Noisy solar controllers

[haiqu]

I've been using a very cheap solar controller (like $12) and since I got the HF radio working occasionally noticed a sound like an unsuppressed engine nearby. It's a really loud but low frequency burbling sound that you can't mistake once you've heard it.

First time it happened I looked out to see if there was a motorboat passing, but there wasn't a soul about anywhere. Then I spotted the indicators on the solar controller. The battery had maxed out and the controller was chopping the incoming current to keep it within limits.

While I was out yesterday I sighted a Jaycar Electronics shop so I popped in and bought two 100uF 25v electrolytic capacitors to see if I could fix the problem. I applied the first across the terminals to the solar panel and the noise went away, but if I changed frequencies it was back again. The second cap went across the battery terminals. Viola! No more noises.

Here's a photo of the CMP12/24 controller I use:

[smurphny]

I haven't noticed any Rf interference from the solar controller, which must be basically just a diode but I have noticed a LOT of interference from the "pure sine wave" inverter. I actually have to turn it off when using the SSB to retrieve data using the Pactor modem/computer or all I get is a scrambled image of Weatherfax maps. SSBs seem to be very sensitive to radio noise. Ferrite beads seem to be fairly effective but I'll have to try your suggestion about using capacitors to remove the noise from the inverter. It would be nice to be able to leave it on while using the computer/SSB.

[haiqu]

If you're getting a general RF hash then it may be radiated noise, which no filter is going to fix. I have the same problem with my electronic cigarette, the processor throws out RF junk like crazy. The answer in that case is to switch off while using the radio. With the solar controller I could identify the source as a low frequency switching noise.

But hey, trying caps certainly won't hurt!

[haiqu]

Here's another source of radio frequency noise and interference (see photo below). I use an Xtar MP1S Li-Ion charger for my e-cigarette batteries (18650 type) and the VHF has been really noisy.

Solution was to add a 100uF 25V electrolytic capacitor internally across the cap on the board that goes to the +ve terminal. Reception went from unreadable to very clean and the squelch is no longer tripping in and out.

To open the enclosure, remove the four tiny rubber feet and extract the screws below with a Phillips head jewellers screwdriver, which gives full access to the board.

In all cases, when adding electrolytic capacitors be mindful of their polarity. Positive to positive and negative to negative.