Tow vehicle charging batteries

[safari 28]

I suspect my batteries are not getting charged from the tow vehicle. I spend so many nights in parks, it is always plugged in. last night boondocked at a casino and the batteries did not charge much after a day long drive. I have new batteries, converter works great when on shore power and at the park?? Any quick check to make sure things are right?

[thecatsandi]

Originally Posted by safari 28

I suspect my batteries are not getting charged from the tow vehicle. I spend so many nights in parks, it is always plugged in. last night boondocked at a casino and the batteries did not charge much after a day long drive. I have new batteries, converter works great when on shore power and at the park?? Any quick check to make sure things are right?

What make and model is your TV. Some Don't have the fuse installed...

[reddogfox]

Michelle
In my half ton 2007 GMC the trailer charging fuse was optional. At first I did not add a fuse because I feared running down the truck battery if I forgot to unplug when parked. After two years I installed the 40 amp fuse and it seems to help keep the batteries charged without a problem so far.

[2airishuman]

Originally Posted by safari 28

I suspect my batteries are not getting charged from the tow vehicle...

cuze they aren't, at least NOT much.

hoping/expecting to significanly CHARGE the coach batteries via the alternator and wiring is futile.

it can take a WEEK of driving (50 hours+) to effectively juice 2 group 27s...

many threads on this,

including calculations,

wiring, fuses, user reports...

and so on.

seek and ye shall find...
_____________

it's a rookie urban online gypsy myth

that the tv does MUCH to juice 'em.

cheers
2air'

[Jim Foster]

If the voltage regulator on the TV reads the TV battery as fully charged, it will shut down so as not to overcharge the TV battery, thus not charging the trailer battery. The trailer battery will slowly equalize with the TV battery and get charged up, but that could take a long time.

[AirsDream]

2air's certainly right on two points: 1.) IF you have the wiring, etc. hooked up, you'll get a trickle from the TV to the house batteries, but not much more, and 2) many threads on this. Since about '07 or so, GMC pickups (at least 3/4 ton diesels) came from the factory without the charging circuit hooked up at your fusebox, so you might be gettin' nuthin if that's what you're towing with. But if I recall correctly - and I might not - in this condition you also get no trailer brakes. You could check whether ANY juice is available with a simple voltmeter; but to get an accurate read on how much is flowing, you'll need an ammeter. Any RV tech located anywhere ought to be able to help you with this.

[safari 28]

Interesting. looks like I need to dig deep into this one. I have a prodigy brake controller and 2008 Ford f150. I sure do not want the trailer to drain on the truck however.

[2airishuman]

the 150 came with the proper bits (fuses and stuff)

and WILL supply enough juice to the coach batteries to offset any trailer braking needs.

and the 7 pin is SUPPOSED to be ONE way flow

and the truck battery IS isolated from being drained by the trailer...

but looking at the older threads on this could be useful too.

think about HOW FAR down the trailer batteries are...

40, 50, 100 amps down?

then sort out HOW MANY amps per HOUR are available from the 7 pin...

in THEORY and IDEAL conditions, then in actual use.

u can certainly recharge a LAPTOP or CELL PHONE or ipod IN the truck...

but it may take ALL day (while driving) 2 do this.

but again HOW MANY amps is that vs the 2 deep cycle things on the trailer???

to paraphase "electrizics is electrizics"

cheers
2air'

[Rawn77]

I have a somewhat different experience than those of the other posts. This past season I've been boondocking every other weekend. I had a conventional whitebox travel trailer (new AS Flying Cloud 27 on order; such anticipation) with 2 group 24's. I would operate my lights, lcd tv, and the fan for the heater each night; all night. I would then drive the next day for about 6 hours. At the end of each day of driving my batteries were always fully charged.
Maybe it was my TV (Mercedes ML320 BlueTec), but I can't imagine it charges any differently than other TV's.
I've never done any tests to determine the exact amount of amps and volts going through the umbilical cord; just my experience at the end of each day seeing that my batteries once again were at full charge.

[safari 28]

I drove all day and the batteries indicator on the wall of the streamer was showing 1/2 charged. On shore power showing 3/4 charged. It just seemed last year it would charge as I drove all day. As usual, it gets complicated and I thank all for your feed back. Still, brakes work great, all the running lights are perfect, I wonder if any of the 7 pin connectors is getting dirty or rusty? Maybe its just me???

[RichHog]

Thanks for the clarification on this. I drove a day last summer expecting a charged system and got to a site without power. Was surprised that the battery didn't get much life after a day on the road.

[2airishuman]

Originally Posted by safari 28

...I wonder if any of the 7 pin connectors is getting dirty or rusty? Maybe its just me???

if something is DIFFERENT from previous experience LOOK for changes.

dirty connectors, LOOSE connectors, blown fuses, damaged wires and so on, at either end of the juice line.

a multimeter is useful...

just old threads on the same issue, PLENTY others too...

http://www.airforums.com/forums/f37/...ing-18941.html

http://www.airforums.com/forums/f449...cle-43917.html

http://www.airforums.com/forums/f398...cle-42615.html

http://www.airforums.com/forums/f159...ing-34309.html

http://www.airforums.com/forums/f448...nda-21420.html

http://www.airforums.com/forums/f449...cle-11414.html

http://www.airforums.com/forums/f37/...car-24550.html

cheers
2air'

[safari 28]

thank you for threads. all good stuff and now I have a feel for what can be expected.

[thecatsandi]

Originally Posted by reddogfox

Michelle
In my half ton 2007 GMC the trailer charging fuse was optional. At first I did not add a fuse because I feared running down the truck battery if I forgot to unplug when parked. After two years I installed the 40 amp fuse and it seems to help keep the batteries charged without a problem so far.

Another thing to consider. the size of the alternator. I have a diesel and tow package that includes a 110A alternator. There are options for 160A alternator and a second 110A alternator. I also have a volt meter installed. I can watch the regulator and see if it charging or topping off.
I have solar panels installed on my trailer. In 4-5 hours of driving the two G27 batteries get fully charged.

[CanoeStream]

Originally Posted by reddogfox

At first I did not add a fuse because I feared running down the truck battery if I forgot to unplug when parked.

Some time ago Foiled Again woke up one morning to a dead truck. I seem to recall reading that more recent tow vehicles have a diode installed to prevent current flowing from the trailer into the truck. Somebody more knowledgeable would have to verify this. I probably won't get out of the habit of unplugging the umbilical when I park for a quick getaway and don't unhitch at night.

If you have a Prodigy brake controller, be sure not to fiddle with the umbilical while the TV ignition is on -- the Prodigy will fry. I've also blown a fuse in my previous TV when changing marker light bulbs with the ignition running. Back to the thread already in progress ...

[rluhr]

Originally Posted by Rawn77

I have a somewhat different experience than those of the other posts. ...I would then drive the next day for about 6 hours. At the end of each day of driving my batteries were always fully charged.

No, they really weren't fully charged. The voltage was back up to a level that the battery monitor interpreted as "full charge," but the batteries were well below their full amp capacity.

The standard battery monitors put into most travel trailers are incredibly inaccurate. They guess the state of charge based on voltage, which is kind of like guessing how full your truck's fuel tank is by sniffing the fumes. Did you notice that the battery monitor rather quickly dropped to the "yellow" status after a short period of power use?

As 2air points out, you can read more about this in other threads. The only truly accurate battery monitor I've ever seen is the type that measures the amps going in and out of the battery using a shunt. We use a Tri-Metric 2020 for example, and there are many other brands as well.

Originally Posted by Rawn77

Maybe it was my TV (Mercedes ML320 BlueTec), but I can't imagine it charges any differently than other TV's.

You're right, it doesn't, except that the Mercedes has some extra-fancy computer controls to manage signals to the 7-way plug. The "charge line" from a tow vehicle isn't designed to really do much charging. The wire is too thin, the amps are too few.

Originally Posted by Rawn77

I've never done any tests to determine the exact amount of amps and volts going through the umbilical cord; just my experience at the end of each day seeing that my batteries once again were at full charge.

That's why you've been misled. Voltage-based battery monitors lie. I wish RV manufacturers would stop using them. They're worthless.

The only way you're going to get an accurate reading from one of them (if you can even call RED-YELLOW-GREEN "accurate" under any circumstances) is if the batteries have been at rest for at least an hour. No charging, no discharging, and no load when you check their status. Then and only then is a voltage-based reading close to an accurate estimate of amps remaining.

So, to the original poster: There may be nothing wrong with your tow vehicle. Before you start diagnosing a problem that may not exist, consider that 2air got it right.

Repeat after me, all together now ...

Originally Posted by 2airishuman

it's a rookie urban online gypsy myth

that the tv does MUCH to juice 'em.

If you want your batteries to charge while you're towing, get a solar panel. That solution really works!

[safari 28]

Originally Posted by CanoeStream

Some time ago Foiled Again woke up one morning to a dead truck. I seem to recall reading that more recent tow vehicles have a diode installed to prevent current flowing from the trailer into the truck. Somebody more knowledgeable would have to verify this. I probably won't get out of the habit of unplugging the umbilical when I park for a quick getaway and don't unhitch at night.

If you have a Prodigy brake controller, be sure not to fiddle with the umbilical while the TV ignition is on -- the Prodigy will fry. I've also blown a fuse in my previous TV when changing marker light bulbs with the ignition running. Back to the thread already in progress ...

Can the prodigy be damaged and still activate the brakes?, I have had to wiggle the umbilical to get the c reading back on some occasions. All done with engine running etc. I remember my wife saying she smelled something burning. I now use a asparagus rubber band to hold it in. Brakes work great. This is why I wonder if the 7 pin is rusty or dirty.

[safari 28]

Originally Posted by rluhr

No, they really weren't fully charged. The voltage was back up to a level that the battery monitor interpreted as "full charge," but the batteries were well below their full amp capacity.

The standard battery monitors put into most travel trailers are incredibly inaccurate. They guess the state of charge based on voltage, which is kind of like guessing how full your truck's fuel tank is by sniffing the fumes. Did you notice that the battery monitor rather quickly dropped to the "yellow" status after a short period of power use?

As 2air points out, you can read more about this in other threads. The only truly accurate battery monitor I've ever seen is the type that measures the amps going in and out of the battery using a shunt. We use a Tri-Metric 2020 for example, and there are many other brands as well.



You're right, it doesn't, except that the Mercedes has some extra-fancy computer controls to manage signals to the 7-way plug. The "charge line" from a tow vehicle isn't designed to really do much charging. The wire is too thin, the amps are too few.



That's why you've been misled. Voltage-based battery monitors lie. I wish RV manufacturers would stop using them. They're worthless.

The only way you're going to get an accurate reading from one of them (if you can even call RED-YELLOW-GREEN "accurate" under any circumstances) is if the batteries have been at rest for at least an hour. No charging, no discharging, and no load when you check their status. Then and only then is a voltage-based reading close to an accurate estimate of amps remaining.

So, to the original poster: There may be nothing wrong with your tow vehicle. Before you start diagnosing a problem that may not exist, consider that 2air got it right.

Repeat after me, all together now ...



If you want your batteries to charge while you're towing, get a solar panel. That solution really works!

You know, life is a humbling stage of events. I have over 210 nights in her, and tugged her over 26k miles nationwide in just over 2 years, and still a Rookie. This forum is indeed a good for check on your ego.

[SilverRanger]

"I have had to wiggle the umbilical to get the c reading back on some occasions. All done with engine running etc. ... I now use a asparagus rubber band to hold it in."

Wow! On my 1997 Chevy TV, I used one of my kid's hair tie/ pony tail holder things (kind of like a mini bungee cord with a fluorescent colored plastic ball on each end) for the same purpose, with no damage to the Prodigy.

Necessity is the mother of invention.

[thecatsandi]

Originally Posted by CanoeStream

Some time ago Foiled Again woke up one morning to a dead truck. I seem to recall reading that more recent tow vehicles have a diode installed to prevent current flowing from the trailer into the truck. Somebody more knowledgeable would have to verify this. I probably won't get out of the habit of unplugging the umbilical when I park for a quick getaway and don't unhitch at night.

If you have a Prodigy brake controller, be sure not to fiddle with the umbilical while the TV ignition is on -- the Prodigy will fry. I've also blown a fuse in my previous TV when changing marker light bulbs with the ignition running. Back to the thread already in progress ...

Ford disconnects the charge line when you turn off the ignition. GM and Dodge did not last time I checked. I am glad I have a Ford!