Senior Member
Joined: 11/12/2020
Location: CanadaPosts: 138
| Posted: 11:44pm 09 Jan 2025 |
^Thanks Otto. I think the panels themselves work well, but with reduced sunlight and snow and clouds, the output can be considerably less.
So after deciding to mount my solar panels in groups of 3, I figured I needed to buy or build a MPPT controller. Fortunately there are more low end MPPT commercial units around which support 72v systems. Amazon carry a brand called Solafans which was the lowest cost and had reasonable ratings. They cleared out some lower current versions, so I bought one.
I did some testing and found (with my tools anyway) that the efficiency is pretty good. Not sure how close you can run this to 55A, but I really only need 30.
The power part of the MPPT uses a very similar circuit to Poida's thread, except it uses 3 inductors and for each inductor, one dual diode and mosfet. I thought at first that the unit was only using one inductor at lower power levels, but the board had a conformal coating, I I was just not pressing hard enough with the scope probe. When I pressed hard, I managed to short the ground tab on the probe, to one of the switching transistor/diodes and managed to vaporize the leads. Fortunately it only killed the Mosfet driver chip, and I happened to have one in a bad inverter on hand.
The unit has a relay on the input and output, so the output relay did not energize, due to the circuit fault.
So thus far this month, I have averaged 2.8Kw per day into the battery with a maximum of 4.69kw today. It was a perfect day, being very cold with very few clouds.
At this time of year, this is enough power to run my gas furnace blower motor. So I need an utility powered battery charger which I can run at night.