Questions during lipo/solar install

[Mashmaster]

I have a 2003 Minnie 31C motorhome. I have been planning on converting batteries to Lithium and adding Solar for a while now. I finally started the process of conversion and now have some questions.

Steps completed:
1) Converter charger replaced from Magnatech to Progressive Industries replacement. Pretty easy replacement, took a couple of hours.
2) replaced Lead Acid batteries with two 100ah Lithium batteries (with self heating)
3) built plywood battery box for the under step battery storage container.
4) added and installed renogy 30A DC-DC charger with MPPT.
5) tested 2000watt inverter.

Steps to be done:
1) add positive and negative bus bars to clean up the cables in the battery box.
2) complete install of DC-DC charger. (see question below)
3) Install 400W of solar panels , 4 100W panels.
4) Run solar wires to Renogy DC-DC MPPT controller.

Questions:
1) Where is the Alternator positive cable to go into the DC-DC controller? The existing positive cable connected to the Lead Acid batteries isn't it. It feeds the 12v system, this is the confusing part.
2) Where is the best place to run the solar wires from the roof to the battery compartment?
3) Can I feed the output of the Inverter back into the Converter Charger box to energize the existing AC outlets?

What's working:
1) The 12v system seems to be working (lights, steps)
2) when plugged into shore power the batteries get charged and stop at 100%

Anything else I am missing? I feel like I am close.

including pics:

 

[creativepart]

Your install sounds good. But your questions need some rethinking of how things work.

The D2D charger doesn’t need an alternator connection. Just power it from the chassis battery. You will need to locate the latching solenoid that connects the alternator to the house batteries and the chassis battery and disconnect the house side from the solenoid. This will prevent the alternator from charging your LFP batteries and that job will be handled by the D2D charger.

And absolutely do not connect the inverter to the converter. That would create a circular loop where the batteries are inverting 12vdc into 110vac powering the converter which is using that power to convert 110vac into 12vdc to charge the batteries. See the problem?

The proper way to do this is to either use the inverter wired directly to a couple of smaller loads or much better is to set up an inverter powered sub panel with a few carefully chosen circuits powering limited items.

You’ve chosen a 2000w inverter and 200ah of batteries. That’s going to limit what you can power with the inverter. Certainly you can power TVs, phone chargers, satellite Receivers or streaming devices. You will be on the edge of overloading if you connect the microwave, a toaster oven, coffeemaker or hairdryer. They would likely work but will use a lot of power in a short amount of time. They certainly could only be used one at a time.

Does that inverter have AC passthrough or transfer switch? If not then you may be limited to how you can connect the inverter to loads. For instance, if you connect a TV to the inverter that will power the TV, but if the inverter doesn’t have AC passthrough what happens when your not using the inverter and are on shore power?

As to running the solar wiring a common solution in an older RV is to run the wires through the RV Fridge roof vent, down behind the space behind the fridge and from there to the solar charge controller. Alternatively some have space to run the wires down beside a plumbing vent pipe. There’s no one answer you just need to find a spot.

Depending on your goals you’re likely to find the LFP batteries a big help powering your 12v loads for longer than your previous LA batteries. But not as helpful when using them to power a lot of 110vac loads with the inverter. The inverter is great but it’s not the same as running shore power or using a portable generator.

You are on the correct path, but be aware that there are very real limits to your small system.

 

[Bnystrom]

In our View, the positive from the alternator is a red cable that comes into the battery box from the right side. The positive from the converter is green and comes in from the left. IIRC, they both connected to one side an 80 amp fuse mounted to the back of the box, with the battery positive connected to the other end.

Your chassis is different, but I mounted our DC-DC charger under the passenger's seat, where the boost solenoid is located, and used the stock wiring to the battery box.

 

[Mashmaster]

OK, update today. Ran a new line from the chassis battery to the DC-DC converter, added a positive bus bar. We spent a long time trying to find the line from the chassis battery to coach. Couldn't find it. Still trying to figure out where that ends up.

Charging now works from Engine and also Shore Power.

 

[Mashmaster]

Your install sounds good. But your questions need some rethinking of how things work.

Thanks for the feedback. It is appreciated.

The D2D charger doesn’t need an alternator connection. Just power it from the chassis battery. You will need to locate the latching solenoid that connects the alternator to the house batteries and the chassis battery and disconnect the house side from the solenoid. This will prevent the alternator from charging your LFP batteries and that job will be handled by the D2D charger.

Thanks, will look for the latching solenoid. Spent a lot of time looking today but unable to find it. Is is under the engine or one of the solenoids in the cargo bay with the breakers?

And absolutely do not connect the inverter to the converter. That would create a circular loop where the batteries are inverting 12vdc into 110vac powering the converter which is using that power to convert 110vac into 12vdc to charge the batteries. See the problem?

The proper way to do this is to either use the inverter wired directly to a couple of smaller loads or much better is to set up an inverter powered sub panel with a few carefully chosen circuits powering limited items.

You’ve chosen a 2000w inverter and 200ah of batteries. That’s going to limit what you can power with the inverter. Certainly you can power TVs, phone chargers, satellite Receivers or streaming devices. You will be on the edge of overloading if you connect the microwave, a toaster oven, coffeemaker or hairdryer. They would likely work but will use a lot of power in a short amount of time. They certainly could only be used one at a time.

Does that inverter have AC passthrough or transfer switch? If not then you may be limited to how you can connect the inverter to loads. For instance, if you connect a TV to the inverter that will power the TV, but if the inverter doesn’t have AC passthrough what happens when your not using the inverter and are on shore power?

Would a transfer switch solve the circular problem? figured the only thing that couldn't be run on 2000W would be AC. Obviously would need to ensure not doubling up on high watt items.

What is AC passthrough?

As to running the solar wiring a common solution in an older RV is to run the wires through the RV Fridge roof vent, down behind the space behind the fridge and from there to the solar charge controller. Alternatively some have space to run the wires down beside a plumbing vent pipe. There’s no one answer you just need to find a spot.

Depending on your goals you’re likely to find the LFP batteries a big help powering your 12v loads for longer than your previous LA batteries. But not as helpful when using them to power a lot of 110vac loads with the inverter. The inverter is great but it’s not the same as running shore power or using a portable generator.

You are on the correct path, but be aware that there are very real limits to your small system.

Noticed on my breakers(solenoids) one spot that was empty was labelled Solar. Was surprised that was something even mentioned in 2003. Apparently my rv came with a 750Watt inverter by where the tv was originally, found a DC power plug there with no inverter. hmmmm. Also a button switch in that same area with no labels or idea what it is for. other that a tiny little green LED.

No real space to add more batteries. Wasn't thinking that I would need a 3000W inverter.

 

[creativepart]

Thanks, will look for the latching solenoid. Spent a lot of time looking today but unable to find it. Is is under the engine or one of the solenoids in the cargo bay with the breakers?

I believe on a Class C it could be in the engine bay. In my Class A it's behind a removable panel just above the DC resettable fuses and it has a sticker on the panel explaining that it's behind the panel.

Would a transfer switch solve the circular problem?

No it wouldn't. Think about what your Converter does. It takes 110vac and converts it to 12vdc and uses that to run 12v loads AND to charge your batteries. You can turn the Converter off with a circuit breaker, but then you'd have no lights, etc. So, if you use inverted power to feed the Converter you will be using inverted power to charge the batteries that are powering the inverter. A circular charge/discharge loop.

What is AC passthrough?

Just as it sounds. It lets 100vac shore power pass through the inverter to power anything connected to the inverter from shore power. When no shore power is available the inverter powers the AC loads, but when shore power is available the inverter does nothing but pass through the power.

Noticed on my breakers(solenoids) one spot that was empty was labelled Solar. Was surprised that was something even mentioned in 2003.

Yeah, in 2003 many manufacturers installed tiny 10,15 or even 50 watt solar panels to trickle charge usually the chassis battery. These little panels didn't have enough power to even need a solar charge controller and were usually direct connected to the battery. These quickly were discontinued as "real" solar panels of 100+watts became the standard size.

No real space to add more batteries. Wasn't thinking that I would need a 3000W inverter.

You may not need a 3000w inverter. You will just need to be very careful with what loads you use it for. Also, if you want to use all 2000watts the gauge of the cables to the battery matter because a heavy load will draw massive amps from your batteries requiring thick cabling to handle that amperage. Anything less than 10ga wire will heat up and could be dangerous. I'd say 8ga or even 6ga is a minimum. But that also depends on the distance from the batteries to the inverter. The 110v out of the inverter isn't as critical. Just regular house hold romex is plenty good because of the higher voltages involved.

I'll say it one more time, your new LFP batteries are a great addition. But I think you'll find that your inverter, while really helpful for smaller loads, is not a substitute for a outboard generator for heavy loads. Notably, the microwave, coffee maker and toaster oven. The inverter may power those items fine, but they may quickly deplete your batteries and that may trigger a low voltage cutoff in the inverter as your voltage sags over more than a minute or two. You'll only know for sure when you give them a try.

As a test, run an extension cord from your uninstalled inverter as in your photo. See how it does running your microwave (assuming you can get to the microwave's power cord in a cabinet adjacent or above the microwave. Or try running a toaster oven.

 

[Bnystrom]

Thanks, will look for the latching solenoid. Spent a lot of time looking today but unable to find it. Is is under the engine or one of the solenoids in the cargo bay with the breakers.

I don't know how your electrical system is configured, but in Sprinter-based vehicles it's under the passenger's seat. It will be somewhere inside the vehicle. The connection from the chassis battery/alternator to the coach batteries is the red with the yellow band.

Would a transfer switch solve the circular problem? figured the only thing that couldn't be run on 2000W would be AC. Obviously would need to ensure not doubling up on high watt items.

Here's what I did for the AC side in our system (see pic):

• Our generator and shore power share a manually changed power cord (it plugs into shore power or into an outlet in the electrical box to use the gennie). I split the incoming 30A circuit into a 30A circuit that goes to the inverter and a 15A circuit that powers the converter and fridge. That eliminates the circular charging loop. Both circuits have their own breakers that are outside of the main breaker/fuse panel.
• The reason for separating the fridge is that I prefer to have it run on propane when the inverter is running, but the default is for it to use AC. With this configuration, I don't have to manually switch it from AC to propane, but it's not necessary to do this if you don't want to; it's just a convenience.
• Our inverter has an automatic transfer switch built in and has pass-thru as well. It's wired to the main AC breaker, so every AC outlet and device is powered. We have enough inverter and battery capacity to run our A/C, but as you said, it won't work with a 2000W inverter. As long as you don't try, it won't cause any issues, like your inverter shutting down from the excessive load. You can always turn off the A/C breaker if you feel the need.

What is AC passthrough?

When plugged into shore power, the inverter passes the shore current through, rather than taking power from the batteries and inverting it. You can think of it as an inverter bypass, but you may have to turn the inverter on to use shore power.

 

[creativepart]

I don't know how your electrical system is configured, but in Sprinter-based vehicles it's under the passenger's seat. It will be somewhere inside the vehicle.

That location is unique to Sprinter Vans.

The OP's motorhome is built on a Ford F53/E450 V10 chassis. There are videos on YouTube and commenters here that show the latching solenoid in the Ford's engine compartment. But it could also be near the batteries or main 12v resettable fuses. He'll find it.

I did some searching and one guy said:

In my 2005, the solenoid is under the starter battery and behind the passenger side head lights. Yours may be different.

And another posted this. The image of the solenoid looks correct and what you should be looking for:

 

[Morich]

There are online drawings for that info. This is the main electrical if you need to get further into different sections:
https://www.winnebago.com/Files/Files/Winnebago/Resources/Diagram/Wiring.htm
But for the info on the mode solenoid, it is here under chassis wiring:
https://www.winnebago.com/Files/Files/Winnebago/Resources/Diagram/2003/03_331c_wire_141166.pdf

Look down to the last sheet on this group for pictures of what you should find. I suspect it may be in a compartment outside just back of the drivers seat?
Look for the detail labels?
Detail DB is the cover to find, DA is front view with cover off and DC rear view of those breakers.
View DD is what is inside, with the cover off and the breaker panel pulled back!
This mode solenoid is what connects the coach and chassis batteries together at different times.
Part of what this area does?
Click this snip to see better!
Batteries had tape markers when new but tend to get lost over time!



Small wire LR brings 12v from dash switch when we want to jump start a weak chassis battery with the coach batteries! There is a coil inside the solenoid that runs down to the FM on a mounting screw and LR/FM make the solenoid operate to close contacts between the left chassis cable and right coach cables!
They also close when we start the engine to charge coach while driving!

You do not want these connected directly as the lithium batteries can draw so much current so quickly it can burn out your engine alternator after too much use!
That is part of the problem, I've not worked on directly but only read about, so prefer to let them advise!

Correction!! Look in compartment just to rear of coach batteries on passenger side! Detail BD!

 

[Bnystrom]

You do not want these connected directly as the lithium batteries can draw so much current so quickly it can burn out your engine alternator after too much use!
That is part of the problem, I've not worked on directly but only read about, so prefer to let them advise!

He said he's installing a DC-DC charger, so that shouldn't be an issue.

 

[Morich]

He said he's installing a DC-DC charger, so that shouldn't be an issue.

Correct, but when wading into unknow areas, I find it helpful to also know WHY things are done!

 

[Mashmaster]

Inverter installed and wire run into the cabin. Cable run from the battery to the DC 2 DC charger. Question on the existing cable to connect. Does it run from the battery or the alternator? Do I disconnect it under the vehicle or the solenoids in the storage cabinet that feeds the wire to the house batteries? The ones behind the panel shown in the picture of the inverter.

Thought about what circuits I want to power from the inverter when not on shore power. Fridge, microwave 1000 watt, and circuit with tv and kitchen outlet. Not sure how to do that yet. I am getting confused.

 

[creativepart]

Question on the existing cable to connect. Does it run from the battery or the alternator? Do I disconnect it under the vehicle or the solenoids in the storage cabinet that feeds the wire to the house batteries? The ones behind the panel shown in the picture of the inverter.

You lost me totally on this. I have no idea what the "existing cable" is that you are referring to.

Thought about what circuits I want to power from the inverter when not on shore power. Fridge, microwave 1000 watt, and circuit with tv and kitchen outlet.

If your fridge is a RV AC/LP Fridge you DO NOT want the inverter to power it. Use the fridge on AC when on shore power or LP when not. If you wire your inverter to the fridge you will run your batteries dry in hours. The AC operation of the fridge is a power hog. Fine for shore power but not for inverted 110vac from 12vdc batteries.

Not sure how to do that yet. I am getting confused

I suggest you get an electrician to wire this up for you. If you're confused it's because you are not an electrician.

 

[Mashmaster]

You lost me totally on this. I have no idea what the "existing cable" is that you are referring to.

The line from the alternator or battery that originally fed DC from the engine to the batteries. It looks like the line from chassis battery routes under the engine to where the starter goes but splits there to go aft of the RV. There is only one line from the RV to the positive of the battery. That feeds the 12v system from the batteries and also used to charge the lead acid batteries. I am looking to remove the original line for engine charging since there is now a line that I ran from the chassis battery to the dc-to-dc charger.

If your fridge is a RV AC/LP Fridge you DO NOT want the inverter to power it. Use the fridge on AC when on shore power or LP when not. If you wire your inverter to the fridge you will run your batteries dry in hours. The AC operation of the fridge is a power hog. Fine for shore power but not for inverted 110vac from 12vdc batteries.

Interesting and sad since I was hoping to use it in ac more while driving. In the future I am thinking of upgrading it to a 12v compressor fridge.

I suggest you get an electrician to wire this up for you. If you're confused it's because you are not an electrician.

I will consider it.

 

[creativepart]

The line from the alternator or battery that originally fed DC from the engine to the batteries.

I'm not that well versed on your 2003 Minnie (Ha! Not versed at all), but I'd expect the alternator to go to the latching solenoid. Then that solenoid send power to both battery banks.

But as I said, I don't know for sure. If you don't know you need to find someone more well versed in your RV's charging circuits.

Interesting and sad since I was hoping to use it in ac more while driving.

You "can" do that, but you won't arrive with fully charged batteries. The fridge will use a lot of your battery's current. The LP is vastly more practical for keeping the fridge cold while driving. Or turn off the propane and just the cold fridge stay cold on it's own.

The least efficient use of your inverted 110v power is to feed a resistive heating element. That's a hair dryer, a toaster/oven, a space heater, a coffee maker, a CPAP dehumidifier and, it turns out your RV Fridge. When on LP a flame heats the fridge's ammonia into a gaseous state. When on AC an AC Heating coil does the heating. That's why the fridge is as bad a choice for running the fridge on your inverter as it would be to run an electric space heater.

I will consider it.

I suggest you do, or find an RV Tech that specializes in Solar/LFP installs.

 

[Mashmaster]

My understanding is that you should not have propane on while driving. Is that an old wives tale?

 

[creativepart]

My understanding is that you should not have propane on while driving. Is that an old wives tale?

There are some that still believe this... but the vast majority of RVers don't follow that so-called "rule."

You can turn off your LP and the fridge will stay cold until you turn the LP back on or plug in. Assuming you don't drive 8 - 10 hours a day and stop and open the fridge door multiple times during your trip.

Or you can wire your inverter to the fridge and run it on AC as you drive and arrive without fully charged batteries.

 

[creativepart]

Here's an RV Solar/Inverter tech in Austin:
RV Repair Austin

I know nothing about the company. It's just one I found online.

 

[Mashmaster]

I can certainly just wire up a sub-panel. I have done that before. The question would be if I want to dual purpose a circuit for the kitchen/tv outlets or run new outlets for inverter only power.

 

[Morich]

There may be a different line to consider before choosing?
I have not done it, so lack any deep ideas of what is involved but there are a number of RV that were built as inverter first began to get involved that are not built with the switch in them inverter but added as a second item.
There are inverter which come like what I think you have. We wire the output to certain places and use them only when we turn the inverter on. That limits those outlets for normal use when we DO have AC power.
But then there are newer inverter versions which have a form of transfer switch built into the inverter. Those let the outlets work off regular AC power when we have it or off the inverter when not.
But there are what I might call addon switches which work beside the simple inverter to let it switch as if it had a transfer switch built in!

Maybe worth some looking if you want to use the inverter you currently have? Look at what it takes to add the transfer switch to let AC power flow to all outlets when you have the power, but when no AC power, the switch lets some outlets work off the inverter.

In looking at lots of the Winn drawings, I have seen several RV with the stand alone inverter but also tied to a form of transfer switch which lets the outlets be used both when we have commercial AC as well as when we want it to come from the inverter.

Sorry, no names of the parts and other details but it might be worth doing some checking for details to see if it sounds like an option you would want?
Maybe call some of the online RV parts stores to ask about transfer switches for inverter addon?