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Are my Solar Panels working properly???

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Posted by sandy on August 28, 2007, 2:46 pm
We just purchased a truck camper that has two nice sized Siemens Solar
Panels on the roof.  Previous owner said he thought they'd been
disconnected when the air conditioning was added but when we asked our
RV repairman if they were working, he said they were.  I'm not so

As hubby had a stroke 3 years ago, I'm not the "mechanic" of the
family and a pretty poor one....so please answer in simple "dummy"

The "regulator" (or whatever it's called) shows a continuous red
light.  On some previous solar panels that we had, the light would
cycle on and off.  Also....I can't notice any appreciable charging
when using my multitester on the batteries.  We've had lots of cloudy
weather and I've had to move the truck (which then charges the
batteries) so I'm not sure what results I've actually had.

Also....the previous owner put in new batteries one year ago and when
we took the camper into Les Schwab, they said that both batteries were
dead (and verified that the batteries were only a year old).  I'm
wondering why they dies so quickly.

Could you tell me how to test to see if it's working correctly???  We
live in the boonies of NE Washington and I don't think our "local" RV
man (50 miles away) really knows much about solar.  I've been up on
the roof and see wires heading through the camper roof but no place I
can check them up there.  I have had the regulator off but I'm not
sure what or where to check it.

Thanks for any suggestions.



Posted by dold on August 28, 2007, 6:32 pm

I thought the batteries were "dead".  
How many volts does your multitester show?  
Does the voltage change when in bright sunlight, nighttime, or with the
engine running?

Clarence A Dold - Hidden Valley Lake, CA, USA  GPS: 38.8,-122.5

Posted by sandy on August 28, 2007, 10:55 pm
I guess I didn't mention that we bought new batteries.  I checked the
batteries this morning at 9:15 AM and it said 12.38 (although the
figures jumped around a little before settling on that figure) with
some sun out.  I then drove the truck a couple hundred feet to it's
storage parking place and later did some testing of several electrical
things on the camper including turning on the furnace for a moment and
just turning over (not starting) the generator.  Panels were in the
sun all day and by 2 PM the reading was 12.35.

The reading HAS gone up occasionally by a little (one night I
purposely left 2 lights on to drain the battery.  After turning the
lights off the next morning, the meter read 12.27 at 8:30 in the
morning.  By 10:30, it read 12.34.  But many days it just goes down @
a tenth of a point every couple of hours.

I haven't tried running the truck while testing the batteries and I
haven't tested them in the evening.

I opened up the Soltek regulator/monitor but wasn't sure what to do

Any suggestions???  I appreciate your help!


Posted by Martin Riddle on August 29, 2007, 12:36 am

A battery at rest that is fully charged (Flooded Lead Acid) should be 12.65v
12.38 is around 1/2 charged. see http://www.batteryfaq.org/

I do not think the regulator is working.  You need to start measuring current.
1- out of the Solar Panels, and 2- Out of the
Regulator to the battery.

The regulator is most likely a shunt type regulator. That is, it will short the
current from the solar panels as the battery
charges up.

For more help I would suggest you gather up some model numbers, manufacturer
info, and how many panels there are so that we
can figure out the numbers.


Posted by sandy on August 29, 2007, 1:25 pm
 Thanks for all your help.  We have 2 solar panels (Siemens).  I've got
the measurements somewhere (of course I can't find them right
now...but I'd guestimate something like 2' X 3 or 4' each).  The
regulator is a Soltek Mark III.  We don't have any manuals on any of
it (it's a '97 Bigfoot camper and I'd guess that everything is
probably the same age)

I'm thinking that, although I like the idea of being able to figure
things out and handle it myself, that I'd probably be better off
getting someone who actually knows what they're doing, to check it out
and fix it up.  What was especially confusing was that we sensed that
the solar wasn't working properly and had the RV man check it out
(along with other repairs) and he said it was working.  I figured that
he must know more than I do.

Thanks again...


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