1.5yr Update, Test:
I haven't had to do a single thing to my solar or batteries (except check occasionally for water level on the lead acid batteries). The batteries are kept charged and when boondocking I've never even gotten below 50% on my 200AH battery bank.
Just for fun, and out of curiosity, I decided to do a charge test with my solar/batteries. Yesterday evening I ran a small 120v heater through my inverter to discharge my batteries down to 35% (65AH remaining out of 200AH). I disconnected my solar panels (via convenient breaker) and I let the batteries sit overnight. Today at noon I went to my RV and turned on my solar to see what sort of amps I could get flowing into my batteries. There were two reasons I wanted to do this. First, I wanted to see what the maximum solar amps I would get out of my flat mounted panels flowing into my batteries, and secondly I wanted to check the impact of having DIRTY solar panels (I haven't cleaned them ever...only time they get clean is when it rains).
Here was my test...
Conditions: August 12th, 12:45pm in the afternoon. Bay Area, CA. Sunny, cloudless, 80 degrees. Sun high in the sky but definitely NOT directly overhead. Flat roof mounted panels (two 250w residential panels). Battery at 35% SOC (65% discharged). 30amp MPPT solar charge controller.
This is how dirty they both were:
Here is an image of the dirty vs clean panels:
Before cleaning panels:
25v from panel (measured via solar charge controller)
12.0amp from panel(measured via solar charge controller)
23.6 amp into batteries (measured by Aili battery monitor)
Battery voltage via Aili monitor: 12.7v
After 1 panel clean:
25v from panel (measured via solar charge controller)
13.3amp from panel (measured via solar charge controller)
25.2 amp into batteries (measured by Aili battery monitor)
Battery voltage via Aili monitor: 12.7v
After both panels clean:
26v from panel (measured via solar charge controller)
13.9amp from panel (measured via solar charge controller)
27.3 amp into batteries (measured by Aili battery monitor)
Battery voltage via Aili monitor: 12.7v
Conclusions:
- 27.3 amps out of a 500w solar system seems quite reasonable to me. Thoughts?
- The difference between clean panels and dirty panels was 3.7amps (15.7% improvement).
- My EPEVER 3210 30A MPPT Solar Charge Controller seems to be doing a good job converting extra voltage from the panels into current to the batteries without much loss.
One Question: Is it reasonable to be getting 25-26v from my solar panels? Here is the spec sheet:
Maximum Power: 250w
Open circuit Voltage: 37.6v
Voltage at Pmax: 30.3v
Short Circuit Current: 8.85a
Current at Pmax: 8.27a
Regarding Voltage as seen at my solar charge controller:
The wire run from my panels to my solar charge controller is about 35' and is 10AWG wire. Using an online voltage drop calculator with 35', 10AWG, 30v, and 16amps, it says my voltage drop should be 1.3v (4.4% loss, which seems fine to me). Do you think I am not seeing closer to 28v at my solar charge controller because the sun is not directly overhead? Just curious.
As mentioned in my original post, I only really needed/wanted 200w of solar but ended up putting up 500w (because it was so inexpensive with used panels). I'm not trying to squeeze more charging out of my system as it is overkill for my needs already. I just find it fun to tinker around with it. Solar is fun and addictive!
Happy Camping!
Chris
