T-Pain Is On A Boat: Re: [Electric Boats] RE: testing used Thundersky 90AH LFP90 Lithium Iron Phosphate Batteries

Thursday, November 14, 2013

Re: [Electric Boats] RE: testing used Thundersky 90AH LFP90 Lithium Iron Phosphate Batteries

I have a few cells sitting on a shelf for more then three years now. They still read the same voltage 3.1 volts as when I put them there. As far as I can tell with out something to draw them down they have ridiculous shell life.

On Nov 13, 2013, at 9:30 PM, Mark F <mark.internet@yahoo.ca> wrote:

I checked out the vehicle today.
The pack is 0 volts and has been sitting for 2 years.
I have heard when Lithium Iron Phosphate batteries go bad they go open as opposed to NIMH which short.(not sure if this is correct, just something someone with an electric bike told me)
If so, is it possible one cell went open and the rest may be ok.
Maybe I could get 48 Volt pack for my boat out of it.
If so, what effect would leaving cells uncharged for 2 years have.
I know if it was lead acid it would be dead, but Lithium Iron Phosphate?
Also if left uncharged, can Lithium Iron Phosphate batteries freeze in cold climates?

Thanks

From: oak <oak_box@yahoo.com>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Wednesday, November 13, 2013 12:54:35 PM
Subject: Re: [Electric Boats] RE: testing used Thundersky 90AH LFP90 Lithium Iron Phosphate Batteries

TOM,

The BatteryUniversity web site has nice information on charging Li batteries:
http://batteryuniversity.com/learn/article/charging_lithium_ion_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@yahoo.com" <boat_works@yahoo.com>
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