60 Cell Panel vs 24v Bank MPPT and PWM UPDATE
UPDATE--results with MPPT posted 1 June. Got a chance to run this test today with no clouds but a slight haze up high so not quite 1000 insolation, showed as 8.93Isc vs rated 9.0, however that did ...
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As a follow-up to the question whether the 60 cell panel could work with an MPPT controller (OP was with a PWM) on a 24v battery bank, I was able to run a test today on that using my Eco-Worthy MPPT controller.
Insolation not so good with some overcast and some sun through that, panel temp 33C and Isc around 5 amps
The bank was full, in Float at 14.4v as 12v bank, so knocked that down with microwave on inverter for three minutes, disconnected solar, put batts in 24v mode, connected solar controller but not array yet, and set Absorb to 31v (max setting) and Float to 29v (max setting) By now battery holding at 25.6v ready to start, so connected array
I measured Vmp at the controller array terminals and took battery voltage and amps from the controller's display. I did not note the times, but the whole thing took under an hour since the batts were near full going in. Controller was in Bulk and doing MPPT-- So here is how it went with Vmp, V batt, Amps, output watts
29.0, 26.3, 6.0
29.8, 27.4, 5.01, 138
30.1, 27.7, 3.52
30.4, 28.7, 4.64
30.4, 29.3, 4.81, 142
30.7, 29.9, 4.66
31.0, 30.2, 4.52
31.1, 30.3, 4.04, 137
It stayed at 30.3 saw 30.4 but fell back to 30.3 again so stuck there, still; showing Bulk but not yet to the 31v Vabs setting, so
I disconnected solar, to let battery voltage fall to 27v while I reset Vabs to twice 14.8 at 29.6v and left Float at 29v setting, and reconnected solar.
Saw Vmp 31, Vbatt 29.6 for the blink of an eye and it went to Float (so not in MPPT now) with panel voltage now 35v Vbatt 28.3 and 0.5 amps (panel was showing 5.57 Isc as indication of insolation at the time.)
So the story that a 60 cell panel cannot charge a 24v bank is not true, but we still need to try that at 50C panel as the reason for low watts and not just todays cool panel but poor insolation (if that matters)
The key seems to be the MPPT finds an ever higher Vmp as Vbatt gets higher, so the amps keep coming.
Insolation not so good with some overcast and some sun through that, panel temp 33C and Isc around 5 amps
The bank was full, in Float at 14.4v as 12v bank, so knocked that down with microwave on inverter for three minutes, disconnected solar, put batts in 24v mode, connected solar controller but not array yet, and set Absorb to 31v (max setting) and Float to 29v (max setting) By now battery holding at 25.6v ready to start, so connected array
I measured Vmp at the controller array terminals and took battery voltage and amps from the controller's display. I did not note the times, but the whole thing took under an hour since the batts were near full going in. Controller was in Bulk and doing MPPT-- So here is how it went with Vmp, V batt, Amps, output watts
29.0, 26.3, 6.0
29.8, 27.4, 5.01, 138
30.1, 27.7, 3.52
30.4, 28.7, 4.64
30.4, 29.3, 4.81, 142
30.7, 29.9, 4.66
31.0, 30.2, 4.52
31.1, 30.3, 4.04, 137
It stayed at 30.3 saw 30.4 but fell back to 30.3 again so stuck there, still; showing Bulk but not yet to the 31v Vabs setting, so
I disconnected solar, to let battery voltage fall to 27v while I reset Vabs to twice 14.8 at 29.6v and left Float at 29v setting, and reconnected solar.
Saw Vmp 31, Vbatt 29.6 for the blink of an eye and it went to Float (so not in MPPT now) with panel voltage now 35v Vbatt 28.3 and 0.5 amps (panel was showing 5.57 Isc as indication of insolation at the time.)
So the story that a 60 cell panel cannot charge a 24v bank is not true, but we still need to try that at 50C panel as the reason for low watts and not just todays cool panel but poor insolation (if that matters)
The key seems to be the MPPT finds an ever higher Vmp as Vbatt gets higher, so the amps keep coming.
