Paralleling inverter/chargers with generator "boost"/"support" function

stephendv

Had an idea about how to connect more than one inverter/charger if one of them has the generator "support" or generator boost function. This is just a theoretical idea, but I think it would be interesting if it worked because it would mean that you could parallel different inverter/chargers with different sizes and makes.

So, "generator support" or "generator boost" or whatever the manufacturer calls it, means that you can tell the inverter/charger to augment the power from a connected AC source (usually a generator). So with a 1kW generator and a 2kW inverter/charger that has generator support feature, it means you can draw 3kW from the output of the inverter/charger while the generator's on.

...and since the inverter/charger doesn't care where that AC power source comes from, couldn't you connect another inverter or inverter/charger as the source of that power? e.g.:

500W inverter -> 2kW inverter/charger (with boost feature) then pull 2.5kW out of the combination of the two. As long as the inverter/charger is programmed to know that it's boost feature should kick in when it pulls more than 400W from it's AC input, this should work shouldn't it?

Might be a nice way to run a small inverter most of the time and have a much bigger one kick in, only when needed. Thoughts?

westbranch

Re: Paralleling inverter/chargers with generator "boost"/"support" function

Interesting concept, waiting for the pro's to comment

Cariboocoot

Re: Paralleling inverter/chargers with generator "boost"/"support" function

Yes, in theory you could have a large inverter with gen support connected to a small inverter substituting as the generator.

In practice you'll probably find it's a waste of time because of the sizing, tare losses, and cost.

That is the price of the total equipment being equal to or greater than the price of buying one inverter that can handle the whole load on its own. Keep in mind that smaller inverters do not automatically mean less consumption for the inverter or more efficient conversion.

Try it with the specs of some specific equipment and see what results you get.

vtmaps

Re: Paralleling inverter/chargers with generator "boost"/"support" function

You will have to disable the battery charger in the inverter/charger so that it doesn't try to charge the battery with power from the small inverter.

--vtMaps

mike95490

Re: Paralleling inverter/chargers with generator "boost"/"support" function

If I thought it would work, I'd use it, but the standby power 24/7 of the "big" inverter, sitting, waiting for a "surge" to boost, eats up the savings. I can switch off the charger of the XW, run my suresine 300 into a 240V autotransformer, and feed that into AC1, and reprogram. But the big inverter will be awake 24/7 eating power.

Cariboocoot

Re: Paralleling inverter/chargers with generator "boost"/"support" function

mike95490 wrote: »

If I thought it would work, I'd use it, but the standby power 24/7 of the "big" inverter, sitting, waiting for a "surge" to boost, eats up the savings. I can switch off the charger of the XW, run my suresine 300 into a 240V autotransformer, and feed that into AC1, and reprogram. But the big inverter will be awake 24/7 eating power.

Exactly.
I just tried it theoretically with an OB GTVFX2524 and a tiny Samlex 300. The difference of 4 Watts tare over running the OB all the time didn't seem worthwhile, especially since it would rely on a very limited run time for the OB to make up any Watt hours savings. Add the complexity, including the battery charging problem vtMaps points out, and you have ... yes it works in theory, but it's not very practical.

The main reason being that the amount of power an inverter consumes is not directly proportionate to its output capacity. Most of it is used by the control circuitry, which remains fairly steady regardless of the MOSFETS & transformer needed to handle the high current of the AC out. So the little 300 Watt Samlex consumes about 10 Watts but the big Outback uses 20: 2X the power use for 10X the AC capacity.

It would theoretically be possible to build a modular inverter with a 'control unit' that can operate and sync multiple 'power units' much the way stacking inverters do, only without the redundant control units. You could then have flexible sizing of, say, 500 Watt increments and/or the ability to turn on only as much power capacity as needed. But would it be practical? The money spent on the more complex design could simply be used to up the system power capacity to handle greater losses from a conventional inverter.

Not sure about using buck converter input to make one 12-24-48 Volt capable in a single unit, though. That's a bit more complex, right boB?

zoneblue

Re: Paralleling inverter/chargers with generator "boost"/"support" function

Steca inverters have a hub kind of thing that allows you to stack say 4 of their 1kW inverters. Each one has 10W tare, and the hub brings on additional units as needed. The result: UL listed 4kW inverter with 10W tare.

The catch: the price tag. Ouch. 4K+

stephendv

Re: Paralleling inverter/chargers with generator "boost"/"support" function

You can also stack the smaller Victron units together... and it also comes out as quite a pricey option. The Victron's paralleling is actually what prompted this because it will only work if each unit is 100% identical to all the others. So if you bought a 2kW multiplus in 2006 and a 2kW multiplus in 2008, they may not be parallelable because the firmware is slightly different. Grrrrr.