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Thread: electrical input needed

  1. #11
    Mostly Harmless Hoovooloo's Avatar
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    Re: electrical input needed

    Just a little additional info... We use converters and inverters. Converters typically take a higher voltage and convert it down to a lower voltage. Things like ac/dc wall warts for your phone, battery charger, computer adapter and so on. Inverters allow us to use higher voltage devices from a a lower voltage source. Typically, the inverter will turn the source into an AC output also. This is where our campers and mobile power systems help us use household devices on the road.

    That being said.... Looking at your situation...

    Always build the system backwards. Meaning... Put together a list of items you wish to run on the road. In this example, your hotpot. You stated that it's rated at 800Watts. Good. That is the number we need.

    So, now the math. Others wrote all the important info in previous posts, but let's put it into a path anyone can follow.

    hotpot = 800w which breaks down to 6.6amps at 120volts ac. Power in Watts = current in amps X voltage, ac or dc doesn't matter
    So, now we know that we need an inverter that can supply at least a 960w. This allows a 20% buffer and doesn't overtax the inverter causing early failure. Rule of thumb in electronics, always provide a minimum 20% overage and you won't suffer shorter life due to stress on the components.

    So, 960w needed will work out to 8 amps of available current output. Power / voltage = amperage 960/120=8

    Now we look at the inverter. The 160w safety buffer we placed in the formula should allow for losses caused by thermal and inefficiencies.

    Your inverter is rated at 1500watts. Good. You have plenty of buffer. Now just to look at the limits, lets plug that 1500w into the P=IV formula and solve for our available output current.

    1500w / 120v = ?amps We come up with 12.5 amps available current capacity. So far, we need 6.6amps and we have 12.5 available from the inverter.

    Now, the true test of our system. It always comes down to battery capacity.

    In order to see what our inverter could possibly and actually draw in our case, we need to run the formulas again to find the input values. We know our battery voltage is 12v nominal, but that will drop as the battery depletes. We also know that the inverter will have some losses while inverting the source voltage from 12v to 120v.

    So, at the inverter maximum, 1500w, using the same formula, we solve for amps again P/Vin = Ain 1500/12 = 125. That means that at maximum draw, our inverter can consume 125 amps from our battery. Now looking at our hotpot, let's run the formula again. 800w / 12v = 66.67amps.

    Now, keep in mind, that the wattage will remain the same during it's use by the pot. The inverter is going to try and keep the voltage the same on the output side. That means, as your battery depletes and the voltage reduces, the amperage will need to increase to maintain the 800w output. This will draw down the battery even faster. That is why your battery pulls down so fast.

    Your battery is a 100ah battery, but at what current was that measured? The battery spec sheet should tell you, but don't assume that it will give you 100amps for 1 hour. It is usually measured at some lower rate. i.e. 10 amps for 10hours or 1 amp for 100 hours. And that figure is until depleted. Which you don't want to do to your battery. It will shorten the battery life drastically. Remember the 20% rule. Batteries, depending on type, should not be drained below about 20 - 50%. Newer batteries are better, Li batteries can be drained pretty far down, but no battery will tolerate being drained deeply for long. Take the mfr claims with a BIG grain of salt.

    Back to our example... We know that your hotpot will need a 12v, 67 amp supply from the battery. At an inverter 125amp maximum, you should be running pretty low guage wires from the batteries to the inverter. Probably something in the 6 to 8 range. Otherwise you will have heat losses due to a higher resistance with that amperage.

    The batteries themselves should also follow the 20% overage rule. If your inverter can draw 125amps max, your 12v battery bank should be able to provide 150amp continuous feed. With 2 12v batteries wired in parallel, that means each battery should be able to supply 75amps continuously. That's a lot. You need to determine how long you want to be able to run that load. For your hotpot, that 67 amp load shared by two batteries will draw about 34amps per battery. Rough calculations will give you about 30 - 45min if you have 2 100ah batteries in parallel before your inverter shuts down. Keep in mind that you just depleted your batteries very quickly and it was stressful on them. Don't expect to get many cycles doing that.

    I hope this gave you a good walk through of sizing a power system. Your solar charger of 300w won't make much of an impact. Run the calculation again and see how many amps 300 watts gives you. The key here is the voltage that they used to determine the 300w rating. Is it 12v? then the 300w = 25amp. Which when inverted to 120v = about 2.5amps. Not much. The key to solar is time. Like your piggy bank. a little bit over a long time adds up so you can draw out more for a shorter time.

    Always go back to this formula when calculating loads.

    Power in Watts = Amperage "Current" / Voltage
    Keep your units in check when dealing with small loads. People tend to mess up their milliamps and amps. And be mindful of your voltage being used. It makes a big difference!!!

    I hope this helped.
    Jeff
    2017 Triumph Trophy SE
    Sold - 2013 HD Electra Glide Ultra Limited Anniv. Ed.

  2. #12
    Mostly Harmless Hoovooloo's Avatar
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    Re: electrical input needed

    Looking at the sales data sheet, no, the inverter will not operate above 15v input voltage. Also, I did not see the discharge specs on the battery webpage. You might send them an email requesting more technical data like the rate they tested the 100ah rating at. How far it can safely be discharged and other testing data. They state that the battery will protect itself by shutting down at 9v, but will it shorten the life by discharging it that far. Again, take the info as marketing info that has been presented with best case and new products. I see that the battery is made up of many 18650 type cells. That is pretty typical for affordable batteries like that. As the pack ages, you will see diminished capacity as cells die. Be sure not to leave lithium cells alone during the charge cycle. Cells gone bad and still being charged tend to overhead and can catch fire. Lithium cells don't extinguish easily either. Until you are experienced with these packs and know how they cycle, keep an eye on them and don't just assume they work like AGM. There is a reason why airlines are fearful of these packs. The 18650 cells are used in everything from laptops to toys to UPS systems. How long they last and the number of cycles they provide are related to their care and feeding. Keep them cool, charge them nice and don't over discharge them and they will last a long time. Mistreat them and they will bite back!

    Quote Originally Posted by almosthere View Post
    Don't know if this inverter would work on 24volts.

  3. #13

    Re: electrical input needed

    Think I would try to find some other cooking device.
    So take it and at a campground your ok with electric.

    But, if boone docking is your main thing, cooking with that, it just not efficient I think.
    Go to a big Truck Stop like on I-80 in Iowa, they got lots of cooking stuff Truckers use.

    This inverter takes power just running, and some things take double the draw just to start it.
    You might harm some thing running it at low amps, or the inverter will just stop.

    I had the right to remain silent, but not the ability,,,,, Ron White, I just know enough to be dangerous.

    Buttset from MO.

  4. #14
    Mostly Harmless Hoovooloo's Avatar
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    Re: electrical input needed

    Yea, what he said.

  5. #15

    Re: electrical input needed

    OK Here is another idea I had in the back of my mind. Wind generator, Small one mounted on the trailer,
    while going 60 mph down the road, would that work? Maybe that would be too fast, most are made to
    kick out of gear in high wind. Maybe you could block direct wind, some how mount it, to restrict the air flow...

    OK tell me I am wrong....lol

    Buttset

  6. #16
    Jim C-G's Avatar
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    Re: electrical input needed

    Quote Originally Posted by buttset View Post
    OK Here is another idea I had in the back of my mind. Wind generator, Small one mounted on the trailer,
    while going 60 mph down the road, would that work? Maybe that would be too fast, most are made to
    kick out of gear in high wind. Maybe you could block direct wind, some how mount it, to restrict the air flow...

    OK tell me I am wrong....lol

    Buttset
    You're not actually wrong... the WWII German 263 Comet rocket plane had a little propeller that generated all the electrical needs in flight. I wouldn't go with 3' blades, but you could certainly generate a little electricity while riding. Mind you, I don't think I'd want the drag. The issue will still be the battery storage problem. You would have to carry a couple of large and heavy deep cycle batteries to have any chance of cooking much. There is a reason why travel trailers almost all use propane. I'm going to get a 5 lb. refillable tank as I hate the waste of the disposable 1 lbers.

  7. #17

    Re: electrical input needed

    Honda sells a nice quiet small generator, weight is about the same maybe lighter than a big battery and runs on the same fuel as the bike. Or.... switching from electric to gas cooking opens up great gift opportunities. Birthday, Christmas, anniversary, "just because ". I have not been successful boondocking at 120vac on my motorcycle. Admittedly only tried for the last 10 years for my cpap. Too troublesome for me. John
    KISS

  8. #18

    Re: electrical input needed

    Quote Originally Posted by Jim C-G View Post
    I'm going to get a 5 lb. refillable tank as I hate the waste of the disposable 1 lbers.
    They also make refillable 1 pound cylinders.

    http://www.flameking.com/products/pr...efill-kit.html
    2011 HD Electra Glide Ultra Classic, 1993 HD FatBoy
    2014 Aspen Sentry
    2001 Bushtec Turbo-II

  9. #19

    Re: electrical input needed

    I think the cpap people who need power brings a different need.
    I know some who use these. Propane is a great cooking source.
    So number of days, on the trip is a factor.

    I thought about taking a frugal motorcycle trip, just seeing how little
    I could spend. Free camping, cooking my meals, drinking water.
    Then some steak place, or McD with breakfast burritos, would mess up my plan. lol

    Buttset

  10. #20
    Jim C-G's Avatar
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    Re: electrical input needed

    Quote Originally Posted by lqqk_out View Post
    They also make refillable 1 pound cylinders.

    http://www.flameking.com/products/pr...efill-kit.html
    Seems to be a lot of recalls on the 1 lb. refillable. I seem to have trouble getting someone out to fill my 20 lb. tank right now and expect a lot of attendants will find it a chore to come do a 5 lb-er. I can see waiting a long time for the 50 cent fill on a 1 lb. tank.

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