Another solar question

Submitted: Saturday, Mar 03, 2012 at 13:40
ThreadID: 92261 Views:1524 Replies:4 FollowUps:0
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Hi all, back again looking for some more solar info. I have connected my new system, to the batteries on my camper via a sunsaver 20 regulator. Now my question is regarding what my multimeter should read. I admit that the batteries are fully charged at the moment. When I connect the solar system, The multimeter reads....
Solar panel at the reg - 12.52 volts
Battery side at the reg - 12.52 volts.
Do the above readings sound right?

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Reply By: Aussie Camper - Saturday, Mar 03, 2012 at 14:06

Saturday, Mar 03, 2012 at 14:06
A fully charge battery is about 12.7 volts when there is no charge from the panels.
When its getting a charge to the battery the volts can be more than 14 volts
AnswerID: 479280

Reply By: Ross M - Saturday, Mar 03, 2012 at 17:50

Saturday, Mar 03, 2012 at 17:50
Place a cover over your panel and then measure the battery voltage.
It should read above 12.5v static, now remove the cover off the panel and immediately the battery voltage should rise above static voltage and continue to rise as the battery charges until it gets to around 14 or more.

If it is not rising when uncovered then you have a regulator or wiring problem.
AnswerID: 479300

Reply By: Member - John and Val - Saturday, Mar 03, 2012 at 17:56

Saturday, Mar 03, 2012 at 17:56
"Do the above readings sound right?" No. Suggest check your wiring carefully. It sounds as if solar input and battery connections are tied together. Or maybe the solar panels are not in fact connected and the battery voltage is leaking through to the solar input terminals? (Check the panel voltage on the back of the panel if poss)

With the panels in the sun and disconnected from the controller you should see about 21 to 23 volts on the panels - that's their open circuit voltage.

Battery voltage is very dependent on history over the last few hours, and also on battery chemistry. If disconnected from everything for a couple of hours you should see 12.5 - 12.7 volts on a wet cell battery, usually a little more on AGM.

While charging, you should see at least 13.4V and maybe up to 14.8 (even higher for calcium batteries) measured at the battery. I assume that you are using the Morningstar MPPT controller. This should hold the panel voltage at about 17 to 18V while charging and the battery voltage at around 14.4V until approaching fully charged when it should drop back to about 13.4.

Complicated?... yes!! These numbers too will vary a bit with battery chemistry.

A further consideration - these controllers use pulse technology, resulting in rapidly changing voltages that average out at the right level. Digital meters take a virtually instantaneous reading, rather than an averaged one, so you can get some pretty erratic measurements, and may need to do a bit of mental averaging to get a useful reading.


J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein

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AnswerID: 479302

Reply By: Swaggy1963 - Saturday, Mar 03, 2012 at 18:07

Saturday, Mar 03, 2012 at 18:07
Gday Chris my system that i have only had running for 3 weeks the reading on the solar side of the reg is 17.2 volts and on the battery on the reg I am getting 12.6 but amps is really what you want to know how many amps is going in and how many are going out ie. the current there are to many variables that can affect voltage amps is what you need to know throw the volts in the useless information book.
AnswerID: 479304

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