Hi,
I am building a rather unconventional engine driven generator to charge a 48V 300Ah LiFePO4 battery bank. The generator will output three phase power at at 70 Vrms line-to-line, 135 Hz. This 3ph AC output will be rectified, to give about 90Vdc with output power of 5.5kW.
The genset is a Kubota D722 3cyl. diesel engine coupled to an EM61 Nissan Leaf motor (8 pole IPM permanent magnet motor). I have fabricated a custom flywheel housing and flexible coupling, and mechanically it is working well.
I have already in my system an Easysolar II GX 5kVA with 250V / 100A MPPT charge controller. I am looking at connecting the DC output from the rectifier to the PV input to the charge controller, and using the generator to charge the batteries for 1 - 2 hours per day in winter.
I have read several threads in the forum that suggest a similar thing has been done before with output from micro hydro generators, which tells me that it is at least possible. My main concerns are:
- Transient voltage spikes due to switching of inductive source (generator). Propose to address this with a bank of varistors (Panasonic ERZV20D151).
- Output ripple from the rectifier at approximately 800Hz, plus higher frequency harmonics from the rectifier. How will this affect the charge controller, for example could it cause too high ripple current in the input filter? This is probably my main concern. Obviously I don't want to blow up my charge controller. So I thought about adding a capacitor bank to the rectifier, but how large to make it, and will it have to cope with some high frequency ripple current from the charge controller as well?
You may be wondering why I am bothering with this project. It's interesting for me, and I already have the engine and Leaf motor. Also the the electrical efficiency of the Leaf motor is very good compared with a typical brushed single phase alternator (perhaps 90% vs 60-70%).
