Question about: ANT BMS

I just noticed that my ANT BMS is still giving (leaking?) some voltage (and low milliamps) out when turned off!
Anyone here with an ANT BMS who can check if it’s doing the same?

But all bms do the same, no? As I understood you should have some cut-off switch on bms

The BMS has an on / off switch (pulse)

When I give it a short push (pulse) it turns on, and the BMS is turned on, LED’s and Bluetooth turn on, and I have +50 volts on the output.

When I give a long push (about 6 seconds) the BMS turns off, LED’s and Bluetooth turn off on the BMS.

When I measure the voltage on the output I still get some volts.
I thought that it was some capacitors holding voltage, however I can power a external LED on it, and it stays on. Even after one day of not turning the BMS on.

The FETs in the BMS are likely to be leaking, every FET does it to some level. Some manufacturers / designers put a resistive load on the output that overrules the leakage current and make the output as close to 0V as possible. But if the designer of the BMS didn’t make this a priority it is probably omitted, then you can do it yourself. Depending on the leakage you could experiment with like 10kOhms over the output.

1 Like

I see. I’m going to give this a try.
Thank you.

It’s the same for me with the ICGOGOGO antBMS, switched off I have 13 volts output.

1 Like

Thank you for the update.

The problem is normal on a battery not connected to a load ( ESC / UBEC …) as soon as you connect a load to the output of your battery the voltage drops to 0 volts.
This is a residual voltage.

1 Like

Thank you for the update.
Problem was (for me) that I had a LED as indicator that the battery (BMS) was on/off.
The “leaking” voltage was causing the LED to be still burning (more like glowing) when the BMS was in off position.

Hi! I’m thinking of purchasing an ANT BMS for charging and discharging. What is the controller? Is it necessary?

Controller = ESC
20 characters.


I am planning on using the Smart Ant BMS 300A with a 12s12p 18650 battery.
Regarding the charger voltage, I have an e-bike 54.6V charger, will this work or is the voltage too high?
Do I need a 50.4V?

I have the same charger for charging the e-scooter, for charging 13s. So this charger is not suitable for charging a 12s battery. It’s easy to make a sort of adapter to reduce this voltage by about 4.2V, just a few components and a bit of electronics knowledge.

The smarter thing to do is to upsize the battery to 13s12p, which will bring some major advantages. One is that it will increase the maximum speed of the e-foil. That’s why most builders here use 14s, some even more (15s, 16s, …). I only plan on 13s, but I will get the speed equivalent to a 14s (or 15s) battery with a propeller I design myself.

Hi Kian, What happens with the ANT BMS when you hold the switch down continuously - does the BMS stay on then turn off when the switch is released?

Or does cycle on and off?

Or does it stay on when you turn off the switch needing another long press to turn it off.

I want to build a microcontroller controller circuit to turn the BMS on with a Hall effect sensor + magnet, with audible feedback, water sensors etc , but am still waiting for the BMS to arrive.


It’s a lont time ago, but what I remember is that it turned off (and stayed off even when keeping the button pressed).
When released, and pressed again it turned on again.

I still have the battery with BMS, and will test tomorrow.
If it is different as I described above, than I will let you know.

1 Like