Alternative to grid tie inverter

[RW Salnick]

Rather than pay the $$$ for a grid-tie inverter, I wonder if there is an
inverter that does the opposite of most smart inverters. That is, it
feeds the AC load off of the battery until the battery is low, and then
switches to the AC mains until the battery is again ready to go again.

With this animal, I could run my kegerator in the garage with (mostly)
solar without having to worry about warm beer on cloudy days. I have
three 50 watt solar panels to use, but I'm certain they won't keep up.

bob

 

[Vaughn Simon]

With this animal, I could run my kegerator in the garage with (mostly) solar
without having to worry about warm beer on cloudy days. I have three 50 watt
solar panels to use, but I'm certain they won't keep up.

The system you are describing would be hard on batteries, cycling them
perhaps daily and wearing them out in a couple years or so unless they were very
high-end units. With the little gizmo that Richard P found:
http://www.buyerisland.net/greenpower.htm Your 150 watts of solar could be put
to good use, and you wouldn't even need the battery.

Don't forget to do the $ math though... Depending on your area, the system
you are contemplating would average perhaps one KWh/day; vaguely 10 cents worth
of power per day, $37.00/year. Since you already have the panels, the inverter
would pay for itself in a mere decade or so if you ignore cost of capital. If
you had to buy the panels also...forget it!

Vaughn

 

[Martin Riddle]

| Cool video with that small inverter... the Eagle schematic wipes
| across the screen... I can freeze frame it... cant figger out how to
| grab it yet...

Looks like a basic push pull MSW, no low pass filtering or anything. I don't believe this is what is in the actual device.

Cheers

 

[RW Salnick]

The system you are describing would be hard on batteries, cycling them
perhaps daily and wearing them out in a couple years or so unless they were very
high-end units.

That would depend on the setpoint for cutover to the AC mains now
wouldn't it? Certainly if the batteries were driven flat, you would be
correct. But no knowledgable person would do that, right?

bob

 

[Vaughn Simon]

That would depend on the setpoint for cutover to the AC mains now wouldn't it?

Not entirely. Battery storage always has a cost associated with it.
Batteries cycled daily (even if only a conservative amount) will not last as
long as batteries that are properly floated and rarely cycled. I saw the
figures here a while ago estimating the cost of deep-cycle battery storage
(assuming the electricity is free). As I recall, the answer was several cents
per KWh. You can easily make your own assumptions and do your own math, or
perhaps somebody can produce a reference.

Certainly if the batteries were driven flat, you would be correct. But no
knowledgable person would do that, right?

No. No knowlegable person whould do that, but is does sometimes happen by
accident. In any case, battery storage is not free! Batteries wear out and
their lifespan is determined partially by the number of effective cycles that
you put on them.

Vaughn

 

[Martin Riddle]

Looks like a basic push pull MSW, no low pass filtering or anything. I don't believe this is what is in the actual device.

===================================================
Especially since its a bridge mode output.... how you gonna put that
into a single ended outlet?? I guess a 250W transformer could be
hidden in the box?

Well, a 180w Toroid is 2"x3.5" so yes it could be put in the box.
Another omission from the schematic is sense points on the output
to detect voltage.

Cheers

 

[Martin Riddle]

|
| > Looks like a basic push pull MSW, no low pass filtering or anything. I don't believe this is what is in the actual
device.
| ===================================================
| Especially since its a bridge mode output.... how you gonna put that
| into a single ended outlet?? I guess a 250W transformer could be
| hidden in the box?
|
| Well, a 180w Toroid is 2"x3.5" so yes it could be put in the box.
| Another omission from the schematic is sense points on the output
| to detect voltage.
|
| Cheers
|
|

 

[Eeyore]

===================================================
Especially since its a bridge mode output.... how you gonna put that
into a single ended outlet?? I guess a 250W transformer could be
hidden in the box?

Well, a 180w Toroid is 2"x3.5" so yes it could be put in the box.
Another omission from the schematic is sense points on the output
to detect voltage.

And that's CRITICAL !

Graham