While having breakfast, I realized that my original idea of having forced air ventilation really wasn't so crazy. It means I'll have to get underneath the bus again butI do notice the inflow of air from the window does keep the place cooler. With the extraction fan going at the same time, sometimes I feel a breeze from the window.
I'm finding my fan is cutting out after 45 seconds at the moment. I think there's a problem with the battery or the charge controller or both. A 10AH battery should provide plenty power. In fact I spent $70 and bought a real deep cycle battery a few weeks ago. That has yet to find its way into my system. I'm suspecting that I might have been better with a 100ah battery but we will have to see how it goes. When I build an underbus cage for it, I might just build the cage to take the 100ah battery that Tractor Supply sells and just build it so that the smaller battery will also fit.
Thinking over breakfast I realized that if I put a second bilge blower to blow air from a vent in the side of the bus skirt through the floor then I could have quite some throughput of air. That means adding a second 2.5A fan and coupling them so they can run simultaneously. Then I realized that if I continue with my plan to put a supplemental power input on the side of the bus then I could buy a single 50W or 100W panel and have it either freestanding or simply placed on the hood or something like that. Given some magnets and a sufficient air gap, it could even be temporarily roof mounted while I'm stationary. That should provide sufficient power in addition to my existing panels to power the fans almost constantly. I'd been stuck on using CPU fans since they're cheap and easily available but they're not quite as good as the bilge fans. They're good - don't get me wrong - but I think the bilge fans shift air faster. Or at least they should when I can get the power and solar setup to function correctly. I had been dead keen on filtering the air coming in. Now I'm thinking that might be more of an annoyance to add filtration than it's worth. If necessary I can always tape a filter over the inlet. The important thing is to get the ventilation working. Sadly, a lot of this involves getting underneath the bus and that's dependent upon the critters hibernating.
Out of interest I looked at other batteries for powering my bus house circuits and came away with the conclusion that however expensive lead-acid batteries are, they're still far cheaper than the alternatives. Lion batteries are getting cheaper but until the highly combustibe, unextinguishable fire problems are resolved, they're off the menu. NiMh is a technology I'd accept but nobody ever made a 12v NiMh car battery. That would have been fantastic. Nobody makes NiCads any more - mind they were'nt that great in the first place. I remember everybody struggled so much with the things when I was doing a lot of photography that many professionals just refused to use them. The only other technology is the supercap. Those are pretty expensive however. For my ventilation system they would be ideal. They fill faster than a battery, have a more dependable full voltage, cannot be over-charged and can be drained empty many more times without ill effect.
Until I can get the battery issue sorted out, it looks like my time spent working in the bus is going to be fairly minimal. I've been inside for 45 minutes and the temperature just rose from an initial 82 which was comfortable to 88 which is pretty warm. Outside, in the sun feel like pretty much the same temperature. The difference is, moving air.
Looking at air conditioning systems, I came across a mini-split air conditioner on the Walmart website for about $450. That looked quite good though I could not find any measurements anywhere. It looked small but looks can be very deceiving. It was a RolleiCool Cool-P800 10,000 BTU unit with unknown amperage, unknown size and no real reviews.
One thing is certain. Though there are small gaps under the window wedge-gizmo that I bought for $5 in Lowes a few weeks ago, I think it's good enough that I could probably get another couple - just for cross ventilation until I can get my powered ventilation running properly. Really, for parked use, an AC unit would work best but if I'm mobile at any time then I'm going to have to have my ventilation working correctly.
I've mentioned the mini-split from Walmart that's $450. That's actually quite pricy. I saw a window unit for less than $100 which would have been excellent was it not for the fact I'd have to build some massive ventilation ducting to handle it. The advantage of a mini-split is that the only holes in the floor needed are for two small tubes. In fact, an AC unit that ran off 12v could probably be solar powered. Now don't imagine that is as mad as it sounds. This is the makeup of an AC unit...
An AC unit comprises two coils. One is hot and the other is cold. Now it sounds like my Peltier cooler! Anyway, those two coils are indirectly connected. Between the end of the hot coil and the cold coil is a compressor - on one side only. The compressor takes gas from the cold coil and squeezes it into the hot coil. When gas is expanded, it absorbs heat. When it is compressed, it radiates heat. The other side of the two coils are connected to a restriction device. This is just something with a very small hole that means gas passes through very slowly - much slower than the pump can pump it. This means one side is always at high pressure and the other always at low pressure.
To dispel heat from the hot coil, a fan is often employed or an aluminum heatsink. On vehicles, it's usually a fan. To circulate cold air, a fan is often used in combination with a heatsink on the low pressure side. The gas inside the coils is not mysterious nor is it a complicated chemical compound. Various gasses can be used, ranging from Freon (which is now banned) through to butane, ammonia etc. All the gas has to do is be free of water vapour.
All AC units will have a thermostat and a timer. The cold side will tend to cover itself with ice and water will condense on it too. That needs time to thaw and the water has to be collected and ejected. In an RV, that water could easily be recycled into the flushing tank for the toilet - or just poured out onto the ground. The thermostat simply cuts off the air conditioner when the interior is at the right temperature. The timer will cut the unit off every 20 minutes or so for a few minutes in order that the coil can thaw and deposit the water.
The gas is not expensive - it's possible to use cheap stuff like car AC refrigerant. That's available almost everywhere. The coils are where the costs lie. Usually they're either copper or aluminum. Both of those are costly metals. Plastic is cheap and available but does not conduct heat at all well. As far as the compressor goes - they can be very expensive too. Having said that I did see a vacuum pump that ran off 12v in Harbor Freight for something like $10-$15 a few weeks ago. That would be absolutely wonderful if it could pump the volume of gas needed. The compressor from and electric tire pump is another option though my experience of electric tire pumps drove me to buying a manual, mechanical footpump.
Complicating matters, there is another kind of fridge around that uses a heater. My parents inherited one and it worked well for years then suddenly quit so they just replaced the heater in a 10 minute operation. It was very quiet, took quite a while to get to temperature and it kept food really cold. I have no idea why it finally died and ended its life being used as a cupboard though.
Meanwhile, some excellent news. If you remember, some while ago I purchased on ebay, a remote camera. I figured I could sit in the house or the bus, log into it and see who was at the front door or in the yard. Hours after I made the purchase, eBay deleted the listing and the seller. I was given some ludicrous time interval (something like August 1st to September 1st) to receive the goods and they didn't arrive by midway through the interval and was given no tracking number. I filed a case with eBay who said the seller did not provide a working tracking number and refunded me. I've only been waiting two months for this! I made the purchase in July. It was obvious the seller wasn't going to honor their commitments when their listings and account got deleted. Let's just say the item was suspiciously cheap.
So, where now? Well, in order to competefurther work on the bus, I have to go underneath. Meanwhile I shall redo my rather messy rat's nest of a control panel. I posted the rat's nest a few days ago but I'll post the messiest part again.
As I have a spare charge controller (several in fact) I can mount one on the board. The only thing I will have to do is to put some black tape over the LED display unless I put a door on the unit itself. There just are too many busybodies who'd look at a flashing display and go running off to the police, accusing me of having a bomb in the bus. Then I'd come back and find they'd smashed the door to gain entry, caused untold damage and probably wouldn't pay to repair their wrecking journey. Meanwhile the little sod that went making up stories is probably chuckling to all his buddies about the entertainment he created and laughing at the poor innocent victim.
So, over the last 4 hours the temperature in my motorhome rose from 82 to 93 and has now dropped to 91. That's with a not really working extraction fan and no induction fan. The window screen helps but I'd sure like an induction fan that doesn't need the windows to be opened. Meanwhile I'll probably get another couple of window screens.
I did end up getting some more stuff ordered from China. I can't see my going under the bus for a while so making up my control panel is something I can do outside the bus. I don't need to install that until I'm good and ready. Thinking about boxes, I'm pretty sure an old breaker box would be ideal to put all that into and it probably wouldn't be too hard to find one in some place like Restore.
I'm sorely tempted by the idea of an AC unit. I'm not so tempted by the prospect of spending even $170 for a secondhand portable unit. I do love sitting in my motorhome though.
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