Charging while towing

[terrymorse]

In case the wiring of a DC-DC converter/charger is unclear to anyone, Renogy has a simple diagram to use with their converter:



Renogy's unit can be configured to only charge when the engine is running, but it does require running a separate wire from the ignition to the unit.

Here's where I found that diagram: Renogy 12V 20A DC to DC On-Board Battery Charger

[angelagbra]

I note that these posts are from 2009....but....For some reason, our battery in our TTT does not charge. We have a 2017 Ram truck and a 7 prong plug. Are you supposed to unplug it at night? Could that be the problem? Is there anyone still on this post? Thanks.

[Tom&Shelly]

I note that these posts are from 2009....but....For some reason, our battery in our TTT does not charge. We have a 2017 Ram truck and a 7 prong plug. Are you supposed to unplug it at night? Could that be the problem? Is there anyone still on this post? Thanks.

A lot of us check out the newest posts on the folder, so we're here. How long have you had your TTT? How old is the battery? Has it charged before while you were towing it?

Unlikely it is simply a problem of leaving the plug in overnight. Some vehicles shut off when the auxiliary power when the vehicle's engine is off, others leave it connected to the vehicle battery. I'm not sure about the 2017 RAM truck. The potential issue is really discharging the vehicle's battery.

You may have some bad wiring, or an old battery, or something else. We need a few details to help diagnose it.

Tom

[Pugwinkle]

A lot of us check out the newest posts on the folder, so we're here. How long have you had your TTT? How old is the battery? Has it charged before while you were towing it?


Tom

I'm glad someone is still here!
I have a 7 prong on my TV and a 4 prong on my TD. Do I simply have to change my 4 pin to a 7 pin so that I can charge my battery while I'm driving? If so, can you give me a link to what I need to purchase. I'm in Canada so if you can find something on Amazon.ca or Canadiantire.ca that would be appreciated.

[troubleScottie]

Generally speaking the 7pin does not have the power or wire gauge to allow charging ie 20-40A. It is designed to run small items -- emergency break battery charger for instance

Think like you are attaching a big subwoofer or amplifier for you car. Large gauge eg 4awg. You would do well to run a separate line (well 2) from the battery to the TD with fuse, isolation switch, anderson connectors, glands, etc. Good example on page 15 or 16 with pictures.

The gauge is dependent on distance and power draw. There are charts.

[Tom&Shelly]

A lot of us check out the newest posts on the folder, so we're here. How long have you had your TTT? How old is the battery? Has it charged before while you were towing it?


Tom

I'm glad someone is still here!
I have a 7 prong on my TV and a 4 prong on my TD. Do I simply have to change my 4 pin to a 7 pin so that I can charge my battery while I'm driving? If so, can you give me a link to what I need to purchase. I'm in Canada so if you can find something on Amazon.ca or Canadiantire.ca that would be appreciated.

Ok, so you can't charge the battery with a 4 pin connector, so the question is: Can you change that for a 7 pin connector and then take the aux power out to your battery to charge? Short answer is yes.

We used a 10 gauge wire from the trailer connector to our battery. That and the stock wire from the Tacoma (also 10 gauge, IIRC) and we were able to charge our battery from a night or two's use in about a 5 hour drive.

If you want to improve performance, you might try a DC/DC converter that will step up the voltage a little to what the trailer battery wants to see. I can't recommend a specific device because I haven't tried this. (I am an electrical engineer, and that makes sense.)

Tom

[featherliteCT1]

What would happen if you connected a Lifepo4 battery to the tow vehicle’s starter battery without utilizing a DC to DC charger like the Renogy model shown in the first post of this thread?

[Tom&Shelly]

What would happen if you connected a Lifepo4 battery to the tow vehicle’s starter battery without utilizing a DC to DC charger like the Renogy model shown in the first post of this thread?

It would be bad

https://www.youtube.com/watch?v=wyKQe_i9yyo

Unless the battery has built in current limiting electronics. You need something to limit the current into those kind of batteries. I forgot to mention, in my comments above, I assumed a lead-acid battery. Good safety tip.

Tom

[cdnred]

What would happen if you connected a Lifepo4 battery to the tow vehicle’s starter battery without utilizing a DC to DC charger like the Renogy model shown in the first post of this thread?

It would be bad

https://www.youtube.com/watch?v=wyKQe_i9yyo

Unless the battery has built in current limiting electronics. You need something to limit the current into those kind of batteries. I forgot to mention, in my comments above, I assumed a lead-acid battery. Good safety tip.

Tom

Not sure if I've done this correct or not..? In my TV I've got a 12v AGM battery and in my TD I've got a 12v 40ah LifePO4 battery. I had a local shop install a 7 pin connector so I could charge the battery while towing..

https://www.amazon.com/gp/product/B08G8 ... =UTF8&th=1

Now I'm a bit concerned when you say "It would be bad" and that it should be connected with "utilizing a DC to DC charger". Do you feel that I'll run into problems the way it is setup now or do I need to look at getting a DC to DC charger installed in the circuit..? Since getting the 7 pin installed I haven't taken the TD on the road yet but come next summer I was planning on taking it on a road trip for 6 weeks to Alaska and around so I want to be sure that I won't run into any issues while on the road.,

[bdosborn]

A 40 a-hr lifepo4 battery is going to draw 40 amps or more when charging directly from your alternator. Your 7 pin connector probably has a #12 awg wire for the charging, which is rated for around 20A in most circumstances. I'd use a 20A DC-DC charger if I was going to Alaska, where car parts can be hard to get. Burning up your alternator means you're walking.

Bruce

[featherliteCT1]

I'd use a 20A DC-DC charger if I was going to Alaska, where car parts can be hard to get. Burning up your alternator means you're walking.

Bruce

++

[Tom&Shelly]

Yes: What Bruce says. (Actually, even if I wasn't going to Alaska!)

Tom

[cdnred]

A 40 a-hr lifepo4 battery is going to draw 40 amps or more when charging directly from your alternator. Your 7 pin connector probably has a #12 awg wire for the charging, which is rated for around 20A in most circumstances. I'd use a 20A DC-DC charger if I was going to Alaska, where car parts can be hard to get. Burning up your alternator means you're walking.
Bruce

Bruce, thanks for your help. I'll start looking into it and see about getting one installed. I wasn't sure cuz I owned an A-Frame camper before which had an AGM battery in it. It was wired to get charged from the TV directly thru a 7 pin plug. I took that A-Frame from Ontario up to Alaska down the West Coast and over to Arizona then back home on a 3 month trip with no issues. I thought it would be the same type hookup for my TD but am glad that I asked before leaving..

Helmuth

[bdosborn]

Yeah, an AGM battery is a lot easier to charge when driving. You just hook it up and go. The LiFePO4 is different and draws a lot more current then you'd guess. I watch a lot of van conversion videos on YouTube and it seems to be pretty common that they replace their alternators after they install big LiFePO4 batteries.
Here's the one I use in the trailer: Renogy Charger
Here's the one I use in the van:Victron Orion
I prefer Victron over Reneogy but not by much with the DC-DC chargers. My Renogy has worked fine.
Bruce

[cdnred]

Yeah, an AGM battery is a lot easier to charge when driving. You just hook it up and go. The LiFePO4 is different and draws a lot more current then you'd guess. I watch a lot of van conversion videos on YouTube and it seems to be pretty common that they replace their alternators after they install big LiFePO4 batteries.
Here's the one I use in the trailer: Renogy Charger
Here's the one I use in the van:Victron Orion
I prefer Victron over Reneogy but not by much with the DC-DC chargers. My Renogy has worked fine.
Bruce

That Renogy seems to be priced right for $100 on Amazon. I've got a 12v 40ah LifePO4 now but I'm thinking that maybe down the road changing it out for a 12v 100ah LifePO4. Will that 20A DC-DC charger be suitable for both cases or should I go with something like a 40a or 50a right off with going with the 100ah down the road..? Is there any relationship to battery ah compared to amp rating for DC-DC chargers..?