LIFEPO4 Battery discussion thread

Why do we top balance and not bottom balance? I didn't know bottom balance was a thing but apparently it is.
 
cavedog said:
Why do we top balance and not bottom balance? I didn't know bottom balance was a thing but apparently it is.
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If you ask me, its 6 of one half a dozen of the other. If you bottom balance then top is out, if you top balance then bottom is out.

When would you bottom balance? In the 5 minutes the battery spends in the dead zone?

The only times I've heard people talk of bottom balancing is with DIY EV's with no BMS so that the load is shared equally at lower voltages so cells don't wear differently. They would painstaking take their time (when building the pack) making sure each cell bottoms out at the same time then would pick a charge voltage when one cell peaks.

Its impractical to bottom balance is my theory which is why everyone top balances while battery is absorbing.

If you have badly matched cells (cells with different capacitys) then balancing top or bottom means nothing as the lower capacity cell always leads the charge.

eg: bat 3, you get all cells reading 3.45V at 55.2V. You will still have cell 8 bottoming out first, but the other cells voltages might be a bit higher than what's happening now.

So each battery will have a different charge voltage if bottom balance.
 
Just noticed this recently and I have not managed to get my battery to 100% for a little while due to winter and wondering it it will rebalance over time, but the circled piece went from 89% to 99% within 5min, why would that happen?


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Zurg said:
Yeah but think about how long they last.
The safety aspect, I can up the voltage but there's no reason to.

Also I have a decent connect for cells.
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My lead acid car battery was 10 years old before I replaced it. Sounds like we are reinventing the wheel here.
 
duderoo said:
Can you elaborate some more on what I should see and what should happen over time?
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You wont see anything as we cant see any detail regarding the battery. I can only assume the jump from 89% to 99% will get smaller the more time it sits at 99%.

You could set a schedule for battery to be at 100% for one of the time slots should help speed things up by giving balancer a few hours every day if you're in a hurry. Would be giving eskom money though.
 
wingnut771 said:
I wouldn't call it a special.
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It's the lowest priced lifepo4 battery in SA as far as I can tell.

Are they any good at all? It's hard to find details about them except the reviews with so many people saying they are good but do they offer the capacity as advertised and how long do they last.

4 of them in series that is R8764 for a 51.2v pack. Seems well priced for new* cells.
 
cavedog said:
It's the lowest priced lifepo4 battery in SA as far as I can tell.

Are they any good at all? It's hard to find details about them except the reviews with so many people saying they are good but do they offer the capacity as advertised and how long do they last.
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They're all the same imho so just get the cheapest. Lowest price doesn't mean special, just means others are ripping you off or selling older stock when price was higher.
 
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