On Thu, 18 Feb 2010, Tony VE6MVP wrote: > Also we're thinking of having a backup power generator being a lawn > mower motor hooked up to an auto style alternator and a rioughly eight > or ten hour fuel tank. If the batteries get too low then we'll just > attempt to get into the site, fire up that home made generator and > walk away. We'll make sure it looks like a rusty piece of garbage so > no one who wanders by is likely to steal it. Any comments?
Generators and fuel are a lot of trouble. > (Apparently the snow drifts can get quite bad so we might need to borrow a > snowmobile for the last > 400 yards or so.) This is when you have to ask yourself: "Is it really worth the hardship to keep this repeater on the air at this site?" > We're thinking of putting the batteries in a chest freezer disguised > by thin plywood so it just looks like a box. We're told by the site > owner that a fridge looks way too much like trailer trash so > disguising it with wood should work. I'm thinking we would put the > charge controller in there for a little heat and the dump load in > winter > > Are we nutz? Have I asked some stupid questions? Yes, and no. For the former, you're in good company. The freezer idea isn't new; there's one repeater up somewhere in Canada that is near a rock peak mounted in a large freezer. It, along with the repeater trustees, were flown in with a helicopter. For your situation, it might be best to use a pair of freezers, and install a hasp and padlock on them. Put the batteries in one (or both) and the repeater in the other. If you can find self-resetting circuit breakers, I would use those for the batteries, and individually protect each battery from a common bus. This way, if you develop a shorted cell in one battery, or a dead-short across several or the battery itself, the problem becomes self-isolating. Of course, you have to be able to develop enough power from the other batteries to exceed the circuit breaker's trip rating. You'd be better off using fishing batteries than lawn garden batteries. Don't forget to make a gas collection/vent system using aquarium tubing or surgical tubing. Well, if you need a gas collection system, you don't have sealed lead acid (SLA) batteries, which means you're adding electrolyte or water a few times a year. SLA is the better way to go, but you have to watch the battery temperatures to prevent damage to the batteries during the warm months or when charging on a really good power day. Damage means the battery vents, and that's no good. So you need a good charge controller, and decent diversion load. I suppose if one was really inventive and handy with some metal tools, you could make a vertical rack and suspend a large weight from it. Then attach a screw/gear lift motor from the diversion system, and have a small, regulated generator from a different gear ratio making a few watts of power. 10,000 feet of wire-rope and an old oil well.... -- Kris Kirby, KE4AHR Disinformation Analyst
