Solar Panel Mod Controller

I had gathered the 60 watt capacity for the panel from somewhere upthread (or in one of the other similar threads), but I had never stumbled on a spec in the repair manual itself. Turns out it was in there waiting for me to find it, among the "operation precautions" at the front of the solar ventilation diagnosis section:



... so, maybe up to 80 watts tops, depending on exactly which V and I numbers Toyota gave there. Eleven years ago when it was made, anyway.

I think this buck converter is still probably not going to go poof in the near future, but I may continue to keep my eyes open for a version that does constant-current mode with the sensing on the high side.

All in all, a pretty satisfying mod. After less than a week of sitting (and not all of it sunny), my aux battery now happily sits at 12.7 V after dark, which I grew up thinking was a pretty decently charged lead-acid battery (even though some higher numbers get bandied about here). That's a lot better than it was after a year of COVID and before this mod. The charge voltage in good sun stays right at 13.1 and doesn't fool the low-voltage disconnect into thinking the car is ready.

A pleasant thought is that a day in decent sun with this could nearly or completely offset the load of a small efficient fridge.

 

Not necessarily. If those figures are Isc (short circuit current), and Voc (open circuit voltage), as PV modules are commonly specified, then it cannot be an 80 watt unit. PV max power is always less than the product of those two figures, 60 watts sounds reasonable.

OTOH, if those are the Imp and Vmp at the maximum power point, then it could be an 80 watt unit. But that current and voltage are usually buried below the topline specs. The safety folks focus on Isc and Voc.

Here is a representative modern PV I-V curve. Back in the old days, the curve didn't fill the rectangle nearly as well, so I dropped much faster with increasing V.

 

I'm sure your analysis is closer to correct. I just simplemindedly multiplied the two numbers Toyota supplied, just to get a quick upper bound on what the power could be.

Reworded the earlier post slightly.

 

The maximum output of my solar module was 63W so far.

Posted via the PriusChat mobile app.

 

Noticed robust ventilation action around midday today, while supplying 13.1 V to the battery at the same time. Now that's what I'm talkin' 'bout.