adding inverter

[Mister Mike]

So I had the below diaram installed in my van. The installer recommended the Renogy 700 inverter however after reading the reviews I went with the Victron Energy Phoenix 800VA 12-Volt 120V AC Pure Sine Wave Inverter. I thought I’d be fine running a 600 watt microwave but watched a video tested one and the input was 900 watt.
I thought I’d add a 3000 watt modified inverter next to my Victron 800 and use the 3000 watt for just the microwave and a air fryer that showed 700 watt draw.
I asked the tech how this could be done and was told to "hook it up the same way I hooked up your Victron 800. I asked if I should put a switch in between them and he said “if you want to”.
I’m at the final stage of a 2 year build and I couldn’t bear the thought of screwing something up now.
I’m totally a rookie so I’ll include a little info and maybe you can let me know how to do it.
Thanks! Mike

1)No on-off switch was not installed
2) The batteries are the 280 Ah I got from China
3)The viltron is within 2 feet from the batteries and the Shunt. I believe I can for the 3000 watt inverter right next to the 800 watt with enough room f to ventilate.

 

[chrisski]

I had a 12 volt 2000 watt inverter installed to run a microwave and used 4/0 wire. If you do install a 3000 watt inverter, wiring between the battery and inverter will need to be made thicker than what you have now. You'd probably want a bus bat with thick wire to the battery positive and a separate busbar for the negative. You'd put just as thick wire to the inverter, and smaller wire to the other devices.

This is my 8 Stud Busbar I use for my 24 volt build.


I would avoid an off switch on the DC side of the inverter. The battery will spark each time its connected to the inverter. Having a switch just moves this spark to a switch. I do recommend a remote on/off switch or shut the inverter off whenever not in use. Something that size probably drains between 12 and 24 watts an hour, so that adds up.

The final question I have, is will your BMS handle the amperage for a microwave? A 600 watt cooking power microwave microwave approaches 100 amps draw from the batteries. My guess is more than that. My 1100 watt cooking power microwave draws 135 amps at 14 volts.

EDIT: Here is a chart I made of different Amperage Draws on a 12 volt and 24 volts system.

 

[Mister Mike]

I had a 12 volt 2000 watt inverter installed to run a microwave and used 4/0 wire. If you do install a 3000 watt inverter, wiring between the battery and inverter will need to be made thicker than what you have now. You'd probably want a bus bat with thick wire to the battery positive and a separate busbar for the negative. You'd put just as thick wire to the inverter, and smaller wire to the other devices.

This is my 8 Stud Busbar I use for my 24 volt build.

View attachment 122043
I would avoid an off switch on the DC side of the inverter. The battery will spark each time its connected to the inverter. Having a switch just moves this spark to a switch. I do recommend a remote on/off switch or shut the inverter off whenever not in use. Something that size probably drains between 12 and 24 watts an hour, so that adds up.

The final question I have, is will your BMS handle the amperage for a microwave? A 600 watt cooking power microwave microwave approaches 100 amps draw from the batteries. My guess is more than that. My 1100 watt cooking power microwave draws 135 amps at 14 volts.

EDIT: Here is a chart I made of different Amperage Draws on a 12 volt and 24 volts system.

View attachment 122049

 

[Mister Mike]

Thank you for your input. I’m so ignorant regarding this subject but looking it over it looks like I’d be changing a lot of wires. I remember the tech who put it in mentioned that going to a larger inverter would constitute heavier wire.
Please tel me some good news. I need some badly. The images below are what I’ll have to cook with. The air fryer is hooked up to a watt a meter.
It stayed steady at 6.90. but my wife is telling me to cook if I want to cook meat the air fryer may run for 20 minutes.

I have :280 Ah lithium and a​

Victron Energy Inverter, Phoenix 12V 800VA 120V​

Victron Energy Inverter, Phoenix 12V 800VA 120V​

 

[Mister Mike]

So if I’m correct, let call it 700 watts divided by 12 volts it’ll draw. 58.3 ah in one hour. Correct?

 

[chrisski]

An inverter pulls 15% for DC to AC losses so the math is:

700/12/.85

Which is around 65 amps. There’s more too it— The inverter will push the 700 watts no matter what voltage, so if the inverter has a low voltage cutoff of 10 volts, the math would be:

700/10/.85 or around 80 amps. The wires and fuses need to be built for that. But if you have a 3000 watt inverter, the math for that is:

3000/10/.85 or a possible load of 345 amps. That’s some thick wire for ampacity.

IME if you have a 3000 watt inverter, a guest will user it to the full 3000 watts, so it needs to be wired for that.

The loads you’re talking, I don’t think they have a surge,if they did the inverter would draw a bit more than 700 watts to get started. Because of that, sometimes a 700 watt load will need an inverter 2 X to 8X to cover starting surge.

 

[chrisski]

An inverter pulls 15% for DC to AC losses so the math is:

700/12/.85

Which is around 65 amps. There’s more too it— The inverter will push the 700 watts no matter what voltage, so if the inverter has a low voltage cutoff of 10 volts, the math would be:

700/10/.85 or around 80 amps. The wires and fuses need to be built for that. But if you have a 3000 watt inverter, the math for that is:

3000/10/.85 or a possible load of 345 amps. That’s some thick wire for ampacity.

IME if you have a 3000 watt inverter, a guest will user it to the full 3000 watts, so it needs to be wired for that.

The loads you’re talking, I don’t think they have a surge,if they did the inverter would draw a bit more than 700 watts to get started. Because of that, sometimes a 700 watt load will need an inverter 2 X to 8X to cover starting surge.

 

[mysolarrv]

Since you mentioned that you want to add a 3000W inverter to power the microwave. I think it's good to point out that a cheap 3000W inverter is probably a 'modified sine wave device' and it will not work correctly with a common AC microwave as they need a clean AC signal (pure sine wave) to function properly. Maybe the better option, rather than invest in a pure sine wave 2000W inverter (which could easily power a 600W microware), is to look into buying a DC microwave. Just a thought.

 

[Mister Mike]

I went to Amazon and entered (12 volt dc microwave oven for rv) and couldn’t locate anything. Then Camping World and entered DC Microwave Oven) and still nothing. What am I missing or could you send a link to a product you’re referring to?
Thank you and everyone else who chimed in

 

[Supervstech]

Since you mentioned that you want to add a 3000W inverter to power the microwave. I think it's good to point out that a cheap 3000W inverter is probably a 'modified sine wave device' and it will not work correctly with a common AC microwave as they need a clean AC signal (pure sine wave) to function properly. Maybe the better option, rather than invest in a pure sine wave 2000W inverter (which could easily power a 600W microware), is to look into buying a DC microwave. Just a thought.

 

[Mister Mike]

You wrote
"rather than invest in a pure sine wave 2000W inverter (which could easily power a 600W microware), is to look into buying a DC microwave. Just a thought."
The video demonstrates the difference between pure and modified but the question still linger, Where do you see a DC microwave?

 

[Mister Mike]

Okay, well I’m back to square one.
If I hook myair fryer drawing a continue 795 watts to my (see below)

Victron Energy Inverter, Phoenix 12V 800VA 120V​

and assuming everything else is designed to handle the 800 watts will I destroy my inverter if I drew the 795 continues watts for 20 minutes?​

 

[Bud Martin]

Here is the spec: I use my equipment at 80 ~ 85 % of the rating

 

[mysolarrv]

You wrote
"rather than invest in a pure sine wave 2000W inverter (which could easily power a 600W microware), is to look into buying a DC microwave. Just a thought."
The video demonstrates the difference between pure and modified but the question still linger, Where do you see a DC microwave?

I swear I saw a couple of models when I did a Google search for microwave ovens for long haul truckers, but maybe I was mistaken. For my camper, the microwave is built into the cabinet above the stove, so it would be a major pain-in-the-neck to try to swap microwaves from AC to DC (if they really exist). My current solution was to hook up a 1500W pure sine inverter and wire in a 20A AC relay where the microwave is connected to the power panel to act as a transfer switch when I am dry camping or have access to shore power. The problem I am running into is my inverter is pulling too much power from my DIY battery and going into a low voltage shutdown (not the inverters problem). But I guess the point I am trying to make is, a 1500W pure sine inverter should work fine for an air fryer or small microwave oven (can't power both at the same time). What if you replace both of your other inverters with a medium sized pure sine inverter? That would simplify your wiring and such, but obviously would be an additional expense and the frustration of pulling out stuff that you already paid to have installed.

 

[chrisski]

Since you mentioned that you want to add a 3000W inverter to power the microwave. I think it's good to point out that a cheap 3000W inverter is probably a 'modified sine wave device' and it will not work correctly with a common AC microwave as they need a clean AC signal (pure sine wave) to function properly. Maybe the better option, rather than invest in a pure sine wave 2000W inverter (which could easily power a 600W microware), is to look into buying a DC microwave. Just a thought.

If such a thing exists as a 12 volt Microwave, I would not want to be the first on my block to install this. This would likely pull at least 100 amps which is some pretty thick cable, and placement of the microwave would mean voltage loss if too far from the battery, meaning thicker cables. There’s a reason you don’t see low voltage high wattage items for sale.

 

[12VoltInstalls]

approaches 100 amps draw from the batteries. My guess is more than that

Probs

thought I’d add a 3000 watt modified inverter

Do not use a mod sine inverter.
Use pure sine

Mod sine may be the death of your microwave for one. For another it might even pull more amps than a pure sine depending on how it creates the ‘steps.’

 

[mysolarrv]

If such a thing exists as a 12 volt Microwave, I would not want to be the first on my block to install this. This would likely pull at least 100 amps which is some pretty thick cable, and placement of the microwave would mean voltage loss if too far from the battery, meaning thicker cables. There’s a reason you don’t see low voltage high wattage items for sale.

Yeah, I wondered about that myself. It would have to hook up like a large inverter with heavy gauge wires. There is no way you could run it off of a cigarette lighter plug. :D

 

[Mister Mike]

unfortunately the installer didn’t know a 600watt microwave draws more wattage than my inverter can handle 800 watt inverter can handle. I guess when I find the time I’ll see exactly the size wiring and other components he used to figure out what putting a 2000 wtt pure inverter will entail. Thanks all for your help

 

[mysolarrv]

Okay, I did find a DC microwave here --> DC Microwave , but it looks like they are no longer available (sorry about that).
So probably best to match a proper sized pure sine wave inverter with an existing AC microwave oven. A modified sine wave inverter technically will work, but will probably burn out the microwave oven prematurely (among other issues such as noise/buzzing/low-output). Any decent inverter manufacturer will recommend the proper size cables to use, my guess is probably around 1/0 AWG for a 2000W inverter.