Have I ruined my Sinopoly 100 AH batteries?

[Maple Dave]

I bought 16 cells, Sinopoly 100AH prismatic cells. They all read 3.30V when new last fall. I drew them down to 3.0V and then connected all in parallel to bottom balance them. Then I connected them to my system, 1480 watts solar, a XW 6048 inverter, an SCP (system control panel) and a XW 60-mppt CC. The battery bank is located in a cold environment, so after watching a video by will about using a 12V heating pad and since my battery bank is 48V (actually 50-53V) I got a 48 to 12V DC converter to power the heat pad.
This battery bank is used for 1 thing only, to run a 120V emergency back up heat. Back-up because the main heat in the very small room protecting expensive equipment is a propane wall furnace which needs no power to run. The battery bank is in an insulated battery compartment. (If the emergency heat is ever needed it runs for 6 minutes/hr if the outside temp is 0 degrees F and I have a generator to recharge the battery bank if needed).
The story, my grid power never went out nor did the propane furnace fail. This inverter is grid tied, (as is a second array, 4840 watts grid tie only).
The panels got covered with snow for 3 days. During that time the air temps were in the 20's and low 30's F. It seems just the heating pad drew the battery bank down to low temp shut off (49V) and that shut off the inverter and charge controller. Result, the 16 cells now set in my living rood to see if they can be saved. They read 1.6 V and 1.7V because that 65 watt heat pad kept drawing them down with no charging possible because the SCP had shut everything down.
I bought a 120V charger, balancer (Tenergy model TB6B) which is designed to charge from 1 to 6 prismatic cells. I had planned to use that, but the manual says not to use it if the cells are under 3.3v.
Are these savable or are they garbage because of the voltage they are down to.
Advice please.

 

[Craig]

I dont know but I'm willing to bet they are going to revive just fine they may however have a few less cycles in them. Im looking at the exact same situation this winter my panels got covered way too long and everything drained to maybe even lower than yours. Wont know for a month or so what state they are in.

 

[SolarRat]

I bought a 120V charger, balancer (Tenergy model TB6B) which is designed to charge from 1 to 6 prismatic cells. I had planned to use that, but the manual says not to use it if the cells are under 3.3v.

I have a similar charger. It will probably say "low voltage" and not charge, but you can get around that.

The other day I had to revive an 8ah pouch cell I got that was down at 0.6v. I hooked it up to the charger, set it to 1S LIPO and the charger yelled at me because of the low voltage. The charger is just playing it safe because it thinks you may have hooked up a different chemistry cell (they do 1.2 zinc cells too). So, I just fooled it during the test by paralleling in a charged 18650 cell, but any 3-4v volt cell will work. As soon as it starts the charge, remove the good cell, you don't want or need it hooked up for more than 5 seconds. I started with a very low 0.1 amp charge until it reached 2.6ish volts (took many hours) then bumped it up to 0.2 amps for a while, then 0.4a...and so on. It ended up accepting about 9ah in the 8ah cell and charged to 4.15v (li-ion). It's now sitting at 4.13v but I haven't done a capacity check yet.

Instead of jumping a good cell on the lipo setting, you could just use a PB (lead) setting at 2v, and it will work also to get some juice back into them.

At 1.7v you probably did some damage...how much is unknown at this point. I'd get them all above 2.5-3v separately and slowly, then parallel them and charge as one. Good luck!

 

[electric]

@Maple Dave how long did they sit below 2.0V ? Hours or days? Are they swollen on their large side?
The only way to know if they are garbage is to try to charge with low current and see if they accept and hold the charge.
For example, charge to 3.65V and let them sit in open circuit, nothing connected at all. See how fast and how low the voltage will settle down.
If it settles below 3.4V within a few hours, then cells are probably toast. Might still be usable in other applications, but I would not trust them as emergency backup. Swelling is usually a clear sign of damage.
It is sad, but this is what happens when you don't use a BMS to cut ALL LOADS.

 

[ghostwriter66]

GOOD NEWS / BAD NEWS

This has happened to me a couple of times while i am testing something and get carried away and then i remember at 0200 at home that I left the damn batteries hooked up at work ... and when i get into work everything is beeping and ppl have left nasty notes for me on the work station usually pertaining to me having gone to a Public University ... anyway .. I digress

I WILL TELL YOU RIGHT NOW THAT I DO NOT SUGGEST DOING ANYTHING I RECOMMEND BELOW --and I wish you luck -- from what I have seen -- no cell can be discharged below a voltage of 2.5 V or severe damage will occur in most instances.

SO hypothetically .. three ways to get it up to 3.3 to see if it will charge -- ONE if you have a desktop power supply that can drop down to 3.3V then do that and set the amps at a .2C charge ... SECOND if you don't have that then put the batteries TEMPORARILY in with good batteries and see if the voltage will equalize it that way .. BUT you have to watch it closely and make sure that the 1.7V cells have not collapsed and will literally short itself out ... THIRD -- take the 12.8V LiFePO4 battery and hook jumper cables to it -- and the other end to your car .. and force a charge

Once again -- I would NOT do any of those because its not safe ... At work unfortunately the joke is if there is ever a fire to come to my workstation because most of the extinguishers are at my desk ... But i have seen all three done ... unfortunately only 1 of the 3 sets of batteries ever came back somewhat to life ..

Once it does charge then let it set .. if the volts drop after about 2 hours then test each one but probably they are toast ...

Let us know what happened ...

Once again I have given you BAD advice that you should NEVER follow ...

 

[Maple Dave]

@Maple Dave how long did they sit below 2.0V ? Hours or days? Are they swollen on their large side?
The only way to know if they are garbage is to try to charge with low current and see if they accept and hold the charge.
For example, charge to 3.65V and let them sit in open circuit, nothing connected at all. See how fast and how low the voltage will settle down.
If it settles below 3.4V within a few hours, then cells are probably toast. Might still be usable in other applications, but I would not trust them as emergency backup. Swelling is usually a clear sign of damage.
It is sad, but this is what happens when you don't use a BMS to cut ALL LOADS.

There is no swelling. They have been like this since Jan 19, 2020, when I discovered the inverter had shut everything down. On Jan 15, 2020 the battery bank was at 52.8V and the CC and inverter were OK. It happened sometime between 1/15 and 1/19 when I discovered the shut down.. They had a BMS attached, but unfortunately the heating pad was direct wired so it was still running with the BMS having shut down. My error.

 

[Maple Dave]

The Tenergy TB6B charger has settings for lead acid as well as other chemistries.

 

[SolarRat]

The Tenergy TB6B charger has settings for lead acid as well as other chemistries.

Right, and if the lipo setting gives you trouble you can use the lead setting to get enough charge into them until the lipo setting works. That charger wont go up to 48v, so you'll have to do one cell at a time. You *could* do a few cells in series at a time but I wouldn't recommend it. You could also parallel the cells and treat it as one large cell, but I'd start with them individually at first and see how it goes.

 

[Maple Dave]

I'm starting the charging of cell #1 today. I think I will shut charging down before we go to bed and see what voltage I have in the morning and go from there.

 

[ghostwriter66]

I'm starting the charging of cell #1 today. I think I will shut charging down before we go to bed and see what voltage I have in the morning and go from there.

If you are charging any cell that you think is remotely damaged then you REALLY need to stay with that cell while charging ... lots of bad things can go wrong ...

 

[electric]

lots of bad things can go wrong ...

When bad things go wrong, does it mean things are all right?
Sorry, just busting your chops, no offense.
Totally agree not to leave the charge unattended when suspecting a bad outcome.

 

[SCClockDr]

A metal table/stand in the driveway or on the brick patio with clear weather.

 

[Maple Dave]

If you are charging any cell that you think is remotely damaged then you REALLY need to stay with that cell while charging ... lots of bad things can go wrong ...

We are staying right here with it. 15 minutes in, no heat build up in either the charger nor the cell. Cell took .14 volt so far. I started the charger at just .1A. Unless someone sees an issue, I think I'll go to .2A when the cell gets to 1.9V and then step up from there slowly, until I get to 5.0A. I'm thinking of getting all 16 cells to the 5A charge in PB battery setting, then start again with cell #1, LiPo set to 3.3V, .1A to start. Might be able to step A up .1 every 30-60 minutes, time will tell.

 

[electric]

with 100AH cells I wouldn't even bother with fractional Amps, I'd start with 1A-2A and go to 5A-10A when cell is above 2.5V

 

[SolarRat]

We are staying right here with it. 15 minutes in, no heat build up in either the charger nor the cell. Cell took .14 volt so far. I started the charger at just .1A. Unless someone sees an issue, I think I'll go to .2A when the cell gets to 1.9V and then step up from there slowly, until I get to 5.0A. I'm thinking of getting all 16 cells to the 5A charge in PB battery setting, then start again with cell #1, LiPo set to 3.3V, .1A to start. Might be able to step A up .1 every 30-60 minutes, time will tell.

You can safely go a bit higher. At 1 amp or even .5a the voltage should rise pretty quickly as there isn't much capacity at that low a voltage. The PB charger at 1s will probably terminate near 2.2v though. Once you get them up to the 2.5ish range I'd parallel them all and give them the full 5 amps that charger can handle...will take a few days for all of them to get from 2.5 to about 3.3ish. Then it's up to you if you want to keep going or put them back in series and see how it goes with your normal charger.

 

[SolarRat]

And keep track of how many amps are going in and how long each cell takes, that way you can mark cells that seem out of the ordinary for closer watching later. If all behave about the same you are probably in the clear.

My cell that was down at 0.6v seems to have recovered nicely and is holding it's charge after a few days sitting, so it looks promising for you.

 

[SolarRat]

Note: My voltage numbers above are just guesstimates. At first, you'll see the voltage rise pretty quickly. Then it will get to a point where it will seem the voltage barely moves for hours...that will let you know you are out of the knees and in the meat of the capacity, the flat part of the cycle (probably starting around 3.3v). That's where I'd feel safer about boosting the current past the 2a per cell range. JMHO tho...

 

[Maple Dave]

You are right, I went .1A, .2A, .3A, .5A, 1.0A, 1.5A, 2.0, 2.5, 3.0 and then 3.5A. It appears I can increase faster. so for the battery is at room temperature, and the charger is only very slightly warm, just enough to barely feel the warmth above room temp.
In tomorrow's trial I think I'll go 1A, 5A 8A then 10A. Today the changes were at 15-30 minute intervals, tomorrow I'll try 30 minute intervals, on cell 2

 

[electric]

You should really quickly get all cells above 2.5V. Don't let them sit too long below 2.5V as Lithium plating is slowly going on over time.
Once all cells are above 2.5V and holding, then you can take time fully charging them.

 

[Maple Dave]

I'll try, the charger I bought has a max in PB of 5A, 2V to keep them separate until they get higher. At that it might take 16 days or even more (I have 16 cells). If I could assemble them into 4 packs I could do the 5A at 12V, then I have another lead acid charger with a 2A and a 10A setting, and another with a 2A and a 15A. After that I have an old PWM charge controller for 24V that I could tie 8 and do on 2 panels I have, 150 watts each. Any Ideas to get them to 2.5 or higher faster with what I have, or suggest another charger if necessary. The TB6B I have can do 50A once I get on LiPo, but only 5A on PB.