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12V battery only charging to 13.4

MedicineMom

New Member
Joined
Dec 4, 2024
Messages
46
Location
PNW
We recently built a lithium battery 4p4s. Each cell is 304AH. We have an intellipower converter, and two generators a 4550W and an 8550W. We cannot get our bank to fully charge, and sometimes it won't make it through the night. The highest it's ever gotten is 13.4. I checked both sets of negative and positive terminals on the converter, and got 13.9 and 14.03.

When we installed the system, we did not have the proper tools available. All we had was a ratchet, and we arced two cells. All of the cells have the same voltage whenever I check them(with multimeter), they're monitored on a JK BMS.

Prior to these batteries, we had lead acid hooked up to the RV and over time, they seemed to have less and less capacity. It got so bad that nearly every night the batteries would die, or be close to it. I didn't care that much at the time because we already had the new bank. The new bank seems to be doing the same thing. So I thought maybe it's the RV. We found one bad ground, replaced that. A parasitic draw test produced 0.04a.

I cannot figure out how to determine if the battery capacity is shot due to the arcing(would the degradation increase over time though?), if the converter is not able to fully charge as it doesn't put out enough voltage, or if this ancient RV is just sucking power. We only run the furnace at night, we use a wood stove during the day.

My next idea is to disconnect the negative and test by turning off all the breakers, then flip them on and run the circuit one at a time.... But that probably wouldn't explain why we can't charge past 13.4

Would a capacity tester be of assistance here? If anyone has a link for one that would be appreciated.

Could the capacity be degrading due to never being fully charged?

Any help, advice, or input is greatly appreciated!!
 
We recently built a lithium battery 4p4s. Each cell is 304AH. We have an intellipower converter, and two generators a 4550W and an 8550W. We cannot get our bank to fully charge, and sometimes it won't make it through the night. The highest it's ever gotten is 13.4. I checked both sets of negative and positive terminals on the converter, and got 13.9 and 14.03.

When we installed the system, we did not have the proper tools available. All we had was a ratchet, and we arced two cells. All of the cells have the same voltage whenever I check them(with multimeter), they're monitored on a JK BMS.

Prior to these batteries, we had lead acid hooked up to the RV and over time, they seemed to have less and less capacity. It got so bad that nearly every night the batteries would die, or be close to it. I didn't care that much at the time because we already had the new bank. The new bank seems to be doing the same thing. So I thought maybe it's the RV. We found one bad ground, replaced that. A parasitic draw test produced 0.04a.

I cannot figure out how to determine if the battery capacity is shot due to the arcing(would the degradation increase over time though?), if the converter is not able to fully charge as it doesn't put out enough voltage, or if this ancient RV is just sucking power. We only run the furnace at night, we use a wood stove during the day.

My next idea is to disconnect the negative and test by turning off all the breakers, then flip them on and run the circuit one at a time.... But that probably wouldn't explain why we can't charge past 13.4

Would a capacity tester be of assistance here? If anyone has a link for one that would be appreciated.

Could the capacity be degrading due to never being fully charged?

Any help, advice, or input is greatly appreciated!!
If you have four cells in parallel and you shorted something out, maybe one of your 4P sections is only 3P or 2P or 1P. Do you have wired or BT comms with the BMS so you can tell what it's doing? When it 'stops charging' is it still drawing current?

There are a lot of possibilities, rather than try to iterate through them all I'll reiterate @robbob2112 's request for pictures.
 
4p equals 1208 amp hours.
What are the charging specs of your charger?
Assume the cells were shipped at 30% state of charge equals 900 amp hours.
A 100 amp charger would need 9 hours at 100 amps to fully charge that battery.
I don't think your battery is charged.
 
4 batteries with 4cells each, one BMS
do they have bluetooth? if so do you show amperage constantly going in? at 14v you should be getting well over 90% charged. if you have an amp meter i would check the amperage if the bms doesn't have a bluetooth app or some kind of monitor, wiring in 4p can take a bit of different wiring to make sure each battery is supplying its fair share.

did the batteries ever make it to 14.2+?

can you provide the model of the converter?
 
4p equals 1208 amp hours.
What are the charging specs of your charger?
Assume the cells were shipped at 30% state of charge equals 900 amp hours.
A 100 amp charger would need 9 hours at 100 amps to fully charge that battery.
I don't think your battery is charged.
We have charged it from the time we wake up, until the time we go to bed. It allegedly can go to 14.6 but we haven't seen anything above 14.03 come out of the converter. It's a 60 amp charger, but the JK I've only seen at 50. Mostly 20-30. We planned to have lots of storage as we aren't in a sunny location in the winter.... I thought 1204 would be good. We turn the generator on in the morning, until it gets to 13.4, since it won't ever go any higher. And again in the evening. When we first installed them we ran the generator for days straight, just turning them on at night. We are suspecting the charger plays a role in this situation. I also have crappy charge controllers, but they are set to the proper settings.
 
If you have four cells in parallel and you shorted something out, maybe one of your 4P sections is only 3P or 2P or 1P. Do you have wired or BT comms with the BMS so you can tell what it's doing? When it 'stops charging' is it still drawing current?

There are a lot of possibilities, rather than try to iterate through them all I'll reiterate @robbob2112 's request for pictures.
I measured the voltage at each cell a couple days ago. Everything said 3.24 at the time. And yes, it continues to draw current, usually 25-29 amps. I never considered that. I do have BTcomms. We are still running things in the RV, so could that be why it's drawing current. That could be a short as well?my only issue with that is that the short had to have happened months before we installed these new batteries as it started with our old ones. Could a short in the panels be drawing current? I am curious if the RV has more bad cables we cannot see. It's a 2003 with all original parts. I'll get a photo tomorrow morning
 
do they have bluetooth? if so do you show amperage constantly going in? at 14v you should be getting well over 90% charged. if you have an amp meter i would check the amperage if the bms doesn't have a bluetooth app or some kind of monitor, wiring in 4p can take a bit of different wiring to make sure each battery is supplying its fair share.

did the batteries ever make it to 14.2+?

can you provide the model of the converter?
Yes it is usually still drawing 25-29 amps, and it is monitored via BT. It has never gone above 3.4
When I measured the voltage at each individual cell, they all said 13.24 is there another area I could be checking? The converter is an intellipower 9100 for lithium.
 
Yes it is usually still drawing 25-29 amps, and it is monitored via BT. It has never gone above 3.4
When I measured the voltage at each individual cell, they all said 13.24 is there another area I could be checking? The converter is an intellipower 9100 for lithium.
so if each cell is showing the same voltage, there is no damage to the cells.

order to check to things.

turn off everything in the rv, and check the amperage. it should be close to 0

turn on the battery disconnect and let the propane and Carbon monoxide detector fire up, it should still be low, maybe an amp or 2


even if the propane furnace fires up, that should only be between 6-9 amps, unless you have a 5+ incandescent lights on, they take about 2-3 amps each per light x2 for a double fixture.

when you say its drawing 25-29, do you mean its pulling 25-29 from the battery or its still charging at 25-29?

i own a similar converter, if the wiring is inadequate or far from the battery's voltage drop will cause the charger to slow way down, due to the voltage loss.

i strongly believe the charger is simply not done charging, it should reach roughly 14.6 and you should see the amperage taper, but you need to make sure you don't inadvertently have an inverter, or tank heaters running etc..

you may want to consider a smart shunt, to see how many AH a day you are pulling, you may simply not be replacing them
 
Does the battery still take charging current? Or does the BMS disable charging? Are the parallel cells all connected together, as in the BMS voltage tap wire connects to all four at each level? The wires between each level need to be able to handle a lot of current to prevent one cell going higher or lower than its horizontal neighbor. I wouldn't worry about the cells that got the wrench across them. The charging voltage on LiFePO4 batteries is very flat. The voltage rises rapidly after about 97 or 98% charged. The BMS should keep the cells under 3.65V each and over 2.5V. Like TomC4306 said, 1208Ah takes a long time to charge. If you're only charging at 20A, it'll take 60 hours to charge from 0 to 100%.
 
As long as it's still taking current, it is not full.
When it is full at a particular charge voltage, 14 volts, current will decline to zero.
When the current declines to zero at a particular charge voltage then they are full.
 
so if each cell is showing the same voltage, there is no damage to the cells.

order to check to things.

turn off everything in the rv, and check the amperage. it should be close to 0

turn on the battery disconnect and let the propane and Carbon monoxide detector fire up, it should still be low, maybe an amp or 2


even if the propane furnace fires up, that should only be between 6-9 amps, unless you have a 5+ incandescent lights on, they take about 2-3 amps each per light x2 for a double fixture.

when you say its drawing 25-29, do you mean its pulling 25-29 from the battery or its still charging at 25-29?

i own a similar converter, if the wiring is inadequate or far from the battery's voltage drop will cause the charger to slow way down, due to the voltage loss.

i strongly believe the charger is simply not done charging, it should reach roughly 14.6 and you should see the amperage taper, but you need to make sure you don't inadvertently have an inverter, or tank heaters running etc..

you may want to consider a smart shunt, to see how many AH a day you are pulling, you may simply not be replacing them
I believe it is still "charging" with 25-29 amps... I could be mistaken. Our cables are oversized, and everything is very close. We do not have the inverter on, or a tank heater running. Our water tank heater is run on propane anyways. We have discussed getting a shunt, but it will be a couple weeks before we can aquire one.

We will do another draw test and see if we can detect where the power is going.

We have charged the batteries for a few days straight before, obviously not during the night. But that makes me believe all this power is going somewhere, especially if the cells are doing okay. We did a parasitic draw test with everything off. Then my husband flipped the breakers on one by one(but everything was still off so not that accurate lol) we got 0.04 amps at the highest reading.

The BMS shut down the batteries due to low temp. This morning when we got the heater running it kept saying there was a short circuit and the release failed a few times...
 
Or they are unbalanced and you hit COVP. 🤷‍♂️
Does the battery still take charging current? Or does the BMS disable charging? Are the parallel cells all connected together, as in the BMS voltage tap wire connects to all four at each level? The wires between each level need to be able to handle a lot of current to prevent one cell going higher or lower than its horizontal neighbor. I wouldn't worry about the cells that got the wrench across them. The charging voltage on LiFePO4 batteries is very flat. The voltage rises rapidly after about 97 or 98% charged. The BMS should keep the cells under 3.65V each and over 2.5V. Like TomC4306 said, 1208Ah takes a long time to charge. If you're only charging at 20A, it'll take 60 hours to charge from 0 to 100%.
It does not disable the charging. The only time it has done that is due to low temps, or system under voltage.

I'm not quite sure what you mean by the tap wires being connected at each level. I'm going to attempt to post a picture, maybe that will clear things up.

Is there a different converter or charger you'd recommend? One we can plug into the generator would suffice.

I don't think we can run our generator for 60 hours straight. We are going to start hydropower this spring to circumvent the lack of sun.
 
Or they are unbalanced and you hit COVP. 🤷‍♂️
I assume that means cell over voltage protection. I did see one thing in my BMS log that stated cell over voltage, I thought that was odd. They are not perfectly balanced as of yet. I have set my COVP to 3.53, per someone else's recommendation. Should I have it at something else? So you're saying maybe one cell it's over voltage so the rest stop? We recently got the BMS but even before that it wouldn't go above 13.4. 3.53×4=14.12
 
As long as it's still taking current, it is not full.
When it is full at a particular charge voltage, 14 volts, current will decline to zero.
When the current declines to zero at a particular charge voltage then they are full.
The current according to my BMS, does not cease ever... So could the converter just be at too low or a voltage or amperage to do the job? The converter states it is a 60amp charger and and will charge with 14.4 V I believe. I have seen the current go up to 50 once, but have never got that reading at the converter itself.
 
your comment about breakers concerns me, DC side of the world at least in that era was fuses. breakers are for the AC side of the world. can you take a photo of the fuse/breaker panel, and a screenshot from the bms. and photo of the charger wiring to the batteries.. please provide a photo of the actual model number of the charger as well
 
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I assume that means cell over voltage protection.
Yes, sorry for the acronyms, sometimes I spell them out and sometimes I assume...
I did see one thing in my BMS log that stated cell over voltage, I thought that was odd. They are not perfectly balanced as of yet. I have set my COVP to 3.53, per someone else's recommendation. Should I have it at something else?
Not sure who would have recommended that, I'd go with 3.6 or 3.65, at least till they get balanced.
So you're saying maybe one cell it's over voltage so the rest stop? We recently got the BMS but even before that it wouldn't go above 13.4. 3.53×4=14.12
Yes, when any one cell hits COVP (or CUVP on discharge) the BMS will at least disable charging, if not take the entire battery offline, until it's 'woken up' by the appropriate procedure, which varies depending on BMS and protection engaged.

I can almost read the part number of the JK(?) BMS, but if you could tell us exactly what one you have, maybe someone with the relevant experience could help with settings. Is it active or passive balancing? I don't think there's a passive balancer anywhere that'll balance 1216AH 'cells', and the usual 2A active balancers will take a week to fix a 25% imbalance...

4P on 304AH cells is going to take a lot of charging and a lot of balancing until you know it's right. I'd have built four individual 304AH batteries, at the very least for ease of access and maintenance. That thing's gotta weigh 300 pounds, and the cells aren't even restrained. In fact, it doesn't even look like there are separators between the cells?

Please tell me this isn't a mobile setup...

Please post pictures of the intererconnect wiring and (especially) the fuses.
 
Yes it is usually still drawing 25-29 amps
Where are you measuring the current? If the converter is on and supplying loads, and you are measuring converter current it may never go to zero.

If (only) the battery is drawing current and still hasn't hit 100% SOC, then keep charging.
 

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