2000 watt inverter

[Winterbagoal]

Originally Posted by AJMike

Thanks for the information.

The guy who did the initial installation appears to have left me with several issues. The wiring is probably 10 feet and should be 4 gauge, based on the tables. He did run 4 gauge from the starter battery to the connection block, but then used 6 gauge for the wiring to the charger and used a MAXI fuse holder with only 8 gauge wire. I am not an electrician but I assume when the table specifies 4 gauge wire it means for the entire length of the connection, regardless of connection blocks used. If that is wrong then my assumptions are wrong and it would be helpful if someone told me.

Anyway I had someone give me an estimate for upgrading the wire to 4 gauge for the entire length, and to replace the fuse holders, and while he was there I asked for an estimate for upgrading the inverter wiring. He suggested 2 gauge but perhaps I need something bigger than that. It is good to know that the remote switch will work with the larger inverter as well.

I plan on checking the gauge of the existing wire run from battery bay to my inverter (I think it's about 5-6 feet), to see if I might get away with it as it sits.
One of my concerns was losing control of the inverter by remote, because it's in the forward outside passenger side storage compartment (right next to the steps where the batteries are). My remote switch is on/off, nothing fancy like a "monitor version" with error codes display. I just like being able to turn it on/off, if necessary, without exiting the vehicle.
p.s. - You sure are getting a lot of *help* with this one.

[AJMike]

Originally Posted by jimkamery

AJ, not sure your electrical theory is correct. A normal high power microwave is 1100 watts which is 9.2 amps on the 120V side, no matter how short of a time it is running for. Assuming 13.2V from the batteries, you will draw 83.3 amps from the batteries for however long the microwave is running.

I am not sure I follow you.

The microwave in our RV is about 1500 watts. Our electric tea kettle is 700 watts so the microwave is roughly twice the power of the tea kettle. It (the tea kettle) draws about 5% of our power (10 AH) in about 4 minutes of use so the microwave should draw twice that power - about 10% (20 AH) in 4 minutes. I don't see how it can draw 9.2 AH no matter how short a time it runs. Perhaps I am missing something but I would think that twice the power should mean twice the power.

I just don't see how a 1500 watt microwave can draw 83.3 AH in 3 or 4 minutes. In an hour, sure, but not in 3 or 4 minutes.

[jimkamery]

Originally Posted by AJMike

I am not sure I follow you.

The microwave in our RV is about 1500 watts. Our electric tea kettle is 700 watts so the microwave is roughly twice the power of the tea kettle. It (the tea kettle) draws about 5% of our power (10 AH) in about 4 minutes of use so the microwave should draw twice that power - about 10% (20 AH) in 4 minutes. I don't see how it can draw 9.2 AH no matter how short a time it runs. Perhaps I am missing something but I would think that twice the power should mean twice the power.

I just don't see how a 1500 watt microwave can draw 83.3 AH in 3 or 4 minutes. In an hour, sure, but not in 3 or 4 minutes.

Power and amperage are 2 different measurements. Power is measured in ampere-hours or watts and amperage is the amount of current drawn at any given instant. Power in watts = amps x volts. A 1500W microwave will draw 12.5A of current while it is running on 120VAC. Conversely, it takes 113.6 Amps to create 1500W of power at 13.2V. I take it you have a power meter by the way you are talking about amp-hours and that is a good start, but you also have to look at the real time amperage the device is drawing. That amperage and the distance between the batteries and the invertor determine the AWG size of wire you will need for a safe connection.

[creativepart]

Mike, I wanted to mention that I have 400aH of plain old AGM batteries and a Magnum 2000w PSW inverter. I’ve only tried running the microwave on it a couple of times but hit the LBCO voltage at about 45 secs. The amp draw was enough to drop my battery bank voltage to 12.2v. It was momentarily that low and bounced back after the inverter shut down.

My AGMS can’t supply more than a 100 amp continuous draw ( .25 C) your LiPo bank can supply 1C so I doubt you’d have much problem but due to our experience we always start the genset if we need to use the microwave.

I assume Jim above is talking about amp draw, not amp hours.

[AJMike]

Originally Posted by jimkamery

Power and amperage are 2 different measurements. Power is measured in ampere-hours or watts and amperage is the amount of current drawn at any given instant. Power in watts = amps x volts. A 1500W microwave will draw 12.5A of current while it is running on 120VAC. Conversely, it takes 113.6 Amps to create 1500W of power at 13.2V. I take it you have a power meter by the way you are talking about amp-hours and that is a good start, but you also have to look at the real time amperage the device is drawing. That amperage and the distance between the batteries and the invertor determine the AWG size of wire you will need for a safe connection.

I think we may have been talking at cross purposes.

When I run the 700 watt tea kettle it draws about 65-70 amp, but since it is only used for a short time it ends up drawing about 4% or 5% of the power from our batteries. Given that I would expect that the microwave, at about 2.2 x the power, would draw perhaps 140 amps and consume about 10-11% of the battery power.

All other things are equal - the extension cord I am using to run the tea kettle is the same extension cord I would run for the microwave as the two are both located in the kitchen. There might be slightly more loss due to the higher draw of the microwave but I still don't see more than perhaps 12% battery loss from 4 or 5 minutes running the microwave. The actual draw of 140-150 amps might be some stress on the system. I am not sure about that.

In any case all of this may be moot since I am not sure that occasionally running the microwave is worth the financial cost in upgrading the inverter and the wiring, so this may well be nothing more than idle guess work on my part.

[AJMike]

Originally Posted by creativepart

Mike, I wanted to mention that I have 400aH of plain old AGM batteries and a Magnum 2000w PSW inverter. I’ve only tried running the microwave on it a couple of times but hit the LBCO voltage at about 45 secs. The amp draw was enough to drop my battery bank voltage to 12.2v. It was momentarily that low and bounced back after the inverter shut down.

My AGMS can’t supply more than a 100 amp continuous draw ( .25 C) your LiPo bank can supply 1C so I doubt you’d have much problem but due to our experience we always start the genset if we need to use the microwave.

I assume Jim above is talking about amp draw, not amp hours.

Yes. Thanks for the comment.

I realized after I had posted that I had confused amps and AH ratings, and posted back clarifying what I originally meant, but screwed up in explaining. But as I posted back, all of this may well be moot since I am not sure I am willing to spend $1000 just to avoid running the generator when using the microwave. Especially considering how rarely we use the microwave.

[Winterbagoal]

Originally Posted by AJMike

I think we may have been talking at cross purposes.

When I run the 700 watt tea kettle it draws about 65-70 amp, but since it is only used for a short time it ends up drawing about 4% or 5% of the power from our batteries. Given that I would expect that the microwave, at about 2.2 x the power, would draw perhaps 140 amps and consume about 10-11% of the battery power.

All other things are equal - the extension cord I am using to run the tea kettle is the same extension cord I would run for the microwave as the two are both located in the kitchen. There might be slightly more loss due to the higher draw of the microwave but I still don't see more than perhaps 12% battery loss from 4 or 5 minutes running the microwave. The actual draw of 140-150 amps might be some stress on the system. I am not sure about that.

In any case all of this may be moot since I am not sure that occasionally running the microwave is worth the financial cost in upgrading the inverter and the wiring, so this may well be nothing more than idle guess work on my part.

I believe you're correct about your usage versus draw down on your 200Ah of available battery.
The following website has a chart which supports your interpretation of the length of time you actually run the appliance, to determine what percentage of the power you will use from your battery bank.
Look at the far righthand column under the "8D" type battery which has 200Ah in it to start, which is what we both have in our lithium battery banks at full charge. At the bottom of the list of appliances, there's a "1500W large microwave" which the chart says will run for .5 hours until the bank is depleted. If you divide the 200Ah available by 30 minutes (0.5 hours) it will draw approximately 6.6Ah per minute. So, in your example of running your microwave for a few minutes to warm or defrost something, you'll only use 6.6Ah times the number of minutes you run the microwave for. So, your interpretation of the real world situation is true. Assuming a relatively efficient inverter is used.
https://www.jamestowndistributors.co....do?docId=1019

[Wyatt]

Originally Posted by rx4fishing

I am certainly not at expert, but if your microwave does not work with the 1000w inverter, just changing to a 2000w inverter will not make the microwave operate. The microwave would have to be wired in the inverter circuit for that to happen I believe.

Good point. Almost missed...

[Lmonger]

Xantrex XC2000 817-2080 with Bluetooth remote does the job. Found one at HodgesMarine.com ~$650. Desired Main panel disabled PD9245 and added a temp-activated fan for cooling on hot days.