Should work fine for a series charger. I would go to 3.65V (58.4V) w/BMS installed to shorten parallel balance time. Likely not viable as an MPPT input as the input voltage needs to be notably higher than the output. If you were charging 12 or 24V batteries, then using as an MPPT input would be the best way.
Top Balancing "How to"
- Thread starter snoobler
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Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
I do NOT Agree with Snoobler...
Go over 3.650 AT YOUR OWN RISK. Manufacturer Specs for the specific cells you are using are the guide , step outside or recommended specs, well it is YOUR MONEY not that of anyone telling you to ignore what a manufacturer says. The makers KNOW what they made and what parameters to use. ALWAYS defer to the Manufacturers Specification / Datasheets.
Go over 3.650 AT YOUR OWN RISK. Manufacturer Specs for the specific cells you are using are the guide , step outside or recommended specs, well it is YOUR MONEY not that of anyone telling you to ignore what a manufacturer says. The makers KNOW what they made and what parameters to use. ALWAYS defer to the Manufacturers Specification / Datasheets.
The MFGs are conservative. For a few minutes, running up to 4.0V won't be an issue, but should be avoided regardless. Above that is where the electrolyte breaks down rapidly.
3.65V is chosen as the top voltage, because there is no additional capacity to be found above that.
TLDR: 3.65V is fine for top balancing, and poses no risk of cell damage. Spending thousands of hours at 3.65V will degrade a cell, but we are talking a few hours.
3.65V is chosen as the top voltage, because there is no additional capacity to be found above that.
TLDR: 3.65V is fine for top balancing, and poses no risk of cell damage. Spending thousands of hours at 3.65V will degrade a cell, but we are talking a few hours.
Dogsareloud
New Member
A short balancing countdown video I made a few minutes ago. After slow charging for almost 4 days, the amperage is starting to click down, and the battery voltage is starting to go up. Went from 3.37 to 3.55 in under 90 minutes. It's all coming together...
Balancing Countdown LiFePo
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This video is a perfect example of why you shouldn't charge as a pack without a BMS, and why you should resist the urge to crank up the voltage to speed up parallel top balancing! Sorry, not directed at you, but it very clearly shows how things will sit there with little or no change for days, and in the space of a couple of hours, things change dramatically and present a very real possibility of over charging and damaging cells. Thanks for the post and video.
Dogsareloud
New Member
Exactly...I watched this thing like a hawk....Its tempting to raise the voltage...Don't do it !...
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FilterGuy
Solar Engineering Consultant - EG4 and Consumers
Exactly..... If the voltage was higher, things would happen even faster. The thing I keep saying is that the most important tool to have for top balancing is patience.
Once top balanced and capacity tested do I need to charge and balance again or just charge and use?
the reason for asking is all the cells now have a different resting voltage after being capacity tested. They were tested individually.
Will the normal charger and bms sort this out or do I need to do something else about it?
the reason for asking is all the cells now have a different resting voltage after being capacity tested. They were tested individually.
Will the normal charger and bms sort this out or do I need to do something else about it?
FilterGuy
Solar Engineering Consultant - EG4 and Consumers
You should be able to charge and go.
Thanks, that’s what I figured but thought it was better to check than make a mistake.
just put the 2nd last cell on to test, should be able to instal the battery Sunday uk time.
cheap AliExpress battery tester has worked hard this week. 6 cells tested since Monday afternoon
just put the 2nd last cell on to test, should be able to instal the battery Sunday uk time.
cheap AliExpress battery tester has worked hard this week. 6 cells tested since Monday afternoon
Hedges
I See Electromagnetic Fields!
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If they were first top balanced and then individually capacity tested, they are no longer top balanced and have to be once again top balanced.
If after top balancing they were connected in series and then capacity tested, the same current would have been drained from each cell. Recharged as a pack, they would return to top balanced condition.
Pyke13, the safe answer is from Hedges.
John Frum
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Hedges
I See Electromagnetic Fields!
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The contradiction is this: I think @FilterGuy missed the point that Pike apparently top balanced first, then individually capacity-tested the cells thereby unbalancing them.
John Frum
Tell me your problems
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I missed it too.
Hedges
I See Electromagnetic Fields!
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You can connect in series and charge, so long as you have a BMS monitoring individual cell voltages and with a relay or other disconnect mechanism. (As you should have any time you use the pack.)
If they're out of balance you'll find out and can finish off the top balancing.
