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Power Inverters
You'd need an allowance for losses and I think AC motors are maybe around 90% efficient. The inverter would have to be able to handle the start up surge, which would be greater than current for the rated HP. Most motors have surge ratings.
Sure inverters work, solar power folks run their entire houses off them. A 2hp motor would be far beyond a tractor's alternator's capacity and would draw down the battery pretty fast.
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I'm not sure there's an easy answer for the charger question but maybe others have some experience. Two batteries in parallel would half the load resistance. In theory that may blow the charger. However, the charger may have a limiter, or high loads may drag down the output voltage. It might be good to contact the charger manufacturer and get their recommendation.
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I've heard that batteries may not come up to full charge unless they're changed for 24 hours at a trickle rate after higher rate charging. Could be that the minimum charge rates would even out if the packs were trickle charged.
Manufacturing differences could result in varying maximum internal resistance but I wouldn't know how much variation to expect. The different minimum charge rates may affect the amp-hour rating rather than the initial voltage/current delivered. If so then one battery with lower capacity in a series connection would reduce the time a backup pack would support the system rather than the voltage/current delivered initially. It's all speculation on my part. Somebody who knows batteries may have something more definite to say.
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Oh man, too bad about your neighbour and it's not an easy time for you either. The exterior bedroom door idea is a good think to think about. We have a fire safety video in our Library that shows a frame house going from start to completely engulfed in about 10 minutes. The messages is that even with smoke detectors--if hear it there's no time to do anything but get out immediately. Standard houses really aren't good for many seniors and people with limited mobility.
Very good info from AC and I learned something about batteries. Maybe we'll get back to the subject.
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Good that the trickle charge thing helped. Somebody who knows batteries such as AC proably will weigh in on this. As far as I know you get the full effect pretty quickly and you can't expect to get all batteries to very similar charge states. Even if you do you they likely wouldn't stay there after some use. There may be further room to tinker by doing hydrometer checks on individual cells and adding a bit more acid here and there. I'm being vague here since I don't know if that'd work or be a good idea even if it did.
I would keep in mind that AC said that the application would be unlikely to damage the batteries anyway--no guarantees though. For me it'd be fun to keep experimenting with things but I would keep in mind that it might end up crafting a solution that then needed to search for a problem.
I seem to remember that this is for a computer network. My individual PC backup has a USB connection to the computer. It's supposed to backup open files and then execute a Windows shutdown when the battery supply starts getting low. Something like that also should prevent the battery mismatch problems described.
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Sounds like a good outcome and there's been decent comments all around. Maybe we've all learned something. For myself I might have guessed that hooking a charger across several batteries in parallel would increase the charge time but not the load on the charger if I though about it. It didn't occur to me at the time and now I know. It makes a lot of sense that chargers would be designed to limit current at low load resistance.
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Gas Generator Weather Protecti
03-11-2004, 07:34 
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