Did anyone try this? Ac Charge controller + battery bank + inverter

[minh808]

Here's some background and what i want to do.

I'm on a solar FIT program in Hawaii that pays me for the excess power i create but charge me for what i pull from the grid. So in the day i use what i produce but get charged at night when i pull from the grid. The rates that they offer is a ripoff with a buy price of 39 cents and pay out price of 19 cents.

What i want to do is to charge a battery bank up with the excess power i create during the day with a AC charge controller and pump that back into my home at night though a girdtie inverter. This in theory should keep my meter from spinning forward at night.

Anyone has any experiences with this or have any advice. TIA

[inetdog]

Here's some background and what i want to do.

I'm on a solar FIT program in Hawaii that pays me for the excess power i create but charge me for what i pull from the grid. So in the day i use what i produce but get charged at night when i pull from the grid. The rates that they offer is a ripoff with a buy price of 39 cents and pay out price of 19 cents.

What i want to do is to charge a battery bank up with the excess power i create during the day with a AC charge controller and pump that back into my home at night though a girdtie inverter. This in theory should keep my meter from spinning forward at night.

Anyone has any experiences with this or have any advice. TIA

The fundamental problem with your otherwise good idea is that once you have added in the cost of batteries, additional inverter, etc. your true cost for the power you use from the batteries at night will be far higher than the 39 cents per kwh you are paying.
You can do better by conserving and by load shifting so that any loads that don't absolutely have to run at night run during the day, during the time your meter would be spinning backwards, instead.

[Sunking]

Agree instead of paying 39-cents you would be paying closer to $1.50.

Since when is it a rip-off for a company to buy a product and sell it for a profit? Your utility can generate rate the electricity or buy it wholesale for less than they are paying you for it.

[JimD]

[The best way to make it work would be to get off the grid altogether then you would be paying yourself 39 cents for your electricity The cost would not be that great if you finish the system yourself your got the panels and the controller and the invert er you use to tie into the grid feed into your breaker panel instead of the grid.Your biggest cost will be battery's. I just got 24 250 AH 6V battery's for 118 dollars a peace.It's a investment but 3 years you will probable be home free. Your pay at least 20 a month just to have a account with the grid even if you don't use any electric. I am off the grid and have not payed a electric bill since 1993 it works fine. Good luck JimD .

I'm on a solar FIT program in Hawaii that pays me for the excess power i create but charge me for what i pull from the grid. So in the day i use what i produce but get charged at night when i pull from the grid. The rates that they offer is a ripoff with a buy price of 39 cents and pay out price of 19 cents.

What i want to do is to charge a battery bank up with the excess power i create during the day with a AC charge controller and pump that back into my home at night though a girdtie inverter. This in theory should keep my meter from spinning forward at night.

Anyone has any experiences with this or have any advice. TIA[/QUOTE]

[Lasitha]

Grid-tie and Batteries.

I'm not an engineer, Just a beginner.
But I don't think you can connect a battery to a Grid tie inverter.
( Because a battery can supply unlimited current, initially. ? )

[inetdog]

I'm not an engineer, Just a beginner.
But I don't think you can connect a battery to a Grid tie inverter.
( Because a battery can supply unlimited current, initially. ? )

A pure grid tie inverter will be designed to operate from a higher voltage source (series string of panels) than you usually see from a battery bank. Even 48 volts is below the starting point for an MPPT GTI.

But even if the input voltage were acceptable, you are right that the MPP tracking mechanism would try to see how much power it could get from the batteries by reducing its voltage while trying to draw more current. When facing a voltage source like a battery instead of a current source, like a PV array, the tracking mechanism will end up pulling far too much current.
Whether this will cause damage to the inverter, blow fuses, just cause it to shut down, or to run at an odd current/voltage combination will depend on the design details of a particular MPPT inverter.

[russ]

Actually utilities are not stupid. Most have surplus power available at night - if they could store and time shift those kWh to daytime it would be a big deal for them.

Utilities don't do it because the concept is a loser.

[green]

For the money invested it would make more sence to increase the size of your grid tied system and produce more excess during the day to offset nightime usage.

Green

[Naptown]

Are you producing more than you are using?
I just checked the net metering laws in Hawaii and it is net metering credited at the same retail rate until excess at the end of the year is produced which is then goven to the the utility
Go to dsireusa.org and click on hawaii and net mettering.