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Rv setup - will inverter run the battery charger?

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Ryang

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Mar 18, 2020
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Hi all

I’m just about to go from the test bench, into the caravan. And as I was planning the rv install and 230v I got thinking.

Currently the shore power runs into a safety switch, which loops to 2 power circuits and the ac circuit.
The current battery charger runs off a standard power point off the second power circuit. (No inverter currently)
When shore power in on, the charger is on. It’s under a bench and a pain to get to...

New setup, I was going to hook the inverter output into the main safety switch to power all circuits in the same manor that shore power would.
However, thinking about this, when the inverter is on, the all in one units charger would therefore activate.

Does anyone know how to get around this. Is there some sort of setting inside the mpp/Easun inverters that solves this? Am I missing something obvious?

Am I best to wire the charger gpo to an external switch and have to turn it on to charge? (I am hacking he inverter power switch in this way)

Thanks in advance
 
The situation you describe is true in an RV where you are choosing to power the circuits by connecting the shore power cord to the inverter, which is powered by the same batteries that the shore power charger is trying to charge. In my RV, The converter is on a circuit breaker, which I turn off before connecting the shore power cord to the inverter. While I'm there, I also turn off the breakers for my air conditioning and the electric element on my water heater. I have no business running any of those off the inverter, except perhaps for a stress/load test.
 
I agree with tripping the Converter breaker like @cwstnsko describes, but with a caravan there may be an alternator feed in addition to shore power, and I'm not sure how to isolate that.

Leaving the converter on is a bad idea. I have a fifth wheel RV, so no alternator. I forgot to trip the converter breaker and I noticed my inverter was drawing an extra 700 watts. I also heard a clicking noise, and at this point I tripped the converter breaker. I think the clicking noise was the RV's self resetting circuit breakers by the battery.

I know how much of a pain this converter is to get to. Mine blew the internal fuses before I got solar, and I had no idea where it was, and was able to trace wires back to find it hidden under a cabinet in the middle of the RV.
 
Thanks guys.

I’m thinking the best solution is to wire in a second illuminated switch for the charger. Red for charger, green for inverter. And just manually flip the correct ones. I want illuminated so if I go to bed with the inverter in I’ll see it as soon the lights go out.
I’m not keen on rewriting circuits. It’s to hard to run wires in a caravan.

btw: I am planning to power the hot water and stove with the inverter. Solar is free renewable energy. I’d rather use it than loose it. Propane costs $. So if the suns up the inverter and hot water will be on. Just a different way of looking at it I guess.
 
You don't mention how large of a PV array you are planning for, but some of the most challenging things to plan/account for in mobile installations tend to be; absorption fridges running on electricity, any water heating and cooking appliances, and electric space heaters. Any of these generally require a much larger array/inverter to keep up with demand. Have you done an energy audit to figure out what you project your overall usage to be? I agree that if the suns out, and the battery is topped off, it's better to use any extra power to minimize propane usage, but it might require more PV capacity than will fit on most RVs to fill all those needs.
 
The "easy" solution is to put in an inverter/charger combo. It understands when shore/generator power is on and that's when the converter(charger) is powered.

Those of us without the inverter/charger combo are left to find alternate solutions. Manual switches can be forgotten. Automatic switching can get complicated. One way or another, the converter needs to be isolated when the inverter is running off batteries.

At this time, I have chosen to put in a small inverter without tying it into the rest of the trailer's AC system.
 
Ryang said:
I am planning to power the hot water and stove with the inverter.
Click to expand...
What are your plans for panels and battery for this?

I have a 12 volt system with four 6 volt flooded lead acid golf cart batteries (12 v 458 AH, 5200 WH), and I would not consider running electric hot water or a hot plate through my system. I have my batteries and 120 volt inverter wired with 4/0 wire.

This last weekend, we plugged a crock pot in on warm, and unbeknownst to us, it drew 1100 watts when plugged in and turned on. At night, when the crock pot turned on to warm our roast up, Battery voltage dropped from 12.6 to 12.0, which means its drawing too much from my batteries and probably turning that into heat somewhere. That was too much of a drain on my system, and shut off the crockpot. I also only have 2600 WH to spend overnight.

I have a 700 watt coffee maker I'll be adding, and that will be the biggest electric appliance I will be operating.

I would like to be able to go with a 1700 watt electric kettle, but if I do that, I will go with a 24 volt system. If I were to do electric hot water in my RV, I'd want to go with 48 volts and a whole lot more panels.

Ryang said:
Solar is free renewable energy. I’d rather use it than loose it. Propane costs $. So if the suns up the inverter and hot water will be on. Just a different way of looking at it I guess
Click to expand...

As far as free renewable energy, I many, many years of camping left before this "free" solar energy gets paid off. Only putting that out in case you're doing this to save money.
 
Ryang said:
btw: I am planning to power the hot water and stove with the inverter. Solar is free renewable energy. I’d rather use it than loose it. Propane costs $. So if the suns up the inverter and hot water will be on. Just a different way of looking at it I guess.
Click to expand...

If you have excess capacity in the solar then by all means use it. During the day I run a 500 watt space heater when I know there is excess solar power (after the batteries are charged, of course). To run an electric cooktop I would need a much larger inverter than I have now. That would likely require a switch to a 24v battery bank instead of the 12v I have now.
 
HRTKD said:
I run a 500 watt space heater when I know there is excess solar power (after the batteries are charged, of course).
Click to expand...
I haven't used my system much, and knowing when the batteries are charged is a learning point for me.

I have a battery monitor, a BMV-712, and when I used it this weekend, I used about 1 KWh overnight. The following day, I was producing about 200 watts early in the morning, and my SOC showed 100% within the hour, so I know that is not correct. I think I must have something set up wrong. I'll look at the settings over the weekend. I think right now the Battery monitor is looking for voltages, and when it goes to a 14.6 VDC absorption voltage, which is above the 12.75 fully charged with no load on a multimeter, it reads as 100%.

So for now, I'm waiting until as much energy goes into the batteries as I pulled out the night before.

I was surprised about the excess capacity during the daytime after my batteries were charged. After the sun was up, my 3 kwh per day of production could easily run my fridge when the sun was shining. I definitely got more power out of it than I designed it for. Better than the other way around.

I'm confident I got 2 full days of power in the batteries; I'd just keep the fridge on propane. I think I go through a gallon of propane a day for the fridge, so anything to save gas will help.
 
There is a resync feature in the BMV-712 app. I haven't used it because mine seemed to have figured things out on its own. I did have to set the available Ah. I tweaked a couple other settings, but for the most part have been using the defaults.
 
HRTKD said:
did have to set the available Ah. I tweaked a couple other settings, but for the most part have been using the defaults.
Click to expand...

I may try the resynch after I've taken it out a few times. I've set my AH to 458. State of Charge is supposed to be determined by two parameters: charged voltage and tail current. Maybe I'll work on tweaking those if the BMV712 does not auto work next time I take it out.

I have the "charged voltage" set to what the manual recommends of 13.2, and I set the "tail current" to the manual recommended 4%.

Until then I'm going to work on my "Charged Voltage" so its:

"The charged-voltage-parameter should always be slightly below the end of charge voltage of the
charger (usually 0.2V or 0.3V below the ‘float’ voltage of the charger)."

My Battery Data sheet has a Float voltage of 13.5, so it appears I have the "charged voltage correct."
 
I do have an all in one. I just don’t understand how it’s smart enough to differentiate between itself and shore power.
So, the million dollar question, can it? Had to go a cheapie (would of like a victron). It’s a easun isolar 24v 3kva plus.

I have approx 1300w of solar on the roof, 6700kwh of battery (8s Xuba 280). Want to be off grid for 4 days.
 
Ryang said:
I do have an all in one. I just don’t understand how it’s smart enough to differentiate between itself and shore power.
So, the million dollar question, can it? Had to go a cheapie (would of like a victron). It’s a easun isolar 24v 3kva plus.

I have approx 1300w of solar on the roof, 6700kwh of battery (8s Xuba 280). Want to be off grid for 4 days.
Click to expand...

While I don't have an all-in-one myself, I would think that it would quite easy to tell if the converter/charger should be energized to charge the batteries. If the AC input to the all-in-one is active then power up the converter/charge. No AC = no converter/charger.
 
HRTKD said:
While I don't have an all-in-one myself, I would think that it would quite easy to tell if the converter/charger should be energized to charge the batteries. If the AC input to the all-in-one is active then power up the converter/charge. No AC = no converter/charger.
Click to expand...

I don’t agree. If the inverter is powering the same circuit th charger is in, the AC power would present the same. I would expect. I can’t see how it can tell. Hence the original question.
 
Ryang said:
I don’t agree. If the inverter is powering the same circuit th charger is in, the AC power would present the same. I would expect. I can’t see how it can tell. Hence the original question.
Click to expand...

I'm going on the assumption that the "charger" is internal to the all-in-one. The charger is not a standalone component.

Using the Victron Quattro as an example, the charger is built into the Quattro.
 
HRTKD said:
I'm going on the assumption that the "charger" is internal to the all-in-one. The charger is not a standalone component.

Using the Victron Quattro as an example, the charger is built into the Quattro.
Click to expand...
Correct, being an all in 1 the charger is built into the unit
 
This is why I’ve asked the question.

could anyone please tell me if they know the answer?
 
So I decided just to test it out and loop itself on the bench.

When I plug into the mains the unit bypasses successfully and runs.
When I loop the charger Into the inverter output, the unit
1. Does not go into bypass - expected
2. Does ,not charge
3. Does a really annoying error beeping but throws no error

So the answer is, it doesn’t create a loop, but if I don’t have away to turn off the charger, It will be really annoying.


So I will create a charger. On off switch next to the inverter on off switch.

Would be great if this could be don,ie via the software, but I don’t believe it can. At least not On WatchPower mobile version.
 
Ryang said:
New setup, I was going to hook the inverter output into the main safety switch to power all circuits in the same manor that shore power would.
However, thinking about this, when the inverter is on, the all in one units charger would therefore activate.
Click to expand...
Does that mean when the inverter is operating, AC will be present on the exposed pins of shore power plug?
When inverter is turned off and shore power is plugged in, is line voltage applied to output of inverter?
(neither of those situations would be good.)

I don't know if such interlocks are possible in an RV breaker panel, but for my home panel I added a sheetmetal interlock so either the 200A main breaker or else 100A generator (inverter) breaker can be on, not both.
If you could do that and tap off shore plug side of main breaker to add a fuse feeding the charger.
(whether your old stand alone charger, or the line input of your new inverter/charger.)
 
Ryang, a picture would help me understand what you tested.

I've been thinking about this and I don't see why the below wouldn't work for a situation where the RV doesn't have an all-in-one or inverter/charger.

Converter Bypass Diagram.jpg
The converter gets power only when shore power or the generator is on. Run the inverter off of just the batteries and the converter will never come on.
 
Update

I really missed the obvious in the all in one Install.

problem is solved byshore power - direct to all in 1 - charger. all in one - switchboard. It does it bypassing automatically and everything will work.
Also means no live power to the external plug (very good point).

been and interesting learning here

thanks for your inputs
 
Consider a surge arrestor (like from Midnight) to protect against anything coming down the power line when you're plugged in.
I suppose you might travel somewhere where weather happens.

Does your all-in-one provide switched grounding of neutral, depending on whether you're on shore power or not?
 
HRTKD said:
I've been thinking about this and I don't see why the below wouldn't work for a situation where the RV doesn't have an all-in-one or inverter/charger.

Converter Bypass Diagram.jpg
Click to expand...
This is a block diagram of an automatic transfer switch which uses a contractor relay to automatically shut off power to the converter whenever I use power from the solar inverter. There's also a light that goes on whenever the converter is powered on. I got the idea from a YouTube video who did most of the work.
Atomatic Transfer Switch.jpg
 
Hedges said:
Consider a surge arrestor (like from Midnight) to protect against anything coming down the power line when you're plugged in.
I suppose you might travel somewhere where weather happens.

Does your all-in-one provide switched grounding of neutral, depending on whether you're on shore power or not?
Click to expand...
It’s a good point. The all in one has earth to the inverter, but not back out from it. There is a ground point though.
 
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