Hi John,
I intentionally under-charge my cells to 3.4-3.5V. CALB specs a charge voltage of 3.6V, but there is very little capacity gained from 3.5V to 3.6V, and I like to have a bit of margin available.
-Tom
---In electricboats@yahoogroups.com, <oak_box@...> wrote:
TOM,
The BatteryUniversity web site has nice information on charging Li batteries:
Their page suggests a charging voltage of 4.2V for Li. You suggest below charging to 3.5V per cell...
Is that "charging voltage" vs. "resting voltage" (after charging), or is the lower voltage specific to these batteries?
John
From: "boat_works@..." <boat_works@...>
To: electricboats@yahoogroups.com
Sent: Tuesday, November 12, 2013 11:42 PM
Subject: [Electric Boats] RE: testing used Thundersky 90AH LFP90 Lithium Iron Phosphate Batteries
Testing is easy:
Check individual resting voltage.
If near 0V they are probably toast, but you can try to gently charge them (a couple amps), and see if the voltage rises during charge. If not, they're goners.
If they are 2V or more you can charge them to about 3.5V per cell. This is almost a full charge. Resting voltage should be around 3.35V
Once charged, either:
1. Time the discharge into a constant load (lights, heater), measure the current, stop the clock when cell measures at 2.5V under load (or maybe 2.8V or bit more if you want to be conservative), so you can calculate the Ah capacity of the cell.
or
2. Apply a load, and monitor the Ahs consumed with an Ah counter (LinkPRO, JLD404, etc.). Keep an eye on the voltage., stop test at 2.5V or so.
I'll bet that if the sellers of the car say the cells are bad, they are bad.
-Tom
---In electricboats@yahoogroups.com, <mark.internet@...> wrote:
I am thinking of purchasing a vehicle with these batteries.
They say their pack is dead.
Any suggestions on how to test the pack or cells and what to worry about if they are used batteries.
Or should I just consider the pack bad and recycle them?
Thanks
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