Charging camper batteries while driving down the road

[oldelmer1]

I believe this has been discussed before, but here goes again


After two g for 6 hours today, I checked the voltage on the batteries and
they were down to 11.9v. I've checked my ram 3500 and
I have power on the correct pin for recharging the battery.

I was talking to a friend who toads his car behind his motorhome
And he uses one of these for his road.

http://www.brakebuddy.com/phone/towed-vehicle-battery-charger.html

Do any of you think this would work for charging g the camper batteries
while driving down the road.

 

[Oregon_Camper]

Problem is your residential refrigerator is using ~3x what your truck is putting in.

Now...your truck could be different, but most have a very very small gauge wire running back to 7-pin plug. Small gauge wire = Low Amps. You just can't get enough amp down that wire.

You can do one of the follow:

1 - Directly wire in a new thicker gauge wire to battery.
2 - Buy Lithium batteries and drive 6+ hours a day and never worry...as you will have 13.6v all the way down to ~10% charge....but they are ~$1,000 a piece
3 - Install ~200 watts of solar on the roof, combined with a nice MPPT controller and you'll be good (assuming you drive during the day & you're not a vampire driving at night )

 

[danemayer]

There doesn't seem to be much in the way of explanation of what the device does. But I have to wonder why it would be any different from power coming across the existing umbilical.

Do you know the battery voltage at the beginning of the day?

If this is something that used to be better, it may be that your batteries aren't holding a full charge. After disconnecting shore power, wait about 15 minutes before connecting the truck, and then take a voltage reading. The 15 minutes is to let any "surface charge" wear off. Keeping the truck disconnected will make sure you're not reading the result of a charge from the truck.

A fully charged battery will read 12.6V or very close.

Even at that, if the batteries are more than 2 years old, you might want to take them to an auto shop or service location to have them load tested.

And of course, make sure the water level hasn't dropped, leaving 1 or more cells low.

 

[Flick]

I believe this has been discussed before, but here goes again


After two g for 6 hours today, I checked the voltage on the batteries and
they were down to 11.9v. I've checked my ram 3500 and
I have power on the correct pin for recharging the battery.

I was talking to a friend who toads his car behind his motorhome
And he uses one of these for his road.

http://www.brakebuddy.com/phone/towed-vehicle-battery-charger.html

Do any of you think this would work for charging g the camper batteries
while driving down the road.

Looking at the specs for the brake buddy, I don’t believe that it will do what you want. It says it will maintain a charge but won’t charge a battery if it’s dead which leads me to think that any rv that has any amp draw won’t allow it to keep up. It’s meant for, as you said, maintaining a charge in a vehicle you’re towing. Your truck should do a better job than the brake buddy. What’s been suggested in another post would be the best route. However, I reckon they’re cheap enough to gamble on it that it perhaps might work.

 

[hoefler]

Your invertor is drawing between 20-25 amps 12 volt, when the refridgerator is running. Your Ram has a 10ga 30amp wire and fuse feeding your trailer. If it is warm out, your refridgerator is running, more. The charge line is barely keeping up with the invertor, let alone charging the batteries.

 

[SNOKING]

Three issues:

1. Wire size
2. Distance
3. When the truck batteries are charged up the voltage level comes down to low to "create" much of a charge to the trailer. Number one and two above do not load the trucks system enough for the alternator to raise the voltage.

Solution would be more amp hours in the trailers battery bank or the solar noted above^. Increase wire size really does not help solve the issue, as you still will not get the trucks alternator to raise the voltage enough to charge much.

At 11.9 the batteries are nearly fully discharged. This is not good for battery life. It is much better to work in the up half of available amp hours. Attached is my spread sheet for 2x110 amp hr 12V batteries in parallel. Spread sheet is available to anyone that wants it. You plug on battery bank amp hrs in cell I-2 and it does the math. Chris

State of Charge	Sealed or Flooded Lead Acid battery voltage	Gel battery voltage	AGM battery voltage
100%	12.70+	12.85+	12.80+
75%	12.40	12.65	12.60
50%	12.20	12.35	12.30
25%	12.00	12.00	12.00
0%	11.80	11.80	11.80

 

[danemayer]

Three issues:


3. When the truck batteries are charged up the voltage level comes down to low to "create" much of a charge to the trailer. Number one and two above do not load the trucks system enough for the alternator to raise the voltage.

I'm curious about this. On my RAM and on the previous GMC, I'm pretty sure that every time I ever checked the info console while the engine was running, it showed alternator output at about 14V.

Have Ford, GM, and RAM started using variable output alternators? Do you know when and whether they all do?

 

[wdk450]

I hope you have taken voltage readings on the trailer batteries with no shorepower and first the truck disconnected, and then with the truck connected through the umbilical cable and motor running. The 2nd reading should be higher, and reflect the truck's charging voltage. My older RAM had a 25 amp fuse on the charging line that kept blowing with my rig. I installed a 20 amp self resetting circuit breaker in the charging line at the trailer's connection to the umbilical cable, so that the trailer's charging draw shouldn't blow the truck's charging fuse.

The MOST IMPORTANT FUNCTION OF THE TRUCK'S TRAILER CHARGING CIRCUIT IS TO PROVIDE CHARGING CURRENT TO THE TRAILER'S BATTERIES FOR ACTIVATION OF THE TRAILER'S ELECTRICAL BRAKES IN THE EVENT OF A TRAILER DISCONNECT FROM THE TRUCK, VIA THE EMERGENCY DISCONNECT LANYARD SWITCH. Low batteries in the trailer make this emergency system less effective.

 

[oldelmer1]

Dan, my RAM also shows 14 Volts.

WDK450, I will check the voltage after I disconnect the AV power and wait a few minutes before taking a reading, then connect up the truck and take another reading and post it on here.

 

[SNOKING]

I'm curious about this. On my RAM and on the previous GMC, I'm pretty sure that every time I ever checked the info console while the engine was running, it showed alternator output at about 14V.

Have Ford, GM, and RAM started using variable output alternators? Do you know when and whether they all do?

RAM voltage is not a real measurement. Computer generated more like a idiot light than a meter. If the output of the alternator only work at a fixed rate it and could charge a low battery, then it would damage it after it was recharge by over charging it. In newer RAM's voltage is sensed at the passenger side battery, the ECM looks at battery temp and outside temp. BTW 13.8 is considered float voltage in smart chargers, where a wet cell battery does not loose excessive fluid. As far as I know charge rate is still controlled by voltage. It all goes back to ohm's law. E=IR

 

[Dahillbilly]

RAM voltage is not a real measurement. Computer generated more like a idiot light than a meter. If the output of the alternator only work at a fixed rate it and could charge a low battery, then it would damage it after it was recharge by over charging it. In newer RAM's voltage is sensed at the passenger side battery, the ECM looks at battery temp and outside temp. BTW 13.8 is considered float voltage in smart chargers, where a wet cell battery does not loose excessive fluid. As far as I know charge rate is still controlled by voltage. It all goes back to ohm's law. E=IR

Check this out, available from Amazon or direct from www.allstartruckparts.com. Neighbor has this set and swears by it.
[ALL STAR TRUCK PARTS] 12V 140 Amp Dual Battery Smart Isolator Pro Complete Kit - VSR - Voltage Sensitive Relay Specially Designed for ATV, UTV, Boats, RV's, Campers 5th Wheels Off Road Vehicles

 

[SNOKING]

^^ One would need a two conductor double shielded(on both male and female ends) HD plug between the truck and trailer, the trailer would need HD wiring between the pin box and batteries, and a large fuse or circuit breaker should be at each end(under the hood and at the trailer batteries as current could travel either direct if a short occurred).

 

[Flick]

I'm curious about this. On my RAM and on the previous GMC, I'm pretty sure that every time I ever checked the info console while the engine was running, it showed alternator output at about 14V.

Have Ford, GM, and RAM started using variable output alternators? Do you know when and whether they all do?

Funny story, at least funny now, we just got home about a week ago from a 3000 mile trip to Utah and Colorado. On the way up, we kept getting a message the “ charging system needed to be serviced now”. We finally decided to stop in Albuquerque at a Ford dealer. After unhooking in their lot, they ran it thru their quick lane and they said they found a loose ground wire and voltage was good. After hooking back up, the message came back on before we even got out of the parking lot. We put up with the message coming on every 5 miles all the way to Heber City. Once there, I checked the voltage and found it to be 13.4v on the truck but no voltage to the rv batteries thru the wiring harness. Back to Ford in Heber City where I finally found the answer to my problem. When we bought the truck in November, no one told me that Ford intentionally leaves out the relay and fuse for the charging system to the rv and that they are in the glove box. The only thing needed was the 30a fuse because if you have a brake controller, you won’t need the relay. The brake controller sends the message to the computer to send juice to the trailer. Problem solved. Peaceful trip home.

 

[Jim.Allison]

Here is my solution. First you guys that want to run residential refrigerators while running down the highway, PROBABLY need just a little more than what your 7 pin is supplying to your batteries on the average trip. Your electric brakes are powered by a combination of your 7 pin and your onboard batts. The energy comes form the batt and is later replaced by your seven pin, but if you are running your residential unit too, then it also has to replace that. There will come a point where it cannot keep up. The only way to increase capacity is add another batt. You should have 2 anyway.

Now if that is still not enough, theN you need a proper fuse and 2 pieces of welding cable, very cheap on Amazon and you can get it color coded as well. DC volts do not travel well over long distance, so the length of a truck and the demand will have to be determined you will probably find that a #2 welding cable will do the trick. Get a positive and a negative and a set of cable unions.

Connect these welding cables to your truck batteries making sure to install an appropriate breaker (probably about 60 A DC), then run these parallel to your 7 pin and up into your rig. Install the unions in a convenient place on your tow vehicle so you can disconnect. You will probably want about a 60 amp DC breaker near you truck battery. The breaker protects your alternator not the welding cables, decide how much demand you can place at peak on your alternator and go from there. Tie the #2 welding cables into your coach batts. You will have plenty of power to run the breaks, and the inverter for the fridge. As well as most other DC items in your Rig. An un expected advantage is that your ground will be superior in every regard.

This method will allow the 7 pin to remain undisturbed, it is alright to have a parallel line and you don't have to change anything on the toe vehicle or the coach.

 

[SNOKING]

The only down side I see to ^^^^ is that these new trucks electrical systems and electronics are very touchy about interference and electrical glitches. If you have a major electrical/electronics issue, the dealer might reject warranty if you see ones installation of such cabling. Also, I would not use the trucks chassis as the ground return! A automotive electrical engineer would be able to address what kind of electrical filtering would be appropriate for such an installation.

Chris

 

[oldelmer1]

I did check the voltage before I connected the camper to the truck, 12.4 volts .

I connected the truck and the voltage didn't change.

Drove for 6 hours and when I got home voltage was 11.6.

I do see the big red(with a black wire) going from the junction box disappearing into the camper but can't find it anywhere around the batteries.

Anyone know where it goes.?

Thanks all.

 

[danemayer]

There's a chance your buss bar near the batteries looks like this picture. If so, the breakers closer to the bottom are the ones that should connect to truck power and breakaway switch.

 

[SNOKING]

I did check the voltage before I connected the camper to the truck, 12.4 volts .

I connected the truck and the voltage didn't change.

Drove for 6 hours and when I got home voltage was 11.6.

I do see the big red(with a black wire) going from the junction box disappearing into the camper but can't find it anywhere around the batteries.

Anyone know where it goes.?

Thanks all.

If the refer was running via the inverter it would pull in a short time the voltage down to that level of 12.4 when you unplugged. At 11.6V a good inverter would have gone off line for low DC input voltage. Do you have two group 27 batteries in the trailer? Are these to original 4 or 5 year old batteries? A couple 6V golf cart batteries in series would stand up two this type of service much better. If you have room, four in serial/parallel would be even better. It my boats I used Dyno (a Seattle company)260 amp hr 6v batteries. They lasted around 10 years. The last installation was 6 of them for 780 amp hrs. They were charge under way with a 150 amp alt on starboard engine with a smart regulator and at the dock with a 75 amp 4 stage charger in a Heart Inverter. Port engine was responsible for the start bank. No free lunch here, use amp hrs and you have to be able to put them back in.

BTW in use vs at rest voltages are two different things. The table I posted earlier would be at rest voltages. That is no load applied for a hour or so. Some sources say over night however in at in use service that is hard to do. Chris

 

[oldelmer1]

Chris,

Yes, they are the original two group 27 batteries and 4 or 5 years old.

Im going to test them as soon as this cold snap goes away.

I still need to find where the big red wire goes, but again, too cold.

Thanks.....

 

[CDN]

Hello,

Jim Beletti has a mod thread adding a DC to DC converter and a heavy gauge connectors

https://heartlandowners.org/showthr...undance-262-RB?p=613459&viewfull=1#post613459