voltage drop

Submitted: Friday, Dec 30, 2011 at 08:32

ThreadID: 90895 Views:2241 Replies:6 FollowUps:4

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musketeer1

we have a vitrofrigo compressor fridge in our van and we have just put a new 90 watt solar panel on which makes 3 solar panels totaling 240 watts and we have just replaced 2 batteries ,we have been experiencing a voltage drop of up to 1 amp and yesterday we had to put the gennie on for over an hour and a half so the batteries could be powered back to 13volts after a full day of good sunlight,we have recently had the mobitronic removed and wired directly to the batteries,any suggestions would be greatful,also where is the drip tray on the fridge as I can't find it although I could be having a man look lol

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Reply By: MEMBER - Darian, SA - Friday, Dec 30, 2011 at 09:24

Friday, Dec 30, 2011 at 09:24

My 150L 2 door Vitrifrigo has a flexible plastic pipe for getting rid of water - it is plumbed out through the van's floor, directly underneath the fridge. As for power setup - the electroguru's here will need more information in order to help you - make and model of panels, batteries, solar controller etc.

AnswerID: 473596

Follow Up By: musketeer1 - Friday, Dec 30, 2011 at 13:35

Friday, Dec 30, 2011 at 13:35

thanks darian we found it

FollowupID: 748442

Reply By: Dennis Ellery - Friday, Dec 30, 2011 at 11:52

Friday, Dec 30, 2011 at 11:52

Your information and terminology is too vague – I suspect it will be difficult to sort out your problem on a forum like this. Best take it to an electrician who’s experienced with 12v solar systems.

AnswerID: 473610

Reply By: Bob Y. - Qld - Friday, Dec 30, 2011 at 13:39

Friday, Dec 30, 2011 at 13:39

There's your problem: "....voltage drop of 1 amp...."unquote. But seriously, all this has happened since you fitted the latest panel, and had the mobitronic (what the hell's that???) wired direct to battery.

I'm thinking either you have wired the latest panel incorrectly, and it's robbing power from the other 2, or this mobitronic thingy is u/s.

Did you fully charge the new batteries before using them?

Bob.

Seen it all, Done it all.
Can't remember most of it.

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AnswerID: 473617

Reply By: Battery Value Pty Ltd - Friday, Dec 30, 2011 at 19:14

Friday, Dec 30, 2011 at 19:14

Hello musketeer,

if your fridge is similar in size to Darian's then I guess even 240W of solar panels could be borderline.

It seems the batteries get discharged because the solar panels supply less than the fridge consumes.

BTW 13V measured at the batteries is nowhere near of fully charged.
You want to see 14.4~14.8V for a couple of hours measured right across the battery terminals (unless you've got gel batteries which have a lower charging end voltage requirement).

As Darian said earlier, we need more information about your setup if you want us to try and pinpoint the problem.

cheers, Peter

AnswerID: 473646

Follow Up By: Old_Bob - Friday, Jan 06, 2012 at 12:09

Friday, Jan 06, 2012 at 12:09

Are you sure you're not confusing charging voltage with 100% charge voltage?
Standard lead acid batteries 100% of charge state are about 12.6V to 12.8V.

FollowupID: 749136

Follow Up By: Battery Value Pty Ltd - Friday, Jan 06, 2012 at 13:36

Friday, Jan 06, 2012 at 13:36

Hi OldBob,

presuming the OP has AGM batteries which are superior in many ways to wet cell starting batteries, when used in a solar application, the expected ocv is higher for reasons given below.
But yes, in case the OP does use wet cell starting batteries for his solar gear, then you're right, a modern Ca/Ca battery has an ocv of ~12.8V, and older technology Sb/Sb is closer to 12.6V.

Asian sourced AGM batteries have slightly stronger electrolyte.
They do this to bump up the ionic conductivity for high charge acceptance and high discharge capability.
Another welcome side effect of higher electrolyte concentration is improved battery efficiency which can be 3~4 times higher than that of a typical flooded cell starting battery. This comes in handy when storing solar power with gains of 10% and higher compared to flooded cell.
The drawback of stronger electrolyte is of course higher rate of grid corrosion especially under high operating temperatures (e.g. when mounted under the bonnet).

cheers, Peter

FollowupID: 749148

Reply By: fisho64 - Saturday, Dec 31, 2011 at 01:24

Saturday, Dec 31, 2011 at 01:24

how do you measure a volt drop in amps?

AnswerID: 473666

Reply By: LeighW - Saturday, Dec 31, 2011 at 10:17

Saturday, Dec 31, 2011 at 10:17

Lets see the specs for your fridge show it consumes around 40W - 50W at 12/24V, it doesn't state clearly that the wattage is the same for both 12V & 24V.

So your fridge will either use around 4AH or 8AH, so using a 50% duty cycle will use 48AH per day or 96AH .

Your solar panels supply 240W which is around 17AH assuming 10 hours of bright sunshine thats 170AH.

Therefore in sunny weather assuming no other load than the fridge you should have no problems charging your batteries with your setup.

Therefore it would appear you have an electrical issue of some sort to deal with.

Cheers

LeighW

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AnswerID: 473675

Follow Up By: musketeer1 - Saturday, Dec 31, 2011 at 13:21

Saturday, Dec 31, 2011 at 13:21

thanks guys ,it sounds like we are back to our 4th visit to the auto electrician ,we always assumed we would have enough power to look after the fridge as well as our minimal amount of power we use throughout the day. the brands of the solar panels are kyocera folding panel and 2 sharp fitted panel on the roof,we have the correct wiring and 2 new deep cycle batteries 110 & 100.

FollowupID: 748523