RV Battery Help

andyrud · February 2012

I just installed 2 95 watt panels on the roof of my 2002 small motor home RV, a Morningstar Controller, and a Trojan
12v 27TMH 115 amp hour true deep cycle battery in the battery compartment. The
battery compartment only has room for one battery and this is the largest
battery I can get in there. I want to add a 2000 watt true sine wave inverter
to power a small GE 600 watt micro wave oven to cook TV dinners and to power a lap top
computer. (The oven spec. tag says .95KW .) Do you think I can draw the
necessary amperage from this battery to power a 600 watt micro wave oven for at most
about 10 minutes between charges or would I be over drawing the battery? Trojan battery specs says this battery will discharge 75 amps for 51 minutes. At 50% DOD that's about 75 amps for 25 minutes. I figure my needs would be for only 10 minutes. Will the battery handle this much discharge or self destruct? What can I expect from this scenario?

Thanks in advance,

Andy

simmtron · February 2012

Re: RV Battery Help

I'm not an expert but I wouldn't do it. Way to much draw on one battery. Also I would go with a much smaller inverter, a 2000 watt sine wave inverter uses a lot of power just to run the unit. I have 4- T-105's (appox 400 Ah) in my motorhome and only run a 650 watt sine wave inverter for everything, I don't run the microwave off the batteries , generator only. i would run a small MSW inverter if only using one battery, maybe 400 watt inverter. We live fulltime in our RV and are on solar only (generator only for long runs of cloud) My 2000 watt Xantrex inverter that came with the RV is disconnected.

andyrud wrote: »

I just installed 2 95 watt panels on the roof of my 2002 small motor home RV, a Morningstar Controller, and a Trojan
12v 27TMH 115 amp hour true deep cycle battery in the battery compartment. The
battery compartment only has room for one battery and this is the largest
battery I can get in there. I want to add a 2000 watt true sine wave inverter
to power a small GE 600 watt micro wave oven to cook TV dinners and to power a lap top
computer. (The oven spec. tag says .95KW .) Do you think I can draw the
necessary amperage from this battery to power a 600 watt micro wave oven for at most
about 10 minutes between charges or would I be over drawing the battery? Trojan battery specs says this battery will discharge 75 amps for 51 minutes. At 50% DOD that's about 75 amps for 25 minutes. I figure my needs would be for only 10 minutes. Will the battery handle this much discharge or self destruct? What can I expect from this scenario?

Thanks in advance,

Andy

Windsun · February 2012

Re: RV Battery Help

At .95 KW, at 12 volts that translates to about 80 amps, so it could be done. At 10 minutes that would be around ~15 amp-hours. The biggest problem would be the wire size between the battery and inverter, you would need at least 2/0.

niel · February 2012

Re: RV Battery Help

i think what simmtron means is that such a load could draw down on the battery voltage sufficiently to kick it off sooner than he may want it to and it's possible it may do this from the very start of the load. an 80a draw from a 115ah battery is definitely pushing things.

simmtron · February 2012

Re: RV Battery Help

Exactly Niel. We don't even use the microwave anymore. Don't miss it either.

Windsun · February 2012

Re: RV Battery Help

niel wrote: »

i think what simmtron means is that such a load could draw down on the battery voltage sufficiently to kick it off sooner than he may want it to and it's possible it may do this from the very start of the load. an 80a draw from a 115ah battery is definitely pushing things.

A good AGM battery could probably handle it, your typical Marine battery, probably not. The internal resistance of the battery might drop it below what the inverter needs.

Ken Marsh · February 2012

Re: RV Battery Help

Give it a blast Andy. I would.

You have several things going for you.
UL requires the amperage stated on the tag to be the max possible amps.
On the average it will not draw that much.
600 watts would be 50 amp then add another three or four for the inverter.
Do your microwaving when the sun is out and it will supply 20% of your current.
If it doesn't make it, no problem. You just have to reset your inverter.

One thing about Trojan. When they are new they commonly do not have specified capacity.
I ask their engineer about this and he said they do this on purpose to make them longer life.
After they make the battery they do an aging to develop the current capacity of the battery.
Trojan does this less hence gets longer battery life.
They start out under capacity but ramp up during the first few dozen cycles.
Figure an new battery will be down 25 to 30%.

andyrud · February 2012

Re: RV Battery Help

Thanks Everyone.

Ken, that is what I am going to do. I have a Exeltech 2000 I bought for a temporary inverter while my Magnum was in for repair and it is not being used. As soon as I can get up to the cabin I will give it a try. I'll let everyone know what happens. Again thanks everyone for the info,

Andy

Windsun · February 2012

Re: RV Battery Help

The 600 watt rating on the microwave is the OUTPUT power, the input power is about 20-25% more.

niel · February 2012

Re: RV Battery Help

actually my old one was about 34% higher. not sure what my new one (1000w emerson) is doing as i'll have to remember to check it some day. the old one was called something like galanz or something like that and was 900w micro power. it read about 1200w on killawatt. even higher for va at about 1350va.

Windsun · February 2012

Re: RV Battery Help

I have one of the newer Panasonic Inverter models, and it puts out 1250, and draws 1450. So around 85% efficient.

niel · March 2012

Re: RV Battery Help

well i tried to get a reading on my new emerson micro, but it was all over the place with its readings and beeping at me. i guess i won't ever be running that with my inverter not that i'd want to.

RV Battery Help

Comments

Categories