asked
I would like to charge a 24 volt battery direct from a 48v battery. Can I use a solar charge controller such as the MPPT 75/15 to do this
Yes you could do that, I have not done this, but ion theory it should be fine from my point of view.
if you did it would allow the mppt unit to out put upto its max current transfer, I would limit that down to say 50% for a while just to see how it went heat wise but you could slowly ramp that up as you got more comfortable with heat, 50% is way on the safe side
@tristarboats I agree with @Paul B you will need to be careful not to exceed the input current limit of your mppt.
You should use a step down converter or better a B2B charger for that. Using an MPPT is not a good idea because, well ... it tracks the MPP
By doing this I have blown up an MPPT from another manufacturer some years ago. I also thought this would work since it was officially allowed to overpower the PV generator. But it did not.
Thanks, both. That is a good point. I have never had to adjust the parameters of a charge controller before. Can I do this through the Victron connect app via bluetooth.
Careful. The BlueSolar chargers specify a maximum PV short circuit current. In some circumstances, the MPPT will intentionally shut down and short circuit the PV input. It's a safe thing to do when connected to a PV panel but likely the last thing it would ever do if connected to a battery on its input.
I have a dead BlueSolar MPPT here because I had exceeded the maximum PV short circuit current. All worked fine during normal operation but, after a firmware upgrade, it went into that shutdown mode and the panels cooked it.
This is not supported, and fully on your own risk!
-if- you try this, please put a fast blowing fuse / breaker in front of the MPPT with a rating below the max current rating of the MPPT, that would make it a little bit less unsafe.
