The strange world of the Peltier dehumidifier

Sitting in my bus today, I was dripping with sweat. It wasn't particularly hot - it was about 90F which is pretty OK. The problem was the 74% humidity. My mind turned to air conditioning and to dehumidification. The ventilation fan seems not to have cut on in forever so I'm assuming either the battery or that particular charge controller is at fault. I would have connected my latest charge controller and my latest battery but since my timer has not arrived, it's not practical.

My clothes were drenched in sweat with obvious sweat marks. Clearly not a situation that's welcome. The solution will probably be to get the ventilation working. Needless to say that's not an option right now. Remembering I have a Peltier unit that I put together out of curiosity, I decided to try it with a 12V battery. The temperature of both sides was 92F when I connected the power. I left the power connected for exactly one minute at which point the high-temperature side was over the point at which my thermometer could measure (about 200F). The lowest point I measured on the cold side was 86F. On a subsequent test, the hot side rose to over 200F again and the cold side kept climbing. When I gave up trying it was at 126F.

Previously when I used a 9V battery, I could feel a warm, cool difference. I have no idea what's going on now. It's allegedly a 12v unit so it should be doing more than that. There should have been a bigger difference. The only thing I can think of is the heat from the hot side was making the cold side warmer and that while there was a 70+ degree difference between the sides, the unit was just working as a heater rather than anything else. Quite disappointing really.

That puts me in mind of somebody else's blog entry in which they blogged about "The useless world of the Peltier effect dehumidifier". It's a very enticing technology but all the reviews I read so far are very mixed. People either rave about expensive Peltier dehumidifier or condemn them soundly. I would imagine there's a tendency for those that spend silly money on things to praise them in order to defend the fact they spent silly money. I would tend to question the bad reviews as to whether they operated the things correctly. Based on the conflicting evidence from my tests - one in which the one side was actually cold and one in which the cold side was quite hot I'm going to declare this to be yet another one of those dubious bits of electronics.

I moved on and added side brackets to my aluminum box. One didn't go quite square but what's new. That whole construction has been a fight with holes going where they wanted to go rather than where I wanted them. I'd start a hole and drill straight yet somehow the hole would end up way off where it was marked, even though when the cut started, it was spot on. Somehow the drill is drifting through the material. I'm guessing it's not a good quality of aluminum. I've had strange spots in metals before. I recall drilling some steel with a drill press when all of a sudden the drill stopped cutting. I changed drills several times and oiled the work to no avail. I ended up with a carborundum bit getting nowhere before finally cutting with a diamond tip drill. That went through like a hot knife through butter. Just because it's steel or aluminum doesn't mean it's the same all the way through - especially these days when almost all steel or aluminum is recycled and there's no telling what grades are mixed in.

It's still 66% humidity but only 91F so I'm still drenched with sweat. The humidity is more of a killer here than the heat. I'm positive that when I can finally connect my solar arrays and run everything off a single battery with a timer on my extraction fan that things will be a lot less humid and probably a lot cooler.

After the riveting, I pondered how to put my cables in and decided in the end to put them in a cable sleeve then to cut a notch in the side of the unit with my trusty angle grinder large enough to accommodate the sleeve. Then when everything is wired and the sleeve is poking out, the back can be slid into place and the whole lot screwed to the wall - wiring to be completed whenever. That's not a major task. It's fiddly but not major. Obviously 66% humidity and 91F is not conducive to doing much aside from sitting still and blogging.

The problem with blogging is while I'm blogging, I'm not doing anything toward construction. The other problem is that where I am, the wifi doesn't quite reach. I think it has to do with being in a steel bus. It's a bit of a Faraday shield. My MiFi pad is just plain uneconomical to use and the next step is a smartphone and that's more more than I want to be bothered with. It would be ideal if my flip phone offered a wifi hotspot. Sadly I don't know of any that do and I'm pretty well positive only a few of us would buy such a thing.

So why not buy a smartphone? Well, Walmart's $35 a month for a smartphone with 2GB of data would fit the bill nicely but for two things. First I don't want to have to have a monthly bill that's $20 over what I pay now. Secondly I don't want a smartphone. They're expensive to buy, have rotten battery life and take up too much pocket space. That's without mentioning that nobody calls me anyway!

So, I wired everything together with my magic box, including some nifty soldering of Radio Shack's pain in the rear non-standard pushbutton switch. Finally I put the back on the unit and touched up some of the paint.

In my construction work today I decided to do it the easy way and mount the unit on the front of the horizontal beam with a little protruding below the beam. The wires will run in my cable sleeving along the beam and into the cockpit via a small hole in the partition wall. I'll secure everything with my remaining cable clamps and drywall screws.

Earlier today I connected the bank of fuses using my piggyback connectors. It doesn't look pretty but it is functional. It's now possible to use the entire bank of 4 fuses. Tuesday being my next available day, I should be able to complete the wiring. Today there's just not enough time to do anything other than install the basic unit.

How far am I toward completing the motorhome? Well, aside from getting it retitled and getting the new magic box wired it, it's done for the moment. The 12v system needs an upgrade - it needs the new battery installed and the rear charge controller replaced by a timer that runs off the front charge controller. The two solar arrays need to be linked and I need to think about installing a cold water inlet and possibly putting in a 120v instant water heater so I can have hot water at the handbasin. As far as hot water for the shower goes, that's possible though I have not really got a foolproof method of doing it yet. Air conditioning might not be needed if i can get the ventilation working properly.

All day I've been having difficulty in trying to post photos. I've got three ready to post but whether they'll be attached by the time I publish is unknown. Blogger lets me select the images then just farts around showing me a silly little ball that keeps changing color while progressing no further despite heading off for a cup of tea while I waiting. I'm not 100% sure that it's purely a blogger problem or whether the unreliable HighesNet satellite connection could be also causing problems.

Today has been a series of problems. One of the first was that I put my freshly painted magic box back out to dry and the sky was gloriously sunny. Ten minutes later, it was pouring with rain so the paint now has poc marks. It's not as bad though as when I painted V1 of my toilet. It began to rain and washed all the paint off. Speaking about V1, I'm on V2 now and there might be a V3 after the plumbing I'm toying with comes to pass. I left space under the toilet area for a black tank. Fresh water currently goes in jerry cans but there is space behind the fuel tank for a 15 gallon water tank. There's also plenty real estate behind the rear wheels. I've shied away from that though as I figure for dry camping then jerry cans are best and for hookup, there's no need. With a flush toilet, disposal at a hookup site is easy. With a dry toilet, disposal while dry camping is easy.

While I waited for the paint to dry, I pulled out my trusty 10AA battery pack and tested my magic box. Everything worked as it should. The next stage - putting it on the wall and securing the cable using a cable clamp. That bit was surprisingly easy although I could not locate a suitable cable clamp. That's probably a trip to Harbor Freight sometime.

Illuminating the magic box should have been straightforward but for the fact the handle has fallen off yet another of my LED lanterns. It doesn't matter how much I pay for LED lanterns - they just seem to be absolute junk. On the other hand, that's pretty much my experience of all LED products. Nevertheless, I did manage to light it up and can see that my spray can of metal paint is a few shades darker than my wall paint but not obnoxiously so. My magic box is mounted on the wall, has been fully tested and is in working condition for whenever I complete the operation by installing the cables.

I can honestly say I'm glad to have completed my magic box and that it came out looking so good. I know all the minor imperfections but it's safe and it works. Wiring as I said, will have to be completed on Tuesday. That will give me a fully working battery monitoring, charger monitoring charging station for electronics. If nothing else, that makes the motorhome viable for today's technology.

Meanwhile I mentioned my battery drain issue and somebody suggested taking all the fuses out then replacing them one by one with a bulb attached between the ground of the battery and the bus ground to see which fuse lights the lamp. That sounds an excellent idea!

I can honestly say working in the heat on my motorhome is the kind of sauna that most people would pay good money for. My skin must look 20 years younger by now. Any younger and I'll be carded at the bars!