Problem with a lithium battery

[tumbi1]

Hello,

I have 4 new 12V 100ah lithium batteries I bought about 7 months ago and haven't used yet (to make a 24V 200ah combination), that I am getting close to being ready to connect up to a solar generator I have been putting together. However one of the batteries has suddenly dropped down to 4V, and the display on it won't light up. The other 3 are still fine with about 83 or so % charge and 13+ volts. Does it just need charging or is it likely faulty? It is frustrating as I was getting close to connecting everything up.

I don't have a lithium battery charger either, only a 'normal' charger you would charge up something like a car battery with, which from what I have read you shouldn't use with lithium batteries.

 

[DThames]

You can use any charger with the proper voltage if YOU manage what is going on. For example, let it charge for 5 minutes, turn off the charger and see if the voltage came up any. LiFePo4 can be charged to about 14.4v. Many care chargers will try to go to 14.8v, which may still be fine but not ideal. The battery should have a BMS to shut it down to protect from over charging. The BMS should have shut down if the voltage got a little below 12v, so 4v seems odd.

 

[chrisski]

Is charging with a SCC an option? I’ve done that before.

If the batteries refuse to charge the BMS could be tripped. The manual will tell you how to untrue it, but could be as simple putting a good battery for a second with a resistor second.

 

[Substrate]

I don't have a lithium battery charger either, only a 'normal' charger you would charge up something like a car battery with, which from what I have read you shouldn't use with lithium batteries.

That's correct - generally don't use it. Depending on model, when it detects a low-voltage battery, it may attempt to use de-sulfation pulses thinking it is lead-acid.

Since you spent good money on 4 new 100ah batteries, the best idea is to consider a charger part of that purchase price. Those made for LiFePO4 typically have a built-in bms-reset if that is your true issue. Somewhere in the 10 to 20A range would be ideal. It is recommended to charge each one up *individually* prior to putting them into parallel/series service.

However - if you bms has NOT tripped and 4v is the true terminal voltage BE CAREFUL. Do NOT use too much current at first to bring it out of the discharge knee.

At this distance, I'd recommend a very SMALL LiFeP04 charger, like 2-5A max just to be on the safe side. One of these will either wake up and reset the bms, OR if your batt is truly sitting at only 4v, bring it up slowly and safely out of that deep discharge knee. Doing it with too large a current in this condition can really damage them. Do it slowly, and there is a chance it will recover without harm.

Even at only 2A, if it is deep in the discharge knee, it will come out of it relatively quickly. Once the terminal voltage reaches about 12.5 volts, you can use a larger amperage charger as usual (or your solar array).

Note - I think I've seen Ampere-Time, Redodo and some other 10-20A LFP chargers actually state that they incorporate a very low current charge phase when encountering a low-voltage LFP, (in addition to the usual bms-reset) but I have no hands-on with them to measure.

Does your battery manual mention anything special about a 4v condition?

 

[tumbi1]

That's correct - generally don't use it. Depending on model, when it detects a low-voltage battery, it may attempt to use de-sulfation pulses thinking it is lead-acid.

Since you spent good money on 4 new 100ah batteries, the best idea is to consider a charger part of that purchase price. Those made for LiFePO4 typically have a built-in bms-reset if that is your true issue. Somewhere in the 10 to 20A range would be ideal. It is recommended to charge each one up *individually* prior to putting them into parallel/series service.

However - if you bms has NOT tripped and 4v is the true terminal voltage BE CAREFUL. Do NOT use too much current at first to bring it out of the discharge knee.

At this distance, I'd recommend a very SMALL LiFeP04 charger, like 2-5A max just to be on the safe side. One of these will either wake up and reset the bms, OR if your batt is truly sitting at only 4v, bring it up slowly and safely out of that deep discharge knee. Doing it with too large a current in this condition can really damage them. Do it slowly, and there is a chance it will recover without harm.

Even at only 2A, if it is deep in the discharge knee, it will come out of it relatively quickly. Once the terminal voltage reaches about 12.5 volts, you can use a larger amperage charger as usual (or your solar array).

Note - I think I've seen Ampere-Time, Redodo and some other 10-20A LFP chargers actually state that they incorporate a very low current charge phase when encountering a low-voltage LFP, (in addition to the usual bms-reset) but I have no hands-on with them to measure.

Does your battery manual mention anything special about a 4v condition?

Thanks - I have a 20A lithium charger coming - I'll check its settings before trying a charge. I have been looking at the VoltX site (the manufacturer) for a manual, but so far no luck. I'll update this as soon as I get the charger.

 

[Bud Martin]

BTW, some charger requires to see at least 10V (for 12V) at the battery terminals for the charger circuit to come on, if that is the case the charger will not wake up the battery's BMS.

 

[Substrate]

Yep - it is nice to see all the budget clone makers putting their badge on these new chargers that are low-voltage aware. (Power Queen, Redodo, Ampere Time, even Time USB, you name it)

Their marketing material show a "T1 Pre-Charge Stage" instead of just hammering up. Maybe just some additional insurance so that the end user (who doesn't visit the forum), has a pleasant experience without having to know anything and reduce returns.

It's a good trend.

 

[tumbi1]

Thanks all - I finally got my hands on a low current charger, and the battery woke up instantly, and it is now fully charged.

 

[Tim Tim]

Thanks all - I finally got my hands on a low current charger, and the battery woke up instantly, and it is now fully charged.

Are you from Tumbi Umbi NSW?

 

[tumbi1]

Are you from Tumbi Umbi NSW?

Yes, but we moved from there over 20 years ago.

 

[Tim Tim]

When you said you were looking at VoltX batteries and I saw your nic then I had a guess that you were. I think VoltX are only in Australia. I’m at Nelson Bay NSW.

Glad to see you got your battery going .