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Old 02-10-2013, 05:20 PM   #1
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'ganging' solar panels

I am doing my first ever trip without hookups for 4-5 days. I expect pretty low power use (reefer, water heater, and the occasional light only). Over the years I have collected some solar panels, all intended to charge 12v. batteries (3 are VW supplied units for keeping car batteries charged while away, and one is intended to run a solar water heating circulating pump).

They all put current into a test set up, with the 3 VW units, paralleled together charging at about 0.45 amps. The other unit puts out about .5 amps by itself.

Can I "gang" these all together (connect in parallel), connect directly to the batteries, and count on no damage and a higher charge rate? Or will the weaker ones somehow lessen the stronger one?

Thanks,

Don
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Old 02-11-2013, 01:02 AM   #2
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Without technical reference, I would say the panels should be matched for each controller. If you have a lesser productive panel in the system, it just is a dead anchor and will not produce unless it is the only one getting sun. In this case all panels would have to have blocking diodes to avoid back feed. Think of liquid pressure in a pipe line with multiple feeds. If the pressure is higher on one line, then no fluid will be fed from the low pressure line.

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Old 02-18-2013, 01:59 AM   #3
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Ideally all of your panels should have the same voltage and amperage. If they do not, and they all produce similar voltage but different amperages, then connect them in parallel. If they produce different voltages but similar amperages, connect them in serial.

The general guidelines are to do your best to procure panels with similar specs, else as the previous poster said you can get into trouble where the overall system output will be brought down by the weakest link, you need to be careful about diodes, etc...
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Old 02-19-2013, 12:06 AM   #4
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Well, thanks for all the advice, but...

Just spent 5 days "boondocking" with all four panels hooked up, no diodes, just connected in parallel. Worked great, the Death Valley sun brought me back to 100 % each day.

Sometimes simpler is better...

Don
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Old 02-19-2013, 01:27 AM   #5
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hey - if it works it works... Sounds like a fun trip.
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Old 03-01-2013, 12:39 AM   #6
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matched panels or not, some amps coming in are better than none, free panels and free power are certainly better than nothing. Matching voltage of the panels is more important than amps, and even then the lower volt panels still make power just get over powered by the higher volt panels if they're working. kinda like a go cart with a lawn mower engine in back and a hemi in the front, with both engines running the mower engine will provide speed at low end but you won't feel anything once the hemi fires up
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Old 03-01-2013, 07:34 AM   #7
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Quote:
Originally Posted by DJW View Post
Just spent 5 days "boondocking" with all four panels hooked up, no diodes, just connected in parallel.
Actually, most solar charge controllers already contain blocking diodes, so that when you're charging from other sources (such as shore power) the current doesn't flow the wrong way through the charge controller. If you were using panels without built-in charge controllers, that might be a different story…
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