diy solar

diy solar

400V/48V 3-phase charger or PSU with active PFC and approx. 5kW


New Member
Nov 15, 2021
I am currently looking into options to have an independent backup charging solution @ 3...5kW for a grid-tied solar/battery storage system. The backup generator should be sized to charge from 30 to 80% SoC in a couple of hours at maximum fuel efficiency. Therefore it should be running at it's sweet spot somewhere between 60-75% of load and should not have to provide lots of reactive power. The charger therefore needs to have a good efficiency and a good PFC. I probably do not need a fancy charger with lots of phases, a constant voltage and limited currrent PSU should be fine in that SoC region. However, some kind of soft start is probably mandatory to avoid stalling the generator instantly while starting the charge.

Options that I am currently aware of:
* Meanwell RST-5000-48 PSU: got quite expensive recently and hard to source, soft start needs externally provided current set point, efficiency not outstanding
* 3 individual Chinese 230V chargers: would need external protection circuitry in case of single phase failure - efficiency and real-world cos phi unknown, (synchonized) soft start probably tricky
* dual-input combined inverter/chargers (Quattros instead of Multiplus)

The third options seems to be by far the easiest one - but there seems to be a problem in the combination of ESS and using weak generators in input 2. Additionally, a purely DC-coupled backup charging solution seems to be more modular and easier to scale in case of need.

Any real-word experiences out there?