Re: [EVDL] A123 ALM 12V7 drop in LiFePO4 battery
Put the zero volt battery on charge. It will very likely be just fine.
The BMS disconnects the output when the cells drop below a some
selected voltage. Thus, seemingly zero volts output. Also, the cells
themselves are completely unharmed by running them to zero volts.
Thus, put the battery on charge and it will likely be just fine.
Here is what I wrote about these batteries just a few weeks ago on this list:
There are a few important advantages of LiFePO4 over lead-acid:
1) The A123 12V7 will pretty much last forever in your UPS or
emergency light or alarm system. (20 years at least.) The lead-acid
will need to be replaced every 3-4 years, give or take.
2) You get 13 volts during the entire discharge, even at full load.
3) Under a 30 amp load, the A123 12V7 will deliver the entire 4.6
A-hrs holding 13 volts. The lead-acid will deliver, at most, 2.4
A-hrs at _half_ that load, and will sag down below 11 volts doing so.
Here are the discharge curves for the typical 7.2 A-hr lead-acid "brick":
If you have a typical UPS on your computer, it has one of
these 7.2 a-hr lead-acid bricks in it. Your PC and monitor likely
draws 150 watts. About 1.3 amps @ 115VAC. To provide the required
150 watts, the 13 volt A123 12V7 will need to supply 11.5 amps and
will do so for 24 minutes. The 12 volt lead-acid will need to supply
12.5 amps and will run for maybe 12 minutes, about half as long as
the A123 12V7.
The UPS will run twice as long, weigh half as much, and I
doubt you will ever have to replace the battery.
There is a lot of air inside the case of the 12V7 because
they wanted a direct drop-in for the 7.2 a-hr brick. Not _quite_
enough room, however, for another row of 26650's to give 6.9 A-hrs.
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