Community Forums

tbbg II · 07-24-2013, 05:21 PM

A couple weeks ago I finally decided to investigate the solar charging circuit. I was pretty sure it wasn't working (the LED did not illuminate) and the chassis battery continued to discharge when not on shore power. I had purchased a new panel some ago. The old panel certainly looked bad. The new one (from somewhere on the interweb), was somewhat larger, so it required a revised mounting system. It is larger both physically and wattage. Challenging, but not technically difficult. Once installed, the LED was still out and more to the point I detected no juice going to the batteries.

So, I pulled the dash panels to expose the octopus of wires. I did detect solar voltage on one connector and battery voltage on the other. That told me the indicator was bad. I could find nothing similar to the OEM indicator on the web, so I ordered one from Newmar. It is now some $33 delivered. One can find honest to goodness low amperage solar controllers fro less, but I decided to maintain the original appearance. The new indicator has heavier wires than the old one and the wires to the solar connector were “backwards” in terms of polarity. I did sufficient testing to confirm it wouldn’t work as wired, so I switched the wires in the solar connector. I will say that it is possible I miswired the new panel. I have no way of determining that now as the old panel sort of disintegrated. If the old panel was also miswired, then the LED would never illuminate and the batteries would never charge from the solar system. The PO always had the bus on shore power, so he couldn’t help. Anyway, it works now. I confirmed current flowing into the batteries and watched it fall off as a cloud obscured the sun.

I dissected the old indicator and found the diagram floating around this forum is not quite what Newmars have. In fact, I am not sure what is depicted by that diagram would actually work. I think the LED would stay illuminated whenever the sun it out and not necessarily when current is flowing to the battery. Here is a sketch of the system as installed on my bus. Note the negative wires are simply joined together inside the indicator box. I have asked a EE buddy of mine to explain why there are three diodes in series. I’ll add his explanation when available. I could find no fuses anywhere in the existing circuit, so I added one on each side. One for the solar panel and one for the batteries.

GaryKD · 07-24-2013, 05:41 PM

Hi tbbg II,
As best I can tell, the light is to provide the owner a "warm fuzzy". My light went out. However, juice was still flowing to the chassis batteries. Could I leave well enough alone, heck no. I wanted the light to work. Went through what you went through. Quite a project for just wanting a red light to come on.

Luv2go · 07-24-2013, 06:14 PM

tbbg II: The schematic you attached shows the LED in parallel with 3 normal diodes in series. Basically the LED starts glowing at approximately the same voltage as the voltage developed across the three diodes as current starts flowing through them. The current from the panel must go through either the LED or the diodes and into the battery, so when the LED is glowing the battery is definitely getting charge current. The reason why the 3 diodes in series are there is the solar panel can put out more current than the LED can handle, the diodes handle the excess current, but still puts it into the battery.

So GaryKD is right, the LED is really there to give you a "warm fuzzy" feeling. Unfortunately without the LED it is hard to tell whether current is flowing into the battery or not, it's definitely nice to have working.