[aprssig] Are solar charge controllers a safe powere tap?

al wolfe alw.k9si at gmail.com
Wed Sep 6 16:06:59 CDT 2017

    Solar controllers are notorious for generating noise. They mostly
use switch-mode control. That said, some are better than others. Your
best bet would be to measure the noise at the controller and at the
battery terminals with an oscilloscope or lacking that, a sensitive AC
voltmeter. Much of the noise can be filtered out with LC networks in
the power line to the radio. Other radiated noise is going to be
difficult to deal with.

    Generally, getting power at the battery works the best as the
battery is usually bonded to the trailer frame near the battery. Also,
the battery typically has the lowest impedance to noise of any part of
the electrical system. Often the battery charging system is not
directly bonded to the frame and relies on the negative lead to the
battery for grounding.

    The bottom line is that all bets are off as every situation is
different. You will need to try various grounding, bonding, shielding,
and filtering until the noise is at a livable level.

    Good luck with this.

Al, k9si

> Subject: [aprssig] [off-topic] Are solar charge controllers a safe
> 	power tap?
> Greetings, all.
> This might be a little off-topic, but I'm having difficulty finding a wiring
> path in my RV to get direct battery power for my rigs (especially my remote
> monitoring APRS project), and wanted to bounce an idea off the collected
> wisdom.
> The battery compartment on my motor home is pretty isolated from the
> passenger areas, so I was looking for an easier/safer place to tap. I had
> had a solar power system added to the motor home, and the charge controller
> (a Blue Sky MPPT controller) is mounted in the inverter compartment (5 feet
> from the battery compartment) with 2/0 cable linking the charge controller
> output to the coach battery terminals. Since it is much easier to get to the
> charge controller than to the batteries (in terms of running more cable), I
> was wondering if it would work to parallel off the charge controller output,
> or whether that would inject too much noise into the radios.
> Any advice welcome.
> Andrew Pavlin, KA2DDO

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