Charging while towing

[haha49]

Gotta agree with Len here. This tends to get way over complicated around here. I don't believe it's all that difficult to disconnect your plug at night or when you stop for an extended period of time. Like he said, travel trailers have done it that way since....well pretty much since forever and it works!
If you like all the fancy dodads and can wire them in then go for it, if not just run a wire, stick in an inline circuit breaker at each end and just 'pull the plug'.

You can wire in a second battery in the tow car and put an isolator on it. Then run a wire from that battery to the trailer now the power is under the hood of the car nothing on the hitch. More then 1 way of doing it and the isolator keeps the car from going dead.

[Thelgord]

I was looking into this, and I think I may have a solution, well for me anyway. My tow rig has the 7-wire plug, one of which is an AUX 12v power supply that is switched on with the key. So I went searching around Amazon, and may have found a solution for less than $25.

Start with a solar charge controller, like this one for $10.99:
https://www.amazon.com/Docooler-Control ... controller

This requires 14-16vDC for input, and after reading through the pages there are a lot of good suggestions, including DC to AC to DC. I wanted a simpler solution, then I found this little gem for $12.99:
https://www.amazon.com/Pawtec-Universal ... ar+charger

It's a universal laptop charger that can output 15V (other voltage options are selectable) @ 90W from a 12V source. So if you are pulling during bad weather, or if you don't have your solar panels out while driving, this could act as a 90W solar system while driving, all for $23.98 (plus shipping if you don't have prime).

[RJ Howell]

I am a great fan of the KISS principle, unfortunately that may well not be the smartest most efficacious solution. Part of the education concerning the care and feeding of deep cycle batteries has come from those with solar experience. And part of that experience is you cannot effectively use mismatched batteries. As pointed out what you're doing with charging both the tow vehicle battery and your trailer battery is a parallel circuit. In a parallel circuit as I understand performance is set by the weakest battery. Because RV dealers have been doing it for years, does not mean they're doing it correctly. And in this case some/most use a two charging circuit system, one for the tow-starting vehicle and another for the house batteries. Some are in fact using the Balmar regulators.

Didn't know hw into this I was going to have to read before someone mentioned using a Battery to Battery charger. Thank you for doing so. I do agree that simple is most often the best direction, yet not all times and I see this as one of those times.

The charging system in your TV is designed to re-charge that PbA starter battery. So just that alone should say, you need something else to your house battery. Two different size, two different types (chemistry), two different purposes, this just goes on, yet the key word here is different. Most newer B to B chargers are programable for what your house batt wants to get it to full charge and excepting the house battery of almost any type of chemistry.

I'll continue through the thread and see if it's brought up again.

As always MHO on the matter.

Edit: Close to an hour later... Loads of info in this thread!
I'm a 2-3 day camp > drive > 2-3 camp person and we'll do this for up to 2 months exploring a region. Mostly the solar keeps the battery up strong. For me I'm looking at two things: First proper charging of the house batt's while driving (if required) and I hope to switch to a lithium battery. I have a 38ah lithium I use on the property and charge that by solar. Thinking I may move it into the camper. That means I need to add a DC to DC charger to keep the battery up when driving. Since my existing system is design PbA only, I'll have to disconnect the Converter charger. This at least gives me two ways of charging. On those rare occasions we do have shore power, I can always just plug in the wall-wort charger, if required.

Here's what I have planned.


Since I have wiring in place it should just be jumping in at points. Hopefully... I'm looking at the Renogy 12/12 20amp charger. Thinking it all I'd ever need if required while I drive. Just under $125 so not crazy on costs.

Thoughts anyone?

[troubleScottie]

Most likely you will have to add a new heavier wire from the tow vehicle (TV) to the trailer (TD). It does mean another hole somewhere to reach the DC-DC charger.

The standard wire in a 7 pin connector is too light to allow this charging. It could be used for say charging the electric brake break away battery, which is just a trickle charger. Or some other low amperage devices.

While you are at adding the wire, you should consider a solenoid to isolate the TV from the TD battery. The DC-DC charger may serve this purpose but a specific isolation is better. Also consider using an Anderson connectors with a mounting bracket/cover. There is a very nice one available from Australia. The ones in the US are more than sufficient.

BTW some of the DC-DC chargers have solar inputs too. Basically, this is because solar is the same process with high voltages. For example, REDARC BCDC1240D Dc-Dc Charger 12V40a Out.

[capnTelescope]

Start with a solar charge controller, like this one for $10.99:

Funny you should mention that. Now that I know enough about solar to be dangerous, I was thinking the same thing. A solar controller doesn't know or care where its DC input comes from, so if it's not solar DC, it shouldn't matter. DC-to-DC!

I'm looking at the Renogy 12/12 20amp charger. Thinking it all I'd ever need if required while I drive. Just under $125 so not crazy on costs.

More DC-DC! I just installed one of these in my new Casita, and it appears to work, i.e. the "12"volts out is greater than the "!2" volts in. I haven't used it enough to really know how well it actually works, but I'm optimistic.

While you are at adding the wire, you should consider a solenoid to isolate the TV from the TD battery.

Amen. You don't want to run down the TV battery because you were "charging while parked" overnite. Bad start to your new day. Be disconnected when the TV is turned off.

The charging system in your TV is designed to re-charge that PbA starter battery.

Which is what got me into the DC-AC-DC rabbit hole. Way back in 2014, they didn't have popularly priced solar power, so it never occurred to me that a solar controller would do the job.

[RJ Howell]

I'm looking at the Renogy 12/12 20amp charger. Thinking it all I'd ever need if required while I drive. Just under $125 so not crazy on costs.

More DC-DC! I just installed one of these in my new Casita, and it appears to work, i.e. the "12"volts out is greater than the "!2" volts in. I haven't used it enough to really know how well it actually works, but I'm optimistic.

To me wattage is wattage. If voltage went up then amperage went down. What I think I'm learning of the DC/DC charger is the alternator is giving far more than is required, well is my case anyway (and seems in yours).

The charging system in your TV is designed to re-charge that PbA starter battery.

Which is what got me into the DC-AC-DC rabbit hole. Way back in 2014, they didn't have popularly priced solar power, so it never occurred to me that a solar controller would do the job.

That's where I again believe the DC/DC Charger does the game. I'm not quite convinced a simple $20 solar charger will do it. Here's the difference to me. The Solar Charger is built to receive 20-24Vdc open circuit (?) and only the rating of incoming amps, let's say like mine 20amps. Cool! Now through the TV alternator in the mix passing 14+ Vdc and 40-80amps at it... I haven't tested this theory cause I don't wish to be right and throw away a good solar charger..

I wish to say thank you for offering up advise. That's what I was hoping for!
Like you I have a commercial trailer and changing how I re-charge. I'm going lithium and working through the system. What I have found that the system is basically the same for all chemistries of batteries in such we need to control according to.

I'm becoming a fan of this Renogy 12/12 because it is supposed to take the input from the alternator and is programable for different chemistries. For $121, I'm in. What I like in what I'm doing is it will transfer to what I do build. These commercial campers come close, just don't get quite there.

I am curious how you wired into your Casita. For me, I'm going to dis-connect the Converter/charger and rely mainly on my solar and dc/dc (while driving). Here'my flow chart:

[troubleScottie]

Yet another PS. You might want a fuse just before the DC-DC charger on the feed from the TV. Might be over kill but that is a long length of wire ( TV battery - length of vehicle - tongue - charger ).

Using a breaker with a switch means you can also disconnect the TV at the charger if needed. I do not know how isolated the two DC inputs are. So while running the solar, you might not want to have the TV connected. Obviously disconnecting from the TV would produce the same result.

[capnTelescope]

I wish to say thank you for offering up advise. That's what I was hoping for!

You are quite welcome! Second only to my build, this is my favorite topic.

To me wattage is wattage. If voltage went up then amperage went down. What I think I'm learning of the DC/DC charger is the alternator is giving far more than is required, well is my case anyway (and seems in yours).

Agree. Typically, your TV alternator is rated at about 100 amps. I don't know how many of those amps are used to keep the TV running.

I'm not quite convinced a simple $20 solar charger will do it.

I'm not, either, for the same reasons you gave us.

You might want a fuse just before the DC-DC charger on the feed from the TV. Might be over kill but that is a long length of wire ( TV battery - length of vehicle - tongue - charger ).

Can't hurt, might help. Actually, the input side of the DC-DC charger represents a load, and the trailer-side plug represents the source that the fuse would protect. So a fuse "up front" of the TD would be more better than one in the back. If in doubt, do both. I didn't add any additional fuse other than the one coming off the TV battery.

On the DC-DC charger output side, I reused the original equipment breaker going to the battery.

I am curious how you wired into your Casita.

From the TV + battery post:
Thru a fuse to a 12v solenoid
from the other side of the solenoid into pin 4 of the 7-pin TV socket, 10 gauge wire or better.
to the TD 7-pin, Pin 4
***Edit*** Inside the Casita I added a junction block from the connector cable to the rest of the trailer. **/edit***
to the DC-DC charger input, 10 gauge or better.
From the DC-DC charger output to the trailer battery thru a circuit breaker. ***NOTE*** This would be a good line to fuse at both ends. YMMV.

NOTES:
Any reference above to "the TD" Also applies to the Casita.

The DC-DC charger is located near the battery as possible.

The solenoid (https://www.amazon.com/dp/B0064MX7US/?coliid=IXUAR280M3JDX&colid=1FJRWAP74FKDC&psc=1&ref_=lv_ov_lig_dp_it) is activated by any acceptable to the TV hot-when-running TV circuit, through a fuse (of course) to one side of the solenoid coil and on to TV chassis ground. Stay away from fuel injector and ignition coil circuits. My Taco didn't like it when I did that. I would suggest a power window supply circuit. ***Edit*** I used one of those circuit taps to do this ***/edit***

The Casita's Power Dynamics thang had the pin 4 wire connected directly to the trailer battery at the factory. You MUST disconnect that wire. The DC-DC charger output is not connected to/thru the PD at all.

[pchast]

An inexpensive solar charger has been working for me, about 6 years now..
I have 2 medium size emergency light style AGM batteries. I only have a
few led lights and a stereo radio.

[RJ Howell]

Yet another PS. You might want a fuse just before the DC-DC charger on the feed from the TV. Might be over kill but that is a long length of wire ( TV battery - length of vehicle - tongue - charger ).

Using a breaker with a switch means you can also disconnect the TV at the charger if needed. I do not know how isolated the two DC inputs are. So while running the solar, you might not want to have the TV connected. Obviously disconnecting from the TV would produce the same result.

I've been debating location of a inline fuse. Believe it was you that mentioned earlier (I am paying attention to you). My though was after the DC/DC charger. You are talking before.. I guess I believe the unit protects itself, yet why not add one. I looked at that DC/DC unit faulting and protecting all downline from it.

Thank you for your input!

[RJ Howell]

An inexpensive solar charger has been working for me, about 6 years now..
I have 2 medium size emergency light style AGM batteries. I only have a
few led lights and a stereo radio.

I've heard from a few that do just what you are. One actually charges up his 80ah house battery with it (from the TV) and he uses some heavy wattage everyday! I'm still scratching my head over it and wondering why it hasn't burned out yet.. So ya, folks are having success, yet I won't go there. It's just not built to be used as your using it.

It's working for you, so good!

[RJ Howell]

[
The Casita's Power Dynamics thang had the pin 4 wire connected directly to the trailer battery at the factory. You MUST disconnect that wire. The DC-DC charger output is not connected to/thru the PD at all.

My Commercial trailer is an rPod, 182g. Looks like a pregnant TD! I've been told the same on the rPod and am tracing the wiring back and investigating. If this is true, then I have to have a junction/splice/buss bar at the panel. On mine the #4 (12vdc hot) pin goes directly aft to the panel. I hope to get to that part soon.

[capnTelescope]

An inexpensive solar charger has been working for me, about 6 years now..

There you go, it works! I was wondering.

I've been debating location of a inline fuse.

Generally, a fuse/breaker is used to protect the wiring, since the insulation is going to be the first source of fuel for a fire if there is a short. So closest to where the juice is coming from is where you want the fuse. In our case, the juice is coming from the TV. So, on the trailer, a fuse at the TV (front) end of a wiring run is appropriate, and on the TV, the fuse needs to be right off the battery. Just the TV battery fuse "should" do the complete job. YMMV.

It's just not built to be used as your using it.

I think it's mostly marketing. How many people want a DC/DC charger vs. how many want a Solar Charge Controller?

On mine the #4 (12vdc hot) pin goes directly aft to the panel.

We're twins! That's better stated than whatever I said before. My Pin 4 was wired to the same panel terminal as the battery +. Must disconnect to use a DC/DC charger.

[RJ Howell]

I've been debating location of a inline fuse.

Generally, a fuse/breaker is used to protect the wiring, since the insulation is going to be the first source of fuel for a fire if there is a short. So closest to where the juice is coming from is where you want the fuse. In our case, the juice is coming from the TV. So, on the trailer, a fuse at the TV (front) end of a wiring run is appropriate, and on the TV, the fuse needs to be right off the battery. Just the TV battery fuse "should" do the complete job. YMMV.

Notes below on what I found today

It's just not built to be used as your using it.

I think it's mostly marketing. How many people want a DC/DC charger vs. how many want a Solar Charge Controller?

Like I said, I know a few doing so and surprised they're working.. Guess it means opening two up and comparing modules.

On mine the #4 (12vdc hot) pin goes directly aft to the panel.

We're twins! That's better stated than whatever I said before. My Pin 4 was wired to the same panel terminal as the battery +. Must disconnect to use a DC/DC charger.

Notes below

'capnT' what I found today was interesting. My incoming 12vdc from the #4 pin is tapped to the outgoing battery cable just before my panel at this 30a auto-breaker. This shows me the panel is protected, yet my battery is not from the alternator. Yup, I need a fuse inline! That side is not protected!


Disappointment was to find my Converter/charger is integrated with the panel.. Bummer.. This makes a change out to lithium a bit harder or should I say a bit more challenging.

I do also have to say that those that wired my trailer need adult supervision when working. What a mess in there!

[capnTelescope]

I do also have to say that those that wired my trailer need adult supervision when working. What a mess in there!

Mine, too. From what I've read, it's an industry standard.

'capnT' what I found today was interesting. My incoming 12vdc from the #4 pin is tapped to the outgoing battery cable just before my panel at this 30a auto-breaker. This shows me the panel is protected, yet my battery is not from the alternator. Yup, I need a fuse inline! That side is not protected!

Can't hurt, might help.

Image

Disappointment was to find my Converter/charger is integrated with the panel.. Bummer.. This makes a change out to lithium a bit harder or should I say a bit more challenging.

Is the wire with the yellow insulator from the trailer battery? and the two together go to the TV and the panel? If so, then the one from the TV would be the one to power the DC/DC charger. The output from the DC/DC charger would go to this breaker on the panel side. Could that be the fuse you want?

Let's talk about my Teardrop for a second. I have two chargers in my Teardrop, one that plugs into shore power, and a solar charge controller for my solar panels to plug into. They are both hardwired to the battery. In your case, the PD panel is the shore power charger and the DC/DC charger would be the equivalent of (drum roll, please) my TD solar charger. This is proven to work, by yours truly.

The TD battery does not discharge back into either of the two chargers when they are off. Chargers are made that way. Also, the unpowered charger will just think the other charger is the battery. Not that an unpowered charger is exactly a deep thinker. 12 volts is 12 volts to the powerless. Power to the powerless!