i would much rather do the charging myself, separately, where i can take full control and improve efficiency.
I guess there's a lot of different ways to approach the problem. We lived here for 7 years with separate charging, trying all sorts of different ways to integrate it, and I could never get it to work.
It comes to a point where when you live off-grid you want to start living and doing something else rather than baby sitting your system all the time. And after almost a decade you get to the point where you want some of the conveniences that people on grid power have.
With our new system, that cost us slightly better than $20,000 with inverters, batteries and generators, it has put us into a whole new world of convenience and comfort that I wished I would've done something long before I did.
As an example, our inverters are rated at 8 kW but they will put out 20 kW for 11 seconds and 14.4 kW for five minutes. We can have 2 kW normal loads and my wife turns on her induction range, jumping the load up to 7.5 kW. Then she runs down in the basement and throws a load of clothes in the dryer and turns that on, jumping the load up to 13 kW. And she can do this without even having to ask if we got the power to run it.
On the inverter end the peak load threshold is exceeded at 8 kW and the inverters wait for 2 minutes to see if this load is temporary or if it's going to be a long term thing. At 2 minutes if it's still there it fires up the generator and warms it up at no-load for one minute. During that minute it syncs its sine waves on both legs with the sine waves from the generator. At three minutes into the heavy load the inverters load the generator gently up to full load, which reduces the load on the battery bank to 7 kW.
An hour later the timer shuts the clothes dryer off, but whatever my wife is cooking in her range is still cooking, so the load drops below the peak load threshold. The inverter looks at this and if it stays below for 15 minutes it will shut the generator down.
However, 60Hz generators run at peak efficiency at full load, and least efficiency at zero load, measured by kWh/gallon of fuel burned. The inverter is smart. It's not going to let that generator run at partial load. It looks at the bank status and uses part of it's power to charge the batteries if they need it, and the balance to carry the load, which further reduces the load on the batteries and keeps that gen at peak efficiency. If this condition keeps up for 15 minutes with the total load below 8 kw, and the batteries are above the minimum set for the 2 hour auto-start timer, the inverter disconnects the gen from the load, lets it run no-load for two minutes to cool it down, then shuts it off.
This has made our home so that you can come visit and you can't tell we don't have grid power. I spent the better part of 7 years trying to build an integrated system like this from components, but I could never match what boB and Robin and the other guys at Trace/Outback/Magnum were able to do with their integrated off-grid units. In fact, not even close to as seamless as our system works today.
My total chores have been reduced to checking the water in the batteries once a month, changing the oil in the generator once a year, and calling up the LP truck to come top off our 500 gallon LP tank once a year. And that's it. Otherwise, when I feel like it, I look at the meters and gauges now and then to see what the system is doing. But I don't even have to do that because it takes care of itself and I can go fishing instead of babysitting a bunch of equipment.
I'm not saying it's impossible to build an integrated system out of stuff that you collect from here and there. But after 7 years I got tired of it and with the prompting of my wife spent the money on a "turn key" system that "just works". And, baby, let me tell ya' that after you experience a "just works" system like that it makes you wonder just what the hell you were trying to do cobbling it together out of "stuff".
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Chris
