Dumb idea.
If there was a way to quickly turn series connections into parallel connections (turn a 12s2p battery into 1s24p), would the batteries balance within minutes?
I’ll gladly throw the Conflict Unity under the bus here:
This is what shitty QC on your solder joints looks like. The wire is not making sufficient electrical contact with the connector (therefore a ton of extra resistance), and there is vastly insufficient solder (so when it gets hot, it doesnt take much to de-solder).
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Roughly, yes.
Then the smaller and smaller voltage differences between the p-groups would result in smaller and smaller amounts of balancing current. Experiments would need to be done to know when to say “it’s good enough”.
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I can imagine some kind of sliding rail on the side of the enclosure.
_ _ _ _ _ _ _ _ _ _ = series connections
- - - - - - - - - = parallel connection
But fuck me, if you bump into something mid ride. LMAO
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You just need a button…and lots and lots of MOSFETs.
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Someone did this
I don’t think more balance current is the problem, the problem is that some of the old school bms just balance while charging.
This compared with the trend of bigger and bigger packs or higher charge currents on small packs just doesn’t work out.
We also tend to use charge only bms, which does have in average 40-50mA of balance current. That’s on a 1600Wh pack… hm, idk.
I think our answer to this is not higher balance currents, but smart bms with active balancing after the charger was disconnected.
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Don’t some of the standard passive balancers also have the option to charge when not balancing? Hopefully only when above a certain voltage though.
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Hmm… 
I think there was something mixed up… or it’s too early for my brain to work. Need coffee 
But yes you are right.
I think there are some different types out.
Some balance while charging over a specific voltage and some over charge and drain till a specific voltage which sometimes do need the charger to be plugged in to make it work.
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I figured this idea would never be used, as a small logic bug or some physical design error could lead to shorting the entire pack out at once pretty easily…
Like 1s24p and 12s2p mode get activated at the same time…
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We don’t.
A good battery should barely need any balancing to begin with.
Now I have a bad p group on one of my boards that gets out of balance a lot but faster balancing is just a bandaid for deeper problem in the battery.
I should probably get off my ass and change it …
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Even cars & even expensive ones dont have this feature implemented. It is called active balancing. Such system tends to be large & expensive. Unless you want to pay several hundreds bucks for saving a few mW per use, it is not worth it. The energy payback would never be reached for the BMS higher price tag in most cases. Active balancing could be useful only for very special projects having a restriction on power where every mW count e.g. mars rover… I don’t think consumer electronics fits into this category.
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I don’t think going above 100mA balancing is required in most cases even for quite large Ah packs for LEV. Heat dissipatiom becomes a problem & makes the BMS larger when going with higher balancing rate. Just use new & identical cells to build new packs. Use a good BMS to make sure you don’t kill the cells during normal use and the difference in balance will stay low until the cells have reached their end of life.
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Active balancing is not feasible/sensible for Light Eletric Vehicle (LEV) use price, board size or need wise. It’s more suitable for industrial + grid-scale applications. These systems are capable of balancing currents of up to 10s of Amps.
On the FlexiBMS Lite you can set balancing to be enabled outside of charging/charger being connected, which I would generally recommend doing if you’re trying to balance a heavily unbalanced pack. Unless you can leave the charger connected.
The way the balancing logic in the Lite works, is that there is a configurable voltage that a cell needs to be over before it’s allowed to be balanced. Then there is the allowed cell difference voltage (delta-V), which is compared to the lowest cell in the pack.
As an example. 4S pack: 10mV allowed cellV difference, balanceVoltage 4.000V
- 3.980V
- 3.995V
- 4.000V
- 4.010V
Cells 2, 3 and 4 need balancing as they are not within the allowed cell difference from the lowest cell + allowed difference → 3.980V + 0.010V = 3.990V. Only cells 3 and 4 are allowed to balance at this time as they are equal or over the balanceVoltage of 4.000V.
When the pack is charged, then cell 2 would also go over 4.000V and start being balanced towards the cell 1 until it’s within it’s the cellV difference from it.
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Yes, the 1.2 amp one is not applicable, but the 5amp one is functional.
And the best part of them is, they ALWAYS work, according to disparity. So, it doesnt balance AS YOU CHARGE. And doesnt waste electricity.
The company I work for make packs of 180Ah per parallell group (modular system, build as you like). Balance current per P-group is around 500mA. So far no problems 
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How many cells per p-group for that 180Ah?
People want more balancing current because they don’t know any better.
Then there’s also the idiots who try to make a pack with refurbished cells, mixing end of life cells with 95% testing cells. (I also used to know this idiot who mixed laptop cells with drill cells, the pack failed within two weeks)
I played around with the idea of an active balancing system, but then realized that the sheer cost of integrating all these flyback converters and the fact that factory new cells from the same batch will stay in balance all the way to end of life. An active balancing system really doesn’t have a practical use.
Really, these BMS are a MONITORING system, cutting power when one cell gets too low or too high.
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its 4x17 cells if I recall correctly
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The one that I have does 2A and balances using a super cap, not resistors, never heats up. Functions off pack power, external power not needed. Another nice feature that’s not apparent till you use it, it measures the balance wire/connector resistance and compensates.
Ive removed all the BMS from my packs, since usually it was a bms that killed a p group. I’m happy with checking balance monthly. Made harnesses for varying S counts for easy plugnplay.
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