Keep it Separate?

[dixonge]

I have Googled this about a bazillion different ways and based on the lack of results/answers, I'm beginning to wonder if I'm doing something unique/rare. And if so, maybe there's a reason for that?  :dodgy:

So - in the beginning my solar project involved replacing the existing batteries under the steps. That would keep most wiring intact, less to rewire or re-engineer. Converter/inverter could go in a nearby compartment, keep wire runs short. Might have to give up the 'emergency start' feature since new batteries would be 6V golf cart deep cycle with minimal cranking amps.

And then I got around to actually *measuring* the space under the steps. Oops...

So then I was faced with putting the batteries in the compartment with the converter/inverter and rewiring the cables under the step to connect in where the new batteries would be, including the disconnect switch connection. This is complicated by the fact that the existing house batteries are 12V connected in parallel, and the new ones are 6V connected in serial. Which wire goes where? Do I connect to existing wiring differently? Seemed complicated.

A separate but related issue was wiring the inverter into the AC side - would have to run wire to under the bed where everything else is and connect to the correct spot in the transfer switch. 

At some point a thought occurred to me - why not just keep the solar batteries completely separate? The benefits would be:

• Keep existing perfectly good batteries as a backup
• Keep existing emergency start functionality
• Existing batteries get recharged when driving
• Avoid extra wiring hassle by one of two methods:

1. Plug shore power cable into 30Amp outlet connected to inverter
2. Plug inverter AC outlet into existing AC plug using male-to-male cord and plug with power indicator light

If I plug the shore power cable into the inverter the system would basically see that it was running on shore power and the built-in converter would charge the existing house batteries, effectively charging them from solar. If I plug the inverter into an AC plug, I would need to use the battery disconnect to the house batteries.

So - other than being unique and presenting a couple of risks not usually present in a solar setup, is there any good reason for me to do this differently?

 

[B and C]

Battery wiring two 6v vs two 12v


What you have now


What you want

Pull your existing battery cables back and connect to your new batteries.  If your cables aren't long enough, get new cables that are.

Make sure you can check the water level in your new batteries easily.  You will want to check weekly to start then monthly should be sufficient.  You will need to add distilled (not tap) water to them.

 

[B and C]

Your second question is much more complex.

The better way to do what you want is to get a single (or double) pole 120V relay.  Take the wire going to your converter in the breaker panel and connect it to through the normally closed contacts.  Take one of the outlets of your inverter and connect it to an extension cord you have cut the female end off of.  Wire the black wire in the extension cord to the relay coil and the white wire to the other side of the coil.  This will prevent the converter from trying to charge your batteries while the inverter is using your batteries.  Plug your shore power cord into the other 120v outlet on the inverter.  You may need a 20 amp to 30 amp adapter cable.

If all this sounds like gobbly gook to you, don't attempt this by yourself.  Get someone that is versed in electricity for help.  I would hate to see you burn down your rig.

 

[dixonge]

Battery wiring two 6v vs two 12v


What you have now


What you want

Pull your existing battery cables back and connect to your new batteries.  If your cables aren't long enough, get new cables that are.

Make sure you can check the water level in your new batteries easily.  You will want to check weekly to start then monthly should be sufficient.  You will need to add distilled (not tap) water to them.

New batteries are about two inches too tall to fit where the existing batteries are located (under steps). New batteries are in a compartment about 4-5 feet away (the closest one). Would need to extend some cables and shorten others to reuse. 

Your second question is much more complex.

The better way to do what you want is to get a single (or double) pole 120V relay.  Take the wire going to your converter in the breaker panel and connect it to through the normally closed contacts.  Take one of the outlets of your inverter and connect it to an extension cord you have cut the female end off of.  Wire the black wire in the extension cord to the relay coil and the white wire to the other side of the coil.  This will prevent the converter from trying to charge your batteries while the inverter is using your batteries.  Plug your shore power cord into the other 120v outlet on the inverter.  You may need a 20 amp to 30 amp adapter cable.

If all this sounds like gobbly gook to you, don't attempt this by yourself.  Get someone that is versed in electricity for help.  I would hate to see you burn down your rig.

Plugging shore power in to the inverter is one possibility I discussed. However, I think you may have missed the part about keeping the existing house batteries and using the battery disconnect as needed?

 

[dixonge]

Just verified that while connected to shore power using the battery disconnect switch does NOT kill DC coming from shore power through the converter. TV and lights still work. This means it only stops the charging from the house converter, and stops power from the batteries *if* not connected to shore power. That answers one question. The other is just shore cable vs. plugging in to an outlet like this guy...

[video=youtube]

 

[B and C]

New batteries are about two inches too tall to fit where the existing batteries are located (under steps). New batteries are in a compartment about 4-5 feet away (the closest one). Would need to extend some cables and shorten others to reuse. 

Plugging shore power in to the inverter is one possibility I discussed. However, I think you may have missed the part about keeping the existing house batteries and using the battery disconnect as needed?

Doesn't sound very safe but don't know without looking at it directly.  I restate that if you are unsure of what you are doing, get someone local that knows electricity to help you.

 

[izifaddag]

Just verified that while connected to shore power using the battery disconnect switch does NOT kill DC coming from shore power through the converter. TV and lights still work. This means it only stops the charging from the house converter, and stops power from the batteries *if* not connected to shore power. That answers one question. The other is just shore cable vs. plugging in to an outlet like this guy...

I don't know if anything I show you now is going to help but I'll throw it in and you decide.
When I designed my system I opted for a transfer switch. They can be very expensive but I got a cheap one from eBay. It works very well. 
When I pull the 110v line shorepower the transfer switch automatically switches over to inverter. The 2 outputs of the transfer switch are linked together then run to the electrical system of the camper. It is impossible to have both on at the same time. As per your video the AC unit is bypassed so it can only run on shore / gen power. 
Below shows the actual setup, a bit of a birds nest but it works. The diagram is not my best work but it does show quite clearly how my setup is planned. In the photo the transfer switch is the thing with the blue dial in the middle. 

 

[izifaddag]

The box marked inverter charger is wrong it should just read charger. The charger only charges the battery while 110v is applied. As soon as the 110v is removed, the charger is denied voltage, there is a clunk, 1 second delay and the inverter takes over.
A 12v dc line is run separately directly from the battery.
This is a work in progress. Trips, buss blocks and my large 100ah LiFePho is to be added.
When I get time, if that ever happens.

 

[dixonge]

Below shows the actual setup, a bit of a birds nest but it works. The diagram is not my best work but it does show quite clearly how my setup is planned. In the photo the transfer switch is the thing with the blue dial in the middle. 

Now I need to know what software you used for the diagram...

 

[dixonge]

Doesn't sound very safe but don't know without looking at it directly.  I restate that if you are unsure of what you are doing, get someone local that knows electricity to help you.

If I knew anyone in this state I would do that. Unfortunately I do not, thus I am on the internet...

 

[izifaddag]

Now I need to know what software you used for the diagram...

Google Drawings. Not the best diagrammatic tool but I use it because it is free. I access it from inside my Google drive - my free online 15gb storage space. I hope the diagram helped. 
If you want to know more about the transfer switch I'll give you a web address.

 

[dixonge]

[font=Tahoma, Verdana, Arial, sans-serif]a hand-drawn diagram of my system, as I understand it and intend it...[/font]

 

[B and C]

The other is just shore cable vs. plugging in to an outlet like this guy...

Wow, just goes to show you that everyone on the internet is a expert (NOT).

Notice he was not using his existing house battery but a separate battery on a cart.  By not using his house battery, he sidestepped the charging/discharging loop of his converter.  Gotta be careful of what you get off the internet (including me LOL)

 

[B and C]

Your diagram shows the solar batteries charging the house batteries through the inverter.

Please get some sort of help even if you have to go to a RV place and pay them to do it.

What state are you in? There may be someone on here in the same state that you could get to for some help.

 

[highdesertranger]

this is a perfect example of some stuff on you tube is just plain wrong.

never ever in a million years don't do it. do not ever make a situation where the male end of extension cord is live. period. that is some of the most dangerous advice on a how to video I have ever seen.

highdesertranger

 

[dixonge]

Your diagram shows the solar batteries charging the house batteries through the inverter.

Which is resolved if I flip the disconnect switch, correct?

 

[dixonge]

this is a perfect example of some stuff on you tube is just plain wrong.

never ever in a million years don't do it.  do not ever make a situation where the male end of extension cord is live.  period.  that is some of the most  dangerous advice on a how to video I have ever seen.

highdesertranger

But it wasn't live until after it was plugged in. That's kinda why he added the remote on/off.

I do agree that it at least allows for the *possibility* that a live male plug might exist at some point, if you unplug it while the indicator light is still on. It's not as idiot-proof as a female plug.

 

[B and C]

It is not a matter of if, it is a matter of when you forget to turn the batteries off and that is if it will work. Happened to a good friend and has now put in the relay as I suggested. Your diagram is probably wrong on another front. My converter has a circuit breaker in the circuit breaker panel and you would need to disconnect the converter there or in the wire feeding the converter as I suggested. Check your panel. You just show boxes and not the actual switches or how they are connected. Check your wiring closer. It needs to be exact, close is not close enough.

You are flirting with burning your rig down. Look at youtube on rig fires. Edit to add: Of course they will never admit on camera that they have made modifications to the wiring.

Your diagram does not show where your battery switch is in the circuit.

A switch the best I can draw here i\_ is a closed switch, i /_ is an open switch.

 

[Weight]

To address the inverter to shore power charger. ->Don't.<- To accomplish your idea, you could use a battery combiner or battery to battery charger. Rod talks about marine, but we are just land schooners. Here. read through some of his advice about charging. https://marinehowto.com here is some specific; https://marinehowto.com/automatic-charging-relays/

 

[dixonge]

Your diagram is probably wrong on another front.  My converter has a circuit breaker in the circuit breaker panel and you would need to disconnect the converter there or in the wire feeding the converter as I suggested.  Check your panel.  You just show boxes and not the actual switches or how they are connected.  Check your wiring closer.  It needs to be exact, close is not close enough.

Your diagram does not show where your battery switch is in the circuit.

A switch the best I can draw here  i\_ is a closed switch, i /_ is an open switch.

Yes, the path is Shore power cable > AC circuit breaker > converter - there is a separate breaker for it. However, according to the manual if the battery disconnect switch is set to OFF the converter will not charge them.

So the disconnect switch is between the house batteries and the converter and also the DC fuse panel. The house battery connection to the alternator is controlled by the battery isolator controller.