100amp LiFePO4 12v battery for 1000w microwave?

time2roll

Photon Sorcerer
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.
Yes exactly. Even the 2x AGM you installed was a bit light. Should have been 4. I recommend 280+ Ah with LFP to drive the microwave through the inverter. Yes you can often squeak by with less but it leaves a system that could be unreliable or wears out prematurely.
 

Iceman218

Solar Enthusiast
Also a neophyte but recall that a LiFePO4 has a BMS to limit discharge current and a LA does not. My bet is the continuous current is over the 100 amps. My Convection Oven draws 130 amps continuous on high power. About the same as my microwave. But we do not use the microwave much. Our house microwave needed a 20 Amp circuit to run normally. A 15 Amp circuit did not trip but made the microwave at 60% ish Power.
 

puppysong

New Member
This is a very interesting question.
Usually we talk about the power of the microwave is the output power, while the microwave also has an input power.
Since the exact model not listed in this case, so let's use a similar model High Pointe's EM925AWW-B as an example. According the
deiscription:

Microwave Input Power Rating: 1500W
Microwave Output Power Rating: 1000W

According to what @azdp checked, the conversion efficiency of the APS2200 PSW inverter is 90%.
So it needs at least 1666W at the battery side, which means at least 138A current is needed.

The maximum continuous output current of Chins' battery is 100A, so it can't provide the enough power to the microwave.
Although the maximum peak current is 300A, it can only make the microwave start, but not to make it work properly.

In the case of insufficient input power, it makes sense that the heating time of the sandwich becomes longer.
It does seem that two batteries are needed to solve this problem. Can temporarily add a battery to verify.

If the above explanation holds true, the interesting part here is that when the input power of the microwave is about 3/4 of the rated power (1280W->inverter->1152W), the heating sandwich time is actually extended by 10 times (2min->20min). Wow! Or does it just use multiple start-peak-moments to complete the heating?
 
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azdp

New Member
More testing, answers and questions:

First, the microwave is a High Pointe ECO28BMR with 1000w output and up to 1500w power consumption with convection.

Today I ran an extension cord directly from the inverter to the microwave and heated a half cup of water for 30 seconds. Barely luke warm. Using home current had produced hot water. Then heated a full cup of water for 3 minutes during which I checked the battery/inverter wiring and it never warmed at all. Also, the inverter's over load and over hot warning lights never came on but the fan did start after about 2 min 30 sec. The cup of water was hot, could not keep a finger in it. So, it's obvious the single battery cannot power the microwave at an adequate level. I already have a 2nd matching LiFePO4 battery that I had intended for another use, but I'll add it to the trailer in parallel.

Now I have questions on how to go about running the shore cord to the inverter to power the trailer (as done for years) without the trailer's converter trying to charge the battery at the same time. More info in following post.
 

azdp

New Member
thumbnail_IMG_1795.jpgthumbnail_IMG_1797.jpg

Sorry for the overly large photos. Question: How can I run the shore line directly to the inverter to power the trailer, BUT, not have the trailer converter trying to charge the batteries at the same time? It looks like the converter supplies about 20amps of charge to the batteries when needed. In the top photo, the #6 fuse says CHARGE LINE / SLIDE MOTOR. I'm assuming Charge Line is the converter charging the batteries. So, once the trailer is set up for several days of use, can I just remove the #6 fuse to avoid having the converter charge the batteries?

If that is not the answer, the 2nd photo shows that Breaker B powers the Converter. Could that single breaker be shut off to prevent charging or would that also stop all functions the converter might provide? I want the charging to stop, but everything else to work normally.

I appreciate all of the helpful answers you've all provided. Has been helpful to me and will be for others.
 

time2roll

Photon Sorcerer
Either the breaker or the fuse will work fine. I would be inclined to just leave the converter breaker off until you need it on. My converter has been off for years. My solar keeps the battery topped off.
 

McRod

New Member
View attachment 57496View attachment 57497

Sorry for the overly large photos. Question: How can I run the shore line directly to the inverter to power the trailer, BUT, not have the trailer converter trying to charge the batteries at the same time? It looks like the converter supplies about 20amps of charge to the batteries when needed. In the top photo, the #6 fuse says CHARGE LINE / SLIDE MOTOR. I'm assuming Charge Line is the converter charging the batteries. So, once the trailer is set up for several days of use, can I just remove the #6 fuse to avoid having the converter charge the batteries?

If that is not the answer, the 2nd photo shows that Breaker B powers the Converter. Could that single breaker be shut off to prevent charging or would that also stop all functions the converter might provide? I want the charging to stop, but everything else to work normally.

I appreciate all of the helpful answers you've all provided. Has been helpful to me and will be for others.
Connect the 30 Amp main breaker line to the inverter "AC in", then run that same size line from the "AC out" back to your breaker panel and connect it to the 30 Amp main breaker. Then turn off breaker "B" in your breaker panel. Done.
 

azdp

New Member
Either the breaker or the fuse will work fine. I would be inclined to just leave the converter breaker off until you need it on. My converter has been off for years. My solar keeps the battery topped off.
I like this answer, sounds easy. So, turning off the converter breaker does not stop any other trailer functions from working; lights, radio, pump, heater, etc? I also charge with solar and two 100w panels has done well to top off the battery. Should work fine for 2 batteries that are not drained as much.
 

azdp

New Member
Connect the 30 Amp main breaker line to the inverter "AC in", then run that same size line from the "AC out" back to your breaker panel and connect it to the 30 Amp main breaker. Then turn off breaker "B" in your breaker panel. Done.
You make this sound so easy and you obviously know the wiring. So far, I can't 'picture' your instructions. Since your advice ends with 'turn off breaker B', what is the advantage of doing the additional wiring rather than just turning off breaker B? I'm all for doing the easiest work-a-round without additional mods if not required. Thanks.
 

azdp

New Member
Your also missing your 40Amp reverse polarity protection fuse from your DC panel.
Thanks for mentioning that. After taking the photos I noticed that slot was empty, but I've never removed any fuses from the converter. They either forgot to install it or left it out for some reason. Should I definitely replace it?

The printed instruction says replace with only a Littelfuse type 257. I'm guessing it's the same type of fuse as the others, just 40 amps.
 

azdp

New Member
This is a very interesting question.
Usually we talk about the power of the microwave is the output power, while the microwave also has an input power.
Since the exact model not listed in this case, so let's use a similar model High Pointe's EM925AWW-B as an example. According the
deiscription:

Microwave Input Power Rating: 1500W
Microwave Output Power Rating: 1000W

According to what @azdp checked, the conversion efficiency of the APS2200 PSW inverter is 90%.
So it needs at least 1666W at the battery side, which means at least 138A current is needed.

The maximum continuous output current of Chins' battery is 100A, so it can't provide the enough power to the microwave.
Although the maximum peak current is 300A, it can only make the microwave start, but not to make it work properly.

In the case of insufficient input power, it makes sense that the heating time of the sandwich becomes longer.
It does seem that two batteries are needed to solve this problem. Can temporarily add a battery to verify.

If the above explanation holds true, the interesting part here is that when the input power of the microwave is about 3/4 of the rated power (1280W->inverter->1152W), the heating sandwich time is actually extended by 10 times (2min->20min). Wow! Or does it just use multiple start-peak-moments to complete the heating?
Your thorough reply is appreciated, and it all makes sense. I do have a 2nd battery that I will add. Besides the sandwich, either frozen or refrigerated, I also tried heating refrigerated burritos with the same results. I might do 5 2-minutes runs with apparently no results (still cold) but then after another 5 runs it suddenly starts to get warm. With each run I'd watch the battery voltage drop from say 13.4 to 13.3, then to 13.2, then 13.1 and finally going down to about 12.6 before getting the needed result. The solar panels do a very good job of recharging the battery. The LiFePO4 battery seems great to me. I can start at 13.3v and run a laptop for 3-4 hours, recharge a couple of DSLR camera batteries, run radio for hours, lights 5+ hours, watch a DVD movie on 32" flat screen...and by the time I go to sleep the battery level is still at 13.1v. Very impressed. That scenario does not include any microwave use, but once I add another battery I think all will be well.
 

Iceman218

Solar Enthusiast
I put a lighted lamp switch on the converter 110V inlet. While I could flip the breaker, then there would be no indication the converter was off. The light switch is bright when the circuit is off and dark when the circuit is on. So now instead of flipping the breaker back and forth, I just flip the light switch to off when running on the battery.
 

McRod

New Member
You make this sound so easy and you obviously know the wiring. So far, I can't 'picture' your instructions. Since your advice ends with 'turn off breaker B', what is the advantage of doing the additional wiring rather than just turning off breaker B? I'm all for doing the easiest work-a-round without additional mods if not required. Thanks.
It's very easy. Turning off breaker B turns off your converter, which you asked about stopping it from charging your batteries - iirc. Your converter is most likely not lithium compatible anyhow, so I wouldn't use it as a charging source. You need to verify that.

The wiring instructions is how to get your inverter to run all your AC appliances.

Two separate tasks.
 
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McRod

New Member
Thanks for mentioning that. After taking the photos I noticed that slot was empty, but I've never removed any fuses from the converter. They either forgot to install it or left it out for some reason. Should I definitely replace it?

The printed instruction says replace with only a Littelfuse type 257. I'm guessing it's the same type of fuse as the others, just 40 amps.
It's not the same fuse. It's a type 257.
 

Jims94vmx

Solar Enthusiast
Turn off the breaker and you will be ok. Then for giggles try the microwave hot water test.....your battery was doing double duty like I mentioned earlier....as you pulled power out using microwave, you were also pulling power out using you converter. You put another 50% draw that way. I agree a 2nd battery will be better, but I think it may work with 1 in a pinch.
 

azdp

New Member
Turn off the breaker and you will be ok. Then for giggles try the microwave hot water test.....your battery was doing double duty like I mentioned earlier....as you pulled power out using microwave, you were also pulling power out using you converter. You put another 50% draw that way. I agree a 2nd battery will be better, but I think it may work with 1 in a pinch.
I agree about the converter wasting power. The specs say it has a 35 amp output for charging and trailer loads. I'm guessing that is 20 amps for charging and 15 amps for loads. I've already tried running power directly from the inverter to the microwave with no converter involved. The microwave functioned, but weakly. I'll be adding the 2nd battery which should provide enough juice to run the microwave at full power.
 

azdp

New Member
This is WFCOs lithium version of the converter in your RV.


Not that the existing one won't charge your lithiums, it just won't charge with the correct charging profile.
Thanks for the link. Since I charge with solar and have never used shore power I think I will leave the converter as is. But, do you happen to know....while towing the trailer and using a 7 pin plug, do the trailer batteries get charged directly from the tow vehicle or does it go through the converter?
 

Iceman218

Solar Enthusiast
The 7 pin connector has too much voltage drop to effectively charge a battery. It can run a 12V refrigerator at 12V. but 12V is not enough to charge any battery. So during towing, Solar is your best bet.
 
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