Derating 24v Solar Panels?
I'm considering running two 250w/24v poly panels; tracked/pointed during spring/fall, and flat during the summer; thru the Tracer 3215BN 30a mppt controller. I can also get 200w/24v mono panels, local...
Forum Discussion
I didn't make a log Friday for the A/C test but I did check hourly and flat with room for ventilation the highs I saw was 45a from my three 250w panels in series. I've seen one hit 18.5a tracking but it wasn't 95F like it was Friday. I have seen higher numbers when it was cooler but not drastically higher.
So flat the two 250w panels will push a 30a controller but not as often as you will tracking. Even then not buy much and it is likely designed to clip anyways.
Another point is that unless you pull a big bank down a lot over night, or pull big loads mid day, you will likely be in float by the time you could see peak amps. For us overnight draw mid summer is at it's lowest with the least furnace run and shorter time between nightfall and bedtime when we run the lights and TV/SAT. Both the trailers 95 Ah grp 27 and the inverters 350 Ah 8-D are in float by night fall, the resting voltages the next morning are 12.5+ for the grp 27 and sometimes the healthy 8-D barely burned off it's over voltage. both batteries are in float before 9 am when I split the two 245w's up.
I have only tracked the 250w's a few times and then switched to flat so that I didn't become addicted to the power and believe me, it's addicting. I could point the twin 245's at the spot the sun would come up in and by the time the frost melted off I was getting 23 of the 34a peak they would do when the sun was higher. Even after running the coffee maker the two systems would have the 8-D in float rather quickly and I'd switch one over to the trailers battery for the rest of the day unless we ran the microwave.
Now then, for the rest of the day once the early morning haze burnt off and the sun got a bit higher, that 490w tracking was good for 32-34a until the sun got low again. That was both mid summer and Sept. numbers with average temps in the high 70'sf. As I said the 250w polys hits higher tracking than the 245w mono's.
So you are more likely to max out the controller tracking in cooler temps than flat in the heat.
So flat the two 250w panels will push a 30a controller but not as often as you will tracking. Even then not buy much and it is likely designed to clip anyways.
Another point is that unless you pull a big bank down a lot over night, or pull big loads mid day, you will likely be in float by the time you could see peak amps. For us overnight draw mid summer is at it's lowest with the least furnace run and shorter time between nightfall and bedtime when we run the lights and TV/SAT. Both the trailers 95 Ah grp 27 and the inverters 350 Ah 8-D are in float by night fall, the resting voltages the next morning are 12.5+ for the grp 27 and sometimes the healthy 8-D barely burned off it's over voltage. both batteries are in float before 9 am when I split the two 245w's up.
I have only tracked the 250w's a few times and then switched to flat so that I didn't become addicted to the power and believe me, it's addicting. I could point the twin 245's at the spot the sun would come up in and by the time the frost melted off I was getting 23 of the 34a peak they would do when the sun was higher. Even after running the coffee maker the two systems would have the 8-D in float rather quickly and I'd switch one over to the trailers battery for the rest of the day unless we ran the microwave.
Now then, for the rest of the day once the early morning haze burnt off and the sun got a bit higher, that 490w tracking was good for 32-34a until the sun got low again. That was both mid summer and Sept. numbers with average temps in the high 70'sf. As I said the 250w polys hits higher tracking than the 245w mono's.
So you are more likely to max out the controller tracking in cooler temps than flat in the heat.
