Solar panel problem

Dear All
Hoping for some device.
When we connected our 80watt solar panel to our caravan's Anderson plug the other day at Lawn Hill, the in -line fuse blew. The solar panel and the van both have their own battery management system. Does this cause some kind of compatibility problem? The solar panel was spitting out 18-19 volts. Would very much appreciate advice.
From Kevin and Megan
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Reply By: Member - Megan and Kevin D (AC - Sunday, Jul 29, 2012 at 21:17

Sunday, Jul 29, 2012 at 21:17
Oops. Looking for advice not device! Although the latter my turn out to be required.
AnswerID: 491896

Follow Up By: Dennis Ellery - Sunday, Jul 29, 2012 at 22:11

Sunday, Jul 29, 2012 at 22:11
With some controllers, if you disconnect the battery from the controller – then controller loses its program and you have to reset it before connecting the panels.
Otherwise you can get unexpected voltages going past the controller.
If you controller is not programmable then this is not the problem and you should look for defects in the wiring.
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FollowupID: 767530

Reply By: Sand Man (SA) - Sunday, Jul 29, 2012 at 22:15

Sunday, Jul 29, 2012 at 22:15
When you say both have there own battery management system, does this mean they both have their own solar regulators?
You should only have one regulator between the solar panel and the van batteries.
If the van has an on-board solar regulator, you need to bypass the built-in regulator on the solar panel.

I have a camper trailer with an on-board dc-dc converter. It has a solar panel input port and this regulator is much better than the one on the bi-fold solar panel.
I installed a second cable to the panel , bypassing the regulator on the panel so I can connect direct to the dc-dc charger port, which then regulates how much current is applied to the batteries.

When I connect the solar panel to my auxiliary battery in the vehicle, or to a Thumper battery pack I sometimes use, I use the original cable which employs the on-board regulator on the panel.

Bill


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AnswerID: 491901

Reply By: Member - John and Val - Monday, Jul 30, 2012 at 08:55

Monday, Jul 30, 2012 at 08:55
Hi Megan and Kevin,

Hope it's warmer where you are than here in Canberra. Heaviest frost for quite a while!

As I understand the problem - the inline fuse is in the line running to the solar panel . All the following assumes that is the case and should be ignored if that is not so.

The maximum panel current will be a bit under 5 amps, so it shouldn't blow any fuse rated at 5A or more - personally I wouldn't use a fuse there, but if I did would use 7.5 or 10A. (If the blown fuse was in fact rated at anything much less than 5A it may have just been doing what it should, and should be replaced by a higher value one.) If though the blown fuse was rated at over 5A there are 2 possibilities - a crook fuse, or (somehow) the current was coming from the battery, and there was a short circuit somewhere between the fuse and the panel. The short circuit could be a wiring insulation issue, or could be a breakdown in the panel's controller (maybe due to being connected with + and - reversed?? highly unlikely). In this scenario there still remains the question of how battery current got past the van's onboard controller, but that's a bit imponderable as it depends on the type of controller and just how it is wired into the system.

IF my assumption that the blown fuse is between van and panel is correct, I'd suggest check the rating of that fuse and if it's less than 5A, problem solved - replace with a higher rated fuse. In any case, replace with 5A or 7.5A or 10A fuse (no higher than10A) to check that the problem persists. If the new fuse survives, and if your meter can handle 10A, remove the fuse and insert the meter probes in place of it to get a current measurement, but especially to find which way the current is flowing - to or from the panel. Should come from, but if flowing TO the panel, there is a fault in the van controller or its wiring.

If all looks good so far:

As already suggested, there should only be one controller. The one on the panel should be bypassed and removed from the circuit as it's a possible source of your problem and in any case will interfere with the proper functioning of the onboard one. (Some cheap controllers actually load down the panel to control the voltage and if current is being fed (somehow) from the battery to the panel this loading could result in a blown fuse.)

I'd disconnect (electrically) the panel controller from the panel and check the unloaded panel voltage - should be around 21-22V. If it is, then the panel is ok. I'd run the raw panel output directly to the van through the fuse - depending on the type of controller in the van, the panel voltage (when charging) should be either about 13.5-14.0 or around 17-19, and meter readings may be pretty erratic. I'd also remove the fuse and substitute the current meter to measure the current being delivered by the panel . (When swapping between voltage measuring and current measuring be very careful of your connections and meter settings. It shouldn't be an issue in this instance, but if there is a battery involved it's easy to damage the meter by attempting to measure voltage when set up for measuring current. )

Hope that makes sense and is some help.

Cheers

John
J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
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AnswerID: 491913

Reply By: Member - RockyOne - Monday, Jul 30, 2012 at 09:09

Monday, Jul 30, 2012 at 09:09
My folding Outdoor Connection 80 watt folding solar panel unit I bought at a far better price than the big guys, at Wallaby Jacks in Emerald Qld, sturdier unit too, says on the instructions ' Solar Panel must be connected to the battery directly' then everything else draws power from the storage unit (battery) as, with a motor vehicle, you don't run your lights directly from the alternator, but rather the battery. I guess the battery will also act as a line filter smoothing out fluctuations in power. Just a guess.
AnswerID: 491914

Follow Up By: mchapo - Wednesday, Aug 01, 2012 at 07:33

Wednesday, Aug 01, 2012 at 07:33
Totally agree Rocky
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FollowupID: 767658

Reply By: Member - Megan and Kevin D (AC - Monday, Jul 30, 2012 at 11:03

Monday, Jul 30, 2012 at 11:03
Hi All
I just lost part of my reply! Anyway, thank you for all the useful and helpful comments. The fuse I blew was a 15 amp close to the van battery - hence the bit of panic rather than browsing the other useful material on Exploroz - which I should have done first! As also suggested I am having success connecting the panel directly to the battery terminals and also to the plug for the towing connector when the can is not hooked up.

Again your comments are highly appreciated.

Kevin
AnswerID: 491919

Follow Up By: Member - John and Val - Monday, Jul 30, 2012 at 14:01

Monday, Jul 30, 2012 at 14:01
Hi Kevin,

Sounds as if the fuse was not directly involved in the solar charging path. Good!!

re direct connection of panel to battery - DON'T !! Although you will charge quite well without a controller, you must have a controller between the panel and the battery to ensure that the battery is not OVERcharged. I suspect that when you say "I am having success connecting the panel directly to the battery terminals" that you are actually connecting to the panel via the panel mounted controller, which will look after the overcharging issue. Ditto for connecting via the anderson plug used for charging from your vehicle; you must have a controller to prevent overcharging, and that one would need to be the one on the panel.

If you have a controller mounted close to the battery it would be preferable to use it, rather than the one on the panel, but either (not both) will do the job. (It's better to have the inevitable voltage losses on the panel side, rather than the battery side, of the controller.)

Cheers

John
J and V
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FollowupID: 767546

Reply By: Member - Megan and Kevin D (AC - Monday, Jul 30, 2012 at 19:55

Monday, Jul 30, 2012 at 19:55
Thanks John
Yes, Idosingsing the solar panel built-in regulator. With all the hindsight I think the blown fuse was caused by some other event , perhaps an accidental short!!
Sorry to hear it,s so cold back home. I would be too embarrassed to let you know that it's been 11 to 32! So I won't say a word.

Cheers
Kevin and Megan
AnswerID: 491942

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