IDEA Inverter based supplement to generator backup

Even though it should be pretty reliable, you are adding a lot of complexity for (probably) a very small gain. Stock up on diesel and stop beating yourself up on how to make an incremental improvement.

I looked at a Giant UPS for a new house I'm consulting on, and the float charge power requirements were astounding!

I don't think that Ferrups is very efficient. Hook it up with a light load and do an input/output power comparison before you commit yourself to this project. The good thing is that it is sine wave out. In that respect, it is perfect for running a 'frig.

Vaughn

You know, maybe it is not very efficient, but I already have it...

Maybe you are right... Stocking up on diesel is certainly easier!

Ever hear of a UBS? Best power made them in years past - a big UPS, such as you are considering, with a reasonable battery pack, and a DC generator that looked after providing power when the bateries got low, and recharged them. Get an old reefer deisel (or a Kubota or Yanmar - or even an old Lister)and put a big bus or ambulance alternator on it and connect THAT to your UPS. If you get a 220 volt UPS - and they WERE made - you can run both legs, And the GOOD ups units of that size even had a built in transfer switch - which isn't required if you run a dual conversion UPS on a full-house basis.

The Ferrups is perhaps the most innefficient UPS built - but before the days of switching power supplies, there was nothing that could provide cleaner, better regulated power. They did NOT like switch-mode power supplies - they got even more inefficient when running switch-mode loads. Today, a good PWM unit can provide power almost as clean, at about 10 times the efficiency (or 1/10 the power overhead).

Well, my plans revolve around using what I already have, as opposed to buying more stuff.

I too have 750 VA Ferrups in my basement. Even went to the trouble of bringing the battery connections out of the box using those nice Anderson connectors for a BIG external battery. But as others have stated, it is inefficient because it is a FERRO-RESONANT transformer. Notice that there is a cooling fan inside just to remove heat. I hooked it up to the AEMC Power Logger and found it eats 100W doing nothing. With no AC input, and no load at all on the output, about 8A flows from the 12V battery. Yes, it is virutally bullet-proof. But for my hobby application, I didn't want to pay

I use a small inverter to run the blower on my coal stove (I heat with coal) and a few lights If the power goes out I can still have normal heat and not run my generator in the middle of the night. If I need to run the fridge, water pump or anything else with higher power demands I run my generator.

Hey Ig, The FerroUps will do OK, for what you intend, with the understanding that it isn't very power efficent at low loadings. That just means that you will be running your genset a bit more to make up for that lack of effcency. I just scored a 36Vdc Forklift Battery for my operations, that had a total of 200 hours of use. (the forklift died, and no parts available for that old of unit) I will be splitting the bank into two seperate systems, one 24Vdc for my Trace 4024, and one 12Vdc to run the 12V Buss in the Cabin. The Trace will be charging the 24Vdc bank, and I have a very nice 40 Amp Regulated PowerSupply to float across the 12Vdc bank. Nothing like a 1200Amp/Hr battery to keep things running while the gensets rests.

Bruce in alaska

Very nice. I will check out forklift batteries in my area.

This is approximately what I do. Why pile operating hours on the generator when, most of the time, the load is minimal?

That does indeed make sense. Thanks.

If you want another idea on getting big batteries for cheap, call the local telephone companies, or big computer centers with big inverters, and see what they will have in their "Surplus" pile.

Those users have several strings of 1200AH, 2400AH, 4200AH and larger single cell lead calcium deep-cycle wet cells that you can assemble into any voltage you want, and the whole string of 26 is usually retired at the very first sign of aging of any one cell - meaning most of them have several years left in them.

Normally they just send them back for recycling, at several hundred pounds of lead per cell, and they are heavy enough that shipping them long distances to be recycled is an issue. But if you get there first and reserve the next batch they pull...

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A nice idea. Thanks Bruce.