13s charger for low SOC charging

[e-beach]

OK, back to the original question.

My 12 amp charger is a Kingpan. It died after one year when the 110/220 v switch fried itself for unknown reasons. After a lot of messing around with it I got it going again and it has been fine since. My 5a charger is a generic Chinese charger I got off eBay. I installed a trim pot into it to make the voltage adjustable. The fan on that one has gone out several times and has needed replacement. I am waiting on a new fan at the moment to replace it yet again. 4th time.

I don't own one, but Grin's Satiator is probably worth the money. Unless you don't mind fussing around with a charger modification. that could take more time effort than then you bargained for.
https://www.ebikes.ca/product-info/cycle-satiator.html

However you can save money with a charger that has a voltage trim pot. That means you need to understand enough about charger electronics to customize your charger. Around here people use Meanwell chargers and customize them. You can find info on Meanwell modifications if you search for them.

Yes, constant current until constant voltage.

As for a BMS, my BMS has been working flawlessly for 7+ years. It doesn't have a label on it so I couldn't tell you the brand.

Yes, the BMS has to be plugged into the charger to function. Through a plug. The charger is not hardwired to a BMS unless the charger is on board and then it should be switched.

Your BMS should have a wiring diagram to show you what to wire together.

IMO, set you charger to 52v under load (like at the end of charging your 13s battery when it in CV).

Set your bms to balance at 4v.

 

[john61ct]

52V will be slower for no benefit, no need to be **that** conservative, 53V is the lowest I'd go.

And the "start-balance" setpoint needs to a bit lower than the charging setpoint.

How much lower, depends on

how often you get to full,

how imbalanced the pack is, and

the actual current rate used for balancing, often way too slow, always lower than the mfg rating.

The ideal is, that balancing is completed within a few minutes of CC-CV transition, and long before the charger algorithm ever stops charging.

If you need to artifically extend the Absorb cycle for more than say 20min once in a while,

just to allow the BMS to finish charging,

that means you need to either start earlier, or get balancing gear with a higher effective current rate, maybe even the active type.

This "should be" much less an issue with newish top quality well-matched cells, but then again, every pack eventually starts to wear out.

For those using secondhand or salvaged cells, it's a huge issue for getting decent capacity out of a few more cycles. . .

 

[amberwolf]

This is something I don't really ubderstand fully: does a BMS have to be plugged into a Charger to balance the cells? Or is that not neccesary?

With the most common type of BMS, that simply drains high cells, yes, it does have to be connected to the charger during balancing.

What happens is the lowest-capacity cell will get full first, so it's voltage reaches the balance point, so the BMS turns on it's balancing shunt for that channel (cell group), to drain that high cell a little, to let the other ones catch up.

Some BMS only have one "balance point" so they just turn off the charge port input during this stage, until the high cell drops below the setpoint and the balancing shunt turns off. Then it resumes charge, and repeats this until the other cells have caught up to this one. If other cells are high, then it does the same for those.

Others check the current that's flowing, and if it's below the current the shunt can pass around the high cell, it lets the charging continue during balancing, but otherwise do the same as the above.


But basically if the charger isn't connected, the only thing that will happen is that if a cell was already above the balance point it'll continue to drain down, until it is below the balance point, but none of the other cells will be charged any further (and they are not yet full, or even to the balance point).


With the cahrger connected, it'll keep cycling thru this on each cell that needs it, until they've all reached the same voltage (whatever the balance voltage is).


With a BMS that does capacitive charge shuffling, where it takes charge from the high cell and puts it into the low cell, it can (depending on design / settings) do this without the charger connected. But it can't bring all the cells up to the high cell voltage level, without the charger.

 

[Vbruun]

Thanks for the great replies!

I think I ubderstand IT way Better now

 

[Vbruun]

I'm going to experiment with using the hvc of the BMS and og that Works alright, I won't do more.

If not, I Will start working through some of the options listed here