Solar charge controllers: experience and more questions...

Hi everyone,

I still haven't given up on the idea (health and money allowing) of puttingtogether a safe, off grid mobile home for all seasons.  I think that using solar would be the simplest, most portable option to charge the battery bank.  To begin with, I wouldn't have the intention of using an inverter at all, or at least almost never.  My goal would be to have everything run off of DC (direct current).

Now, I know that you're supposed to use a charge controller to make sure that the batteries get correctly charged (and not over-charged) from the solar panels.  The problem is that even looking at most "good" charge controllers these days, you can tell that they're probably quite dirty, electrically, what with their "smart" controls and digital screens.

What I want is a "clean" charge controller that doesn't emit filthy RF. 

Bill Bruno, you mentioned one from the company Northern Tool.  You said it doesn't use PWM (pulse width modulation).  Can you, Bill, or anyone else, tell me (I apologize if I've missed this somewhere or forgotten) if an absence of PWM (and a digital display) are the only things to look for that would result in a clean (RF-free) charge controller?

And are there any methods that could be used to further "clean up" a chargecontroller if it's PWM-free but may still have some dirt otherwise?

As for the "experience" part of the message subject, I spent a weekend withmy girlfriend in a small trailer she's renting out in the country.  The trailer had been rigged up with a couple of small-medium solar panels on the roof, and there was a charge controller on the wall, in the sleeping loft. (!)

By the time I got there, there wasn't that much daylight left, but the nextday, she had to go out, and I just decided to check the inverter with an AM radio (the inverter was mounted lower down, and didn't do anything unlessyou hit the "ON" switch), at which point it emitted an audible hum which was further picked up by the AM radio as RF noise, and put out a magnetic field.

But it so happens that the moment I turned on the AM radio, there was a nasty sounding, high pitched buzz on it, throughout the whole trailer, though worse in some spots than others.  I stepped out of the trailer, the noisestopped.  Stepped back in, there it was.  It took me about half an hour to figure out that it was a sunny day, and the charge controller was doing it. 

Every minute, maybe less, the display on the charge controller said "1.0 AMPS", so I guess every time it put an amp to the batteries, it emitted the RF, which was conducted in the whole trailer, through the wiring and metal body!

I found a ladder and went up to the roof where the panels where, put the radio on top of them, waited a minute, and radio just started screaming!

The lesson of this was that, yes, some charge controllers are really dirty;so much for solar being "clean energy" (at least in the way that most people apply it, what with inverters and controllers).

And that's what made me want to ask more about charge controllers here, from anyone who knows what else to look for (other than an absence of PWM), orsuggest models, apart from the one at Northern Tool.

One other question: does anybody know if you can link multiple charge controllers together? Let's say I found a "clean" charge controller, but it didn't have enough capacity for a big battery bank - could two or more be linked together for more juice to the batteries, while keeping it clean?

Oh yeah; the charge controller I talked about? When I took a good look at it, it said on the front "3 Phase Pulse Width Modulation Controlled".  D'oh!

Thank you, everyone.

R.




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