Monday, June 30, 2014

More On Solar

One of the great frustrations there for a while on solar power was that if you bought enough of a charge controller to handle a really big array, then you were spending a pile of money for a charge controller.  If you wanted to start small and build up your solar panel array, you could save money by buying a small charge controller, but then you would have to upgrade it.

I am not immediately sure of the output capacity of the Battery Tender that I currently have at work in the telescope garage, but I suspect, based on the current version of it, that is probably 9W or 10W.  That isn't going to work if I want to add a 40W panel.  I know that there are problems if you try to combine two different power output panels to a single charge controller--often you end up with the lower output panel limiting the output of the higher output panel.  But I presume that it is possible to feed the output of two different charge controllers into the same storage battery -- or do you end up with that same problem of the lesser source limiting the greater source?  Or is it necessary to use a diode to prevent power from working its way back from the battery to the other charge controller?

Because of the manner in which I will be using these, it might just be simpler to use the low output system for lighting, and the high output system for running an automatic garage door opener.


  1. A question to ask is: why are these electronics so expensive?

    The cost of materials for a charge controller is pretty small. My guess at the answer to my question is the huge amount of subsidy money flowing into solar.

    Sorry, I can't answer your specific question. I'd have to see the details on the charge controllers to know.

  2. I've bought a couple of charge controllers for $20.00 or so, and they worked OK. Am now using an MPPT controller to get more output from our 2-panel array on the travel trailer.

  3. Clayton,
    I found this page on Amazon with charge controllers starting at less than $20.00:

    Just did a Bing search for "solar charge controller".

    I thought I had an older controller laying around here and would have gladly given it to you, but I couldn't find it, sorry.