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Inverter question
By BadNIMBY, Section Controls Posted on Fri Oct 3rd, 2008 at 11:54:50 AM MST
possibilities

Hello all
I am trying to find out if there are inverters/controllers which can be used in conjunction with a battery bank where:
The household electricity demand is supplemented by the energy being produced by the wind turbine via the battery bank and therefore lowering the amount of electricity drawn from the grid.
I am not wanting to grid tie but for the household supply to be drawn preferentially from the turbine with any shortfall being made up from the grid.
I know this will have to be matched to the 50hz grid supply, but have turned a blank searching the internet.
Thanks all for you time.
Will

Inverter question | 9 comments (9 topical, 0 editorial)

Re: Inverter question (3.00 / 0) (#1)
by Flux on Fri Oct 3rd, 2008 at 07:07:12 AM MST
(User Info)

What you are asking for is a battery based grid tie inverter and they do exist.

You can't do what you ask without grid tie. You could use something that I know as a static switch that would switch from inverter to grid but not synchronise to it. This is more often used to back up a failed grid supply but you could use the grid to back up an inverter. It would be complicated and messy and you would either use inverter or grid and I can see certain appliances being badly confused by regular change overs.

Really without going grid tie and synchronising you might as well use manual change over for appliances that you have enough power for. It will change constantly depending on the energy available. You could automate it on a few non fussy appliances but generally things will object to being switched from one supply to another when in operation. If the change over is fast, things like computers will ride through it but if not fast enough they will "brown out". Things like lights may not be too bad with a glitch now and again. Motor loads will need an exceedingly fast change and that is not particularly easy or safe with two independent supplies. The best standby backup schemes can change in about one cycle of the supply but any home built thing would need far longer to change safely.

Not sure what you will find commercially you are basically looking at UPS.

Flux

Re: Inverter question (3.00 / 0) (#2)
by richhagen (richhagen (a t) Juno.com) on Fri Oct 3rd, 2008 at 07:24:50 AM MST
(User Info)

Inverters such as Xantrex SW series and Outback's FX series have an 'LBX' mode that will switch between passing grid power through the inverter for the loads when the batteries are low, to powering the loads from the batteries when they are higher. It is an either/or setup, basically synchronizing the frequencies and switching the power source from grid to batteries or vice versa. On the Xantrex model I have, and those I have seen, you can not turn off the battery charge function which draws power from the grid to charge the batteries when they are low, but you can turn adjust the charge amps down to about 2 amps if I recall correctly. I have never rigged an Outback Inverter in this way, so I don't know about switching off the battery charger while in this mode. Like Flux says, I do not think it would be possible to do what you are asking about without calling it grid tied, so this 'LBX' mode is about as close as I can think of that you can get with a commercial inverter. I recall that Xantrex indicates in their manual that you generally do not need Utility approval to operate in this LBX mode as you cannot feed power back into the grid. Rich
'A Joule saved is a Joule made'

Re: Inverter question (3.00 / 0) (#3)
by richhagen (richhagen (a t) Juno.com) on Fri Oct 3rd, 2008 at 07:27:30 AM MST
(User Info)

The utility approval part is probably mainly for the U.S., since I see you are using 50hz power, I will assume you are somewhere else, so you should check your local regulations before using an inverter in that type of mode. Rich
'A Joule saved is a Joule made'
[ Parent ]

Re: Inverter question (3.00 / 0) (#4)
by boB on Fri Oct 3rd, 2008 at 11:26:01 AM MST
(User Info) http://bob.gudgel.org

LBX mode just switches on the charger when the battery voltage gets below a certain point. This is what you want I think. No utility blessings needed as far as I know.

boB

[ Parent ]

Re: Inverter question (3.00 / 0) (#5)
by Flux on Fri Oct 3rd, 2008 at 12:16:17 PM MST
(User Info)

That is an option that I didn't think of. If you can manage a lot of the time on the inverter and the inverter can supply all your needs then you can use the grid to charge the batteries when you are low on power. This solves all the problems of change over.

The efficiency will be lower than using grid power direct but if it is only a small back up occasionally the convenience will make it worth the trouble.

Flux

[ Parent ]

Re: Inverter question (3.00 / 0) (#6)
by ghurd on Fri Oct 3rd, 2008 at 12:38:32 PM MST
(User Info)

I am working on my "ghurd kit" to do that, set at 12.2V or so to turn on a standard grid powered battery charger until a considerably higher voltage.
Seems to be OK so far, but long sloppy bare wires shorted and fried something related to the relay. A bit concerned about the battery being grounded in North America, have not had time to get it sorted out.
G-

[ Parent ]

Re: Inverter question (3.00 / 0) (#7)
by TomW on Fri Oct 3rd, 2008 at 01:25:16 PM MST
(User Info)

boB;

I use "HBX" [High Battery eXchange] mode on my FX2524 [perhaps incorrectly] It will go on grid to keep batteries safely within their voltage limits by going on grid, charging the batteries and powering loads from the grid and then dropping the grid when the batteries get to a set voltage. I run certain loads off the inverter and it helps me sleep at night knowing the loads will be supplied pretty much regardless of my incoming RE levels. My tired batteries just don't have a lot of bottom to them so on long stretches of low RE it keeps things on the inverter using all the RE there is then going to grid charge as needed.

Just how I do it with an Outback here. You need a "Mate" to do this I believe. For sure to set it up.

Mileage may vary.

Tom.

"Education consists mainly of what we have unlearned."--Mark Twain
[ Parent ]

Re: Inverter question (3.00 / 0) (#8)
by boB on Fri Oct 3rd, 2008 at 11:05:19 PM MST
(User Info) http://bob.gudgel.org

Yeah, HBX, LBX, same thing... Trace called it LBX, OutBack calls it HBX,
but it's the same idea. Use renewable energy whenever possible. Use the grid
as little as possible. If the batteries are not so good or you just want to
be good to them, adjust the settings as good as they'll let you I guess.

Other systems without LBX/HBX have to be made specially with a separate
relay and control etc. It's nice to have it built into the system.

boB

[ Parent ]

Re: Inverter question (3.00 / 0) (#9)
by TomW on Sat Oct 4th, 2008 at 04:33:34 AM MST
(User Info)

boB;

Thanks for the clarification. I thought I had somehow remembered the "H" wrong. Nice to know I can actually trust the occasional memory!

I do like how the Outback with a Mate turns a fairly "simple" inverter into a clever piece of gear. It does come at a price, however.

Thanks for the response / info.

Tom

"Education consists mainly of what we have unlearned."--Mark Twain
[ Parent ]

Inverter question | 9 comments (9 topical, 0 editorial)

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