Dropping the Voltage on my Charger

drutledge

drutledge

10 W
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Mar 28, 2011
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Washington, DC
I have a couple of the generic Chinese chargers (probably 'BMS Battery' Chargers if I recall correctly) that I ordered years ago that produce about 87V on one and 65V on the other. I'd like to drop these down to about 49V and 32V for other purposes; I hate to waste two good chargers!

Anyway, I've turned down VR2 on each of these but they don't come down nearly enough, maybe to 83V and 61V respectively. Can I possibly do that by using a different variable resistor? If so what would you recommend?

Picture is of a basic charger like mine but not exactly mine. The layouts on them seem to vary.

659a2s.jpg
 
Hey Brother thanks for the a A123 20ah build 24s now at 1,022 cycles at 90amps now. Bulk charge to 3.5v . Would love to balance but all at 3.48- 3.52v
 
The only experience I have with a 48 volt ping or. charger probably a Kingpin at 59-point Volts.
So used the Ping kingpan 48v charger turned it up to 73volt it blow. Replaced blown cap in Ping burnt in fire charger with a 100v cap and still works went watched and tested or needs to be watched or looked aftered closely. Never never don't ever walk away never idiot .
Remember it's an experiment and we watch the experiment for something to happen when were watching .
 
If walking away I unplugged it if I walk away from my battery charging . Or if experimenting with chargers charging and per cell voltage sit around and learn watch don't ever overcharge per cell voltage.
 
Haha. Just wanted to open the very same thread. I have two of those kingpan chargerd that refuse to go below 62v. They originally were sold as 72v chargers and work fine as such.
But i'd like to have a spare charger for my 12s lipo pack so i need to reduce voltage to 50.4v.
Maybe amyone found a way to do so.
 
999zip999 said:
After the 100v cap I have it turned up to 84volts.. It just a back up I don't trust.
Click to expand...
we want to find a way to turn it DOWN. this is a totally different thing. exploding caps when using the thing over their rated voltage is a logical consequence.
the question is: why can't the voltage not be reduced further? what parts need to be changed to acchieve what the OP and i want?
 
It seems that on the one charger I have that as the trimpot is turned to read higher ohms the voltage drops. Right now it's working with a 5K trimpot. I've ordered some others, 10K etc. So we'll see what happens with those installed. I suppose you could add another resistor in line to see if that works as well. I'm not an electronics guys so I was hoping someone here could quickly chime in whether or not that was the right road to go down. I was also wondering is somehow lowering the output voltage might 'stress' some of the other components somehow.
 
Answering my own question here for the benefit of others: I swapped out a 5K trimpot for a 10K multi turn rotary pot and got the voltage down to 28V on what was, I think, originally a 60.5V charger. The 5K trimpot only got it down to about 38V. Higher ohms = lower voltages on this type of charger.
 
drutledge said:
Anyway, I've turned down VR2 on each of these but they don't come down nearly enough, maybe to 83V and 61V respectively. Can I possibly do that by using a different variable resistor? If so what would you recommend?
Click to expand...
No. There will be one or two other resistors around VR2 to create the divider that sets the voltage. You will have to change them. No way to know what to change them to unless you know:

1) what the divider circuit looks like and what the values are now
2) the reference voltage in the regulator
 
billvon said:
No. There will be one or two other resistors around VR2 to create the divider that sets the voltage. You will have to change them.
Click to expand...

Well, as I stated in my last post, I swapped out the 5K and put in a 10K variable and went from a low of about 38V to 28V. The high end of each is still 90V+. Maybe I got lucky.
 
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