Lithium 58V battery Charger -Adjusting Voltage

[Sergio]

Originally Posted by jeffro22

sergio, I am trying to understand this correctly, but if I have the BMS set to cutoff the charge at 57.4V (high cell voltage set to 4.1) does it matter (within reason) what the charger is set too ? (other than maybe having 2 fail-safes on the HV,)

It could work but there are a few factors to consider, the BMS LV and HV protection should be the last line of defense.

Lithium chargers drop the current very low near the end of the charge cycle as the voltage approaches the cut off setting.

That low current works really well with the BMS balancing shunts as it allow more time for them to work as they only by-pass a very small amount of current.

Most BMSs also have a hysteresis on their LV and HV settings, meaning if you set the HV to 4.10, the BMS will not enable again until the voltage is smaller than that according to your setting.

It may be hard to find a compromise between being able to use the cart after charging and the BMS bouncing on/off if the range is too small.

The way I like to set up the system is for the BMS never to reach either a LV or HV condition and if it does the Controller or charger needs to be re-adjusted.

[jeffro22]

Originally Posted by Sergio

It could work but there are a few factors to consider, the BMS LV and HV protection should be the last line of defense.

Lithium chargers drop the current very low near the end of the charge cycle as the voltage approaches the cut off setting.

That low current works really well with the BMS balancing shunts as it allow more time for them to work as they only by-pass a very small amount of current.

Most BMSs also have a hysteresis on their LV and HV settings, meaning if you set the HV to 4.10, the BMS will not enable again until the voltage is smaller than that according to your setting.

It may be hard to find a compromise between being able to use the cart after charging and the BMS bouncing on/off if the range is too small.

The way I like to set up the system is for the BMS never to reach either a LV or HV condition and if it does the Controller or charger needs to be re-adjusted.

Thanks for the detailed explanation. Still trying to get everything dialed in. I am trying to send you a pm but your inbox is full. Probably on purpose I am sure. Is there anyway I can contact you? I Have a specific question

[jeffro22]

finally got my new charger delivered. I had to try something different as I couldn't seem to get the charger most have been using. I found this one on Amazon for $53

I was able to adjust down voltage without any issues. I was never able to get my old YZpower 8a charger below 58V. I had been using it and tried to unplug around 57V and used the BMS as a backup as a HV disconnect.

Only issue I see with new charger is its only a 4A Charger so not sure if it will be quick enough but will try it out and see how it does.

I was able to adjust the voltage down to 57V with the small trim pot near the output wire. Went ahead and hooked it up and started to charge the pack. SHowed 4A on my bms until around 56.5 v, then it starts to go down to 2-3a and at 56.8 its down to 1a which I am asumming is correct function of the charger.

I am trying to maximize pack capacity, (without shortening the life too much)

is this an ideal setup to charge at 56.8-57 V?

[DaveTM]

I can't seem to find how big your leaf pack is. Is it a 7 module pack or 14?

If you have a 7 module pack and want to get as much out of it as you can, then the upper charge max of 57.0V (or 4.07 per cell) is a good number.

If you have a 14 module pack then the upper charge of 56.0 (or 4.0V per cell) would likely be "better" settings in order to stretch the life of your pack. As long as you have sufficient power to get whatever you want done.....the lower upper limit will extend the pack life.

The 4amp charging rate is going to make charge time longer. But...if that's not a real issue for you then it's not a big deal. But if you want to charge your pack faster, a higher amp charger will be needed.

[jeffro22]

I have a 14 module pack.

Was really wanting to maximize my range as much as
Possible. sometimes it’s just short trips but sometimes we take much longer trips Without much notice And I don’t won’t to run out of charge. Still trying to figure out range and maybe can adjust toys pack voltage down once I get it figured out.

Not sure the 4a will be quick enough charge for me though unless I start to charge over night which I really didn’t want to do. I guess I could use a timer on the plug as a safety back up

It looks like the other charger that most have been using from the amazon seller is available again so I’ll probably go ahead and get it and keep the 4a as a back up