Need basic help understanding a shunt

[TECH_GEEK10]

I have a 48v charger that I modded to have a proper charging voltage for a 36v lithium ion pack. The drop in the output voltage seems to have messed up how much current the charger thinks it is outputting and how much is actually put out. The amount of current output that is actually supplied is about ~0.8A at 36v peak, while the charger is rated for 180Watts / "3Amps at 48v" My guess is that it is sensing a "36v-type" voltage drop across "48v-type" voltage drop circuitry.


My question is do I increase or decrease resistance of the shunt to get the charger to not go into over current cutoff when it is supplying 1/2 an amp.

 

[dnmun]

none of this makes sense. do you have a voltmeter? what battery do you have? why use a 48V charger for a 36V battery?

 

[Gregory]

Decrease the resistance of the shunt by adding a SMALL amount of solder. Re-measure the charge current (not at the end of charge in CV mode where current drops off), repeat.

If the charger blows up you added too much

edit: Beware if you ever turn the voltage back up to 48V, your power will be 30% higher and will cause problems

 

[mybike]

Not the right way to do this
Get a 48v charger with a proper charge amperage it be safer or it will cost you a lot more if things go wrong.