Wednesday, August 9, 2017

New math

I decided in the end to mount the USB and 12V connectors on the galley-driving compartment partition and to have solely the CPU fan in the bedroom. This makes connections a lot simpler though when I run my cables under the bus I might well add extras in case I change my mind later (a possibility).

Looking at my two Chinese connector panels, I removed 3 of the voltmeters and replaced two with Chinese USB connectors and one 12V connector. That should fit nicely on the aluminum box that'll soon be arriving.
Now the maths works out something like this. There are two 2.1A USB sockets plus two 5v 1.2A sockets. Add to that a 2.5A fan and two 0.5A fans. That all comes to 11.1A. The cigarette lighter socket is nominally rated at 12A and the documentation on my combination dual USB and cigarette lighter socket recommends a 14A fuse. That adds up to 23.1A. Add in the one piece unit I purchased the other day and we're up to 27.1A.
If you turn your head upside down, you'll notice my charge controller tops out at 20A. That doesn't overly worry me because I'm highly unlikely to have all the devices running at the same time. Having said that, there's a big case there for putting in a resettable breaker just to make sure I don't go over 20A. Of course I could spend a ton of money on buying a massive new charge controller but until my existing 5 charge controllers, each of which can handle 20A die then there's just zero point in bothering. I cannot possibly imagine any circumstances in which I would use such a massive amount of power.

My fuse array is set up for four fuses. Those will be fan 1, fan2, fan3 and sockets. The sockets need a 6.6v fuse for the USB, an unknown quantity for the voltage meter and something for the 12v socket. I only have two devices that run off a 12V socket and to be honest I do not know their amperage. One is a battery charger for AA batteries (it also runs off 120V) and the other is a 120v inverter that produces 200W. Neither of those, I actually use.

Thus, replacing the 12V cigarette lighter socket with another USB charger socket sounds much more practical. That'll have to be ordered but I think it'll work out far better value. That would take the total power from the USB cluster to 9.9A plus say 0.1A for the voltage meter or a 10A fuse. Combined with the fans totaling 3.5A, I'm now under the maximum limit of the charge controller.
Another issue is that my 4 fuse holders have no interconnection. It seems for that I need something called a piggyback spade connector. I went to one of the multitude of car spares shops. I think it was Advance Auto and could find no piggyback connectors. In the end I hunted online and found a pack of 3 for some awful price then Walmart had a pack of 25 for some ludicrous price. Finally, eBay had a pack of 25 for under $5 including shipping. Though it'll take a few days, they should be here next week. I hate all these delays in my plans.

As far as the other USB connector is concerned, I'll have to order it and wait - that's coming from China. Eventually I might use the dual connector I purchased the other day but not in the currrent iteration.

By the time I want a 12v cigarette lighter socket, I'll probably have upgraded my battery from 35AH and will probably have added extra power input. I did email somebody the other day that makes tiny gas engines for bicycles. They're quite inexpensive and at about 45cc would do well turning a car or motorbike alternation to develop power for a 12v battery independent of solar power. Solar is fine for a wide variety of things but the power produced while it will handle my small demands, won't handle much more. I certainly doubt all the online claims I've seen of being able to run air conditioning and fridges off solar.

Meanwhile, the subject of my mysterious battery drain came up at work and one old fellow that used to work as a bus mechanic then as a driver but who now works solely as an aide piped up saying that he would suspect the alternator. I tend to agree. Reading up on alternators online, it seems this kind of thing happens when the bridge rectifier built in begins to fail. There could be other reasons too but if I can get somebody to test the alternator then I might be closer to a solution. Otherwise I'll have to wait until I can get underneath the bus again.

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