No. of Solar Panels.

[shonky]

Hi, all.

Harking back to my earlier concerns about solar panels - we have on occasion had 26amps using all four panels, and in similar conditions only received 8amps.
Duh! (An expression I hate to use but it seems apt) The solar controller supplies the batteries with varying amperage depending on the battery state, in effect acting like a 20 stage charger, the controller amperage indicating the battery state in reverse - high number bad, low number good. Animal farm comes to mind.
Is this common albeit unspoken knowledge?

[BruceS]

Yep. I've quite often seen or heard someone ask how come X number of panels is only producing a few Amps in bright sunny conditions.
It's like a see-saw .......... as one goes up the other goes down!

[T1 Terry]

You are headed into weird science here. First there is the variable amount of sun light hitting the panels at the right angle to get max output, then the temperature of the panels, not the ambient temp but the actual panel temp, both output and the voltage it will produce that output go down as the panel gets hotter. The STC figure usually quoted means nothing in the real world, those figures are with the panel at 25 deg C, how are you going to have a panel in full sun and it stay at 25 degC? Real operating temp in Aust long hot summer day can be up around 80 degC, that brings the max voltage the panel will produce it's best amps down around 14v, that won't charge a 12v lead acid battery very well because the panel voltage needs to be enough higher than the battery voltage to make the current flow, a bit like water down hill.
So, if the battery voltage is down around 11v, you will see good amps flow, if the panels are cold, you will see good amps flow, as long as the sun is at the correct angle to the panels.
All of this relies on the cables being big enough, but if you have already seen 26 amps then we must assume they are adequate.
An MPPT controller won’t make this any better because they can’t boost voltage like the grid connect units can, connecting them in a series string brings losses and problems of it’s own, so unless you are willing to buy one of the over $700 units and have lots of panels, don’t wast the time, money and effort.

[shonky]

Hi, all

T.I.Terry - thanks for that, but BruceS's explanation is more suited to my mental abilities and pre-conceived notions, and if I'm asked how they work Bruce's explanation is easier to memorise. Thanks again.

[bellett65]

Running out of real estate.Suggested to the M.o.W.a.F. that we replace the 2 80s at the front with 2 x 200, not a nice reaction from that end of the pergola. But they are now more efficient as they are also 75mm closer to the sun.

Peter

[T1 Terry]

You could move the 2 x 80w panels to around the air con and then fit 2 x 200w units up the front, that would give you 960w, plus the portables..... then sell power at the next free camp site

[bellett65]

You could move the 2 x 80w panels to around the air con and then fit 2 x 200w units up the front, that would give you 960w, plus the portables..... then sell power at the next free camp site

Don't think I haven't thought of that. I have been told in no uncertain terms extra water and heater only.

Peter

[T1 Terry]

I can visualise you being told and the tone of vioce too Peter

[bellett65]

I connected half the panels today, the negative wire. I was getting very worried as the multimeter was only showing a 1. Had it set on proper setting 20 volts, still only a 1. then I moved up a notch to the 100 setting. Eureka, I found some volts all 21.45 of them. I'll connect the other half, positive tomorrow, cannot rush these things.

Peter

[bellett65]

All connect up. Was putting in 2.8 from the 2 x 80. Went up to 19.8 when the 2 x 200 hooked in. Happy as a pig in the proverbial.

Peter