MPPT and series solar panels

I prefer panels in parallel, due to the fact that if one panel gets shaded, it can lose almost all its light output.

MPPT controllers built into the solar panels directly is an interesting idea. If done right, the individual cells could be hooked up to the panel's CC individally, and the panel's controller create an output voltage from them. This way, if there are 16 cells on a panel, one cell is completely shaded, it will reduce output by 1/16 of the total panel, not 1/2 or virtually all output as what happens today.

The sun is very low now and the voltage is still 115v.

Salvo wrote:
I don't think you were in boost mode prior to turning on the MW. When the battery is in absorption the CC isn't looking for MMP. The CC is throttling back power.

I don't understand any of what you just said.

I don't think you were in boost mode prior to turning on the MW. When the battery is in absorption the CC isn't looking for MMP. The CC is throttling back power.

Sal

2oldman wrote:
I just went out and ran the MW for one minute on inverter.

The PV input voltage immediately dropped to 92v (from 115) @ 5.2a. After MW stopped, PV voltage stayed at 92 and stayed there...as the controller is now charging the batteries. I can see if the voltage rises as the batteries come back up.

Edit: It's now back at 116v 4:27pm

2oldman wrote:
I just went out and ran the MW for one minute on inverter.

The PV input voltage immediately dropped to 92v (from 115) @ 5.2a. After MW stopped, PV voltage stayed at 92 and stayed there...as the controller is now charging the batteries. I can see if the voltage rises as the batteries come back up.

Wow, I love this info' coming down the pike. The above is just what I was afraid of, using the controllar on my Electric scooter. I might just have to disconnect the controllar if I run the 24v batts down to the set point? That would look silly, the old man with that solar scooter, pushing it down the street. Hmm.

Today mid-day I noticed the Trimetric was at 26.5 amps instead of more like 19. I thought I must have MPPT! :) But it was just cloud effect.

Do all MPPT controllers hold amps to their rated amps "size" even with cloud effect? I have had two types of PWM and they just let the amps through above their "size." I was told that if they persist at over amperage, they will heat up, but cloud effect doesn't last that long. But you are told to observe the 20% margin rule for expected amps (Isc) so, EG, a "20 amp" PWM controller with a 20 amp battery-controller fuse should be maxed at 250w worth of 12v panels (16a Isc)

If the MPPT clips the amps, then you could go to full rating, and just worry about the Voc (temp adjusted higher for cold weather) intake limit.

Makes it interesting about that 20a Eco MPPT for 300w limit what that really means in limit for array Voc at cold temps up the mountain and whether you need to limit your expected max amps to 16a.

You might need two and split your array into two arrays if you go over 250w of 24v panels. Must know the specs for sure or be sorry!

I just went out and ran the MW for one minute on inverter.

The PV input voltage immediately dropped to 92v (from 115) @ 5.2a. After MW stopped, PV voltage stayed at 92 and stayed there...as the controller is now charging the batteries. I can see if the voltage rises as the batteries come back up.

Edit: It's now back at 116v 4:27pm

At the same time SOC does affect all controllers outputs. How well that works depends on the design of the algorithm for the charging curve for the particular battery bank.

SOC has no influence on PV mppt. The charge controller isolates panel voltage from battery voltage. There is no isolation with pwm CC.

Sal

HiTech wrote:
78v is an average max power point voltage of 13 v per panel. Any idea what conditions drive the voltage that low?

Heavy clouds plus low SOC is what I seem to remember.. but, I've never kept records on it. And that was with a 12v battery system.

I'm at 117v right now, floating 4-T605s in series (24v) in full sun. I'll try to remember to see what it is at dusk.. if that helps.