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diy solar

Can you de-bloat XUBA 280aH Lifepo4 cell?

heirloom hamlet

heirloom hamlet

life my way
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The question says it all.

I'm soooo done with following all these top balance suggestions. The cells were great. They didn't need this forced voltage garbage and neither did I.

Now I need to try and fix this overcharged cell or figure a way to get XUBA to ship me 1 or 2. What a shame.
 
How bad is the bloating? Did the safety valve blow? Typically significant expansion/swelling is electrolyte breakdown. Mild swelling is caused by normal cycling.

If the cell shows normal voltage, resistance, and capacity, it may be possible to continue using it. Obviously it depends on your application and C rates.
 
Luthj said:
How bad is the bloating? Did the safety valve blow? Typically significant expansion/swelling is electrolyte breakdown. Mild swelling is caused by normal cycling.

If the cell shows normal voltage, resistance, and capacity, it may be possible to continue using it. Obviously it depends on your application and C rates.
Click to expand...
Pretty bad, not normal, but also not the worst I've seen pics of.
Did someone from the forums series charge up instructions, preluding a parallel balance. This is what I got. The voltage on the battery main negative cell shot up to 4.(friggin)8, and the damage was done.
I quickly got it under a load and it right away plummeted and is playing nice with the rest of the pack. All stabilized at 3.333. I don't know about resistance and capacity, but the voltage is normal.
 
There could be physical damage to the layered anode/cathode sandwich. Voids, etc. I am not familiar with the construction of those cells, but if the separator fails, the cell could short circuit internally. Either slowly, or quickly. A rapid internal short results in the cell heating up and eventually venting its electrolyte. Electrolyte is not pleasant stuff to deal with and is flammable.

You appear to have that pack wired in a 1P configuration, so it shouldn't take out the other cells if you have a proper BMS.

In an over voltage situation the electrolyte between the anode/cathode is broken down into byproducts, including gases. This tries to push the layers of the sandwich apart. If I was just dicking around with a test bed in a safe non-enclosed location, I might be temped to vent the case with a needle, compress the cell flat, and seal it back up. Or maybe just capacity test the cell and let it run. But this is very risky, and not something that should be done with a pack that will see any kind of reliable service.

What peak voltage did the cell see during this event?
 
That is unfortunate. Sorry for your loss.

Can you describe your top balance procedure you followed? The info would be nice to have so other members don't have batteries end up like this.
 
Lately ive seen a lot of people ruining their cells, maybe we should start adding more disclaimers in the top balance guide's, mentioning the possible complications, consequences and examples of failures.

For OP, LIFEPO4 its a very safe chemistry but still risky to use cells in that condition, in my opinion its not worth it any remaining life / capacity for the risk involved.
 
mrdavvv said:
Lately ive seen a lot of people ruining their cells, maybe we should start adding more disclaimers in the top balance guide's
Click to expand...
I think part of the problem is the number of contradictory guides, both in posts here and on Youtube. Conflicting statements about voltage, whether it's safe to do it in parallel, whether you must do them in parallel, or you should not do them in parallel. What voltage(s) to use. Whether you should do it in a stepped manner, or that it's not necessary, or that you absolutely should not do it in a stepped manner. Etc etc.

My batteries aren't here yet, but I admit I have a lot of anxiety about what I should do once I receive them. Personal accounts like this post don't help.
 
ecualibrium said:
I'm soooo done with following all these top balance suggestions. The cells were great. They didn't need this forced voltage garbage and neither did I.
Click to expand...

That is why I chose to never top balance my new, well matched cells and have been a proponent of that policy on the forum.

Here is how I made my choice:

I tend to make decisions based on a risk/reward analysis. The supposed benefit of top balancing is increased capacity, or increased cell life or ? To be honest I'm not sure what the benefit is.

However, for the sake of discussion, let's assume that top balancing gives us a 10% increase in some measurable parameter for a cell.

We have seen reported, more than once, irreparable cell damage during the top balance exercise. When this does happen, AFAIK this has always resulted in a 100% loss of the cell.

So I have a 100% risk to the cell for maybe a 10% benefit? That would be a 10X risk/reward. I would prefer to see a risk/reward of less than a whole number.

Just my opinion.
 
Another reason I like active balancers. With new batteries, just hook them up and wait for them to balance out before connecting battery pack to charger. Just don't make parallel cells until balanced or mate with another cell of close open voltage.
 
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Unless you have a BMS, I would not try to use it unless you have a good battery monitor and the time to log cell voltages at different points in the charge and discharge cycles. I would also consider clamping your remaining cells and possibly that one.
 
RCinFLA said:
Another reason I like active balancers. With new batteries, just hook them up and wait for them to balance out before connecting battery pack to charger. Just don't make parallel cells until balanced or mate with another cell of close open voltage.
Click to expand...
And yet I've seen more than one reputable person post that a BMS, active or otherwise, is not suitable for initial balancing and should not be used for such, and that separate balancing with a power supply should be done before hooking up the BMS.
 
sremick said:
And yet I've seen more than one reputable person post that a BMS, active or otherwise, is not suitable for initial balancing and should not be used for such, and that separate balancing with a power supply should be done before hooking up the BMS.
Click to expand...

And why is that?
 
JoeHam said:
And that's nothing that a passive balancer won't do in regular use.

My new cells (16 of them) had a max voltage discrepancy of 0.003v.

Simply not worth the effort IMHO>
Click to expand...
That is not necessarily true if new cells are significantly mismatched in their state of charge. Resistor dump balancers typically don't start dumping current until 3.4 vdc and they are rather wimpy on balancing dump current compared to a strong charger current push. A higher state of charge cell could get very much overcharged before the lower state of charge cells contribute enough stack voltage to satisfy the overall charger voltage limiting settings.

When I say 'new' I mean just received group of cells whether new or used. True new cells are more likely to be SOC matched but no guarantees that truely new cells have not been sitting on the shelf for months with their own various self discharge rates.
 
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I don't see any issue with using a calibrated, voltage and current limited bench supply for top balancing. Though if the cells are within 25mv of each other, I am not sure it would have much value.
 
Luthj said:
I don't see any issue with using a calibrated, voltage and current limited bench supply for top balancing. Though if the cells are within 25mv of each other, I am not sure it would have any value.
Click to expand...
I'll have a CV/CC power supply, battery capacity tester, and of course a DMM ready to go when my cells arrive. I'd prefer to test each individually, using whatever slow method is safest. I don't care if it takes more than a day to balance each cell... I'm not in a rush. I just need to find a procedure that has somewhat of a consensus vs. multple conflicting guides.
 
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