I plan to use a RS Smart Solar to charge a 48V battery system from power out of a 400V battery.
As I read the RS is limiting the charge current by rising the MPPT voltage to reduce the power.
is it possible to use the RS this way, anyone who did it already?
Thank you,
Juergen
It’s a MPPT solar charge controller, everything else is not supported and out of warranty.
At some point, the MPPT will want to scan for the maximum power point.
That rising of the voltage you’ve read about is done by drawing less current. But when it will want to scan the entire IV curve, at some moment, the MPPT will try exactly the opposite, e.g. to source as much current as possible from the PV “panel” (read 400V battery).
The MPPT has a maximum short circuit current of xx Amps for its input(s).
And the MPPT expects that the “panel” to not supply more than that xx Amps.
Imagine the “surprise” the MPPT will have when it will try to source more and more amps and the 400V battery will give them…
Up until the magic smoke will came out… 
It’s never a good idea to put a power source on the MPPT input, if the power source can supply more than the MPPT input short circuit current.
And the 400V battery for sure can.
I’ve tried below to exemplify the difference in behavior between a PV panel and a power source.
See how the power source has a totally opposite behavior than a panel. Red line is the power source.
The more you try to reduce the power source voltage, the more it will oppose and increase it’s sourced current.
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