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."
- Albert Einstein
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