, can I use it for a BMS?

You might say, OK they all have temperature protection that's good -- but they could have different temperature thresholds so when you are running one module shuts down while the others keep running. I think there are many issues to trying to use the original laptop PCB. To avoid the issues you should start fresh with a central BMS that is special built for your purposes.
 
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