Community Forums

calsteve · 07-04-2014, 02:56 PM

Hi,
We have a 2011 class A.
We would like to use the slow cooker while traveling so dinner is ready when we stop.
I have a 700 watt inverter I have connected to the two 6 volt house batteries and would like to use it for the slow cooker.
I assume the batteries are charging from the alternator while driving. Would this damage the alternator? Would it work okay?
Thanks,
Steve

texnet · 07-04-2014, 02:59 PM

The house batteries are normally charged by the alternator when the engine is running. You need to check the slow cooker and make sure that the 700 watt inverter is large enough to handle the cooker.

Skip426 · 07-04-2014, 03:03 PM

I'd also be looking into putting the cooker in the shower/tub area when in use, the last thing you need , in a panic stop is a hot appliance bouncing around.

calsteve · 07-04-2014, 03:07 PM

Thanks for the feedback.
The slow cooker is 200 watts. So it should work okay.
I plan to have it in the sink while traveling. It will keep it from sliding around and take care of any spills.
Will also add a nice aroma to the air while traveling.

mrboyer · 07-04-2014, 03:10 PM

We do it all the time, but found that we needed to tie the lid down. Just used string from one handle across the top to the other handle and back across on the other side. Also keeps the lid from rattling.

Skip426 · 07-04-2014, 03:33 PM

Quote:

Originally Posted by calsteve

Will also add a nice aroma to the air while traveling.

But can you drive while drooling ?
Don't you need a bib?

az bound · 07-04-2014, 03:39 PM

Quote:

Originally Posted by calsteve

Hi,
We have a 2011 class A.
We would like to use the slow cooker while traveling so dinner is ready when we stop.
I have a 700 watt inverter I have connected to the two 6 volt house batteries and would like to use it for the slow cooker.
I assume the batteries are charging from the alternator while driving. Would this damage the alternator? Would it work okay?
Thanks,
Steve

We have been doing so for over eleven years now, with it in the sink, works just fine.

nothermark · 07-04-2014, 03:39 PM

Allowing for efficiencies you are sucking around 20 A with the inverter. No reason it would not work but you might not be building your house battery charge as fast as you do without it. It also might not be a noticeable difference. ;-)

60Bubba · 07-04-2014, 03:50 PM

How is the charge current going into the house bank from the alternator regulated on Class A's? I've often wondered how much my vehicle alternator will actually put in my towed trailer.

On my last trip, I was running the fridge off 12V. That was pulling about 7.5 amps, and the battery bank monitor still showed +2.5 amps, so by my math that means the alternator was sending about 10A 12V to the trailer battery. Curious how much charging the big boys can get while driving. It would certainly impact how we use the house bank when we upgrade to a moorhome.

Old Scout · 07-04-2014, 04:23 PM

Many smaller inverters are "modified sine wave" current while many newer/ fancy appliances have electronic timers, displays, thermostats, etc which "prefer" true sine wave current. A basic [manual] slow cooker will probably work with MSW inverter. The 2000 watt inverter with 6 six-volt bats in my coach will run our microwave, which I guess is in the range of 20 AC amps. Dont know the math behind the calculation but a 700 watt inverter may not run a 200 watt slow cooker--in other words are both the inverter and the cooker being measured in DC watts? If so, 7 AC amps inverter would power 2 AC amp cooker but that doesnt sound like much amp draw for a cooker????]
PS--the Cummins diesel in our coach has an alternator rated at 160 DC amps. With the engine running and 6 6-volt bats, I feel comfortable using the microwave to re-heating a cup of coffee or a hot sandwich but I dont run it for more than 5-6 minutes.

calsteve · 07-04-2014, 05:32 PM

Thanks for the feedback.
The slow cooker is 200 watts. So it should work okay.
I plan to have it in the sink while traveling. It will keep it from sliding around and take care of any spills.
Will also add a nice aroma to the air while traveling.

60Bubba · 07-04-2014, 05:36 PM

Scout,

Good point about conversion factors. The good news is, "watts is watts". Watts are a measure of work done, and are standard regardless of the voltage.

To determine the watt rating of an appliance, you multiply amps by volts (W=A*V). In other words, a 120 watt light bulb (if there were such a thing) running on house current (120V) uses 1 amp (120V * 1A = 120W). You can re-arrange the equation to solve for whichever variable you want pretty easily.

This makes it convenient to determine if an inverter will run a given load. A 700W inverter uses about 6 amps AC (700W/120V = 5.8A). Measured on the DC side, it uses 58.3A (700W/12V = 58.3A) from the batteries at full load. The trick is that many appliances have higher start up loads.

If you've ever ridden a bike and taken off in a gear that was too high, you know it takes a lot of work to get going until the RPMs get up. Same thing happens for electric motors, etc.

My 1000W sine wave inverter won't run a small vacuum I tried that supposedly draws around 800W. It trips out when the motor starts up because the initial current draw is too high.

This general theory is why RV 12V appliances usually have such a high amp rating. If you do an equal amount of work, such as heating up a pot of coffee, a 120V household appliance uses much less amperage than a 12V appliance making the same pot of coffee.

Generally, DC is much more efficient, but we don't use it in our homes because it has very high line losses. The lower the voltage, the more amps are lost in the power cord, for example. If you ever install an inverter, it will recommend using the shortest wires you can to get to the inverter from the battery, and run a longer extension cord from the inverter to the 120V load. This is done to minimize line losses on the 12V side.

Hope this is helpful or at least interesting. I spent a lot of time brushing up on my high school physics when I was completing my solar power/inverter project!

wa8yxm · 07-04-2014, 05:57 PM

Have done it, Slow cooker goes IN THE SINK, that way if a mess happens.. Hose it down.

Old Scout · 07-04-2014, 06:16 PM

60Bubba--great explanation of the relationship between amps, watts and volts.....I was "guessing" that a 700 watt inverter didnt create a lot of 120v amps [eg 6 amps] but couldnt reconcile that a 200 watt slow cooker only draws 1.6 amps--guess slow means slow.
Not to steal the thread but you mentioned your recent work with solar. As an example, if I were to install a 200 watt solar panel [heard some solar is 27v????], at max sunlight, how many DC amps would the 200 watt panel produce--to say re-charge a 12v battery bank, or be inverted to power a 120v 3 amp frig????? My "calculation" has always been roughly a factor of 10--eg, 200 DC watts--converts to 20 DC amps which converts [invert if you will] to 2 120v AC amps. Accordingly, I was always concerned about the number of solar panels needed to ultimately [thru inverting], produce any significant 120v AC power??????