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 ...
Forum Discussion
Before I switched to 24v, the batteries were full in Float at 14.4v and with the sun behind the overcast, panel temp was 33C and Isc was about 5 amps and Voc was 34.1, which ISTR was posted earlier in this thread. Panel temp could have risen a bit during the times the sun got brighter (the cloud cover varied how much it dimmed the sun as the test went on), I didn't measure that panel temp again.
As soon as the controller went from Bulk to Float, panel voltage taken at the controller array terminals jumped from 31 to 35.
At the end when battery voltage got stuck at 30.3, panel voltage was stuck at 31.1 and amps to the battery was 4.04a, panel Isc was a bit higher at 4.37 according to the controller's "demo" program.
The panel is always affected by both cell temperature and insolation in some combo, so it is hard to match the spec IV curves for each with any real life combo you get.
the spec sheet does have one combo, for NOCT 45C and 800 insolation, but that is just one possible combo. They also have the STC combo of 25C and 1000 listed. I am guessing yesterday it was say 35C and 600, but on sunny days here it is more often like 45C and 1000.
Last summer when my amps were lower than I liked, it was more 50C and 1000. I want to see if 24-24 can do better than that at 50C-1000, but first I needed to see if the 60 cell panel could even recharge the bank at 45C-1000. It can, so now we wait for a heat wave to try it at 50C-1000.
So that is two possible wrinkles out of the way
1. It was questioned (By CA Traveller?) whether a 60 cell panel could do that at all, and
2. could a PWM do it but not an MPPT due to panel voltage being limited to Vmp by the MPPT
A side note on the Eco-worthy where its setting for the absorption stage (done in Float) is lower than to get to the "real Vabs" This means in order to be able to recharge the 24v bank, the higherst you can set it to for the absorption stage is 29v (like 14.5v )so that might affect the definition of "being able to recharge the bank" if you really need 14.8 (29.6)
the Solar30 does not have that "issue" so it can be left to do the absorption stage at 29.6 or even 30.
However, llast summer I found my 6s were happy with getting to 14.8 and then dropping to 14.4 the rest of the day and did get to full baseline SG before dark. They also didn't need any equalizing, being already at full SG. So I would expect the same batteries as 24v would do ok getting to 29.6 and then dropping to 29 for the rest of the day if I did that 24-24 with the Eco-W.
It is a lot easier to swap back to 12v configuration once the batts are recharged in the afternoon, when you don't have to swap controllers too, so I would rather use the Eco-W for both 24-12 and 24-24 if I adopted that routine. Needs that test at 50C panel before deciding if worth the hassle.
As soon as the controller went from Bulk to Float, panel voltage taken at the controller array terminals jumped from 31 to 35.
At the end when battery voltage got stuck at 30.3, panel voltage was stuck at 31.1 and amps to the battery was 4.04a, panel Isc was a bit higher at 4.37 according to the controller's "demo" program.
The panel is always affected by both cell temperature and insolation in some combo, so it is hard to match the spec IV curves for each with any real life combo you get.
the spec sheet does have one combo, for NOCT 45C and 800 insolation, but that is just one possible combo. They also have the STC combo of 25C and 1000 listed. I am guessing yesterday it was say 35C and 600, but on sunny days here it is more often like 45C and 1000.
Last summer when my amps were lower than I liked, it was more 50C and 1000. I want to see if 24-24 can do better than that at 50C-1000, but first I needed to see if the 60 cell panel could even recharge the bank at 45C-1000. It can, so now we wait for a heat wave to try it at 50C-1000.
So that is two possible wrinkles out of the way
1. It was questioned (By CA Traveller?) whether a 60 cell panel could do that at all, and
2. could a PWM do it but not an MPPT due to panel voltage being limited to Vmp by the MPPT
A side note on the Eco-worthy where its setting for the absorption stage (done in Float) is lower than to get to the "real Vabs" This means in order to be able to recharge the 24v bank, the higherst you can set it to for the absorption stage is 29v (like 14.5v )so that might affect the definition of "being able to recharge the bank" if you really need 14.8 (29.6)
the Solar30 does not have that "issue" so it can be left to do the absorption stage at 29.6 or even 30.
However, llast summer I found my 6s were happy with getting to 14.8 and then dropping to 14.4 the rest of the day and did get to full baseline SG before dark. They also didn't need any equalizing, being already at full SG. So I would expect the same batteries as 24v would do ok getting to 29.6 and then dropping to 29 for the rest of the day if I did that 24-24 with the Eco-W.
It is a lot easier to swap back to 12v configuration once the batts are recharged in the afternoon, when you don't have to swap controllers too, so I would rather use the Eco-W for both 24-12 and 24-24 if I adopted that routine. Needs that test at 50C panel before deciding if worth the hassle.
