Homemade Battery Packs

Batteries, Chargers, and Battery Management Systems.
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DrkAngel
10 GW
10 GW
Posts: 4462
Joined: Dec 15, 2010 11:14 am
Location: Upstate-Western-Southern Tier NY. USA

Re: Homemade Battery Packs

Post by DrkAngel » Dec 01, 2017 7:59 am

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Index
Updating 12/17
DrkAngel wrote:
Nov 05, 2017 7:55 pm
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25.9V 26.4Ah #1 finished

7s12p Samsung cells are capable of 120A continuous 240A surge but controllers are <30A and installed 40A fuse (trying new 58V fuses & holder)
Just finished 1, had to test drive it ... rain stopped for awhile.
No BMS installed! Turned out were only 20A continuous.
Mostly worried about parasitic draw when customers let set for the Winter.

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10s2p Bricks disassembled into 8s2p + 2s2p and I was oh so tempted to build as 8s12p ... but needed for 24V bikes and I already have the 7s chargers.
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25.9V 26.4Ah #2 nearly complete
Just need to run the parallels and power rails and install fuse.
High C-rate cells improve cold weather performance!

Samsung ICR18650-22p build is doing remarkably well in the colder weather!
There seems to be no noticeable deterioration in performance between the 70ºF weather of a couple weeks ago and the present 30-40ºF. Top speed stays in the 21mph range and acceleration seems the same.

The ICR prefix indicates Lithium Cobalt, same basic formulation as my previous laptop 18650 and LiPo builds (that suffered horribly from the cold) so I would have to attribute the cold weather performance "preservation" to the enhanced C rate of these Samsung cells.

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Although the same basic formulation, additives, or some other alteration does shift the capacity map substantially!
LiCo laptop cells had capacity till about 3.70V while the Samsung cells map good capacity till 3.40V.
Sadly, this nixes my idea of combining cells, to hybrid the higher capacity laptop cells with the higher output Samsung cells.
While the Samsung would help output capability, a large percentage of it's capacity would be wasted, unless endangering or damaging the Laptop cells by excessive discharge.
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