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Old 11-02-2013, 07:33 AM   #15

2003 25' Classic
Zanadude Nebula , WNY
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Thumbs up Plain & Fancy

Originally Posted by pbearsailor View Post
At the risk of muddying the waters more here, the OP says he's been boondocking for a couple of weeks, is careful about using power, has a solar panel of unknown size, and doesn't know much about electricity.

I boondock a lot and am doing so now. For me, it all comes down to knowing voltage. I check my digital readout (his digital readout on his solar charge controller is likely fine for this) when I get up, before the solar begins to put out charge. With no load on the batteries, it needs to read between 12.2 and 12.7. If it reads less than 12.2, I know I have used more than 50% of my batteries and I try very hard not to do that if I want my batteries to last. If it reads 11 volts I have probably killed my batteries. For me, if I'm around 12.2 in the morning, I'll either need a good solar day or that generator is going to have to run for an hour or two.

My guess is that the OP slowly got behind on voltage over that two week period and will be lucky if he hasn't at least shortened his battery life.

Keeping a close watch on voltage is simple and it works.


Fancy is nice but won't take the place of plain maintenance....consistently.


AF #1

"Sticks & stones can break your bones...and hail will dent your Airstream"

So when is this..."old enough to know better" supposed to kick in?
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Old 11-02-2013, 07:46 AM   #16
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One more thing: if you're not "up to speed" on battery / charging issues, take a few minutes and read this article: The 12volt Side of Life (Part 1) ... the second article that follows this one is also useful background.

It's old but still a good primer. And down just past the middle of the article is a small chart showing state of charge vs. voltage. Print it out and tape it on your fridge. That chart is pretty generic, and all battery manufacturers I've dealt with have their own version of voltage vs. state of charge, but if you don't have anything else to go by, this will tell you a lot. Just remember that to get a reasonably accurate reading on state of charge, you have to be NOT actively charging (no incoming current from shore power or solar panel(s) or generator or tow vehicle charge line), AND you have to have been disconnected from charging for an hour or two with at least some small draw from the batteries as a result of using some power in the trailer.

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Old 11-02-2013, 07:55 AM   #17
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Definitely not enough information about the OP's system.

• What is the wattage of the solar panel(s)?

• What size wire gauge is used to connect the solar array to the controller and then to the batteries and how long are the wire runs?

• How big is the battery bank and what type of batteries are they?

• Is the solar charge controller PWM or MPPT?

In the absence of any amperage or wattage use information, we use the rule of thumb of 1 watt of solar for each amp/hour of battery bank. This will generally allow for the full re-charge of the batteries each day, assuming that you have a relatively sunny day. Also, battery type plays a big role in how the batteries are recharged and specifically what voltages are needed to fully charge the battery bank each day.

There are many other factors to consider in the design of a viable solar battery charging system, but this would take pages to enumerate.

More information is needed to provide any useful assistance to the OP.
Lew Farber...RVIA Certified Master Tech...ABYC Certified Master Marine Electrician
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Old 11-02-2013, 09:47 AM   #18
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Ditto what pbearsailor said (post #10). That's my standard practice. By the way, about 90% of our time in our AS is boondocking.
2002 22' CCD
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Old 11-02-2013, 11:10 AM   #19
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Thanks everyone! I will read and learn.

I unplugged from shore power this morning and ran a few lights for a while. This is what the solar control panel shows:

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The sun is up so solar is starting to charge.
How does this look?

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