Inverter not converting 12V to 120V to run microwave oven

[alanmalk]

Originally Posted by rubicon327

Alan this might not be possible/practical as his inverter is inside under DS dinette seat and batteries are in front storage box

I believe the length of wire is approximately 3 feet.

I'm getting a conflicting picture here. If the inverter and batteries are separated by that much distance, then the length of the wire must be considerably more than 3 feet.

I have a couple of 10ga jumper wires about 20’ long I made years ago out of marine stranded / tinned wire for times like this when I need to extend a test lead.

A jumper can be very helpful when testing two points that are further apart than the meter leads. But the gauge & length is irrelevant when only testing voltage as there is no current to speak of. (Use battery jumper cables if you have them.)

But as we all know - the battery to inverter distance is best measured in inches, not feet. However, if there is no choice then the battery cable should be sized accordingly. Since we're talking 100+ Amps then we are looking at serious $$. And also suspect is the Escape-provided fuse. Do we know what it really is? And is it sized properly to match the wire size? Sure be nice to see what it really is. But spending any $$ is not warranted until it is determined if the problem is wire plus fuse plus connectors, or it is weak batteries. Got to do that voltage drop test between the battery post and inverter terminal - regardless of distance. And a load test is still easier than hauling 6 Volt batteries to a testing station.

[brroberts]

I agree on wire jumper gauge size, depending on what you are measuring. That’s why I made them the way I did. Resistance and capacitance are real.

[Vermilye]

Originally Posted by alanmalk

...I'm getting a conflicting picture here. If the inverter and batteries are separated by that much distance, then the length of the wire must be considerably more than 3 feet...

I suspect it is the fiberglass shell that is in the way of a simple measurement between the batteries & the inverter. In most 19's the inverter is under one of the front seats and the batteries in the storage box so the wire between it & the batteries could easily be under 3'.

[Tonny LR]

Originally Posted by Vermilye

I suspect it is the fiberglass shell that is in the way of a simple measurement between the batteries & the inverter. In most 19's the inverter is under one of the front seats and the batteries in the storage box so the wire between it & the batteries could easily be under 3'.

Jon,
Thanks. you are 100 % correct.

Tonny LR

[alanmalk]

Originally Posted by brroberts

I agree on wire jumper gauge size, depending on what you are measuring. That’s why I made them the way I did. Resistance and capacitance are real.

Of course.
I sure wouldn't want to run a set of jumper cables to my frequency meter!

[alanmalk]

Originally Posted by Vermilye

I suspect it is the fiberglass shell that is in the way of a simple measurement between the batteries & the inverter. In most 19's the inverter is under one of the front seats and the batteries in the storage box so the wire between it & the batteries could easily be under 3'.

Ahh, I see.
Well, another helper with a 10' length of wire is needed. He/She will hold one end of the wire on the battery post and the other end will be near enough to the inverter to use the meter. Positive lead on the battery wire, negative lead on the inverter. Another helper runs the hair dryer and microwave. This will require both beer and apple pie to provide enticements.

[Tonny LR]

[QUOTE=alanmalk;435738]
__________________________________________________ ___________________________
Quote
I'm getting a conflicting picture here. If the inverter and batteries are separated by that much distance, then the length of the wire must be considerably more than 3 feet.
The inverter was installed on the driver side bench, bottom corner, DC terminal facing the trailer front wall. DC wires went through the floor and connected to the batteries in the front storage box. The inverter owner manual states that the distance between terminals and batteries should not be more than 3.2 meter. Since the inverter was factory installed, I would think it was within the specifications.
__________________________________________________ __________________________
Quote
(Use battery jumper cables if you have them.)
I have a set of 10 ft. heavy duty battery jumper cable which is all copper and orange color. Do not know the gauge. Picture attached. Please let me if it will work for the test.
__________________________________________________ ___________________________
Quote
And also suspect is the Escape-provided fuse.
I have no idea what kind of fuse ETI used but I would like to replace it before I run another test. Would a Blue Sea MRBF 1 tern fuse block 30 amp/58 volt meet the standard. Or any suggestions for the best fuse to buy. Any fuse I get should meet any future upgrade if I decide to go with Lithium battery.
I totally agree that a load test is easier than hauling batteries to the dealer for testing

Tonny LR

[alanmalk]

Originally Posted by Tonny LR

The inverter owner manual states that the distance between terminals and batteries should not be more than 3.2 meter. Since the inverter was factory installed, I would think it was within the specifications.

Probably within specifications, but inverter-to-battery distance ought to be a couple of feet or less in an ideal setup. Regardless of total length it is imperative that the correct gauge of wire be used. Your current inverter, used to power a microwave (~1000 watts?) will pull at least 80 Amps, if not more, from the batteries. Later on we can look at detailed tables to determine proper wire gauge for a 6 foot (round trip) voltage drop. Its going to be a big fat wire for sure. But jumping the gun to do that today.

__________________________________________________ __________________________

I have a set of 10 ft. heavy duty battery jumper cable which is all copper and orange color. Do not know the gauge. Picture attached. Please let me if it will work for the test.
Will work for sure. Lamp cord will work. Any normal wire will work for a voltage test. We're measuring low voltage at zero current.

__________________________________________________ ___________________________


I have no idea what kind of fuse ETI used but I would like to replace it before I run another test. Would a Blue Sea MRBF 1 tern fuse block 30 amp/58 volt meet the standard. Or any suggestions for the best fuse to buy. Any fuse I get should meet any future upgrade if I decide to go with Lithium battery.
Blue Sea is a trusted brand. I am not familiar with MRBF-1.

But 30 Amps doesn't come close! We're going to have to visit some non-intuitive logic here.

First, your absolute minimum fuse amperage has to meet the requirements of the load. In this case the inverter maximum output is 1500 watts (?). 1500 watts is 120 amps at 12.5 volts. (Remember, I don't have your inverter so don't know the absolute specs.)

And here comes the puzzling logic: Your fuse is not there to protect the inverter! It is there to protect the actual wire. And you now will ask: "What!??". Simply, when the inverter fails it is dead. No fuse can protect it fast enough. But when it fails it could short circuit internally and attempt to draw as much amperage as your batteries can supply - 1000+ amps! Wires can melt, start fires, and otherwise ruin your day. So a proper installation will use a bigger fuse than the max load, but not too much bigger. If you are using beefy wires that can handle 300 amps for 10 seconds without getting too hot then a 200 amp fuse is about right. But folks with more real world experience might jump in here with better advice. The other big advantage of a 200 amp fuse is that it has a lower resistance, and resistance is the source of voltage drop - our enemy.

I totally agree that a load test is easier that hauling batteries to the dealer for testing

Tonny LR

Don't haul batteries, don't spend $$, at least for a while!

[Iowa Dave]

Hey Tonny,
You’re getting quite an education on this whole battery and inverter thing. I’m glad because next time I have a problem I’m coming to you. Hope everything is good with you and Carol. Merry Christmas and as our power company mascot Ready Kilowatt up here in Iowa used to say in the 50’s, MORE POWER TO YOU!
Iowa Dave

[alanmalk]

Originally Posted by Iowa Dave

...
Merry Christmas and as our power company mascot Ready Kilowatt up here in Iowa used to say in the 50’s, MORE POWER TO YOU!
Iowa Dave

Or to keep it simple, in the words of Tim Allen, MORE POWER!

[Tonny LR]

Originally Posted by Iowa Dave

Hey Tonny,
You’re getting quite an education on this whole battery and inverter thing. I’m glad because next time I have a problem I’m coming to you. Hope everything is good with you and Carol. Merry Christmas and as our power company mascot Ready Kilowatt up here in Iowa used to say in the 50’s, MORE POWER TO YOU!
Iowa Dave

Hello Dave,
Merry Christmas and Happy New Year to you and Rita. MORE POWER TO YOU TOO! This is a wonderful forum and forum members are very knowledgeable and helpful in troubleshooting batteries and inverter. As a retired healthcare worker, I certainly learn a lot on how to test batteries.

Tonny LR

[Tonny LR]

Originally Posted by alanmalk

Or to keep it simple, in the words of Tim Allen, MORE POWER!

Hello Alan,
My jumper cable is not long enough to go through dinette window for me to rum the load test. Also the it had been raining and wet here in Little Rock. It will take me a few days to get parts to conduct the load test. Thank you for all your help!

Tonny LR

[alanmalk]

Originally Posted by Tonny LR

Hello Alan,
My jumper cable is not long enough to go through dinette window for me to rum the load test. Also the it had been raining and wet here in Little Rock. It will take me a few days to get parts to conduct the load test. Thank you for all your help!

Tonny LR

No hurry. We should all be available, at least until the next camping season. Here in Colorado after 3 snowstorms in 2 weeks that may be an eternity.

Don't overthink the long wire. Anything will work as long it reaches "point B" and you can attach it to a meter test lead. It doesn't carry any current - fortunately - because if it did, it would add its own voltage drop to the numbers.

Stay dry, keep warm and plan for much microwave popcorn next spring.

[alanmalk]

Originally Posted by alanmalk

Ahh, I see.
Well, another helper with a 10' length of wire is needed. He/She will hold one end of the wire on the battery post and the other end will be near enough to the inverter to use the meter. Positive lead on the battery wire, negative lead on the inverter. Another helper runs the hair dryer and microwave. This will require both beer and apple pie to provide enticements.

Better make that 20'.

[John in Santa Cruz]

Originally Posted by alanmalk

...
Don't overthink the long wire. Anything will work as long it reaches "point B" and you can attach it to a meter test lead. It doesn't carry any current - fortunately - because if it did, it would add its own voltage drop to the numbers...

I use some cheap 20 ga speaker wire for this sort of thing.

[Tonny LR]

Originally Posted by John in Santa Cruz

I use some cheap 20 ga speaker wire for this sort of thing.

John,
Thank you for sharing the excellent idea. I have a lot of speaker wires to do the job. It definitely save me some money to buy a cable.

Tonny LR

[Tonny LR]

Originally Posted by alanmalk

200 amp fuse is about right.

Alan,
Thank you for the suggestion. I picked 30 amp/58V fuse because I saw another thread that ETI installed a 30Amp/58v fuse on new camper.

Tonny LR

[Tonny LR]

Originally Posted by alanmalk

Ok. Start by turning on the meter and selecting a 2 Volt range. Why so low? Because the likely 1 way voltage drop is in the neighborhood of 0.2 to 1.0 Volts. Small, but very significant.

Next, put the positive (+) lead of the meter on the "test point B), aka, the battery post. And the negative lead (-) on the + terminal of the inverter. Woah, you're saying - this is backwards from earlier tests! Correct. Under the load we are expecting the battery post to be a higher voltage than the other end of the red wire, the + terminal of the inverter. This way you will read a positive voltage rather than a negative one.

Check your meter - it should read zero, or very close. Have your helper turn on the hair dryer. Take your time, not necessary to take a fast reading, it will be reasonably stable. Ballpark guess: 0.3 to 0.5 V. Turn off the dryer and turn on the microwave. Take the reading before the inverter alarm goes off. Ballpark guess: 0.5 - 0.8.

These are the numbers we need to see. If the microwave load results in readings around 0.8 then suspect your wire (too long, too thin) or the mystery device under the bar. (And keep in mind the real drop is roughly what your meter told you times 2. So 0.8 = real drop of 1.6 Volts. New wire or better fuse/breaker is much cheaper than new batteries. And absolutely necessary if you intend to upgrade to a bigger inverter.

Alan,
I performed the test point B today. In order to give you adequate info, I found the wire from the batteries to the inverter to be 4 AWG and the length is 63 inches. My meter does not have a low range setting. Photos' attached.

A 15 feet 14 AWG audio wire was used to connect Positive lead of the meter on the test point B, the battery post. And the negative lead (-) of the meter on the + terminal of the inverter. I turned on the hair dryer which was set on hot and high speed. The inverter shut off at 0.8V.
A couple minutes later, I turned on the microwave and heard the alarm went off at 0.6V . The microwave shut off at 0.8V. The last voltage I saw on the meter was 0.7V. My wife said that the microwave shut off after 8 seconds. I hope that these 2 test results tell us something.
I plan to install a new 200Amp/58V fuse later.

Tonny LR

[Perry Butler]

Originally Posted by Tonny LR

Alan,
I performed the test point B today. In order to give you adequate info, I found the wire from the batteries to the inverter to be 4 AWG and the length is 63 inches. My meter does not have a low range setting. Photos' attached.


I plan to install a new 200Amp/58V fuse later.

Tonny LR

A 4 AWG wire is way too small in my world. This could be your problem.

I used 2/0 wire running two feet for our 1,500 watt inverter.

I also used a 250a T fuse for our inverter. It was felt that 200a would blow too easily.

Food for thought,

Perry

[alanmalk]

Originally Posted by Tonny LR

Alan,
I performed the test point B today. In order to give you adequate info, I found the wire from the batteries to the inverter to be 4 AWG and the length is 63 inches.

That is very useful information. Now we know round-trip length of wire is appx. 10 feet. (10 is a great number for my simple math.) And we also know 4 AWG wire has a drop of 0.0002485 ohms per foot. (Found that on the internet.) So, total wire resistance is 0.002485 ohms in your setup. (Told you 10 was a nice number!) Now, lets assume (wild guess) that your hair dryer (high) and microwave are both using very roughly 100 amps. Using the well-documented formula, E=I*R, or in English, voltage drop = current times resistance: We get (E)voltage drop = (I)100 * (R)0.002485 = 0.2485 volts. Rounding to a useful value, your wire is responsible for 0.3 volts of drop. That a round trip value so your 1 way measurement should have been 0.15 volts. Keep that number in mind for later discussion.

My meter does not have a low range setting. Photos' attached.
A bit unfortunate but we can live with it.

A 15 feet 14 AWG audio wire was used to connect Positive lead of the meter on the test point B, the battery post. And the negative lead (-) of the meter on the + terminal of the inverter. I turned on the hair dryer which was set on hot and high speed.
Perfect.

The inverter shut off at 0.8V. A couple minutes later, I turned on the microwave and heard the alarm went off at 0.6V . The microwave shut off at 0.8V. The last voltage I saw on the meter was 0.7V. My wife said that the microwave shut off after 8 seconds. I hope that these 2 test results tell us something.
Yes. Lets look at these results.
You get in trouble (alarm) at 0.6 V. This is a 1 way drop remember. Total round trip drop has to be more, say in a perfect world the 0.15 V from the calculations. Total drop is then 1 volt (rounding up a bit). First observation. You should be reading around 0.2 but you saw 0.6 (and up). The wire is wire, I hope. And by that I mean not a super-cheap copper coated aluminum that you can buy on Ebay. Ok, its the good stuff so where did the extra 0.4 V of drop come from? Actually, there is only one answer - the fuse installation and any corroded connections in the path. Got to suspect that fuse.

I plan to install a new 200Amp/58V fuse later.
That may solve your problem right there.

Tonny LR

Personal opinion but I believe in doing the cheapest and easiest fix first. Replacing the fuse fits that bill. But, and especially if you are planning to upgrade your inverter - the wire is the next step. You will have noticed by now that we have been ignoring the black wire (the return trip for those tired electrons). I'm afraid in the real world that wire could have the same issues - a bit too thin, bad connections, poor fittings at each end, corrosion, etc. The only thing different between the red and black wire is the presence of the fuse in the red line. So do give consideration to upgrading your wires. You can purchase them with fittings attached, done professionally and protected from corrosion. It won't be cheap but you will be proud of the results and it still cheaper than new batteries - which by the way would not have solved the voltage drop one bit. Voltage drop is only a product of E=I*R, and has nothing to do with starting (or ending) voltage.

And another FYI. Second observation, your guestimated total voltage drop of around 1 volt, at 100 amps = 100 watts of lost power = gone up in heat, but not heat to your hair dryer/microwave. Lost in space...