12 volt batteries, solar panel and inverter.

[grandpa123]

Anyone with information on this would be helpful. I just installed a 7 watt solar panel to keep my two 12 volt batteries topped up. I also would like to hook up a 110 volt inverter to the system to change my 12 volt to 110 and hook this up through my trailer 110 plug in which it would go through that converter to run the micro wave in the trailer.
as the converter changes the 110 volt to 12 volt for running the lights and charging the batteries. What kind of problem can I expect to have. The Micro wave is run very seldom but the wife does like to warm thing up occasionally when we aren't hooked into grid power.

[pianotuna]

Hi,

Cheapest route for you is to upgrade to a hybrid inverter/charger. I would add some more solar charging.

[teejaywhy]

A generator or huge battery bank & inverter just to heat the occasional can of soup?

Suggestion: Propane Stove.

[grandpa123]

Thanks everyone for your input. Really appreciate the knowledge that is out there on this form. I have decided to rethink my situation and will probably go with a 3000 watt Gen in the back of my truck.
Once again thanks for all the input.
Grandpa.

[Golden_HVAC]

I have a E-Meter on my motorhome, and it carefully measures all the power going into and out of the battery bank. This is a $375 accurate meter. It shows that my CO meter, propane detector, and refrigerator combine to consume 35 amp hours daily. This is about what one of my 120 watt solar panels puts out every day.

They are rated at 21 volts and max 7 amps. take the 7 amp output, and multiply by 5 "Peak hours". That is all you get. The panels are in the sun all day, and part of the morning it is less than 5 amps per hour, noon it is near 7 amps per hour, afternoon it is less than 5 amps again, so "rule of thumb" is to take the rated amps X 5 hours.

You can buy larger solar panels for about $1 per rated watt. SunElec.com

As for running the microwave from a inverter, I do not recommend it. I ran mine for about 15 minutes, and had to replace it because it cooks so slowly now. And I have a $750 Trace 1,500 watt inverter/charger, that is wired with #000 wire, and my 4 golf cart batteries can put out 150 amps while it was running. Unless you have so many batteries, and such large wire, it will not work, and investing all that money to just find out that your microwave now cooks really slowly too - well learn from my mistake.

Good luck,

Fred.

[Shadow_Catcher]

We do not have a microwave and about half of our camping is off grid. We do have a 185W high voltage solar panel which meets our needs including for our Waeco 12V refrigerator.
There is one alternative and that is to use the output from the tow vehicle alternator. I have a set of jumper cables that can be run between the TV and battery. The Subaru alternator is rated at 110 amps and it uses .35 gal per hour.
I have a 30A DPDT switch that cuts the converter when the inverter is on and powering the outlets.

[sch911]

SteveAE wrote:
Grandpa,

IF you want to run your microwave from your batteries and recharge them via solar, then you will likely need:
- Four batteries
- A 1200 Watt (or bigger) inverter
- Short and large (diameter) cables between the inverter and the batteries
- And a 200 to 300 watt (minimum) solar system (and plan to use power conservatively at that)
This type of system works well ..... for me. But you best verify that this is really what you want before jumping in as it isn't cheap to do.

Steve

This is the best answer so far IMHO. You'll definitely need to go with an inverter with about 150% of the MW's steady state draw to pull this off. Perhaps a better option for you would be a small generator to recharge your batteries each morning.

[grandpa123]

Beemer. You are right. I had to go take a look. The input is 1.5 KW or 1500 watt. my inverter is only 1000 watt with a 2000 overload. I would suggest my gray matter is not working to good.
Thanks for the thumbs up.
My little Honda 750 isn't any help to me here either.
I down graded from a 23 ft Motor home to a 20ft tow behind this last fall as we don't do all that much camping anymore but like to get out when we feel like it. My motor home had a 4000 watt power plant in it so the wife kind of got use to using the micro wave when ever she wanted. May have to change plans now on the inverter seeing that my solar and power supply wont be adequate to do the job. Thanks

[SteveAE]

Grandpa,

IF you want to run your microwave from your batteries and recharge them via solar, then you will likely need:
- Four batteries
- A 1200 Watt (or bigger) inverter
- Short and large (diameter) cables between the inverter and the batteries
- And a 200 to 300 watt (minimum) solar system (and plan to use power conservatively at that)
This type of system works well ..... for me. But you best verify that this is really what you want before jumping in as it isn't cheap to do.

Steve

[time2roll]

grandpa123 wrote:
Beemer! My micro wave is only a tiny 700 watt. Wife usually warms things up in it at lunch time such as a bowl of soup or such once or twice a day at most.

I recommend a 1500 watt Go Power sine wave inverter.
You really should have 3+ batteries to drive it.

Just power the single microwave circuit with a small transfer switch. Going through the converter will just drain the battery. Lights and such will operate directly off the battery as they do now.

I recommend 100 watts solar as a minimum for the effort.

On edit: make that four batteries, 2000w inverter and 200w solar.

[beemerphile1]

grandpa123 wrote:
Beemer! My micro wave is only a tiny 700 watt. Wife usually warms things up in it at lunch time such as a bowl of soup or such once or twice a day at most.

That is probably power output, how many watts does it draw when operating?

[grandpa123]

Beemer! My micro wave is only a tiny 700 watt. Wife usually warms things up in it at lunch time such as a bowl of soup or such once or twice a day at most.

[RoyB]

With just a couple of 12VDC batteries you can only expect to use a small INVERTER around 300-400WATTS. INVERTERS take alot of DC CURRENT to operate.

I have a 600WATT PSW INVERTER setup in my off-road trailer and I can draw around 300WATTS from the Home Entertainment items, a couple of fans/lights/ and recharge my cellphone and computers. I also have a WX ALERT RADIO and a few other low wattage items running.

We draw around 20AMPS continuous from the battery between 6PM and 11PM and of course there is a constant parasitic draw of 1-2AMPS all the time. This drops my 255AH battery bank to its 50% charge state by 8AM the next morning which I have to re-charge back up otherwise it will do damage to the batteries.

If you are wanting to run a 1500WATT microwave it will take way over 120AMPS of DC current from the battery bank to operate it.

As stated above you cannot do a LOOP where you have a BATTERY running an INVERTER which in turn runs a Converter that charges the battery. Our science doesn't support this loop except in Star TREX movies. If you could do this then you would have an endless source of power.

To do what you are thinking about will require a very big battery bank and then a way to recharge the batteries when you are off the power grid.

Also all you can expect from a 7W Solar Panel is to trickle charge a battery. This is only good for topping off a charged up battery. I doubt if this 7W Solar Panel will even keep up with your always on 1-2AMPS parasitic drain with your trailer.

To re-charge a single 12VDC Deep Cycle battery in a quick three hour time period you will need 14.4VDC with the capacity of 17-20AMPS of DC current to get the battery re-charged to its 90% charge state. A typical 120WATT Solar panel (alot bigger than your 7W Solar Panel) will only produce around 5-6AMPS of DC current when in the high sun and will only do this for 5-6 hours in a typical high sun day. It would take several 120WATT SOLAR PANELS (around 6 of them actually) if you wanted to re-charge a single 12VDC deep cycle battery in a three hour time period that has been drained down to its 50% charge state.

Will take some serious planning and resources on what will support what you want to do camping off the power grid... take a look at some of the full time guys that live in the RV's 24/7 and note how many batteries they have on-board.

Just saying...
Roy Ken

[grandpa123]

Thanks good point, That shouldn't have any bearing on the ignition of the fridge or furnace, as they run directly off of the batteries and propane, I don't have a A/C so no problem there.
We usually hook up to grid power when its available but there are times when we like to boon dock where fishing is good and campers are scarce.

[beemerphile1]

A 7 watt panel is nearly worthless.

Your microwave may use 1,000 watts or more. You do the math on the recharge time.

Other than the teeny tiny panel, your plan sounds okay.