Li-Time over-voltage cutoff at 13.9 volts

[mberding]

I purchased two Li-Time 100ah "Trolling Motor" batteries. I noticed when charging them with a regular AC to DC shore power charger that they'd be putting in power at around 30 amps until they got to 13.9 volts. Then the amperage would instantly drop to zero and the voltage would read 14.4 (the output of the charger).

I've repeated this experiment multiple times, and with two different (both new) LiTime batteries.

To me, it looks like the over-voltage protection is kicking in rather early, so I'm guessing one or more cells isn't well balanced with the others and is triggering over-voltage protection.

I'm very disappointed and am in the process of returning the batteries.

 

[Q-Dog]

What is the the recommended charge rate for that battery? LiTime recommends 10 or 20 amps for all of the 100aH batteries I looked at. Did you try a lower charge rate?

 

[JeromeS13]

With some of these batteries, balancing can take some time. A similar situation happens with other brands, including SOK. Here's a good thread to reference:

Brand new SOK 206Ah doesn't seem to balance?

Hi I just bought and got delivered a 206Ah SOK battery, with heat and bluetooth. I installed it in my camper van where I replaced a 95Ah AGM that wasn't up to the task along with some of the charging related electronics. I considered DIY but for once I figured I would make it easy for myself...

diysolarforum.com

 

[mberding]

The only other charger I had handy was only capable of 10 amps. I put that charger on it and it wouldn't go higher than 13.8, no matter how long I left the charger on it.

With other lithium batteries, (and all batteries, really), the charge rate would slowly drop as the battery approached full capacity. That's what I was expecting here. But instead, it instantly dropped from 30 amps to zero.

 

[Q-Dog]

So, these are not lithium specific chargers?

 

[mberding]

With some of these batteries, balancing can take some time. A similar situation happens with other brands, including SOK. Here's a good thread to reference:

Wow, even the SOK's aren't set up with balanced cells to begin with.
I have little faith that these Li-Time batteries will ever balance. They also don't have the bluetooth BMS to monitor what's actually going on, so I'm just guessing.

 

[mberding]

So, these are not lithium specific chargers?

The 30-amp charger is just a dumb converter that puts out 14.4 volts. The 10-amp charger is a desktop power supply that lets me adjust voltage and amperage.

 

[mberding]

With some of these batteries, balancing can take some time. A similar situation happens with other brands, including SOK. Here's a good thread to reference:

I read through that post and it appears that I need to cycle the battery many dozens of time before maybe it'll start working correctly. And I need to somehow guess the exact charging voltage and amperage to get the internal BMS to actually balance the one or more high cells.

I guess my expectations that a commercially-available battery (with warranty) should have reasonably-balanced cells from the factory.

 

[RCinFLA]

May be BMS cutoff for single cell tripping low cell voltage due to cells out of balance. Second possibility is BMS overheating shutdown due to high discharge current drawn for long period of time. You should be able to feel the heat generated from BMS on outside of case. Most common, but not always, the BMS in mounted on top of cells to allow BMS heating to rise upward to top of battery case and avoid direct heating of cell close by BMS that also causes more misbalancing with other cooler cells.

For balancing, hold at 14.0v for several hours to allow some balancing time and see if it improves. Depending on how much the cells' are out of balance it may take more time at 14v to give BMS more balancing time.

Cells do not balance until cell exceeds 3.4v so need slightly more than 3.4v x 4 = 13.6v minimum to do balancing. Probably BMS only balance dumps at about 50 mA so it may take time. 1% out of balance on 100AH battery is 1 AH / 0.05A balancing = 20 hours of balancing to fix.

Common user caused issue on self contained 12v LFP batteries not being fully charged periodically above 14.0v to allow BMS balancing time. If you take to 14.0-14.2v and hold for 2 hours every few months, it should keep battery cells in balance.

Better to buy 12v LFP with BT monitor link to smartphone to see voltages on individual cells in pack.

 

[mberding]

May be BMS cutoff for single cell tripping low cell voltage due to cells out of balance. Second possibility is BMS overheating shutdown due to high discharge current drawn for long period of time. You should be able to feel the heat generated from BMS on outside of case. Most common, but not always, the BMS in mounted on top of cells to allow BMS heating to rise upward to top of battery case and avoid direct heating of cell close by BMS that also causes more misbalancing with other cooler cells.

For balancing, hold at 14.0v for several hours to allow some balancing time and see if it improves. Depending on how much the cells' are out of balance it may take more time at 14v to give BMS more balancing time.

Cells do not balance until cell exceeds 3.4v so need slightly more than 3.4v x 4 = 13.6v minimum to do balancing. Probably BMS only balance dumps at about 50 mA so it may take time. 1% out of balance on 100AH battery is 1 AH / 0.05A balancing = 20 hours of balancing to fix.

Common user caused issue on self contained 12v LFP batteries not being fully charged periodically above 14.0v to allow BMS balancing time. If you take to 14.0-14.2v and hold for 2 hours every few months, it should keep battery cells in balance.

Better to buy 12v LFP with BT monitor link to smartphone to see voltages on individual cells in pack.

Thank you, that's a very clear description of what's likely going on. I'll try your idea next about setting it at 14.0 volts and leaving it for a day to see what it does.

I just completed another experiment:

1. Pulled the battery out of the box. Was sitting at 12.7 volts (even though it's fully charged). I'm assuming the BMS is in some kind of protection mode, so I'm not getting true battery voltage.
2. Hooked up a small load to wake up the battery. Success. Battery now reads 13.3-ish volts.
3. Hooked up desktop power supply @ 14.3 volts. Amps start at around 9, but quickly drop.
4. At about 2.3 amps and the battery at 14.03 volts, charging suddenly stops. Obviously over-voltage protection has kicked in.

Next, I'm going to set the desktop power supply to 13.8 volts (since 14 is a little too close to its current cut-off) and maybe? that'll be a high enough voltage to let it do some balancing.

 

[RCinFLA]

Thank you, that's a very clear description of what's likely going on. I'll try your idea next about setting it at 14.0 volts and leaving it for a day to see what it does.

I just completed another experiment:

1. Pulled the battery out of the box. Was sitting at 12.7 volts (even though it's fully charged). I'm assuming the BMS is in some kind of protection mode, so I'm not getting true battery voltage.
2. Hooked up a small load to wake up the battery. Success. Battery now reads 13.3-ish volts.
3. Hooked up desktop power supply @ 14.3 volts. Amps start at around 9, but quickly drop.
4. At about 2.3 amps and the battery at 14.03 volts, charging suddenly stops. Obviously over-voltage protection has kicked in.

Next, I'm going to set the desktop power supply to 13.8 volts (since 14 is a little too close to its current cut-off) and maybe? that'll be a high enough voltage to let it do some balancing.

If you trip a cell overvoltage shutdown the BMS should continue to bleed down overvoltage cell by the balancing bleed and reset the BMS back to charging again.

It may take several minutes for BMS to re-enable charging and it will likely trip off again several times before it gets balanced enough to stay on through a full charge on all cells.

Or you can limit charging current to less than balancing bleed current, likely around 40-50 mA, which should prevent a cell overvoltage trip. Make sure to set power supply voltage limit to 14.0-14.2v for when it makes it to full charge.

 

[JRH]

The 30-amp charger is just a dumb converter that puts out 14.4 volts. The 10-amp charger is a desktop power supply that lets me adjust voltage and amperage.

Buy a Victron IP 12-30 smart charger , couple hundred bucks …connects to the network …. it will take your 12 volt batts anywhere you want to take them and programming will keep them there.…..I used mine to balence some BB before putting them in a series parallel config…worked great..

 

[Q-Dog]

Have you discharged the battery before trying to charge it again?

I installed 2 of the 200ah 24 volt AmpereTime/LiTime last week. They charged up fully with zero issues, but I used less than their recommended charge amperage and took a full 24 hours to do each one.

It isn't a race. You need to take your time and give them what they want to be happy. Think of it like foreplay.

 

[mberding]

Have you discharged the battery before trying to charge it again?

I've applied small loads, but have not done a full discharge. I'm not set up with a lot of test or extra equipment, so I don't have an easy way to completely discharge a single 12v battery. Right now I'm in the middle of doing a very slow charge at a controlled voltage to try to get the cells to balance.

You need to take your time and give them what they want to be happy. Think of it like foreplay.

 

[Crowz]

I highly recommend the victron ip22 charger for getting the batteries sorted out. Being able to tailor ever part of the charge process made getting my batteries the way I wanted them a breeze.

Also its awesome having it setup as a safety net using the charger afterwards. I have it set now to start charging if the batteries get down to 30% power remaining automatically. So if I have cloudy days back to back I don't have to worry about it or even check on them anymore. It just charges them back up automatically if needed but otherwise does nothing if everything is working right and the solar charge controllers are handling the job.

 

[mberding]

I highly recommend the victron ip22 charger for getting the batteries sorted out. Being able to tailor ever part of the charge process made getting my batteries the way I wanted them a breeze.

Should I ever need to buy 12v shore power chargers, that one (or the other similar Victron models at slightly higher amperage) are at the top of my list.

Meanwhile, for the system that this is intended to go into, I have a Victron 12/3000 inverter, which handles charging already, so I don't feel the need to buy an additional shore power charger.

Is there something in particular that you tailor about the charging process that makes it handle these un-sorted batteries better?

 

[Crowz]

Should I ever need to buy 12v shore power chargers, that one (or the other similar Victron models at slightly higher amperage) are at the top of my list.

Meanwhile, for the system that this is intended to go into, I have a Victron 12/3000 inverter, which handles charging already, so I don't feel the need to buy an additional shore power charger.

Is there something in particular that you tailor about the charging process that makes it handle these un-sorted batteries better?

Yep. I set it to stay high enough volts per cell in absorption charge but low enough to keep it from overdoing it. This seems to promote balancing from my experiments. Fun part was figuring out where to run it at since I was mixing different batteries from different manufacturers. Bit of tinkering and it sorted out fine.

Its out in the workshop so I don't remember what numbers I used. I remember I wanted to keep it from fully charging fast and wanted to keep it high enough to keep the bms's balancing.

Mine has a lower drain on the batteries in use to it wasn't hard for the 20amp chargers to stay ahead of the load draw even set to a lower amp charger rate.

 

[mberding]

Yep. I set it to stay high enough volts per cell in absorption charge but low enough to keep it from overdoing it. This seems to promote balancing from my experiments. Fun part was figuring out where to run it at since I was mixing different batteries from different manufacturers. Bit of tinkering and it sorted out fine.

OK, that sounds pretty much like what I'm doing right now with my desktop charger. I can set it to exactly whatever voltage I want and tinker as needed.

And I've already been doing the "fun part", trying to figure out how high I can set the voltage without having it trip into over-voltage protection. Right now I think I'm at 13.86 volts or so. Going to go out to the shed later tonight and check on it.

 

[Crowz]

One thing I would recommend if you really want to make the process easier is to buy batteries with the bluetooth bms option. I wish my 12v's had it now but I doubt I'll bother with them since they balance out so easy anyways with the low peak draw that's on them in the parallel setup I have for them. My 48v ones are a must have on bluetooth for me.

If I was starting over from scratch on the 12v ones I'd get bluetooth for sure.

 

[mberding]

One thing I would recommend if you really want to make the process easier is to buy batteries with the bluetooth bms option. I wish my 12v's had it now but I doubt I'll bother with them since they balance out so easy anyways with the low peak draw that's on them in the parallel setup I have for them. My 48v ones are a must have on bluetooth for me.

If I was starting over from scratch on the 12v ones I'd get bluetooth for sure.

Agreed -- The 48v batteries I've built myself have bluetooth BMS's, and I can check and see what's going on. The 12v batteries I've built lately have bluetooth BMS's.

I was trying to just buy something off the shelf and have it work so I didn't have to build my own. That didn't work out so good. Now I'm looking at probably a SOK with their bluetooth BMS as my replacement for this LiTime.