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  View original topic: Half Pint Microwave question
Raynor Shine Sat Nov 03, 2007 7:49 am

So I finished installing the norcold & half pint. My question is, the half pint runs normally with plugged into the outlet, however, when I try it on my inverter, it runs very slow. My inverter is 750 W and the halfpint in 600W. I have the recommended interstate battery w/ go westy aux set up.

Do I need a larger capacity inverter or odddesey deep cycle battery? Any insight?

Thanks

Tomswesty Sat Nov 03, 2007 10:19 am

Raynor,

I have the same set up and run it with an 800Watt. I think the big thing is that it is 600 Watt Power, takes a long time to cook anything. Maybe Dog Pilot can chime in since he runs one too. I am using a Yellow Top Deep Cycle battery with the inverter. Took about 10 minutes to do popcorn the last time I used it. (The little bags) I am using 6AWG wires straight from the battery to the inverter.

tds3pete Sat Nov 03, 2007 10:44 am

It sounds like you're running they system a bit over max. Remember 600w appliances will draw more due to line loss in the system and inefficiencies in the inverter. You could be trying to pull 60 amps out of your battery.

You could test the amp draw right at the battery to see what is actually happening.

You might try running the system with the car idling as a test, and see what that does. Your alternator would then be adding back in to reduce the battery drawdown.

Taylor L Sat Nov 03, 2007 11:55 am

Do you have a link to any info on this unit?

Taylor

tencentlife Sun Nov 04, 2007 2:51 pm

Inverter inefficiency as mentioned and line loss from undersized inverter supply wires can prevent the inverter from producing its rated power. You would need at least 6AWG DC wires to the inverter for it to make its full 750w without browning out (I know, you can't brown with a microwave, but toaster ovens are all at least 1200w so that crispy crust will remain a dream for now). The cheap small inverters sold these days mostly come with undersized supply wires. Just because the wire supplied is a certain size doesn't mean it's adequate for sustained use.

Running the engine may help because the alternator can uphold voltage and prevent battery brownout, but ultimately the DC supply wires should be sized right for both performance and safety.

r39o Sun Nov 04, 2007 8:54 pm

I have a half pint. It ended up in our office instead of the Westy. Microwaves suck the juice. Unless you are on shore power or have an inverter that creates a good enough sine wave, it will just suck your battery dry.

Ya, ya I know well about inverter efficiency, but some devices really want a better sine wave than many inverters supply. A 4 step wave like like many produce just does not cut it for many devices.

You hooked a scope up to your inverter? What the wave look like????

I like a 1KW inverter to run the big stuff and a smaller one to run the little stuff. Reason is the idle current on those puppies can be quite high even when doing nothing.

The general run of the mill inverter just is not all that great.

Raynor Shine Mon Nov 05, 2007 7:34 am

thanks for all the insight, I figured until I upgrage the inverter, shore power is the way to go. I do have the inverter connected to the 2nd battery with 6 guage jumpers.

tds3pete Mon Nov 05, 2007 9:15 am

I got a digital pure sine wave unit from these folks and have been happy with it:
http://www.theinverterstore.com/

Looks like this installed:
http://autos.ph.groups.yahoo.com/group/ev_update/photos/view/5a7d?b=2

tencentlife Mon Nov 05, 2007 9:53 am

That auto-transfer switch on that site is an item some of you Westy-heads would like, if you want to have a single ac branch circuit system:

http://www.theinverterstore.com/the-inverter-store-product.php?model=pwr3axfer30-front-large

Also, Walt's point is important; some ballasts in electronic appliances like microwave ovens won't digest the modified square wave output of the cheaper inverters, and will run inefficiently if they do. It may still be necessary to overrate the inverter by a fairly large factor to compensate for the true power factor after the waveform is utilised. Thankfully, true sine wave inverters are becoming cheaper in the smaller sizes. Their output can be utilised efficiently by power supplies and ballasts in electronic appliances.



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