12v battery/ 12./24v MPPT ~ 24v PV Panel

BFL13 wrote:
You might be there already for leaving it flat. You can test that on the ground while it is still a portable.

On the many half sunny days we get, where it is cloudy morning and clears up by noon or VV, you can still get lots of AH in the half day by pointing the panel.

The very day I would nail down the panel flat on the roof we would get one of those half days, and I would be up there with a crowbar so I could point the panel again like before :)

Considering every day we were up there is was sunny early and socked in by noon......

Even then I bet flat will be enough...for now.

Exactly. PWM charges at pretty close to Isc for most panels most of the time, especially panels where the Vmpp is above the Vbattery. So watts from the panel are way down when using a 24v nominal panel against a 12 v battery. But it works fine if within the capability of the controller. The Voc will just be high when switching PWM pulses on and off.

Jim

Old & Slow wrote:
I may have missed it somewhere reading through this thread. Blame it to being O&S.

Anyone have hands on, charging 12v batts, using MPPT or PWM controllars with 24v panel?

I will try soon but would like someone to perhaps chime in and say, yes, NO problems.

Yes, I have a 24v nominal panel charging 12v batteries. My solar controller is a Morningstar Sunsaver MPPT-15. It works well.

My understanding is that using a PMW controller with the 24v panels will result in less charge to your batteries than using an MPPT controller.

You might be there already for leaving it flat. You can test that on the ground while it is still a portable.

On the many half sunny days we get, where it is cloudy morning and clears up by noon or VV, you can still get lots of AH in the half day by pointing the panel.

The very day I would nail down the panel flat on the roof we would get one of those half days, and I would be up there with a crowbar so I could point the panel again like before :)

Don
True and if I were a big power user I would have noticed.

BFL

That was in absorb mode after I did the coffee pot test and it didn't last long as I had only taken the battery down to 13.4v to get the system out of float for the test. Sky conditions were not perfect either as I was working between cloud banks.

I would be more concerned about getting every last drop of power from the system except it is so over sized for our needs that it doesn't really matter. If I ever find a way to use that kind of power I'll buy a second Eco-worthy and run the 220w panel too.

230/130 x 8.2 = 14.5a for PWM at "12v" Isc. What were the circumstances for that 13a?

Hi JiminDenver,

13 vs 16 = a 19% loss.

Tuna,

One fine fellow said, "Any 'lectrican that has not made a few wires smoke, hasn't been at it long"

I just spent 6 days charging my 12v battery with a 24v (mid to high 30's) panel and a MPPT charger. Works great!

For me there wasn't a huge difference in PWM and MPPT output. 13a max PWM and 16a max MPPT. The 3 amps would have mattered if actually drained the battery enough to stay in bulk long but really the system was in float most of the time.

Hi,

I use MPPT and the input voltage to the controller is 33.

With 24 volts, MPPT would be more desireable than PWM. However, some PWM controllers may not be damaged by 24 volts input. Others may let out the magic blue smoke. Read the manual carefully.

A 24 volt panel with PWM will "waste" a lot of watts. The approximate loss amounts to over 25% of the harvest.

Old & Slow wrote:
I may have missed it somewhere reading through this thread. Blame it to being O&S.

Anyone have hands on, charging 12v batts, using MPPT or PWM controllars with 24v panel?

I will try soon but would like someone to perhaps chime in and say, yes, NO problems.