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40 amp Charge Controller and 3000 watt invertor

danielsjoseph891

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I'm still ordering components, and this actually why I'm posting. I have (4) 100 watt panels that will be connected to a 40 amp charge controller, that will be charging (2) 100 ah 12 v lithium iron phosphate batteries. I was going to go with a 2000 watt pure sine wave invertor but would like to use a 3000 watt because I would like to use a small selection of household appliances. What I'd like to know, plain and simple, as in someone says "do it" or "don't do it", is can I use a 3000 watt with the system I've outlined above?
I assume there is no domino effect on the system, but I'm new to all of this and don't want to waste time shipping it back, or money.
Thanks,
Joe
 
3000 ac watts / .85 conversion factor / 12 volts low cutoff = ~294 dc amps
~294 dc amps / .8 fuse headroom = ~367 fuse amps
By the book you can use 3/0 awg wire with 105C insulation.
But I really doubt your want your wires getting hotter than boiling water.
If you use 2x 4/0 awg then the temperature goes down to 60C.
Assuming your batteries have a 1c continuous discharge rate you will be exceeding their specification.
2000 watts is a practical upper limit for 12 volt systems.
 
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I have a similar inquiry, but in my scenario we currently just have (2) 100aHr FLA batteries and (2) 100w panels supplemented with a dc to dc charger for when in transit on less sunny days. We also have a 30 amp MPPT and a 40 amp dc to dc charger. We have an additional 2 panels we could take from our camp but didn’t know if we needed more than 200 watts of solar with the current battery bank…. We are contemplating converting to LiFePO4 batteries (either 170 or 228 aHr) as it would give up to 80% vs 50% of the batteries available capacity as well as weigh less too. (And we also have a portable gas generator if necessary as well but always prefer using that as little as possible.) The one thing we are missing though is an inverter and just didn’t know what the inverter charger vs the plain inverter would be providing. But it appears the advantage of the inverter charger is that it allows one to also charge the batteries from shore power. I’m not sure we need the additional functionality though with having solar already available. What do those that have the inverter charger and solar combo say as I’m curious if it’s really necessary. TIA!
 
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I have a similar inquiry, but in my scenario we currently just have (2) 100aHr FLA batteries and (2) 100w panels supplemented with a dc to dc charger for when in transit on less sunny days. We also have a 30 amp MPPT and a 40 amp dc to dc charger. We have an additional 2 panels we could take from our camp but didn’t know if we needed more than 200 watts of solar with the current battery bank…. We are contemplating converting to LiFePO4 batteries (either 170 or 228 aHr) as it would give up to 80% vs 50% of the batteries available capacity as well as weigh less too. (And we also have a portable gas generator if necessary as well but always prefer using that as little as possible.) The one thing we are missing though is an inverter and just didn’t know what the inverter charger vs the plain inverter would be providing. But it appears the advantage of the inverter charger is that it allows one to also charge the batteries from shore power. I’m not sure we need the additional functionality though with having solar already available. What do those that have the inverter charger and solar combo say as I’m curious if it’s really necessary. TIA!
The question is ... "q: why do I need a transfer switch?"
a: {
Because sometimes you will be connected to shore power and sometimes you won't.
When you are connected to shore power the neutral/ground bond is upstream from the pedestal and out of your control
When you are not connected to shore power the neutral/ground bond must be within your domain.
This is a life safety and fire safety issue.
The easiest way to do this with an inverter/charger.
It probably costs no more money.
Its worth doing even if you don't need the ac charger function.
}
 
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oops, not sure how to delete the original comment which was mistakenly posted vs should have been as reply below.
 
The question is ... "q: why do I need a transfer switch?"
a: {
Because sometimes you will be connected to shore power and sometimes you won't.
When you are connected to shore power the neutral/ground bond is upstream from the pedestal and out of your control
When you are not connected to shore power the neutral/ground bond must be within your domain.
This is a life safety and fire safety issue.
The easiest way to do this with an inverter/charger.
It probably costs no more money.
Its worth doing even if you don't need the ac charger function.
}
But doesn’t the converter that’s currently in the RV provide that type of protection already?
 
But doesn’t the converter that’s currently in the RV provide that type of protection already?
Not really, because a converter changes ac2dc.
An inverter changes dc2ac
and a transfer switch does what I described above.
You could power the inverter via the converter but its brutally inefficient.
~45% conversion penalty from ac2dc and ~15% compounded to go back to ac.
I know because I'm doing it :).
You would still have the problem of switching the neutral/ground bond.
I'm gonna step off now.
Maybe somebody else has another angle here.
 
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What I'd like to know, plain and simple, as in someone says "do it" or "don't do it", is can I use a 3000 watt with the system I've outlined above?
There's so much that goes into installing solar in an RV, that if you want a simple do it or don't do it, I'll say "Definitely not."

There's a lot of math involved and there may be a small set of circumstances I would think installing a 3000 watt inverter with 12 volt batteries on an RV are acceptable, of which, to run household appliances off two 100 ah batteries is not one of them.
 
There's so much that goes into installing solar in an RV, that if you want a simple do it or don't do it, I'll say "Definitely not."

There's a lot of math involved and there may be a small set of circumstances I would think installing a 3000 watt inverter with 12 volt batteries on an RV are acceptable, of which, to run household appliances off two 100 ah batteries is not one of them.
The original poster has 2 x 100 aHr LiFePO4. But as noted in one of the prior replies, 2000 w inverter is upper limit for 12v system.
 
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The original poster has 2 x 100 aHr LiFePO4. But as noted in one of the prior replies, 2000 w inverter is upper limit for 12v system.
I don't Agree with that statement. A 2000 watt inverter may be OK on 12 volts to run a a 2000 watt device for three or four times a day at a couple minutes each, but if more than that you need to go to 24 volts.

You can disagree with that and that's fine. Some say the 12 volt limit is 1000 watts, others 2000 watts, and others 3000 watts. Someone even claimed to have a 12 volt 4000 watt inverter installed.

If anyone wants some reading these posts are good:

Inverter Size vs Battery Tutorial
12 volt solar for RV or camping
Solar Off Grid Battery Design

Don't just take statements like "2000 watt inverter is the upper limit for 12 volt system" as granted. Not really true. Especially when people are convinced they can use 4 AWG or 2 AWG wiring for these amperages.

For those who don't like the:

12 Volt = 1000 watt inverter
24 Volts = 2000 watt inverter
48 volts = Bigger inverters not to exceed 5000 watts

I'd like to hear why you think that rule does not apply. You can convince me, but there will need to be math and more than just "its worked for me" or "So and So says its OK."
 
I don't Agree with that statement. A 2000 watt inverter may be OK on 12 volts to run a a 2000 watt device for three or four times a day at a couple minutes each, but if more than that you need to go to 24 volts.

You can disagree with that and that's fine. Some say the 12 volt limit is 1000 watts, others 2000 watts, and others 3000 watts. Someone even claimed to have a 12 volt 4000 watt inverter installed.

If anyone wants some reading these posts are good:

Inverter Size vs Battery Tutorial
12 volt solar for RV or camping
Solar Off Grid Battery Design

Don't just take statements like "2000 watt inverter is the upper limit for 12 volt system" as granted. Not really true. Especially when people are convinced they can use 4 AWG or 2 AWG wiring for these amperages.

For those who don't like the:

12 Volt = 1000 watt inverter
24 Volts = 2000 watt inverter
48 volts = Bigger inverters not to exceed 5000 watts

I'd like to hear why you think that rule does not apply. You can convince me, but there will need to be math and more than just "its worked for me" or "So and So says its OK."

Thanks, Im not the OP, but I’ll check out the references! We haven’t purchased an inverter yet, so I’m open to learning what works for others rather than finding out the hard way or repeating others learning curves!
 
12 Volt = 1000 watt inverter
24 Volts = 2000 watt inverter
48 volts = Bigger inverters not to exceed 5000 watts

I'd like to hear why you think that rule does not apply. You can convince me, but there will need to be math and more than just "its worked for me" or "So and So says its OK."
In my investigation of scale and proportion of the core system components I discovered that sourcing components for >~300 amps gets increasingly difficult.

2/0 awg wire with insulation rated for 105C is good for 330 amp in open air.
You can get bigger wire but the tools to cut it get expensive.
And its gets harder to wrestle with it as well.

Breakers get scarce above 200 amps and fuse selection is limited above 300 amps.
Disconnect switches also get scarce and expensive above 300ish amps.
Similar for busbars.

So if all the joining pieces are limited to 300 fault amps.
The service current is 300 fault amps * .8 = 240 amps
So for a 12 volts high frequency inverter 240 service amps * 12 volts low cutoff * .85 conversion efficiency = 2448 ac watts continuous

So 2400 watts for 12 volts, 4800 watts for 24 volts, > 4800 is 48 volts.
For a low frequency inverter the boundaries are lower.
 
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Thanks, Im not the OP, but I’ll check out the references! We haven’t purchased an inverter yet, so I’m open to learning what works for others rather than finding out the hard way or repeating others learning curves!
I have a 12 volt system with a 2000 watt inverter. I make as many cups of K-Cup Coffee in my 500 watt coffee maker as my wife and I can drink. We run the microwave at a couple of meals a day, two minutes at a time to warm up food. If I need to cook a frozen dinner, I take out the generator, fire it up, and use the microwave.

With my 24 volt upgrade I'm doing, I plan on being able to run the microwave as much as I want, to include cooking frozen dinners, being able to boil water in a 1700 watt electric kettle, and running the blow dryer. Not really able to run the 15K BTU Air Conditioning that came with the RV, but if I swap to a mini split I might. That much becomes an electric storage issue.

The OP was talking about 2.4 kwh of batteries. I will have a little over 12 kwh of batteries. IMO, not only do you a need 24 v system to run high wattage appliances, but you need to be able to store the energy to do it.
 
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So 2400 watts for 12 volts, 4800 watts for 24 volts, > 4800 is 48 volts.
For those that you listed, would you use a 12 volt system for these a few times a day for a couple minutes each, or would you feel comfortable running an air conditioner that can pull 2400 watts which will be on all day long?
 
For those that you listed, would you use a 12 volt system for these a few times a day for a couple minutes each, or would you feel comfortable running an air conditioner that can pull 2400 watts which will be on all day long?
Nope :)
I would never run a consumer level high frequency inverter a full load for extended periods except for testing.
And that's is with me in the room with a fire extinguisher at the ready.
As for wire I oversize things significantly for my own use.
I have a 24 volt 1500 watt inverter and 2 awg 105C+ wire on the critical path.
The numbers I recommend to others are minimums based on ABYC standards as described here https://baymarinesupply.com/bosns_corner_wire_sizes
 
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My father in law is a retired fire fighter.
I can't let anything happen to his little girl.
 
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