Charging

[GBBrown]

While TT is plugged into TV you can run the TT off the TV batteries..curious if when TT is plugged into AC or running off generator if the TV batteries get charge? I know there is a under hood fuse that can be pulled to eliminate running off the TV batteries, but was curiious if the 12 volt only goes one way. This make sense?

 

[jelag]

When I park for a long period of time I disconnect the tow vehicle from the trailer to prevent battery drain of my truck...

But when I'm parked for the night and have the gen set running or am connected to shore power I leave it connected so that the converter can keep all the batteries charged...

I don't try and pull a fuse... I just pull the trailer connector...

Hope this helps...

 

[GAmes]

Easy to check. Put a multimeter across the battery poles. If it is higher than 13 volts the electricity is feeding back to the TV.

 

[Cummins12V98]

When I stop for the night using gen or not I disconnect RV plug in bed. No chance of draining truck that way.

 

[Learjet]

When I park for a long period of time I disconnect the tow vehicle from the trailer to prevent battery drain of my truck...

But when I'm parked for the night and have the gen set running or am connected to shore power I leave it connected so that the converter can keep all the batteries charged...

I don't try and pull a fuse... I just pull the trailer connector...

Hope this helps...

^^^ Ditto^^^

 

[Larry Willard]

I usually disconnect the trailer also, but more than once I forgot to pull the plug and never had the batteries discharge.
Larry

 

[GBBrown]

Not worried about running TV batteries down was just wondering if Ram trucks electrical system allows voltage to go from TT back to the truck. Ford does not.

 

[GBBrown]

Easy to check. Put a multimeter across the battery poles. If it is higher than 12 volts the electricity is feeding back to the TV.

A fully charged battery is 12.7 volts and above.

 

[GAmes]

A fully charged battery is 12.7 volts and above.

Maybe in your world, or while the battery is being charged. I just checked 8 relatively new, good 12 volt batteries. The three in my two pickups, the three in my boat and the two in my RV. The highest any of them read is 12 volts, the rest were 11.8 or 11.9
However, if it makes you happy I changed my post to read 13.

 

[kthaxton]

GBBrown is correct. If your batteries are at 11-something, they are not fully charged. There are six cells in a automotive battery and at full charge, they are each nominally at 2.1 volts per cell.
Every GOOD batter I have ever owned has tested in the mid to upper 12's when fully charged and settled.

 

[GAmes]

Settled for how long? An hour, a week, a month? The Dodge hasn't been driven for several days, the RV and boat haven't been plugged in for several weeks.

 

[kthaxton]

Typically about 12-24 hrs to get a settled charge rate after charging.
Does you truck/RV/Boat have a slow steady draw on them? i.e. radio, smoke/gas detector (and whatever else an RV or boat may have active)?

https://www.batterystuff.com/kb/fre...ies-faq/12-volt-battery-reading-13-volts.html

 

[GAmes]

Normal radio draw on the Dodge, detectors in the RV, none on the boat. I can't tell you for a fact that my multimeter is completely accurate either. My point to the OP was 12.7 is a utopian expectation and that if the RV is feeding voltage back to the tow vehicle it can be measured by checking the vehicle batteries' voltage with the RV connected.

 

[Prairie Dog]

Not worried about running TV batteries down was just wondering if Ram trucks electrical system allows voltage to go from TT back to the truck. Ford does not.

Simple answer is yes, the flow of current is free to move in either direction.
GM is the same.

FWIW, I wired my last Dodge (93) for trailering and installed a relay to isolate the TV's battery. With my 03 I actually like it better being directly connected all the time.
Sometimes when dry camping I will spend the first night with the TV connected just to share the load. The next day I disconnect to drive around.

 

[kthaxton]

I thought they used some kind of diode to prevent current from going back to the truck....but I am no where near certain of this.

 

[GAmes]

My '97 doesn't have a diode. I don't know about the OP's '15.

 

[Dieselnerd]

I thought they used some kind of diode to prevent current from going back to the truck....but I am no where near certain of this.

I always thought that when my 2014 was attached to the 5th wheel and I was connected to shore power the truck batteries were being charged too.

Recently I decided to check it out. I put my meter on the trailer batteries and they read around 13.5 volts. The truck batteries read a little over 12 volts. I was disappointed because my older trucks used to get charged from the trailer.

There must be a relay or diode or something because I wasn't getting a charge from the trailer.

 

[ntsqd]

Diodes are a bad idea in a battery charge line. Their "cracking voltage" (drop) means that the downstream battery(ies) never get fully charged. Likewise, if you're expecting to charge trailer or even camper battery(ies) with the alternator thru a 10ga. that is 20 feet long you're wishfully thinking. Look up Ancor Marine's ref section and do the voltage drop calcs yourself. You really want less than 3% Voltage Drop to charge a battery. A 10ga. wire that long isn't going to work. For our bed mounted camper bulk charging at 80 amps with less than 3% Voltage Drop meant that I had to run 6ga. power & ground cables. Clearly cables that big are not needed for topping-off, but if I'm running the engine to charge the camper batteries it means that they are really down. Do not forget that the circuit length is the Total circuit length including the ground path.

Because I use those 6ga. cables for other power demands (OBA, etc.) I put the Voltage Sensing Relay (http://www.bepmarine.com/en/710-140a) in the camper with an 80A breaker in the camper as it's Main, and a second 80A breaker in the engine bay. There are batteries at both ends of that cable, so both ends need a breaker or fuse. I specifically chose manual reset breakers for their disconnect function that will allow working on the cable between them. This unit will allow the alternator to charge the camper batteries after the starting batteries are fully charged, and it will allow the camper's solar system to keep the starting batteries topped-off once the camper batteries are topped-off. With no charge applied to either set of batteries the unit disconnects them from each other.

 

[jelag]

One of the factors to consider here... is that the ECM on the truck controls the charge rate, or charging voltage... Its common for a new truck to have batteries that are never fully charged... if you remember that charging voltage used to be 14.2-14.4 and you'd need to check the water level in the batteries at a regular basis... today's modern trucks with the ECM controlling the battery charge and a temperature gauge under the batteries assures that the batteries are never really fully charged, and in some cases batteries go years and you don't add water...

What this means for us that tow, and dry camp for a couple of days is that our trailer batteries are never really much more than 75% charged, at least that is the way mine are... I often run a static voltage test and have wired in a digital volt meter check that regularly..

I've worked hard to look for and repair any connection that won't pass a voltage drop test.. but I can't see where a 6 or 8 gauge wire from the alternators to the RV would help until I get the charging voltage up where it needs to be...

I've even gone so far as to look into a buck boost... a device that will raise the 13.5 vdc at the alternator to 14.4 at the trailer batteries...

Any thoughts would be appreciated...

 

[ntsqd]

I've no idea about later models, but I've seen nothing to convince me that the regulator in the PCM, or for that matter any ground vehicle voltage regulator is very smart. I think they're actually rather stupid. The one in my '95 is a known failure mode. All they can control is the field current, and all they're interested in is maintaining the system voltage within some particular range. They're not actually programmed to charge the battery, that charging happens is a consequence of pumping enough current into the system to hold the voltage within that range.

Do the voltage drop calcs that I suggested. http://www.ancorproducts.com/en/resources/three-percent-voltage-drop I think that you'll be surprised at just how much the voltage does drop in a small wire over the length of such a charging circuit (include the ground length too because it matters). Now subtract that voltage drop from an already low output voltage and you're deep in trouble. I didn't do the calcs to justify using 6ga. Doing the calcs lead me to using 6ga. At $6 a foot I wasn't excited to be using 6ga., but to keep the VD under 3% that is what the calcs called for.

I do not agree with everything he says and some of the equipment suggested is now a bit dated, but the turning point for me was reading the Handy Bob blog on solar charging. https://handybobsolar.wordpress.com/ It got me to thinking about charging system needs regardless of the power source.

Knowing that the regulator in our '95 is a known to fail component I now carry a stand-alone Mopar regulator and the pigtail to connect it should a field repair be necessary, but I recently purchased a much better regulator: http://shop.pkys.com/Balmar-ARS-5-H-Regulator-12-Volts_p_1734.html It will be interesting to see how the rest of the vehicle behaves with this regulator in place.