Need help with Gary/Fechter Bms

[Icewrench]

Flexy I have two models of charger from evassemble.
They both have trim pots inside. You could likely turn up the voltage a bit to help finish balancing your pack.
Once the bms led 1 changes to full green the charger led should also go green.
Good luck

 

[flexy]

I shall open mine and check, thanks for the help guys.

 

[AndyH]

Does this mean the low cells in the pack will never be brought up to full charge, using my existing charger?

They may not reach the same end voltage, but since there's so little difference between 3.65V and 3.7V with regard to capacity, it's not likely to make a noticeable difference.

I've been using an earlier version (V3.2 - which has a 3.7V shunt) with my Thunder Sky charger (3.62V per cell) and it works fine.

Keep in mind that for the end of charge 'decision' either the charger will 'win' or the BMS will - but not both:

- If the charger voltage is below the BMS shut-off, then the charger will run it's full cycle and the BMS control LED will not switch from red to green at end of charge.

- If the charger voltage is at or above the BMS shut-off voltage, then the BMS will switch to green and stop sending charge current to the pack, but the charger will continue to try to get the pack up to where it thinks 'done' should be - and it'll never get there.

Andy

 

[flexy]

I suspect that my charger and BMS were trying to cancel one another at the charge cutoff point.
As the cells started to reach full capacity the charger started to make a buzzing and it's charge LED would flicker between red and green, the buzz would increase to whine, then as the orange BMS LEDs started to light it would end the charge (the noise would stop).
Is this due to some feedback caused by the BMS reducing the charge current with it's mosfet?

The charger never made that sound before I installed the BMS, it has now died
If there is always going to be a conflict between the charger and the BMS would it be better to use modified meanwells for charging and let the BMS dictate cut off?

 

[fechter]

The end of charge cutoff latches, so won't cause any buzzing. The buzzing is more likely due to the throttling action of the FET before end of charge. Some chargers are adversely affected by the frequency of switching, which was one of the main reasons the design is being changed. A Meanwell will be more likely to work, but could still have the same problem. The length and size of the wires going from the charger to the board can also affect this. Adding a large capacitor across the output of the charger will reduce the chances of a problem.

 

[flexy]

Thanks for the info, so the BMS is working exactly as it should, just a faulty chinese charger (now on it's way home for repair).
I am going to go the meanwell route, just read the epic mod thread . I would much rather have a charging system that I can troubleshoot and adjust myself.