Coach Battery question

[Field Trip]

As we roll down the road does the truck keep the coach batteries charged (assuming the coach is plugged into the truck)?

[Mo_Mike]

Yes, it does (as long as your USE/STORE switch is in the USE position)

[Travelin' Texans]

If your going down the road the truck should ALWAYS be connected to your coach or not only are the batteries not being charged you don't have any stop/tail lights, so don't assume always be sure.

[mtntrek]

As noted above, the 7 blade umbilical has multiple functions. Lights- running, brake, turn, reverse/aux. Brakes from the brake controller, and also a 12V power terminal along with a ground. You won't see any heavy duty charging of low SoC bank from the tow vehicle.
Generally if we start our journey with the battery bank topped off we should be able to offset the running of the refrigerator/inverter and arrive pretty well charged during travel.
Most would advise turning off everything else switchable, lights fans etc.
On departure I tend to stay plugged into shore power until right before pulling chocks. The hydraulic pump for slides and jacks can get the bank down from a float charge.
YMMV.
Happy trails.

[wingnut60]

Staying plugged in until everything is finished that requires power is a good idea--I do that most of the time, almost to the point of forgetting it once or twice....

[rynosback]

Originally Posted by wingnut60

Staying plugged in until everything is finished that requires power is a good idea--I do that most of the time, almost to the point of forgetting it once or twice....

Pulling the plug is the last thing that we do also.

[Cummins12V98]

I bring all my slides in and retract all the landing gear off the RV batteries. My Residential frig is still at 38 and 0 when arriving after a long day of driving like 8 hours. I also use the batteries to fully setup the RV before connecting to shore power. I think it's good to exercise the batteries.

[Bobi, Dick and Ruby McKee]

Originally Posted by Cummins12V98

I bring all my slides in and retract all the landing gear off the RV batteries. My Residential frig is still at 38 and 0 when arriving after a long day of driving like 8 hours. I also use the batteries to fully setup the RV before connecting to shore power. I think it's good to exercise the batteries.

Cummins are you running your inverter to keep the fridge at those temps?

[Travelin' Texans]

I agree with Cummins, you need to use the batteries some or else they charge/float/charge/float all the time.

[Cummins12V98]

Originally Posted by Bobi, Dick and Ruby McKee

Cummins are you running your inverter to keep the fridge at those temps?

Yes I am. It was off the first time I towed for 4 hours and the frig was warming up a bit. Since then no matter how long I have towed the frig is at 0 and 38 upon arrival.

[rynosback]

Originally Posted by Bobi, Dick and Ruby McKee

Cummins are you running your inverter to keep the fridge at those temps?

I keep my fridge at 0 and 38 also. I travel with the fridge running of the inverter with no problems.

[David & Diane]

I have not had a problem yet keeping the refrigerator cold while traveling, but then I have not driven more than a few hours at a time yet. I have an oversized 250A alternator in my truck, so a supply of charging DC should not be an issue.

I was just wondering if it would be a good idea to start the generator if I park and rest for a couple of hours during my driving? Is it necessary to disconnect the umbilical from my truck if I start the generator?

[wingnut60]

In spite of more than adequate alternator power, the trailer batteries getting charged by the truck is severely hampered by the length and gauge of the truck charging system--most trucks barely are able to keep the trailer charged if starting out with a fully-charged system. I have dual alts and the truck still doesn't supply a lot of DC power to the batteries. If every thing in the system is in good shape, then you should be fine traveling with the fridge for 8-10 hours.
As to the generator, no problem starting it while still connected to the truck, have done that many times previously before getting the solar system installed. Still no problem kicking gen on when hitched/connected. Most, if not all, new trucks will not allow power to travel from the trailer to the truck.

[Cummins12V98]

I actually towed from SoCal to DFW TX. The trip took 34 hours and the truck was never turned off including a couple two hour naps. Frig 38 and Freezer 0 upon arrival.

RAM has a 220A alternator.

[clev]

I may be wrong here, but it’s why I didn’t do the second alternator install. Feel free to correct me. The alternator’s primary mission is truck operations and charging truck batteries. The onboard voltage regulator diminishes the charging to the truck batteries when they reach full charge. Even if your trailer batteries are depleted, when the truck is full charge, the alternator will diminish and go into float mode. I’ve arrived at dry campgrounds too many times where my batteries did not recharge after towing 6-8 hours (no fridge on inverter). This was explained to me by a Ford tech when I was researching installing a second alternator.

[Bob Denman]

Rather than even try to add a second alternator: doesn't Ford offer an alternator with a greater charging capacity?
(Assuming that you want to give this a try...)

[Cummins12V98]

" I’ve arrived at dry campgrounds too many times where my batteries did not recharge after towing 6-8 hours (no fridge on inverter). This was explained to me by a Ford tech when I was researching installing a second alternator."


Well at least you have good towing mirrors.

[clev]

Originally Posted by Bob Denman

Rather than even try to add a second alternator: doesn't Ford offer an alternator with a greater charging capacity?
(Assuming that you want to give this a try...)

Bob, I checked into that as well; same problem. When the truck batteries are full charge, the alternator goes to float. The alternator does not read the trailer batteries, and if it did and started charging, the truck batteries would be overcharged. I checked on a second voltage regulator for a second alternator but no one that I spoke with could/would address the issue. I’m old school and still have a 1985 E150 with alternator and separate voltage regulator. I’m still planning.

[Oneilkeys]

I do not pretend to be a battery expert, however, we have had this discussion previously in this forum. In an RV the coach and starting batteries are separate until engine or generator start or you plug into shore power. At that point, when the voltage of the main battery or batteries being charged (the chassis battery by the alternator or the coach batteries by the generator/shore power) reaches 13.1 charging volts, the Trombetta or BCC opens and the batteries are now in parallel. The following is the best explanation during our last discussions on this topic of what happens next.

“Let’s suppose you have 3 different 12V batteries, wired in parallel to supply 12V power to your RV. They can have different capacities on account of size or age, but the same chemistry (e.g. all flooded lead acid or all AGM). Before you start charging, the voltage across each of them is the same–even if one is fully charged and the others aren’t. Charge will flow from one battery to the other two until they’re balanced. With a lead acid battery bank, the internal resistances are limiting to a point that you don’t have to worry about arcing or your battery cables overheating when you connect them (not the case with lithium-ion banks…).

So when we start charging, all of the battery banks are very close to the same point as far as state of charge. Each battery acts like a resistive load, and current will flow to the battery with the lowest resistance, or highest capacity, more than the rest. All of them will reach the end of bulk charging together, when they’ve all reached the same voltage.”

One thread described this as three pails of water hooked together. As you add water to one, it fills up and then the water flows to the next and the next until all are full. The one you are adding water to does not overflow (as long as the inflow is not larger that the connecting pipe can handle).

In an RV, When the charging source is turned off and the voltage on one of the battery banks drops below 12.8v the Trombetta or BCC opens separating the banks.

I am not sure how it works with a truck and trailer situation or how exactly the batteries are wired to the truck alternator. Whichever way they are wired, it seems to me that it is similar in that both batteries are hooked in parallel when the alternator is running and separate when the engine is off. In that case, since the batteries are hooked in parallel when the alternator is charging them, however the alternator senses when the batteries are fully charged and goes into float mode will not happen until all the batteries are fully charged and you cannot overcharge one or undercharge the other.

It may be possible that in a trailer situation, the truck and trailer batteries are somehow not hooked in parallel when the engine is running (I don’t understand how). However this is easy to check. With the engine running the voltage on both the truck and trailer batteries should be about the same (around 13.5v or 14.1v if the alternator has a boost mode and the batteries are way down.

[16ACE27]

Originally Posted by Oneilkeys

I do not pretend to be a battery expert, however, we have had this discussion previously in this forum. In an RV the coach and starting batteries are separate until engine or generator start or you plug into shore power. At that point, when the voltage of the main battery or batteries being charged (the chassis battery by the alternator or the coach batteries by the generator/shore power) reaches 13.1 charging volts, the Trombetta or BCC opens and the batteries are now in parallel. The following is the best explanation during our last discussions on this topic of what happens next.

“Let’s suppose you have 3 different 12V batteries, wired in parallel to supply 12V power to your RV. They can have different capacities on account of size or age, but the same chemistry (e.g. all flooded lead acid or all AGM). Before you start charging, the voltage across each of them is the same–even if one is fully charged and the others aren’t. Charge will flow from one battery to the other two until they’re balanced. With a lead acid battery bank, the internal resistances are limiting to a point that you don’t have to worry about arcing or your battery cables overheating when you connect them (not the case with lithium-ion banks…).

So when we start charging, all of the battery banks are very close to the same point as far as state of charge. Each battery acts like a resistive load, and current will flow to the battery with the lowest resistance, or highest capacity, more than the rest. All of them will reach the end of bulk charging together, when they’ve all reached the same voltage.”

One thread described this as three pails of water hooked together. As you add water to one, it fills up and then the water flows to the next and the next until all are full. The one you are adding water to does not overflow (as long as the inflow is not larger that the connecting pipe can handle).

In an RV, When the charging source is turned off and the voltage on one of the battery banks drops below 12.8v the Trombetta or BCC opens separating the banks.

I am not sure how it works with a truck and trailer situation or how exactly the batteries are wired to the truck alternator. Whichever way they are wired, it seems to me that it is similar in that both batteries are hooked in parallel when the alternator is running and separate when the engine is off. In that case, since the batteries are hooked in parallel when the alternator is charging them, however the alternator senses when the batteries are fully charged and goes into float mode will not happen until all the batteries are fully charged and you cannot overcharge one or undercharge the other.

It may be possible that in a trailer situation, the truck and trailer batteries are somehow not hooked in parallel when the engine is running (I don’t understand how). However this is easy to check. With the engine running the voltage on both the truck and trailer batteries should be about the same (around 13.5v or 14.1v if the alternator has a boost mode and the batteries are way down.

You've got it right, the chassis battery will not overcharge as stated above your post.

In a trailer situation you also have to take into account the resistance and voltage drop across the long wire going from the Alternator to the trailer battery - that's why you may get almost no charging to a trailer battery from the alternator.