100amp LiFePO4 12v battery for 1000w microwave?

azdp

New Member
Our small Starcraft Satellite trailer has a 1000w High Pointe microwave that recently failed to heat my food after switching batteries. I previously had 2 large deep-cycle lead acid batteries used in conjunction with with a Powerbright APS2200 PSW inverter. I've used this inverter for 10+ years with 2-3 batteries and it has never failed to operate any microwave for as long as needed. While camping remotely I plug the shore cord into the inverter to power the trailer. After the 2 LA batteries totally discharged by accident for months while in storage, they needed to be replaced. I bought a CHINS 100amp LiFePO4 12v to replace them. The battery maintains a high voltage while being used to run/charge my laptop for hours, charge camera batteries, run lights/radio/tv/DVD player daily. But, when I try to heat up a breakfast sandwich which usually takes 2 minutes, I have to run the microwave many times for a total of 20 minutes to heat it up. Basically, it's very weak. I use 100-200w of solar panels to bring the battery up to 13.3-13.4v daily.

Does a single 100amp battery lack the power needed to run the microwave? Once I got home I plugged the microwave into my home with an extension cord and it heated a cup of water in just 30 seconds, so it seems to work fine. The inverter appears to work fine, but is there a way to test its output? Also, would it make any difference if I ran an extension cord directly from the inverter to the microwave? Will try that tomorrow. If that works, then is there a problem in the trailer wiring?
 

Jims94vmx

Solar Enthusiast
A quick thought, is your converter off. If not your inverter might be powering your converter to charge battery....
 

azdp

New Member
Actually, I have no idea. If so, are you saying the power is being misdirected? I never use shore power hook-ups, so can I disable the converter by flipping a circuit breaker or removing a fuse? But....this problem has never appeared before. Everything is the same, except for the new battery.
 

Jims94vmx

Solar Enthusiast
When I plug my rv into my inverter I make sure to turn off breaker for the converter.....my 720w of solar actually keep my 2 Battle Borns full. the converter if on can draw a lot of amps trying to charge your battery while you are draining a lot of amps using microwave.

Just to make sure....I am talking about an adapter that goes on my shore power connection, then connecting my inverter with a heavy duty extension cord. I only have a 1500w inverter so I watch my loads carefully .
 

Supervstech

Administrator
Staff member
Moderator
Most 100Amps drop in LFP batteries have a max amperage of 100AMPS, your microwave will pull 300amps on startup… best to add a second LFP
 

pollenface

Solar Addict
I've run an 800w microwave with a 3000w inverter on 2x 50a LFP drop ins. My wiring was fairly direct and I had hot pies. Not all batteries are made equal though...
 

Supervstech

Administrator
Staff member
Moderator
I've run an 800w microwave with a 3000w inverter on 2x 50a LFP drop ins. My wiring was fairly direct and I had hot pies. Not all batteries are made equal though...
800w and 1000w microwaves can have VASTLY different ampdraws.
 

chrisski

Photon Sorcerer
Most microwaves rate the advertised watts as cooking power, but power from the inverter and then the battery total 30% - 50% more.

I have no idea the wattage size of my RV’s microwave, but I use 2100 watts (155 amps at 14.5 volts) from the battery to keep it running.

The battery you got should tell you surge wattage and constant wattage. Some lithium‘s I looked at could discharge at 1C, or 100 amps for a 100 ah battery, so I’d need at least 2 in order to run the battery. The lithium internal BMS limits itself to that.

Lead acid batteries are better to deliver high amps more powerfully than lithiums. That’s why lead acid batteries are starter batteries, but lithium’s aren’t.
 

McRod

New Member
A 1000W microwave is drawing about 75A on a 13.2v system. So in theory, your battery can do it. When the microwave is on, what's your voltage at? What's the batteries discharge specs?
 

chrisski

Photon Sorcerer
A 1000W microwave is drawing about 75A on a 13.2v system.
A 1000 watt microwave probably draws 1300 watts from an inverter with about another 150 watts for DC to AC conversion losses. That’s a bit over 100 amps. The 1000 watts is probably the cooking watts., so I’m putting the actual draw at closer to a little over 100 amps. If it draws 1000 watts, its probably a 600 watt cooking microwave.
 

azdp

New Member
I would aim a bit higher like 13.8 to 14.2 volts.
And yes I think you need at least one more battery.
Thanks for the input. The battery level depends on the length/quality of solar charge. I use a Victron controller that Bulk charges up to about 13.4v and then if there is more time and good sun it will float up to 14v+. I do have a 2nd battery but thought the microwave would not pull up to 100amps. I must be using the wrong math for calculations. Also, the trailer came new with just one standard size lead acid battery, so it seems the 100amp LiFePO4 should handle the microwave.
 

McRod

New Member
A 1000 watt microwave probably draws 1300 watts from an inverter with about another 150 watts for DC to AC conversion losses. That’s a bit over 100 amps. The 1000 watts is probably the cooking watts., so I’m putting the actual draw at closer to a little over 100 amps. If it draws 1000 watts, its probably a 600 watt cooking microwave.
That's probably accurate, but he has to know the batteries discharge parameters. 100Amphours doesn't define the discharge rate, it's simply a gas gauge.
 

azdp

New Member
Most microwaves rate the advertised watts as cooking power, but power from the inverter and then the battery total 30% - 50% more.

I have no idea the wattage size of my RV’s microwave, but I use 2100 watts (155 amps at 14.5 volts) from the battery to keep it running.

The battery you got should tell you surge wattage and constant wattage. Some lithium‘s I looked at could discharge at 1C, or 100 amps for a 100 ah battery, so I’d need at least 2 in order to run the battery. The lithium internal BMS limits itself to that.

Lead acid batteries are better to deliver high amps more powerfully than lithiums. That’s why lead acid batteries are starter batteries, but lithium’s aren’t.
Thanks for the additional info. It's sounding like I need to add the 2nd battery. I previously had 2 group 31 AGMs, one was an Odyssey. They probably handled the start-up surge much better.
 

Bud Martin

Photon Sorcerer
Inverter efficiency also comes into play, typical inverter has about 85% efficiency (https://www.powerbright.com/product/aps2200-12 I do not see the rating), so to produce 1300W on the AC side of the inverter, the power input on the DC side will be much higher than 1300W.
Your Chins battery should also have max current discharge spec, what is it?
 
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McRod

New Member
Thanks for the input. The battery level depends on the length/quality of solar charge. I use a Victron controller that Bulk charges up to about 13.4v and then if there is more time and good sun it will float up to 14v+. I do have a 2nd battery but thought the microwave would not pull up to 100amps. I must be using the wrong math for calculations. Also, the trailer came new with just one standard size lead acid battery, so it seems the 100amp LiFePO4 should handle the microwave.
100 AH battery is just your gas gauge. It's not the discharge rate. Check with the battery manufacturer to get their discharge parameters.

The batteries that come with RVs are not meant to run your AC side. That's why you have shore power. The single 12v battery keeps your LED lights on, and any other 12v DC items running without shore power.
 

time2roll

Photon Sorcerer
Also, the trailer came new with just one standard size lead acid battery, so it seems the 100amp LiFePO4 should handle the microwave.
Did the trailer come standard with the inverter connected to the microwave? Seems very odd if it did.
I don't think any trailer actually comes with a factory battery... dealer just installs the minimum to get you out the door.
 

azdp

New Member
Did the trailer come standard with the inverter connected to the microwave? Seems very odd if it did.
I don't think any trailer actually comes with a factory battery... dealer just installs the minimum to get you out the door.
Not sure what you meant by 'inverter connected to the microwave'. I installed the inverter in 2018 along with 2 group 31 AGM batteries. And yes, the original battery was likely installed by the dealer. The inverter, battery and charge controller are all mounted together in a side compartment. No direct connection between the inverter and microwave. The shore cord plugs into the inverter to power the trailer/microwave. I still need to verify whether the trailer converter is trying to charge the battery in this configuration.
 

azdp

New Member
100 AH battery is just your gas gauge. It's not the discharge rate. Check with the battery manufacturer to get their discharge parameters.

The batteries that come with RVs are not meant to run your AC side. That's why you have shore power. The single 12v battery keeps your LED lights on, and any other 12v DC items running without shore power.
I've used 2 trailers for 9 years since 2006 that have had either 2 or 3 group 31 AGM batteries to run everything but the fridge and a/c unit. I've never been limited in using the microwave ovens as much as needed and have had no problems before now. This is the first time I've tried running things with a single, non lead acid battery. Will do some more testing later Saturday.
 

azdp

New Member
Inverter efficiency also comes into play, typical inverter has about 85% efficiency (https://www.powerbright.com/product/aps2200-12 I do not see the rating), so to produce 1300W on the AC side of the inverter, the power input on the DC side will be much higher than 1300W.
Your Chins battery should also have max current discharge spec, what is it?
I found the efficiency (90%) here: https://www.techbatterysolutions.com/power-bright-aps2200-12-pure-sine-inverter-2200-watt-12-volt/

These are the specs supplied by Chins:
Max continuous discharge current: 100A
Peak discharge current: 300A (Duration: less than 5 seconds)

I wasn't able to check it earlier today, but on Saturday I will run a heavy extension cord directly from the inverter to the microwave to see if it will run properly off the single LiFePO4 battery. If it runs, I'll also verify whether anything like wiring gets too warm with extended use. In the past, nothing ever got hot.
 
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