Tow Vehicle Battery and Alternator

I'm going to purchase and install the 40 amp DC to DC charger. Couple questions though.

A signal control (ignition line) is required to activate this device. Considering the application is a tow behind trailer, can I use the 7 pin trailer harness to tap into for a 12 volt source instead of running a separate line all the way back to the TV's ignition circuit? It would either be the #4 pin (aux) or #3 pin (tail/running lights). I think the tail lights would be a better option as I could control the unit's power via the headlight switch. Thoughts?

Most newer trucks switch off power to the plug with key off. With that said you would need to disconnect or install a diode to keep the trailer from back feeding and causing the charger to stay on. Any 12 volt circuit that would turn off when you want it to will work.


Also, the Renogy wiring diagram shows both positive and negative lines running from the starter battery to the DCDC charger. Is it possible to just wire in a negative line to the chassis of the TV (near the hitch) and run that along side the positive line from the starter battery? I would use a dual pole plug & socket like the Tectran recommended earlier in the thread.


I would not have an issue with using the frame as a ground.(just make sure battery to frame cable is adequate.)
Also, I would wire in a fuse or breaker on the positive feed near the starter battery. Is a 60 amp ok for 6 AWG wire? What is preferred, breaker or fuse?

If you used a breaker, you would not need to carry a spare. Either will work.

Finally, there are dip switches on the charger that customize the charging profile of the battery bank. Considering I'm using flooded GC2 6 volt batteries, what is the recommended absorption and float "end-of-charge" voltages for my configuration?

If it were me 14.7 and 13.2(you could bump up to 13.5 or 13.8 if you are using a lot of power.

grizzzman wrote:
I have the Renolgy 40 amp DC to DC charger. It has 3 stage charging and is adjustable. The truck input was 50 amps and the output as advertised. That was at 14.0 volts truck and 14.7 volts output. The charger has a trigger that you hook to the ignition switch. Hook to the battery. Do not use any less then 6awg wire (I used 4awg at 20 feet) I had a solar controller issue. Idled the truck for 1 TO 1 1/2 hr, and was able to run anything I wanted,including a 12 cup drip coffee maker. But to be fair, I had installed a 2P4S Lifep04 battery on this trip.(I wish that I had not waited so long to go LFP) What a difference!
Good luck with your adventure!

I'm going to purchase and install the 40 amp DC to DC charger. Couple questions though.

A signal control (ignition line) is required to activate this device. Considering the application is a tow behind trailer, can I use the 7 pin trailer harness to tap into for a 12 volt source instead of running a separate line all the way back to the TV's ignition circuit? It would either be the #4 pin (aux) or #3 pin (tail/running lights). I think the tail lights would be a better option as I could control the unit's power via the headlight switch. Thoughts?

Also, the Renogy wiring diagram shows both positive and negative lines running from the starter battery to the DCDC charger. Is it possible to just wire in a negative line to the chassis of the TV (near the hitch) and run that along side the positive line from the starter battery? I would use a dual pole plug & socket like the Tectran recommended earlier in the thread.

Also, I would wire in a fuse or breaker on the positive feed near the starter battery. Is a 60 amp ok for 6 AWG wire? What is preferred, breaker or fuse?

Finally, there are dip switches on the charger that customize the charging profile of the battery bank. Considering I'm using flooded GC2 6 volt batteries, what is the recommended absorption and float "end-of-charge" voltages for my configuration?

From Renogy's instruction manual:

I have the Renolgy 40 amp DC to DC charger. It has 3 stage charging and is adjustable. The truck input was 50 amps and the output as advertised. That was at 14.0 volts truck and 14.7 volts output. The charger has a trigger that you hook to the ignition switch. Hook to the battery. Do not use any less then 6awg wire (I used 4awg at 20 feet) I had a solar controller issue. Idled the truck for 1 TO 1 1/2 hr, and was able to run anything I wanted,including a 12 cup drip coffee maker. But to be fair, I had installed a 2P4S Lifep04 battery on this trip.(I wish that I had not waited so long to go LFP) What a difference!
Good luck with your adventure!

noteven wrote:
Will a DC-DC charger handle the load of a “3 way” fridge while driving with the vehicle connected to the camper via the 7 way plug charge wire?

My system does not keep up as configured by Ford and the RV maker...

Your stock charging system if working properly should provide the 12 to 15 amps needed to run the fridge on 12 volts. The battery will still be low upon arrival so you would need to plug in or charge with a generator upon arrival.

Yes even the 20 amp DC/DC charge converter will make a significant improvement on getting the proper power to the battery if your OEM system is a bit inadequate. Install the DC/DC converter on the trailer close to the battery.

"6. I did install a pure sine power inverter (1500/3000 watt) in the passthrough storage bay. Don't know if it's just the brand, but it fails to run the 900 watt microwave"

A "900w" MW needs about 1200w input (check the power info on its label) so the 1500w inverter should run it ok. (but the running watts for a "1500" would be lower too, so getting close to the MW input)

However, the inverter to battery wires need to be short and fat. Also two 6s will only run that when the 6s are above about 75% SOC. To run that with the batts at a lower SOC, you need four instead of two 6s.

It is likely also that you had other 120v loads on when trying to run the MW, so "power management" is important.

Two AGMs would let you run the inverter more than two Wet 6s before it hits the low voltage alarm, but that is a costly swap for not that much benefit unless you have space and weight issues that preclude having four 6s. Also AGMs require you to know the amps going in when recharging to know when they are full, which means an ammeter (I use the Trimetric for that) which is more money instead of a $10 hydrometer.

The generator mentioned is way over-sized for the job at hand, so unless you already have it, a 2200 would be easier and lighter too. If air conditioning off grid is the idea for a bigger gen, that is another story. For that now the problem is how long can you run the gen before it runs out of fuel. Apparently propane gens are the answer to that one, where you can share your BBQ's propane to run the gen!

CJM1973 wrote:
Thanks for all the insight first.

Details I hadn't mentioned:
{SNIP}
5. We will be bringing an inverter generator (Westinghouse 4500w/3800w) with us. I don't know how "generator friendly" the Alcan hwy is (or the waterfront campgrounds throughout Alaska). I would rather use it as seldom as possible.
6. I did install a pure sine power inverter (1500/3000 watt) in the passthrough storage bay. Don't know if it's just the brand, but it fails to run the 900 watt microwave. A new inverter may be required as the wife is insistent on that appliance for light meals for the kids. I've been reading that 6 volt golf cart batteries in series don't perform nice with large amp draws verses a similar amp hour 12 volt deep cycle bank wired in parallel. I'm also under the impression that flooded lead acid batteries have different discharging characteristics than AGM batteries. I'm considering an AGM upgrade even though my wet cell GC2s are only a year old.

I'm trying to determine what electrical upgrades are most beneficial without breaking the bank. The DC to DC power charger is top on my list. I'm questioning the long run of cable from the front of the TV to the trailer's passthrough storage. Based on what I'm hearing, I'm going to hold off on the alternator upgrade. The TV's little 600 CCA battery could be changed out for a higher capacity battery. An AGM upgrade to the GC2s is a possibility too. Don't know how I can increase amp hours unless I move to Lithium. The task of defining which components to upgrade (or add) is becoming a challenge. Even though winter will keep the coach idle, June is approaching fast and I'll need solutions before the weather breaks.

CJM,

You are doing this correctly, thinking is THE MOST cost effective thing to do right now.

I do not know about the ALCAN, but most places that do not offer shore power will tolerate a generator outside of posted quiet times.

I have done installations with 2eaGC2s for a microwave and they all worked. If yours won't, then check the supply voltage at the inverter when under load. If it is low, either move it closer to the house bank or buy more copper. I had to use welding cable. It did work and pretty well. Asking the GC2s for 150 amps is a little tough, but most will do it. The good thing is she is not baking a casserole. The good thing about copper is that you only have to buy it once. Welding cable is good for this because it is so flexible.

Best of luck

Matt

Will a DC-DC charger handle the load of a “3 way” fridge while driving with the vehicle connected to the camper via the 7 way plug charge wire?

My system does not keep up as configured by Ford and the RV maker...

The alternator provides the charging. the battery only would charge another partially and then only if it's way too dead so it's the alternator

And the wires that need to be upgraded

The DC/DC converter is a good idea too.

CJM1973 wrote:
I forgot to ask; if I do proceed with the DC to DC charger, do I wire it directly to the + battery terminal or + alternator lead? The renogy diagram shows multiple methods.

Also, what type of connector is preferred from TV to trailer? Wire will be 4 or 6 awg.

I think you want the DC/DC charger close to the trailer battery mounted on the trailer. This puts full voltage right on the battery. Manual says not to connect direct to the alternator... I would connect to the vehicle start battery or for a clean look work this into the main 12v distribution fuse box.

For connectors this set is used for trucks good for 100 amps and up to #4 wire. Truck Camper forum has people happily using this item. Available at NAPA. https://www.napaonline.com/en/p/PHI15336 https://www.napaonline.com/en/p/PHI15326

Matt_Colie wrote:
CJM,

Without knowing the specifics of the TV and TT, I fear you are headed for a disappointment. Even if the the TT house bank is on the tongue, we are talking a long run of cable. Remember, to make this work right, you will not be able to count on the frame of anything as a conductor.

With the entire life of a Lead/Acid battery between 12.0 and 12.6, and peak charging limited to 14.4 (or .6), there is no room for voltage drop. So a huge alternator will be a lost cause even if you run welding cable from the alternator to the house bank.

A Renogy charger will be a big help, but you are still stuck with the recharge time being limited by the battery chemistry. Even AGMs, though will charge faster, still have limits. They just get to 90% a lot faster if you can feed them juice.

You do not say what the installed converter is in the TT, but if it is not a modern 3 or 4 stage unit like Progressive Dynamics or Iota (there are others now) that does a boost, bulk and float, I suggest you replace it first.

Then, go an buy an inexpensive little genset. Try not to buy a "Contractor" unit because they are designed to cover up the noise of hammers and Skilsaws. There are more than a few on the market. Then, you will also have the portable for other uses. (You will find some.)

I know of a guy that boondocks with a long cab TV and a TT that ties his generator down in the bed and runs it when underway. He just runs the shore power cable to it. (With some duck tape for control.)

This will all be more simple and reliable than the alternatives, you will just have to put up with some noise some times.

Thanks for all the insight first.

Details I hadn't mentioned:
1. I replaced the OEM WFCO converter last year after I installed both GC2 batteries. It's now a 55amp Powermax 3 stage converter. Seems to be better at keeping the bank topped off when on shore power.
2. I'm preparing for an Alaska trip with the family next summer and am looking for a viable (and practical) solution to keep the batteries near 80-90% SOC when we arrive at each destination. The plan is to boon dock at least 3 out of 4 days during the 8 week trip.
3. I have a budget of around $2,000 for 'power' upgrades (per the wife). I would love to have a couple of LiFEP04 but pricing is just a bit out of touch for a non-fulltime expedition.
4. The trailer is a 35ft ultra lightweight model with a non-walkable roof. I'm leaning against a solar array as it would a daunting task to mount and maintain them on the 1/4" thick roof decking. I would consider a portable unit but how influential will it be under the northern Canadian and Alaskan skies? What's the cost benefit?
5. We will be bringing an inverter generator (Westinghouse 4500w/3800w) with us. I don't know how "generator friendly" the Alcan hwy is (or the waterfront campgrounds throughout Alaska). I would rather use it as seldom as possible.
6. I did install a pure sine power inverter (1500/3000 watt) in the passthrough storage bay. Don't know if it's just the brand, but it fails to run the 900 watt microwave. A new inverter may be required as the wife is insistent on that appliance for light meals for the kids. I've been reading that 6 volt golf cart batteries in series don't perform nice with large amp draws verses a similar amp hour 12 volt deep cycle bank wired in parallel. I'm also under the impression that flooded lead acid batteries have different discharging characteristics than AGM batteries. I'm considering an AGM upgrade even though my wet cell GC2s are only a year old.

I'm trying to determine what electrical upgrades are most beneficial without breaking the bank. The DC to DC power charger is top on my list. I'm questioning the long run of cable from the front of the TV to the trailer's passthrough storage. Based on what I'm hearing, I'm going to hold off on the alternator upgrade. The TV's little 600 CCA battery could be changed out for a higher capacity battery. An AGM upgrade to the GC2s is a possibility too. Don't know how I can increase amp hours unless I move to Lithium. The task of defining which components to upgrade (or add) is becoming a challenge. Even though winter will keep the coach idle, June is approaching fast and I'll need solutions before the weather breaks.