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Open Roads Forum  >  Tech Issues

 > I want to run a microwave on an inverter

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otrfun

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Posted: 10/20/21 10:13am Link  |  Quote  |  Print  |  Notify Moderator

zzyzxpat wrote:

I have an AF 865 camper. I want to be able to run the microwave, 900W, power demand shown to be 1350W, on an inverter for a short period of time, just warming stuff up. This would allow us to not carry the Honda 2200 with us when gone. We move around a fair amount so I should be able to keep the batteries charged. My question is what would you recommend for an inverter size, and if using the microwave for say 10 minutes, do you see a huge battery drain? Thoughts or ideas please. Thank you, Pat
OP, lots of great suggestions here to maximize performance ref the use of various types of inverters and microwaves. IMO, an equally important part of this power/performance triad you may also want to consider is the battery.

We used to run our microwave (1050w line input; 700w cooking) with two GC2's (6v deep cycle batteries). If we were lucky, we might get 40 min. of runtime even with this low-power microwave. After 40 min. the low voltage alarm on the inverter would activate (=<11.0v) at about the same time the batteries were at 50% SOC. End result was 65-70 ah of use (under 100-105a load) before we had to recharge the two GC2's.

We upgraded to a DIY 200ah lifepo4 battery pack (using standard 3.2v 200ah prismatic cells). We now get dramatically higher microwave runtimes of ~105 min. (~180ah) if we discharge the lifepo4 pack down to ~10% SOC. We never get an inverter low voltage alarm unless we discharge down to significantly less than 5% SOC. Bottom line, lifepo4's have outstanding voltage stability while under heavy load.

The two GC2's cost us $220, take up the space of two group 24-27 batteries, weigh 130 lbs., produce only 65-70ah (50% SOC; while under 100-105a load), and have a ~300 cycle lifespan.

Our one DIY 200ah lifepo4 battery pack cost us $750 (including BMS), takes up the space of one group 24 battery, weighs only 40 lbs., produces 180ah (10% SOC; 200ah 0% SOC), and has a ~3000 cycle lifespan (10 times higher).

I believe the above numbers speak for themselves. In a space/weight challenged truck camper these numbers take on even more significance. For us, the best $750 we ever spent.

zzyzxpat

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Posted: 10/20/21 05:33pm Link  |  Quote  |  Print  |  Notify Moderator

Bobbo wrote:

theoldwizard1 wrote:

jkwilson wrote:

If you regularly use that kind of power and don’t have a recharging source like a generator or solar, you likely won’t get them recharged while towing. The generator is still the way to go.

Not true if you are using a DC-DC charger !

I suspect if he had the knowledge and skills to install a DC-DC charger, he wouldn't be asking this question. A DC-DC charger is not a stock item.


Actually I do have the knowledge and skill to run a DC-DC charging system, been around the horn more than once. My only question was others experience on running a microwave for a couple minutes on an inverter, as I haven't done the math on it. I use very little battery power to begin with, all LED lights, run the furnace for 10 minutes in the morning on a cold day, 12V TV and a DVD player which pull less than 2.5 amps together. Thanks for the responses.

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Posted: 10/20/21 05:58pm Link  |  Quote  |  Print  |  Notify Moderator

Veebyes wrote:

2oldman wrote:

I'm just curious, what takes 10 minutes in a microwave?


About the only thing my cook uses the microwave for, & they take awhile, is baking potatoes.

Otherwise the microwave is used to store bread.


I have to confess, the microwave gets a lot of use in our camper. It’s not that we can’t cook, we just don’t want to most of the time.

A frozen meal that would take about 4 minutes at home in the industrial strength nuclear oven from heck can take 10 minutes in my intentionally low powered mwave in the camper. I’m really interested in these inverter mwaves tho. Maybe the best of both worlds?

[emoticon][emoticon]

Huntindog

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Posted: 10/20/21 06:57pm Link  |  Quote  |  Print  |  Notify Moderator

The problem with ANY lead acid battery is that the only time you will have a fully charged battery is on day one of a trip. This because LA batteries slow down on accepting charge as they get closer to full. To fully charge a LA battery takes a VERY long time, and it doesn't matter what the charging source is..... Even a DC to DC charger cannot do it.

The solution is to change the batteries to Lifpo chemistry



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Posted: 10/22/21 11:13am Link  |  Quote  |  Print  |  Notify Moderator

I put in 2 Lion 105 ah batteries and a 3000 watt inverter and 360 watts solar so I use the microwave for short heating cycles of a minute a couple of times without the generator. Also brew coffee, make toast, etc. nice for early morning or late night heating requirements.


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ktmrfs

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Posted: 10/22/21 12:58pm Link  |  Quote  |  Print  |  Notify Moderator

Huntindog wrote:

The problem with ANY lead acid battery is that the only time you will have a fully charged battery is on day one of a trip. This because LA batteries slow down on accepting charge as they get closer to full. To fully charge a LA battery takes a VERY long time, and it doesn't matter what the charging source is..... Even a DC to DC charger cannot do it.

The solution is to change the batteries to Lifpo chemistry


I'll disagree. it doesn't take very long to get to about 90% SOC with a good charger/generator and solar combo. then switch to solar only and another hour or so to top off to 100%. Charging starts at near 100-120A, and when it tapers to about 15A I switch generator off and let the solar finish.

even using solar only we often end up at 100%SOC by afternoon and we aren't real energy concious. And run our panasonic true inverter microwave as needed off a 1000VA inverter. Batteries are 4 GC-2's


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2oldman

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Posted: 10/22/21 01:01pm Link  |  Quote  |  Print  |  Notify Moderator

Huntindog wrote:

To fully charge a LA battery takes a VERY long time, and it doesn't matter what the charging source is..
I agree. I saw my AGMs take over 24 hours to fully charge on home power. That ain't happening with a generator or solar.

Li is nice in that it doesn't care if it's fully charged, takes about as much amperage as you can throw at it, and has no absorb.

StirCrazy

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Posted: 10/22/21 05:38pm Link  |  Quote  |  Print  |  Notify Moderator

EMD360 wrote:

I put in 2 Lion 105 ah batteries and a 3000 watt inverter and 360 watts solar so I use the microwave for short heating cycles of a minute a couple of times without the generator. Also brew coffee, make toast, etc. nice for early morning or late night heating requirements.


thats depends. normaly my GC2 batteries are down to about 80-86% in the morning when I am runing the frnace at night and thy are fully charged by noon by the solare on a good day. would they charger faster if they were LFP, ya probably be about an hour quicker...

if its taking forever you dont have enough solar.

Steve


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time2roll

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Posted: 10/22/21 06:16pm Link  |  Quote  |  Print  |  Notify Moderator

Set the frozen TV dinner out for an hour or two and the heating time is greatly reduced.


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Microlite Mike

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Posted: 10/31/21 02:57pm Link  |  Quote  |  Print  |  Notify Moderator

2oldman wrote:

I'm just curious, what takes 10 minutes in a microwave?


A Big TV Dinner. [emoticon]

I've been running my microwave using a Renogy 2KW Inverter to heat a small TV Dinner or a cup of coffee. Maybe 6 minutes max.

When I installed the Inverter, using two Battleborn 100 ah batteries, wired with 2/0 awg wires running about 2' to the Inverter, and monitored by a Victron BMV 712, I found the Inverter was drawing 125 amp and after a one minute run it used exactly 2 amp hours as recorded on the monitor.

A 6 minute TV dinner uses about 12 amp hours.

Nice thing about the LiFePo4 batteries is the lack of significant voltage sag as you see with Lead Acid batteries. This setup has served me well for over a year now and I use it a lot. For every night I spend at a full hookup site, I spend 15-20 days boondocking.

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