Just a side point to add to the discussion…
Almost no one needs a BMS, with or without balancing (it might be protection-only), when the pack is new and/or everything is working properly.
A BMS is for when the cells start aging or something isn’t working properly. It can significantly extend the life of the pack if it balances and can provide protection against a wide array of problems (device or part failure, incorrect charger voltage, cell failure, spot weld breaks, charge or discharge over-current short-circuits, over- and under-temperature, etc.) the will eventually occur.
So if you value your pack, and even if a BMS is not needed if the pack is new and you are sure nothing can ever fail, then use a balancing BMS right from the start. You’ll need it.
Why do you want to remove all these features with no downsides you’re sounding like @b264
This is WAYYY bigger than a balancing BMS
God the people on this forum confuse me so much. Why take such a principled stance on balancing
but when theres literally no downside (the bms is the size of a fucking single cell like cmon) then why not unless you have some emotion based principled stance on things you dont like.
The reason this does not make sense to us is why do you even have a bms? Its totally okay to charge with a balance charger. But if you have one what’s the bms for?
The balance current is very low on the LLT. I think 65mA, most packs I build are 6p or bigger. The smallest imbalance at that current level usualy takes days if not weeks to balance out if its happening only at the end of the charge cycle
But now you got me thinking… if I am charge at 4p pack at 4amps…its probbaly not balancing anyway…but only slowing down charging huh?
Sorry, I was wondering why balancing would need to take so long to do. The only thing a top-balancer needs to do is compensate for the differences in leakage current for each cell, assuming the initial balancing was already done.
There shouldn’t be any need for lots of balancing until one or more cells has reached end of life and is self-discharging must faster or the pack has been in storage for a lonnnng time.
Setting the balancing threshold to 3.5V would only work if the higher voltage cells at 3.5V will be the higher voltage cells at 4.2V. I’m not sure we can always assume this.
If not then you are actually unbalancing the pack by having a very low balancing start threshold.
This^
I encountered exactly this with a 3 year old 30q pack last week. I had balancing at 3,5V and when I charged it it got even more unbalanced. In the end I just let it balance at 4+V and it has been perfect since that.
So I also set the balance accuracy to .005v once the BMS sees that all cells are within this voltage delta it stops balancing them all together and restarts if they fall out of that delta range… I do not think it will take the pack out of balance
For example this battery, although its almost full, I watched it for about a half hour and balancing only came on for a minute, the rest of the time it was off because as it was charging, they cell voltage levels remained within .005 of each other
