# CGR18650D Cells



## EVsmile (Aug 5, 2011)

Hi all, 

This is my first post on here but I have been a long time reader on this forum (2 years!), I have a steady supply of laptop cells coming to me due to working in IT Support. I am actually an ex army engineer and have already purchased and recieved the HPEVS AC50 pack with curtis controller 1238-7501. My question is what would be the best type of BMS would people recommend and what type of battery setup to achieve the 96 - 108V 550A, I fully understand how to achieve the 96V 550A but is there a better way than standard series and parallel wiring? Also on the charging of the recommended setup, what would be a good charging setup for a budget spend of £1500 or less?

My conversion donor is a 99 plate Miata MX5, I am 99% sure that these cells are the same ones used in the Tesla roadster and I can eventually get my hands on about 4000 due to a laptop refresh taking place over next 4 months.

Any help - espesially regarding the BMS would be extremley helpfull... Many thanks for reading.

EVsmile UK


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## frodus (Apr 12, 2008)

get the 1238 7601, it's another 100A and worth the upgrade.

you could use 18650's, but you'll need a LOT of them, and you'll need to weld them (you can solder, but I don't recommend it, as heat can damage them if you're not careful). If you want to spend the time, go for it.

They're also probably lithium Ion Cobalt. A little higher voltage and a little more finicky with temperature and charging/discharging. I'd recommend a BMS that can at the very least monitor voltage and temperature to cut the pack off. Balancing is up to you, but you need something to protect that pack.


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## EVsmile (Aug 5, 2011)

Thanks for the quick reply Frodus, 
If I can get the cell numbers I need then I will invest in a 2nd hand spot welder. I am expecting about 500 laptop battery packs over the next couple of months and each one has 8 or more cells.

I have been very keen in doing this conversion now for about 18 months with the car sat out the back in a half built state, I have just been waiting for cash to purchase either TS or CALB packs but these laptop cells are free and such a good opportunity to have a go!

What I am looking for is advice on whats out there for a BMS that I could use across either packs of 10 cells or individual cells, the latter being best but very complicated setup. I once saw a website where a guy had built his own from radio shack components and it worked perfectly so I dont mind making my own either if there any plans available out there.


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## frodus (Apr 12, 2008)

not spot welder.... not even close. You need a special tab welder.... not the same thing.

I PM'd you about BMS (and other stuff).


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## EVsmile (Aug 5, 2011)

Quite right, I meant tab welder - have used both in my time and a true spot welder would blow a cell to bits! 

replied to your PM..


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## frodus (Apr 12, 2008)

Haha, good, I was just makin sure!


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