Increase slightly charger voltage

[dnmun]

wait and see if the BMS will make it balance. it will take a long time because the cells you have down around 4.08V are 10% away from full charge so it will take a long time sitting at 42V to fill them up. just "SET IT AND FORGET IT".

you can measure the charger voltage on the battery when it is fully charged.

 

[cwah]

Actually I've just checked the charger....

And voltage is set to... 41.3V!!!!!

That's why the BMS never balanced the cells!!!

What's the simplest way to increase it to 42V?

 

[friendly1uk]

Oh, I nearly missed it. Covered in construction adhesive on the right hand of this picture lays a 10mm* blue trim pot. Fixed to ensure it does not move.

I wouldn't be able to help myself.

Edit: It's board label is simply VR. Not VR3 or VR4. Just VR. Indicating it is the only one, if you follow convention.

P.S Is that toasted circuitboard under the device on the main heatsink not far from the relay.

Edit some more... That VR is mighty lonesome over there. What is 08:33 printed on the board? Could it be a 10 turn?

 

[cwah]

I don't know what is 8:33. Is the trim pot the blue one just on the right of this 8:33 label?

 

[cwah]

And where do i get this white stuff to prevent things from moving?

 

[cwah]

I removed the white stuff on the blue pot next to 8:33.

I moved it a bit and nothing seem to happen.

Now when I check output voltage it doesn't show anything??? Am I missing something? Before it indicated 41.3v and now nothing???

Is it because battery was connected before? Does it need load to trigger the voltage or am I missing something?

 

[dnmun]

yes, there is a relay on the output. you can see it right there in front of you.

you will not be able to measure voltage on the plug. if you can find the voltage in front of the relay that will let you know what voltage the charger is set too.

if you are measuring the voltage on the battery before it is fully charged you are not measuring the charger final voltage, you are measuring the battery voltage at that state of charge.

please just leave it charging, don't fix it. just leave it charging.

 

[cwah]

But I've already moved the blue trim pot next to 8:33 so I don't know to what voltage it's set up now.

I decided to modify the charger because the light turned green so charge stopped.

Is the relay the one written 220v AC to 12v DC?

 

[cwah]

Can anyone help on how I can check the voltage? I tried to put my multimeter everywhere but nothing displays

 

[cwah]

Up

 

[dnmun]

it should be present on the front end of the relay.

 

[cwah]

I am not too sure how to find the front end of the relay.

I've completely opened up the charger:

I suppose it should be somehow somewhere here?

thanks for all

 

[boo]

You can measure the voltage across R7 or R6. I think those are dummy loads for the output.

 

[dnmun]

not dummy loads, they drain the charge off the output caps when the charger is turned off so it doesn't tickle you when you stick your tongue on the charger output plug.

 

[cwah]

Thanks guys. I've set it to 42.3V should be good for balancing now

 

[boo]

Thanks guys. I've set it to 42.3V should be good for balancing now

That's good news.

not dummy loads, they drain the charge off the output caps when the charger is turned off so it doesn't tickle you when you stick your tongue on the charger output plug.

looking on the board again, i bet they are... if the charger is turned off, so the output relay - means no voltage on the output plug.
Some SMPS needs small dummy load to stabilize the output at no load condition specially those PWM ICs with burst mode function. At burst mode, the output ripple will be high (something like a sawtooth waveform). So to avoid high ripple, do not go into burst mode by adding dummy.

 

[cwah]

Yeah finally ahah thanks

 

[dnmun]

the drain down resistors on the output caps is usually about 5kR.

 

[boo]

Nah. Output voltage is less than 60Vdc so its considered an SELV. No need to discharge the output caps.
Its not like those X-caps on the AC line that bleeder resistors are needed to drain the voltage to a safe level after turn-off.