Hi,
I'm building an engine driven generator to charge a 48V 300Ah LiFePO4 battery bank. The generator will output three phase power at 90 Vac line-to-line, 170 Hz. Electrical output power will be about 10kW at best efficiency point. I'm looking at options for how best to use this output to charge my battery bank. I am in fact a mechanical engineer but have some knowledge of electronics at a hobbyist level. From my researches on this subject it looks as though a controlled rectifier / buck converter is what I need - I haven't been able to find an off-the-shelf solution thus far, so am I looking at something custom. Can those with better knowledge on this subject give me a push in the right direction please.

 

since each battery chemistry is different, the best way is to use charger designed for specific chemistry.
some info and 1P charger (30A) can be found at:
https://www.canbat.com/how-to-charg...cial,compatible with Canbat lithium batteries.

 

Every time You go up or down in Voltage, You will loose ~20 to ~30% of the total power available, or more.

Find a standard commercially available Charger designed specifically for
your Battery-Bank-Voltage and Current requirements,
then get a Generator that will supply an Input-Voltage that the Charger is compatible with.

It will be less than half the cost of a DIY solution.

If You just want to see if You can do it,
then You need to supply EVERY DETAIL of your Battery-Bank,
and what it provides Power to,
and how long you expect the Charging time to be,
and whether or not the Charger will be expected to drive your full-Load
while simultaneously Charging the Battery-Bank.
.
.
.

 

I am already committed to this direction with the generator. Power conversion efficiency of 90% plus should be achievable I think. I already have the engine (3cyl Kubota D722) and the alternator (Nissan EM61 PMSM). I already have the 16s lithium battery bank and the BMS for the battery bank. I will have a PLC monitoring battery SOC and regulating charging voltage. The charging voltage range is 32 - 58V for the pack.

 

Every time You go up or down in Voltage, You will loose ~20 to ~30% of the total power available, or more.

What are you talking about? Referring to DC-DC conversion? Transformers? 70-80% efficiency is uncommonly horrible for either.

 

Usually alternators are regulated by the rotor winding voltage, your alternator is a permanent magnet synchronous motor from a Nissan leaf car??

 

is that 90Vac peak to peak or rms?
I'd probably start looking into the rectifiers for big vfds, to get it from ac to dc. As far as the controls to manage the battery charging, thats a bunch of amps above what id like to play with. Maybe look into forklift battery chargers. Most are fully switch mode power supplies nowadays, so you may be able to find one that will accept the weird 3 phase input power you have with no modification. Thats just my two cents.

 

Six pulse rectifier with Thyristors and a choke would be the old-fashioned way to do it, and probably still the most reliable.

 

can You drive the Leaf’s inverter in regen mode? A crunched Leaf showed up in our yard and It sounds like the customer is going to attempt some DIY project.