DIY Dehumidifier / RV battery maintainer

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What does a dehumidifier and an RV deep cycle battery have in common? Not much. Except that I'm using the periodic nature of the dehumidistat to cycle a trickle charger. Last year I posted a description of a real cheap dehumidifier that is available to everyone! Well, certainly cheaper then a 'proper' dehumidifier.

The only real problem with my setup was lack of humidity control. Air conditioners work on temperature, not humidity. This meant I either had to turn to max and let it run 24 hours a day / 7 days a week until I was parched, or guess what temperature setting might get close to the proper humidity level.

Well, last week I realized that there must be dehumidistats on the market - controls that turn a circuit on when the humidity is too high. Ideally these would be line voltage capable (and not some 24v control voltage rating) and so I went to the local hardware store. It took some searching - McDiarmid Lumber, Canadian Tire and even HomeDepot did not have DEhumidistats (some had 24v humidistats, but that would be too much work). Rona had them and for only $20! and they are rated for 10A / 120V - perfect for the A/C unit. I wired it into an extension cord so I could also power a 12VDC adapter for the bilge / fountain pump. The setup works like a charm with the unit nicely maintaining 50%.

So, what about the battery? Summer is over and I have a deep cycle battery from my camper I need to store. Trouble is, the charge needs to be maintained over the next 5 months without over charging. I could buy an expensive charge maintainer, or - and I love this part - since the 12VDC adapter isn't quite strong enough to run the bilge pump, I could have it charge the RV battery and use the battery to run the pump. The pump is on a float switch, so it only runs for about a minute every few days, while the charger will trickle charge for a couple hours every day and keep the battery healthy!

How sweet is that!

Anyway - here's my new setup:

Dehumidistat Charger

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