I think I froze my battery to death

[snoobler]

Each cell voltage is the same since they are in parallel.

At 3.078V, you are at extremely low state of charge. Less than 10% remains.

Recommendation stands. Disconnect all cells immediately.

 

[ckent]

Each cell voltage is the same since they are in parallel.

At 3.078V, you are at extremely low state of charge. Less than 10% remains.

Recommendation stands. Disconnect all cells immediately.

Ok, all cells are disconnected.

 

[ckent]

So is there any reason to not assemble the battery and charge it using my solar while monitoring to ensure voltages stay close together? And then stopping the charging if there is an excessive voltage differential?

My power supply should arrive today, but if my math is correct at 10 amps it will take about 15 hours to fully charge each 150ah cell, 120 hours for the entire pack, so 5 days of charging?

 

[Hedges]

So is there any reason to not assemble the battery and charge it using my solar while monitoring to ensure voltages stay close together? And then stopping the charging if there is an excessive voltage differential?

My power supply should arrive today, but if my math is correct at 10 amps it will take about 15 hours to fully charge each 150ah cell, 120 hours for the entire pack, so 5 days of charging?

If you don't have a BMS, the reason is that a cell is likely to run the moment you aren't watching closely.
If you have a BMS connected which monitors each cell and disconnects charger, then it's fine.

But if one cell is particularly low, could use the supply to charge it up to same voltage as the rest.

 

[ckent]

If you don't have a BMS, the reason is that a cell is likely to run the moment you aren't watching closely.
If you have a BMS connected which monitors each cell and disconnects charger, then it's fine.

But if one cell is particularly low, could use the supply to charge it up to same voltage as the rest.

I have a BMS, and I put all cells in parallel for half the day yesterday to bring them to within a few millivolts of each other. I need to go measure them this morning though and see if anything changed overnight.

 

[snoobler]

I have a BMS, and I put all cells in parallel for half the day yesterday to bring them to within a few millivolts of each other. I need to go measure them this morning though and see if anything changed overnight.

Please let us know the results.

 

[ckent]

Please let us know the results.

Cells 5, 6, 7, 8 are now at 3.10 volts, cells 1, 2, 3, 4, are at 3.091 Volts.

And to be clear, when I disconnected them cells 5-8 were at 3.08, and cells 1-4 were all between 3.076-3.078.

 

[snoobler]

That's encouraging. Based on those results, I would conclude it's safe to put them in parallel again and charge when the power supply arrives.

 

[ckent]

That's encouraging. Based on those results, I would conclude it's safe to put them in parallel again and charge when the power supply arrives.

Could I rebuild the pack and charge them with my solar to get them closer to full before using the power supply to top balance them? I would of course be monitoring them the entire time they're charging to watch for voltage discrepancies.

 

[snoobler]

Only if you install the BMS. Human BMSs routinely fail.

 

[ckent]

Only if you install the BMS. Human BMSs routinely fail.

Yes, my SBMS0 would still be controlling everything.

 

[snoobler]

Ah. Forgot. Given that it's possibly malfunctioned, I would be hesitant to trust it unless you stare at it the whole time. Your call.

 

[ckent]

Ah. Forgot. Given that it's possibly malfunctioned, I would be hesitant to trust it unless you stare at it the whole time. Your call.

I don't believe it malfunctioned. It was use error, I had the inverter on and wasn't watching my SOC, and my inverter isn't low-voltage protected. So the BMS turned off my 12 volt loads, and then low voltage locked and shut down charging as well, but of course couldn't turn off a load it doesn't have access to. I've been meaning to wire the BMS into the inverter switch, but I use my inverter so rarely that it was a low priority task.

 

[Hedges]

Has a "BMS test" process been developed that doesn't risk damage?

My first thought is connect BMS to battery, then swap cells for adjustable power supply one at a time. But things not all connected has been known to blow BMS.

Second though add resistors in series with all BMS sense lines, and use a power supply (maybe through additional resistor) to impose higher/lower voltage and check where BMS does disconnect.

I've been meaning to wire the BMS into the inverter switch, but I use my inverter so rarely that it was a low priority task.

Have your priorities been readjusted?

 

[ckent]

Has a "BMS test" process been developed that doesn't risk damage?

My first thought is connect BMS to battery, then swap cells for adjustable power supply one at a time. But things not all connected has been known to blow BMS.

Second though add resistors in series with all BMS sense lines, and use a power supply (maybe through additional resistor) to impose higher/lower voltage and check where BMS does disconnect.



Have your priorities been readjusted?

That all sounds awfully complicated....

My priorities certainly have been.

 

[Just John]

Has a "BMS test" process been developed that doesn't risk

Just set high and low disconnect values to like 3.3 and 3.2 and see if they work. This also works for temperature, assuming your BMS lets you change the values. This allows safe testing.

 

[snoobler]

I don't believe it malfunctioned. It was use error, I had the inverter on and wasn't watching my SOC, and my inverter isn't low-voltage protected. So the BMS turned off my 12 volt loads, and then low voltage locked and shut down charging as well, but of course couldn't turn off a load it doesn't have access to. I've been meaning to wire the BMS into the inverter switch, but I use my inverter so rarely that it was a low priority task.

I guess I'm missing the whole point of this thread. Didn't the BMS permit charging in low-temp conditions?

 

[ckent]

I guess I'm missing the whole point of this thread. Didn't the BMS permit charging in low-temp conditions?

Thats also something I should have explained better. Again, user error. I had the temp set too high, so I lowered it to allow charging at a lower temp. For example it wasn’t charging until about 10C, which is about as warm as it gets here this time of year. So I reduced the cutoff temp, without double checking or calibrating the temperature probe. So it was really my fault, after increasing the cutoff temp it’s been performing properly.

 

[technerd1988]

This is pretty much what happened to me too ckent. I have a bloated 210ah cell though which they replaced under warranty since my BMS has low temp cutoff. The one cell just failed weirdly and bloated and I didn't notice it till all the cells were less than 2v. The rest recovered and are back to full capacity with the replacement cell

 

[ckent]

Update: It's been about a month now and the batteries seem fine. I did pull them out and top balance them, and they're holding charge and staying with 20mV of each other. No noticeable cell swelling or leaking either.

I did build a simple heater using resistance heating pads and a digital thermostat from amazon to help keep the battery compartment above freezing, and that seems to be working. Although with spring progressing the number of below-freezing nights keeps dropping so I don't know how effective it will be over longer and colder periods. But at 96 watts it will hopefully be able maintain temps above freezing.

This is pretty much what happened to me too ckent. I have a bloated 210ah cell though which they replaced under warranty since my BMS has low temp cutoff. The one cell just failed weirdly and bloated and I didn't notice it till all the cells were less than 2v. The rest recovered and are back to full capacity with the replacement cell

I'm sorry to hear that, but it's nice that it was covered under warranty.