Will the Lithium come back to life after discharge?

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Jan 23, 2019
I have a couple lithium batteries and left them on the shelf for a while, maybe a year.

Now they read only 2.64 volts instead of the 14.6.

These seem to have discharged on the own as I have an Odyssey AGM next to them and it's at 12.7 volts and has been still the same amount of time.

If these are sitting around how often do they need to be charge back up?

Is there some special way to charge them back up when they get that low?
Most chargers have a Low Voltage Lock Out that will keep them from charging a battery at that low a state of charge. The nicer chargers will have a manual override to allow recharging a battery with that low if voltage.

The battery should perk up without too much degradation after recharging.

You might look into a trickle charger to keep them topped off long term.

Renogy sells lithium batteries that can put the battery management system in a very low power standby mode to prevent self-discharge if your use case calls for it.

The battery Managment system is what discharges the battery when it’s not in use. If you send me the model of battery you have, I can see if I can find the data sheet and run you through the calculations to see how often you’d need to top off your current batteries.

These are valence lithium battery u27-12xp 12v 138ah
Hm. Datasheet says <2% discharge per month. I didn't even have to do math :) . If nothing was plugged into those batteries, They should easily be fine being charged up every 2 years or so.

Do you have anything at all plugged into them, like a charger?

Their data sheets pretty thin. You might email them and make sure that in addition to the charger having an under-voltage lock out, the battery monitoring electronics may also have an under-voltage lock out. Datasheet didn't have any info. You might give the vendor an email to get to the bottom of the recharge sequence required for a battery of that voltage. Sorry the datasheet and I are not much help.
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Thanks !!

Nothing plugged in to them they were just on the rack. (Extra batteries)
That seems very odd that they would discharge that much in a year. Usually LFP are happy being stored at 25-50% SoC for months, maybe years.

These particular batteries don't have a BMS so probably not a lockout condition.

Maybe try a lab bench power supply that will do CC-CV and see if they recover.
seems like an unexpectedly high level of discharge, I would not have guessed they'd be that low. Odd. But I've seen many times the recommendation to store lithium batteries at 50%, not 100%, for long-term. Apparently, they don't like the latter.
If you don't have a dumb charger or an adjustable power supply, you could try to connect them to another battery of higher voltage for a short time, just for a quick boost to get the voltage high enough to use a smart charger. A bench power supply would be best so you can limit the current, though, cuz the BMS if any may not like it too high.
They could have been damaged being brought down that low, but easy to find out after charging.

I put them on chargers overnight and the one has recovered and is now fully charged up.

The other one hasn't and is still at 2.65 volts. I think it's dead.

I have a battery minder around and I'll be using that in the future.
On the batt that wont recharge, have you hit it with a few minutes of "Start Engine" on the batt charger ? I leave a solar panel (15amp) to charge my resting batts, seems to keep them alive.
The one that will not come back I tried connecting with jumper cables to another one that is fully charged and left it like that for about 4 hours... but nothing.

It's still at 2.65 volts.

I'll bring it over to a friends house who has that option on the battery charger and see if he can bring it back to life.
My charger has a repair function but often times they are to low to get the charger to activate, when that happens I will add a good battery to "fool" the charger to get a current, leave it piggy backed for a bit then pull the second batt and see if deader remains charging. I have also had luck leaving the 15 amp panel on the deader for days and it seems to get them going. I have found that once they drop dead even if they recover the reserve capabilities are gone and they go good then fall off a cliff and if they are in a system they will pull others down and tax the recharge equip.
Thanks.. I'll try that and see if that works also.
Looking at the specs above, it seems that this thing has an advanced BMS and a cutoff voltage of 10V. Rather fancy battery too. It discharging well below that level and fast does not seem normal. Maybe there is something wrong with the BMS? It does seem to have monitoring capabilities, actually. Did you try to look into the cells condition? How old is it?

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