# What (actual) voltage do your chargers run at?

Or what voltage does your pack get charged up to (immediately after charging stops)?

Not the voltage it’s supposed to charge to, e.g., 50.4V for 12S, but the actual voltage you get from your charger or power supply.

I’m working on some BMS stuff and knowing if a lot of charger voltages are a bit too high or a bit too low would help me out. Thanks!

5 Likes

All the ones I own are within 0.1V of the rated voltage.
Maximum charge current on the other hand varies more.

4 Likes

I charge my 12s10p Tesla Model 3 pack with no BMS, with a YZ-Power 6A charger. Since there’s no BMS in the circuit, I am relying entirely on the charger to cut off at the right time. Every time I fully charge my battery, it has come to a resting voltage of exactly 50.4V (according to my VESC). I have not measured what the voltage of the pack is in the instant that the charger cuts off.

3 Likes

My 12s charger is set to 50.4v

My 10s charger is set to 42v

Both, charge packs to full potential voltage

1 Like

My chargers are 50.7v at 12s

1 Like

2A charger = 42.5v measured via multimeter. My shuntmeter only shows 42.2v interestingly enough. (bms stops at 41.8v ish)
5A charger = 41.77v (lowered via Pot. Not sure its original voltag)
12A 12s charger = 50.2Xv (Lowered via Pot from 50.5v)

2 Likes

Most chargers have a pot you can adjust inside to get the voltage you want. I generaly adjust all my personal chargers to 50.4 sometimes 50v so after charge sag takes its toll the battery rests around 4.17-4.18v per cell.

5 Likes

I have a cheap voltmeter inline between my charger and board. It shows ~0.5v higher than the battery voltage shows on from BT telemetry. It seems to slowly raise voltage as the battery charges.

1 Like

That’s another issue clouding things up…less-than-great accuracy for voltage reporting by some devices.

2 Likes

You know, like a psychopath.

@Battery_Mooch most of my chargers are within 0.1v. I think the make of BMS makes a bigger difference in how closely the end of charge level lands for me.

7 Likes

[lipo charger]

I have no defense.

5 Likes

And I’d add charger as well. I’ve got a 1.5a 12s laptop charger that can almost hit 50.4v. Hits usually around 49v. But if I use my 4.5a charger (adjustable voltages and amps. Paid \$80 for it) and its hit 50.4v all day long. All done through an LLT smart bms

1 Like

Agreed, for me as well.
I’m trying to separate out the charger voltages from the actions of the BMS for that very reason.

1 Like

My Daly BMS stops at 4.15/cell when the light turns green. SOMETIMES it goes all the way to 4.2

1 Like

Yz power-450
Charger claims 50.4V output
Meter claims 50.5V

Tangsfire TS-84W-420200
Charger claims 42.0V
Meter claims 42.2V

Leafboard JY 252200
Charger claims 25.2V
Meter claims 25.5V

Hiboy FCA133-42105
Charger claims 42V
Meter claims 42.5V

This is where it gets weird. I’ve had 3 different 10s/42V evolve brand chargers (2 x 4A and 1x 2A) and they all behave like this:

I have verified that the meter in pictures measures ± 0.1V from my mid level Tenma portable multimeter.

3 Likes

Hmm…I wonder if the charger turns on its output, “looks” for a pack, and if it doesn’t start to deliver current then it turns off and tries again a short time later. I can’t think of why it would do that though.

I’m assuming the charger is stable without being connected to a pack and isn’t just sitting there oscillating wildly.

2 Likes

I agree with the second part certainly.

One point I should have added is that the evolve chargers all seemed to stop charging my board at different points… Generally around 41.2V. When I say “stop charging”, of course I mean led light turned green

I always assumed that was when the electrical elves began balancing the electrons between my p groups until I made that meter and saw it sometimes turned the led green at 41V and sometimes 42.0V.

@b264 also has experienced some of the evolve charger weirdness iirc.

2 Likes

Yes those Evolve / MDA / enertion / Metroboard chargers are nice, they will go to 42.0V but then cut off and not turn back on until the voltage falls to like 40.5V - ish, if I recall. Some of them cut at 41.5V.

2 Likes

It is normal for the green and red light to only represent the charge current dropping below the threshold. It is extremely rare that the light changing colour is terminating the charge.

3 things I think could be are happening hear

A. It could be a very cheep dirty PWM supply

B. It could be trying to ramp up the voltage because the amps draw is so low but detecting the battery is not holding it and restarting the cycle.

C. It might have an over volte protective devise built in. Ramps up the voltage detecting an over volt because the load is so small and cutting the charge then the over volt safety devise resets as voltage is then below threashold and cycle repeats.

Personally I think A or C is most likely

1 Like