02-23-2024, 10:42 AM
I thought you were the expert? You should know that the minimum peak sunlight is 3 hours in VT...and yes, you can harvest a lot of power in the winter. The more calendar days away from the minimum, the more energy you can harvest.
He's a retired veteran who drives about 8 miles a day (to and from breakfast). Once or twice a week, he makes a market run and medical appointments. The battery in his Leaf is in bad shape, fully charged, it might deliver 50-60 miles of range (he did not pay very much for it).
The panels he bought were 10 year old units rated at 220 watts. When we set them up, they were producing about 150 watts each. They came with micro-inverters that were not working well on the reduced output. We tried pairing a single inverter with two panels. This was plenty enough power for a level 1 charger. The original system did not have a battery buffer, so the charger had to deal with fluctuating power (problematic). He eventually acquired an OEM charger from a salvage yard. The Leaf OEM charger is very well designed and handles poor-quality power nicely. On a good day (Sept/Oct) it was possible to harvest ~4kwh of power (10-15 miles of driving).
We redesigned the system about three years ago to use an Inverter/charger and 5kwh of prismatic Lifepo4 cells (recycled cells). The MPPT charger harvests a lot more power than the old micro-inverters for some reason. We reconfigured the panels into ~120v strings, which likely helped the MPPT charger do its thing.
We added a BMS with two relay outputs set to trip at roughly 2 and 3 kwh remaining in the pack (he tweaks this constantly because he has nothing better to do). The system turns the car charger off at the 2kwh level and back on at 3 (~1kwh hysteresis). The idea is to retain a small buffer to operate things in the house while dumping most of the power into the car. There is a bypass switch that you hit on rainy days so all the power is put into the battery bank.
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