Solar Charge Controller

ktmrfs wrote:

BFL13 wrote:
Doesn't have to be "hot climate" to lose amps with MPPT due to panel temperature over PWM in same situation.

Here, east side of Vancouver Island, by the sea, cool breezes, with 230w tilted up (no heat trap underneath) and MPPT, ambient at 16C, I was getting 15.5a to battery, panel temp was 44C. (measured with IR looking up at white part under a tilted up panel)

At ambient 25C nice summer day for here, panel temp now 51C and amps are 13.5 instead of 15.5. (PWM would be 14.5) So we have gone from being 1 amp more than PWM in the Spring to being 1 amp below PWM in Summer.

Some solar info dug up by Googling, says you lose about 10% with MPPT when panel temp is 50C, so my 13.5 vs 15.5 comes out in ballpark where 2/15.5 = 13%

Hate to think what the results would be in a "hot climate" in the summer :)

BTW, the panel specs are for panel temp of 25C standard test conditions. How can they get the panel temp that low? Ambient would be near freezing to get panel temp 25C it seems.

BFL:

I think from your posts on measurements, your using the Trimetric conroller readout for current. That's fine for MPPT controller, since the output is DC. for a PWM controller, the output is usually a pulsed Current (Pulse width modulation). That poses a problem getting an accurate current reading with the trimetric. Been there, done that. The issue is your using a DC current meter to measure and AC current. The trimetric will measure the peak current, NOT the RMS current. To really compare the two controllers you would need to measure the output of the PWM controller with a true RMS current probe, which the trimetric is not. I ran into this early on and the trimetric in my case, with a morningstar PWM controller read a noticeably higher current than measuring with a true RMS current probe.

True, the MPPT output current dropped with temperature, but it still outperformed the PWM, even at 100F, but by then the difference was only a few %.

I used my digital multimeter for Isc at the panels, the ammeter read-outs on the Solar30 (PWM) and Eco-worthy (MPPT) and the Trimetric at various times. I cross-checked to see if amps were out of calibration, got same amps. No idea about RMS it is all DC amps. I don't think the multi is RMS, reads low on MSW inverter output. So the others must not be either since the amps match.

I won't have final proof of what I am seeing until ambients get down to 16C again, and amps come back up to what they were in Spring or not. If we are still using solar then. Summer is nearly over--sob!