How to reduce end of charge voltage on Battery Supports 12S 4A charger

I’ve heard some people were able to adjust the end of charge of these chargers, does anyone knows what components would be needed to get and adjustable end of charge voltage?

Post a picture please. If it’s one of the aluminum chargers, it should be fairly straightforward to get it open. Most of them have a trim pot on the output side for adjusting the output voltage.

Some can’t be changed. Open it. If you see blue pots you can do it. Usually the pot next to output is voltage and the one in the center is amperage. If you increase voltage you must lower amps. If you lower v you can increase amps. If you see 3 pots just ignore the third.


I’ll open my charger today and upload a picture of the internals.

I don’t understand why I’d have to increase the current when decreasing voltage, current is usually lowered automatically when the preset voltage is reached.

You are right. But afaik some chargers keep the amperage making it risky. So you must be careful on that. Edit:if you plan to lower the voltage you are safe no matter what. I just recall a guy that increased voltage and kept the amperage. Since the wats were over the límits of the charger it fried in a few minutes.

Here is the opened charger:

Seems to be a very similar one, I’ll hook a voltmeter and adjust the voltage al 50.00V, hope it works, I’ll report back.

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I remember reading somewhere (don’t ask me for source) that the bms does its balancing once it’s reached full charge.

so if your release voltage is 4.2, but your power supply only reaches, let’s say 4.1v, then wouldn’t that prevent the balancing function?

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I’m interested in knowing this as well…i would like to use a bms to charge my cells, but i would also like to undercharge my cells to increase cycle life. So i am also interested in in knowing if the bms will still do its job if the cells are only charged up to 4.1v.

with the bms you’re getting from me, I had the modules modified so their upper release voltage is 4.1v. so at 4.1v they’ll be balanced


The SuPower BMS starts balancing at 4.15V

I use a variable voltage 12S charger. Usually I only charge to 4.0~4.1V, but every few cycles I go to 4.20V to ensure that the cells get properly balanced

Permanently modifying your charger to a lower voltage might not be the best course of action. Maybe you could add an external knob for the voltage potentiometer so you can easily adjust output voltage

I was able to reduce the voltage from 50.9V (4.241V per pack) to 50.2V (4.183V per pack), so I’m expecting this to avoid the overcharge situation on braking at 100% SOC caused by the BMS shutting down all power to the VESCs.

As I’m unsure which is the other blue pot for current, but I’d like to reduce the charging current to 3A, 2A is too low and 4A is not mandatory for me, for this test I didn’t move current, I hope I don’t fry anything.

Regarding the BMS issue, I’m using one from AliExpress that has fully adjustable settings, so I’ve set mine to start balancing at 3.7v. it’ll waste a couple percent maybe, but it’ll always stay balanced even if I only ever half-charge it.

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Can you point us the link of the BMS you got?

My advice is get one of these, and charge any battery at whatever voltage and current below the max of your current charger Max output is 50V, which gets you max 4.16v/cell on 12s and you can set it to anything below that

Those suck for carrying your backpack

I already got this one, but you don’t want to carry it on your back pack on long trips :grinning:

I’ll try the SuPower charger today adjusted at 4.18v

Can you take a picture with a dollar bill besides it?

Still need to add tiny fan and mount ports

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Here’s my charge setup. 12S 4A CCCV charger with adjustable EOC. It can be adjusted from about 42V to 50.4V by turning the pot knob on the side. I only use 12S so this is perfect for me

I added a power meter to monitor voltage and current. The meter has the same input/outut as my board and the charger, so I can use the charger with or without the meter. Overall the system is very compact and portable. It is not much bigger or heavier than my 12S 2A brick charger.