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Date:         Fri, 9 Dec 2016 08:56:26 -0800
Reply-To:     Alistair Bell <albell@SHAW.CA>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Alistair Bell <albell@SHAW.CA>
Subject:      Re: Friday off-T solar questions:long
Comments: To: Don Hanson <dhanson928@GMAIL.COM>
In-Reply-To:  <CAHTkEuLErPUBnNhvWgp+cbCj2bryCEizrMnFx09Fo_PBdr1ZUQ@mail.gmail.com>
Content-Type: text/plain; charset=utf-8

Quick reply, I'm sure others will elaborate or correct

You have one solar panel charge controller right? But only the newer panel is hooked up correct?

Btw, the figures you state for the new panel, 75 watts and 7.5 amps does not make sense. I can't see you getting 7.5 Amp out of a 75 watt panel.

That aside, you can parallel wire the panels to the single controller. This will increase current and even if panels are not matched, the built in diodes in panels will prevent any back flow to the lower voltage panel.

12.87 volts at battery, assuming no loads on the system and the panels in whatever sun you have, ain't sufficient to charge the batteries. But that's the way with solar on a cloudy day.

I'd advise a better solar charge controller. One with a display showing panel voltage and current flow. You can get PWM based ones for around 50 bucks.

The more sophisticated MPPT (multipoint power tracking) controllers cost much more but they will convert some of the voltage difference between the panel voltage and the battery charging voltage to usable amps.

Alistair

> On Dec 9, 2016, at 8:41 AM, Don Hanson <dhanson928@GMAIL.COM> wrote: > > We're running off the grid in the southern California desert with two deep > cycle batteries and two solar panels. One panel is ancient, with a dull > pebble front and a 4 post controller, about 3' square. > We had only that one, for a few prior winter seasons, and it often didn't > keep up, though our power requirements are low...Last winter we got a > second panel, modern, with a second controller, and I connected that right

> to the original panel's controller, which connects to the batteries. This > set up works OK now, but it's "messy". A lot of connections, two different > controllers, wires and panels to move around and keep upright in the wind,

> etc. So, I'm trying to "Fix" it. > I'm an electrical dunce. That being said, I've just taken the older > panel and it's controller out of the system, thinking that it may be > inhibiting the other panel's electrical input to the batteries. My > digital meter ( I have two, and they match numbers) shows around 17v when > I check at either panel, or when connected like I said up top, same > reading...both inline(?). > Ànyone have any suggestions for an effective way to connect all this up? > Or to measure the input into our batteries? It seems to be putting a little > less power back into the batteries, using only the newer panel alone, but

> I have no clue how to verify that, other than a dorky multiple LED test > panel (like the westie unit) or my digital multimeter...but the digital > meter and different sun intensities, day to day has got me stumped. > Currently(not a pun) in light overcast, I'm reading 12.87v at the > batteries, with the voltage going up about 1/100th each few seconds. > Some numbers for the newer panel, the older one I have no available > data.... Panel says: 75 watts. 16.6v. 7.5 amps. The 2 batteries are > larger dual purpose marine/RV in good condition. > ?😁


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