How to run an inverter without batteries

[johngalt]

I know the answer is "No" when it comes to designing a whole house system, but hear me out. This is just an idea for some inverter power for short bursts without using a battery bank.

If you wanted to run an inverter short-term to power AC tools in your workshop for an hour or two a day would the following work?

Use a PV array with plenty of wattage and connect that to a MPPT controller. From there run the output through a DC line conditioner, for example 10V to 16V in with 12.5V to 13.5V out, which then goes to your inverter.

Set the MPPT controller to equalization mode/conditioning mode so the voltage is a constant 15.5 volts for 8 hours. (one of the settings on my CC)

The idea would be that the larger array could provide adequate wattage to the charger which would then put out an increased constant voltage that would then be conditioned down prior to going into the inverter.

If you ran a setup like this for say 2 hours on a clear summer day during the peak of the day do you think it would work? Of course when you are done cutting your wood, drilling your holes, or whatever the task you shut it all down and save it for the next sunny day.

P.S. The above is assuming you were running a 12V inverter. Of course if the concept was sound then a larger inverter could be run at 24v or 48v by just changing the MMPT settings and using the right equipment and sizing the PV array appropriately.

[Sunking]

You would be wasting your time and money. But hey go prove me wrong, it is your money and time, not mine.

[johngalt]

You would be wasting your time and money. But hey go prove me wrong, it is your money and time, not mine.

My question was whether or not it would work rather than being cost effective. I already have most of the equipment and live in a rural area where power comes and goes on occasion. Sometimes longer than others.

If the fecal matter ever hit the rotary device and I was totally without power for awhile it would be comforting to know whether or not I had the ability to do something productive besides wait around for the power to come back on or the government to come bail me out.

I'm looking at solar as more of an emergency worst case scenario vs. full time endeavor for everyday living. As long as I have local power I'm going to use it. But in an emergency if I can still pump water, run some lights, or use some power tools to fix things then I'm much better off then setting around in the dark.

A wise man once said "God helps those who help themselves"

[Sunking]

I already answered the question. it will not work the way that you propose. Only way it would work is if you built a custom made shunt or series regulator to convert a current source into a voltage source, that is capable of sinking a lot of heat and power. Th emost effective and economical way of doing that is with a battery and charge controller.

[johngalt]

I already answered the question. it will not work the way that you propose. Only way it would work is if you built a custom made shunt or series regulator to convert a current source into a voltage source, that is capable of sinking a lot of heat and power. Th emost effective and economical way of doing that is with a battery and charge controller.

Thanks - I'll look into that.

[Sunking]

Here is what you are going to run into. First you have to determine which is the highest demand tool or appliance you want to run. Let's say it is a table saw with a 1/2 hp motor and start up current is 8X Full Load Amps. Full Load Amps is roughly 25 amps AC. So if you decide to use say standard 12 volt battery panels which you will be forced to do translates to 2900 watts of solar panels to run a 1500 watt battery inverter.So now you are going to sink $3000 to $5000 in panels. Now you have to design a converter and it has to be able to dissipate at least 2000 watts of power to burned off as heat. That will cost you several thousand dollars to have custom built and some very expensive super capacitors which are basically batteries.

If it were me I would just use a 100 watt panel, a cheap $50 10 amp charge controller, a Optima Yellow Top AGM battery, and a 1500 watt inverter. Build the whole thing for less than $500 and can use it any time even at night. To do it your way , $10,000. Knock yourself out. I can even design/build the converter for you.for $300/hour

[johngalt]

Here is what you are going to run into. First you have to determine which is the highest demand tool or appliance you want to run. Let's say it is a table saw with a 1/2 hp motor and start up current is 8X Full Load Amps. Full Load Amps is roughly 25 amps AC. So if you decide to use say standard 12 volt battery panels which you will be forced to do translates to 2900 watts of solar panels to run a 1500 watt battery inverter.So now you are going to sink $3000 to $5000 in panels. Now you have to design a converter and it has to be able to dissipate at least 2000 watts of power to burned off as heat. That will cost you several thousand dollars to have custom built and some very expensive super capacitors which are basically batteries.

If it were me I would just use a 100 watt panel, a cheap $50 10 amp charge controller, a Optima Yellow Top AGM battery, and a 1500 watt inverter. Build the whole thing for less than $500 and can use it any time even at night. To do it your way , $10,000. Knock yourself out. I can even design/build the converter for you.for $300/hour

How many hours would it take? I currently have 1305 watts available and could bump it up to 1740. (12 x 145watt 12v panels) I have 3 more panels sitting idle.

I do not have the inverter yet, but since my last post I did some more research and determined that I would not be operating any power tools that exceeded 1200 watts. (10amps x 120v some even less) and would not need to run more than one tool at a time for maybe a minute or two per application. Cut a board, drill a hole, etc.

I can certainly do the battery route, but was just curious as to how I could game the system by not relying on the one component that I have to replace or may not be able to replace in an emergency situation.

I know this sounds like Gilligan's Island, but that's how I'm looking at it. If I have to accomplish a particular task only using what I currently have available how could I do it? Right now I have the luxury of compiling the things I need in advance. But if the power goes out after this post I am stuck with what I have on hand.

I guess I don't understand how you can use a 1500 watt inverter using one battery for any length of time without destroying the battery and having to replace it often.

I currently have 4 x 153AH 12v Sun Xtender AGM batteries available but don't want to kill them by frequently over discharging them.

Back to the books......

[johngalt]

After further review, it does make more sense to just go with what I've got rather than make things more complicated.

I'll just tie in a 1500 watt inverter to the existing battery setup for the rare occasion when I need some AC power.

Thanks for the input.

[Sunny Solar]

Im sure you must own a vehicle or two? In emergency just use the batteries out of them .Parallel them for extra available output. This solves all the regulation problems at no extra expense. Car /truck batteries can provide a lot of instant power,sure not for long periods of time,but that is not your problem as you have enough solar panels to provide the power your tools will need and you are only going to be using then under good sunlight conditions.





A wise man once said "God helps those who help themselves"
And "God help those that get caught helping themselves"

[johngalt]

Im sure you must own a vehicle or two? In emergency just use the batteries out of them .Parallel them for extra available output. This solves all the regulation problems at no extra expense. Car /truck batteries can provide a lot of instant power,sure not for long periods of time,but that is not your problem as you have enough solar panels to provide the power your tools will need and you are only going to be using then under good sunlight conditions.

That would work too. I also have a small generator. I was just trying to think of the worst case scenario in case I had to "MacGyver" something together if I had no gas or batteries available and could not get any for awhile.