LiTime LiFePO4 w/ LTCP Question . . .

[tpenfield]

Greetings . . .

I have 2 new ( 6 months old) LiTime 12.8v 100Ah (Trolling Motor 'TM') batteries w/ the LTCP feature in my boat. These 2 batteries are in parallel. (see my thread in the marine section for the design/installation details). There are also 2 SLA banks, 1 for each engine in the boat.

The boat has been tucked away for winter for about 2 months . . . the AC chargers (ProNautic for SLA & Xantrex for LFP) are/were set in maintenance mode. I had a chance to check the boat about 1 week ago and the LFP bank is reading '0' (zero) volts while the SLA banks are at 14 volts. The temperatures had been in the range of 20-40˚ F for the prior week. My thoughts were that the LTCP had kicked in, shutting the LFP batteries off. I looked for some LiTime specs to verify and came across this . . .


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I'm not sure if this is the exact spec, but if it is, then I could assume that the batteries have stopped charging, but still are discharging. If that be the case, then the batteries would discharge pretty much throughout the winter, but only resume charging during some of the warmest times.

My boat does have some keep-alive draw for various things, yet is connected to AC power for battery charging/battery maintenance (ProNautic model 1230 for the SLA batteries and Xantrex model 2012 for the LFP batteries).

I had not really examined the LTCP spec's until now, and was a bit surprised to see the temperature differences between the charging and discharging cut-offs. Knowing this, my next assumption is that the batteries continued to drain with the keep-alive loads (not much) and perhaps the low-voltage protection within the BMS has kicked in, which is less comforting. I'll have to get this sorted out, and preferably sooner than later. The boat is 90 miles away though, so my time with it is sporadic.

Any thoughts on what I am seeing? Any LiTime experts here to comment on the situation? TIA.

 

[Texas-Mark]

I think you are right that the low temp kicked in (which should only affect charging) and also that the it may have gone into low voltage cuttoff.

 

[tpenfield]

I think you are right that the low temp kicked in (which should only affect charging) and also that the it may have gone into low voltage cutoff.

Thanks for the reply. In that case, my concern would be if the batteries will be OK for the 4-5 months of winter temperatures. My understanding is that the LFP batteries lose 1-2% of their charge per month when remaining idle.

If the batteries were at their low voltage/charge cutoff, would losing another 5-10% of charge bring them to an excessively low level?

 

[tpenfield]

Just an additional comment . . . it seems problematic the the battery would have such disparity of cut-off temperatures between the charging and discharging. Essentially the battery will continue to supply current (dis-charge) long after it has prevented itself from re-charging. In many cold weather situations it is only a matter of time until the battery reaches its dis-charging limit.

To me it would make more sense if the cut-off limits were the same temperature, so that the battery will not supply current when it has no way to re-gain that current.

 

[Q-Dog]

Many manufactures say if you will be storing the batteries long term they should be cycled every 2 or 3 months.