tool batteries lithium

Batteries, Chargers, and Battery Management Systems.
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ejonesss
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tool batteries lithium

Post by ejonesss » Jul 21, 2015 11:19 am

i picked up at a local scrap yard a dead milwaukee m28 battery pack it is lithium based .

it uses 14 samsung 18650 cells

http://www.google.com/search?hl=en&sour ... arch&gbv=1

it is the first pdf file copy and paste url to prevent samsung and google from tracing reference to this site.

according to lipo charging rules 4.2 volts is the cut off voltage.


when i measured some of the cells i noticed 4.3+ volts.

is the cells being over charged and then the bms is cutting off the charge?


according to the specs for the samsung cells there should be no danger of fire or explosion even when charged to 20 volts at 20 amps that is the test that the specs call for as a safety test.

i have some craftsman c3 batteries and a couple cells went over the 4.2 volt mark and show defective on the charger.

has the safety of lithium cells improved so much that it would take extreme voltage for them to fail?
stuff for Even Newer 4 to 24-cell Battery Management System (BMS)
32 lifepo4 cells 16s2p 40138 green cells √
16s2p 40138 based pack built assembled (building electrical equiv to $2000 eonyx system.*

999zip999
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Re: tool batteries lithium

Post by 999zip999 » Jul 21, 2015 2:46 pm

I'm interested in voltage of all 14 cells if some are at 4.3v is one 2.5v ?

ejonesss
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Joined: Aug 31, 2008 4:21 pm

Re: tool batteries lithium

Post by ejonesss » Jul 21, 2015 3:46 pm

the pack is a 28 volt pack and configured as 7s2p
stuff for Even Newer 4 to 24-cell Battery Management System (BMS)
32 lifepo4 cells 16s2p 40138 green cells √
16s2p 40138 based pack built assembled (building electrical equiv to $2000 eonyx system.*

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Nobuo
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Re: tool batteries lithium

Post by Nobuo » Jul 22, 2015 7:54 pm

Although it won't explode or anything similar at that 0.1V increased, it is harming for the chemistry.

BMS should being warm and draining those pair of paralleled cells at 4.3V. If not maybe it is not a balancing equipped BMS

You should read the whole voltage output also. An even recheck with other voltmeter
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