Whoopsie! A 3.75v Xuba 280aH Cell

[heirloom hamlet]

So I've been following the direction on the forum for top balancing these cells and decided to use the little 5a charger to get them to 3.55 individually, and I have 32 of them. I thought it would at least help me see and feel some progress as I check cells off the list.That was 4 days ago. I set up a single cell at 3.55 and checked on it daily. Still slow. Soooooo sloooowwwww. Like watching the grass grow. Painful. One cell? This will still take a year. I have time, but not a year. Plus, it's ridiculous. Who can do this?

So I decided to up the voltage a bit last night. I figured, like Will said, it would push it faster low and with good monitoring you could just catch it when it's close and adjust the setting accordingly. I thought I'd at least have a day or two from the snail's pace I'd seen thus far. Nope.

One night, and this morning this cell went to 3.75v.

My question is, what have I done to this cell, did I train it to have a (too) high ceiling? Will it always be the one that takes off and screws up an entire pack?

 

[Ampster]

You have overcharged it and should put a load on it to get it below 3.6 volts. If you had set the max voltage at 3.6 it would have reached that voltage sooner and tapered off. Do you have a way to measure Amps going into the cell from your charger? Most directions I have seen suggests putting all the cells in parallel. Doing them one at a time is not accurate.

 

[heirloom hamlet]

You have overcharged it and should put a load on it to get it below 3.6 volts. If you had set the max voltage at 3.6 it would have reached that voltage sooner and tapered off. Do you have a way to measure Amps going into the cell from your charger? Most directions I have seen suggests putting all the cells in parallel. Doing them one at a time is not accurate.

Yes, the charger automatically adjusts the amps as you increase or decrease the voltage. I saw someone else did it individually. The whole battery is massive for this little charger. Felt like it was making almost no impact over many days when in parallel. My plan was to get them up individually, then parallel them and finished off the top balancing then, altogether.

 

[Ampster]

My plan was to get them up individually, then parallel them and finished off the top balancing then, altogether.

If that makes you feel good, it is worth a try. I would set your power supply to 3.5 volts with no load.
My theory is it mathematically would be the same time to push X Amphours into Y Amphours of batteries. You would have to add the number of minutes to connect each cell and the time that a cell got to the voltage and was idle before you reconnected the next one.
On the otherhand, maybe it is not as linear as I am assuming and you way would take less time overall.

 

[ghostwriter66]

As Ampster stated .. i would get it down to 3.6 soonest ... with your charger being soooo small AMP-wise there is a good chance that nothing happened ....

I normally look at the battery spec sheet - and charge up to 92% of rated voltage ... yep and sometimes that only like 0.2V off from 100 ... The trick though is to TOP Balance ALL your batteries together to a certain point .. not to try to get them individually ... DO ALL AT ONCE ...

 

[heirloom hamlet]

As Ampster stated .. i would get it down to 3.6 soonest ... with your charger being soooo small AMP-wise there is a good chance that nothing happened ....

I normally look at the battery spec sheet - and charge up to 92% of rated voltage ... yep and sometimes that only like 0.2V off from 100 ... The trick though is to TOP Balance ALL your batteries together to a certain point .. not to try to get them individually ... DO ALL AT ONCE ...

Okay. I am now.
I intended to do that all along, but I did think it would make me feel a bit better to knock one off the list at a time and see progress... but didn't really end up going that way. Just earned myself an extra heart attack and a couple headaches. @Ampster
Incidentally, I connected the one 3.748 cell (which was holding its charge for hours btw) to a lower cell, while connecting eight together. Within 2 minutes of being paralleled with a 3.304v cell, that high cell was at 3.489v...and the other was up some. Super fast. Mission accomplished in getting the voltage down? Was that an alright way to do it?
Hey, can I put 16 in parallel and put the charger on them even though I will only be making 24v packs?

 

[GMB]

I have 16 of these cells and the small 10 amp charger Will shows in his top balancing video. This is what I did - can't say whether it's right or wrong. I would of hooked them all together in parallel and balanced that way, but didn't have enough bus bars to do that. I have 32 additional bus bars in route now from Xuba so I don't have this problem again...

I charged each cell individually. They arrived at 3.30 volts each and my traditional AGM/lead acid charger wouldn't charge them in a 12 volt configuration because it said they were already charged. So I charged each one individually to 3.5 volts. I set the charger to 4.1 volts until a battery reached a steady 3.38 volts with my volt meter. Then I dialed it down to 3.5 and let it work until it reached that point. Each battery took about 2 days to charge this way. I had my Kill-A-Watt meter plugged in during the charging process and it took about 1500 watts to charge a battery from 3.30 to 3.50. The charger obviously takes power to run, so not sure how accurate that is, but gave me a rough figure to go by.

Once they were at 3.5 volts, I put 8 of them in parallel and let them sit for 2 days. Then I charged them to 3.6 volts in a parallel set of 8.

When I connected them to a load, they went from 3.6 to 3.4 very fast, then settled around the 3.3 range and they did a great job from there on down to 3.0 when I stopped the load test.

This is my first DIY battery bank, so again, can't say whether this is right or wrong. Just want to let you know my personal experience with them during that process.

 

[Ampster]

Was that an alright way to do it?

Yes that works.

 

[Ampster]

Hey, can I put 16 in parallel and put the charger on them even though I will only be making 24v packs

Are these 24 volt packs 2P8S or two 1P8S packs?

 

[heirloom hamlet]

Are these 24 volt packs 2P8S or two 1P8S packs?

They are just intended to be 8S. But I reserve the right to make them 8S2P.
I've never seen that the battery size was limited by the MPPT manufacturer, but this one says you can use a 200aH battery pack. Mine is 280aH. If I out two together they'd be 560aH. I'm not sure why storage size would be limited, but now I'm wondering if that is anything to be concerned with.

 

[Ampster]

It will go faster if you do 8 inparallel. You can always parallel at the pack level at some later point without having to rebalance. Just try to have each pack at similar voltages when you do that. You probably noticed a little spark when you pulled that one cell down with the lower voltage cells.

 

[ghostwriter66]

Okay. I am now.
I intended to do that all along, but I did think it would make me feel a bit better to knock one off the list at a time and see progress... but didn't really end up going that way. Just earned myself an extra heart attack and a couple headaches. @Ampster
Incidentally, I connected the one 3.748 cell (which was holding its charge for hours btw) to a lower cell, while connecting eight together. Within 2 minutes of being paralleled with a 3.304v cell, that high cell was at 3.489v...and the other was up some. Super fast. Mission accomplished in getting the voltage down? Was that an alright way to do it?
Hey, can I put 16 in parallel and put the charger on them even though I will only be making 24v packs?

The honest issue is with 16 batteries you have ALLOT of aH's and a very low (3.2v) voltage so you would really need to have a BIG GIRL charger to push as many electrons around to balance all of those at once ... NOW with that said - there is NO harm in trying ... and you have nothing but time

 

[heirloom hamlet]

The honest issue is with 16 batteries you have ALLOT of aH's and a very low (3.2v) voltage so you would really need to have a BIG GIRL charger to push as many electrons around to balance all of those at once ... NOW with that said - there is NO harm in trying ... and you have nothing but time

So I ended up not trying that, I just did one pack, 8. BUT! I did up the voltage to 3.8, which maxed out the amps at 5.25. The next morning I caught the charger pushing only .2a. The cells were each at 3.689. A bit high, I know. But, after disconnecting, they immediately began to drop and stabilized at 3.615.
I've left them parallel all day. Would you say I could consider them "Top Balanced"? I'd like to connect them to PV charging and see how they do.

I did have an inadverten positive to negative touch moment. Big spark, lots of instantaneous heat, melted chunk out of a terminal. (Me grimacing). The voltage seems as stable as the others, I hope there is not any internal damage done. I don't know how I'd be able to tell.
At that moment I wanted a Delorean with a Flux Capacitor to go back in time a few minutes. Either that or punch myself in the face.

 

[Ampster]

You continue to make the assumption that the battery will charge faster if you set the voltage higher. This time, you may have, caught it in time. You would become better informed if you kept a log as you were charging them. 3.615 volts is not a normal settled voltage. What were the Amps when you had the voltage set to 3.60? The other question is that based on the charger unconnected to the pack, which should be the setting of max volts. Or what you read when the battery was connected to the charger, which would be the pack voltage at the time? If the Amperage went up when you did the latter you were probably already at 3.65 and just over charged them . This is getting painful to watch. If you insist on not following directions,. live with your decisions. They may be top balanced but they are probably overcharged based on the facts that you explained.

They may have been adequately top balanced when you adjusted the voltage.

 

[heirloom hamlet]

You continue to make the assumption that the battery will charge faster if you set the voltage higher. This time, you may have, caught it in time. You would become better informed if you kept a log as you were charging them. 3.615 volts is not a normal settled voltage. What were the Amps when you had the voltage set to 3.60? The other question is that based on the charger unconnected to the pack, which should be the setting of max volts. Or what you read when the battery was connected to the charger, which would be the pack voltage at the time? If the Amperage went up when you did the latter you were probably already at 5.65 and just over charged them . This is getting painful to watch. If you insist on not following directions,. live with your decisions. They may be top balanced but they are probably overcharged based on the facts that you explained.

I assume you meant 3.65, not 5.65.
The amps were about 3.5 when set at 3.6v. I was hoping it was an option if closely observed because Will said in his video it was an option, a risky one perhaps, but that he was tempted because it would speed up the process.
I thought after disconnecting from any charge, some settling was normal. That has been my experience and that of others that I've read.
So, I am a bit confused. It did charge much much faster a a 5a starting point, and it got to the right voltage and was disconnected. Was damage done or is my top balance not accurate or trustworthy?
I'm learning and not ignoring instruction...but I fo read a hundred different ideas in the instructions.

 

[heirloom hamlet]

What Will seemed to imply is that you could up the voltage and amps for a portion of the charge to get yo a closer starting point in the balancing. Like 3.5, and then adjust the dials appropriately to finish off the balance. He says the voltage can be set to 3.65v for the balance. Is this not correct?

 

[Ampster]

The amps were about 3.5 when set at 3.6v. I was hoping it was an option if closely observed because Will said in his video it was an option, a risky one perhaps, but that he was tempted because it would speed up the process.

I changed my original post to 3.65.
Closely watched does not mean going to sleep for a few hours. That is when the damage occurred.

adjust the dials appropriately to finish off the balance. He says the voltage can be set to 3.65v for the balance. Is this not correct?

Yes but it appeared you were already at a a top balance voltage when to took the charge to 3.8 volts. The clue was when you increased the voltage fhe charger went from constant voltage mode back to constant current mode at the higher Amps which you did not actually need.

 

[heirloom hamlet]

I changed my original post to 3.65.
Closely watched does not mean going to sleep for a few hours. That is when the damage occurred.

Yes but it appeared you were already at a a top balance voltage when to took the charge to 3.8 volts. The clue was when you increased the voltage fhe charger went from constant voltage mode back to constant current mode at the higher Amps which you did not actually need.

I see. It seemed from my experience up to that point it was still a very long way home.
No, the cells voltage's were around 3.3v when the voltage/amps were increased.

 

[Ampster]

It seemed from my experience up to that point it was still a very long way home.
No, the cells voltage's were around 3.3v when the voltage/amps were increased.

''Earlier you said,

The amps were about 3.5 when set at 3.6v.

All know is facts that you have shared.

 

[Ampster]

''Earlier you said,
All know is facts that you have shared.

 

[heirloom hamlet]

''Earlier you said,
All know is facts that you have shared.

Yes, when the little charger is set to charge to a voltage, it automatically sets it's amps.

At 3.6v, when connected to the paralleled cells, it set that current at approx 3.5a.

 

[heirloom hamlet]

So the cells were only at 3.3v.

The setting was using 3.5a to charge to 3.6v.

Then it was changed to 3.8v, in order to impose a 5.25a charge.

 

[Ampster]

I assume your power supply has no separate Amperage setting. The Amps change in response to the voltage setting? The max the charger can go is 5.2 Amps?

Yes, when the little charger is set to charge to a voltage, it automatically sets it's amps.

But that Amperage is not fixed either. As the battery fills up at that voltage the Amperage tapers off. This is known as the constant voltage mode. That was your clue that the cells were near the top.

 

[heirloom hamlet]

I assume your power supply has no separate Amperage setting. The Amps change in response to the voltage setting? The max the charger can go is 5.2 Amps?

But that Amperage is not fixed either. As the battery fills up at that voltage the Amperage tapers off. This is known as the constant voltage mode. That was your clue that the cells were near the top.

Correct.
It has a dial for amperage, but when prioritizing the voltage setting, amp control is forfeited. It does peak at 5.25a, however, yes.
And, yes, the amps decline to 0 ultimately as the battery fills up. But five days in, and almost no amperage change. On the forum here, everyone seemed to indicate my charger was puny and it would be a while as low as it was. That's what got me to thinking about Will's comment on his temptation to jack it up a bit to get the charge close, watch it closely, and adjust to top it off.
I just checked those cells, and after the day, 12 hours, they seem to have leveled off and balanced at 3.6v.
Is that a good "Top"?

 

[ghostwriter66]

Correct.
It has a dial for amperage, but when prioritizing the voltage setting, amp control is forfeited. It does peak at 5.25a, however, yes.
And, yes, the amps decline to 0 ultimately as the battery fills up. But five days in, and almost no amperage change. On the forum here, everyone seemed to indicate my charger was puny and it would be a while as low as it was. That's what got me to thinking about Will's comment on his temptation to jack it up a bit to get the charge close, watch it closely, and adjust to top it off.
I just checked those cells, and after the day, 12 hours, they seem to have leveled off and balanced at 3.6v.
Is that a good "Top"?

The simple answer is if all of your cells are charging and dischargin at the SAME rate -- amd you do not have a runaway cell (either one that charges way ahead of the others OR dies quicker than the others) then YES you are balanced ... the first time you hook the batteries to a real SCC then everything will flatten out and you will be fine ...

The #1 killer of LiFePO4 is HEAT ...

#2 is ppl trying to tune their batteries to get it to 99.9999 and messing up and not paying attention and pumping them up too much ... LiFePO4 does NOT like to be OVERCHARGED at all ... at maximum voltage strange things start happening to the little bouncy balls inside of the battery ...

My advice to you is to drink heavily ... wait .. wrong forum ... but try to get all the batteries as a level as you can -- and then see if they hold there for 24 hours .. if so -- then you are TOP balanced enough .... you are actually scaring me with going above the volts you should .. i think you have been lucky so far ... but i wouldnt do it again ....