Increasing charge rate from TV to TC?

DJ-
I was having trouble keeping my Dometic 3-way refer running on LP while on the road, and got tired of trying to fix it, so I've been running it off an inverter for several years now (runs fine on LP when parked or driving slow roads). The AC element pulls about 345 watts, and it typically runs about 50% of the time. I can keep the camper battery at about a 90% charge with the truck alternator.

MEX's recommendations describe my charge circuit upgrades almost to a T, with the exception of a couple of "choke points" that I haven't addressed yet. 1- The alternator-to-bed plug wires are 6 gauge, but I haven't upgraded the wires in the camper pigtail yet. They are still the 8 gauge wires Lance used. 2- The plug in the bed is a 7-way round pin semi trailer plug, which is a much better plug than the typical RV 7-way flat blade, but I need to split the charge wires out of the camper pigtail and use either an Anderson connector or a 2-way lift gate connector set. When I take care of those two items, my charge circuit should perform even better than it does now.

One advantage you have over my truck is the wire length should be shorter on yours. With my crew-cab, it took over 20 feet of wire to go from the alternator, through a continuous-duty solenoid and 55 amp breaker, down along the driver-side frame rail and up to a plug close to the front of the bed.

If you want some wire that's easy to work with, check out Tinned Marine Wire Fine stranded, tinned battery cable that's very flexible.


:):)

~DJ~ wrote:
It is my understanding that the amount of charge going to the truck camper battery is determined by how much the alternator needs to send to the truck battery. So if the truck battery is nearly full the camper battery gets very little charge.

My problem is I installed a 12 volt compressor fridge that consumes nearly 4 amps per hour. The weather has been very warm (100°) so the fridge runs most of the time. At the end of the driving day my 100 amp battery is only half charged (12.50) Just enough to make it thru the night IF I don't sleep in!!!

Just wondering if there is a way to increase the flow to the TC. And maybe something with a voltage regulator?

I have 100 watt solar but is useless in heavy timber. And going to a larger capacity battery doesn't make sense if I can't charge up the one I have.

Please keep any responses in layman's terms!! LOL

Thanks.....DJ

Have I been dealing with the correct thread here?

Car alternator voltage regulators have a BIG problem.....

Most systems sense temperature either inside the alternator or inside the vehicle ECU. Rising temperature causes charge voltage limit to slump. My toad a MoPar slumps almost a half volt when the engine compartment warms up. This complicates things.

Using VERY large wire and topnotch parts in a wiring system between an alternator and RV battery is of prime importance when the vehicle's charging system is going to be replied on to charge the RV batteries. There can be no half-way compromises. Even one small point, connecting the charging lead wire to the -alternator output stud- rather than the vehicle battery is likely a "Make Or Break" difference in whether the system works well-enough or not.

Personally, for my own use I would modify the truck and camper electricals as I outlined in my first response. Secondly for this issue I would substitute an AGM battery for the flooded battery because of the limit of one single battery, and the need for the battery to accept a charge as fast as it can. A 31 AGM can accept 50 amps at voltage regulated levels, and the original poster has a time issue. This calls for no halfway measures. Six gauge wire. Anderson Pole Power Connectors, and connection directly to the vehicle alternator output stud. If that does not solve the issue, a group 31 battery AGM is step 2.

From the school of hard knocks, substantial professional trial and error experience and common sense...

MEXICOWANDERER wrote:
RJ's Fishing has a very true point. Feed adequate voltage to a battery bank and it will charge. For instance a thousand amp hours at 100' distance will charge just fine with 600 MCM wire. You do not want to know how stupendously large 600 MCM wire is.

NinerBikes has a valid point with some batteries being more stubborn to fully charge than others.

So rather than argue congratulate each other on both being "right". :)

RJ's combo works for him... cheap chinesium RJspecial charger at 14.4V with his batteries, mounted just below the charge controller and his group 27's. Same charge controller on my 6.5 amp 120w portable solar panel and a single group 24 was not getting my SG above 1.250 with 14.4V volts at the charge controller. An EQ session cleaned the cobwebs out of that battery with some baby sitting and a full 16.0V for about 20 minutes, after it started at 15.7V.

OP claims he killed a Trojan Group 31 AGM, which has even less internal resistance to charging fully than an open vent LA battery, and will charge fully on 14.4V vs 14.8V for the group 31 Trojan conventional.

Killing a Trojan battery, AGM or otherwise, in short order, takes some doing, misuse, or lack of charging fully or equalizing. It is in a shape and size, as demonstrated by a few around here, that is cranky and problematic to fully charge, it needs a lot of hand holding to get the EQ topped off.

RJ's Fishing has a very true point. Feed adequate voltage to a battery bank and it will charge. For instance a thousand amp hours at 100' distance will charge just fine with 600 MCM wire. You do not want to know how stupendously large 600 MCM wire is.

NinerBikes has a valid point with some batteries being more stubborn to fully charge than others.

So rather than argue congratulate each other on both being "right". :)

RJsfishin wrote:
Pray tell, what does the physical size of a battery have to do w/ getting a battery to full charge, other than time ? So a group 24 battery is the only size that is not a pita to charge ? My 2 27s sure seem to be doing good.
On edit,....just remembered I don't use a hydrometer, so what the hell would I know !

RJ, you are the exception to the rule... and you may not have followed Landyacht318's thread on his group 31's being problematic. You might want to give it a read, if you can find the time to go through all 20 pages or so, it's a historical benchmark in charging problematic group 31's, and Mexicowander makes some astute comments about battery design and accumulator designs, as well as size parameters. Some of the ratio's plate to battery acid capacity, are not right or properly balanced in this size and shape battery.

There's another way, go to the Stealership and order the dual alternator kit.

Ford offer it as either a factory order or dealer installed option, or used to anyways. It gives you 2 x 100 amp alternators.

You can do mobile welding to help pay for your other hobbies. LOL.

The 31, due to shape and size restrictions, is a royal PIA to get fully charged up again. Especially with your alternator, which won't supply a continuous 15.0V, which is what that battery needs to get 100% charged up.

My predictions are you will have continued problems with that group 31 battery. I'd instead get a pair of 6V, wire them in series for 12V, Trojan T-105's and have a lot more trouble free charging. Group 27, 29 and especially group 31's are PIA high maintenance to get them to fully charge and get topped off, you need special charge controllers and procedures to prevent them from losing capacity and getting sulfated and destroyed.

NinerBikes wrote:

RJsfishin wrote:
If it makes you feel better, every Motor Home that was ever built has the full charged chassis battery charging in parallel w/ the 1/2 dead house batteries, and it works just fine. So forget the idea that the full charged battery is stopping the discharged batteries from charging, and instead look for the real problem,......like has been talked about above.
Also keep in mind that ALL RVs have a "propane" Fridge for a very good reason.
I ran a 12v compressor Fridge in a Cabin Cruiser boat for 12 yrs, so I know how bad they suck !

This /\ BAD choice for refrigerator... replace with one made to run on propane so you don't tear up your trucks alternator. As OP stated, his problem is he installed an electric compressor refrigerator. Solve for X, not Y.

Nope. I'll never go back to a gas fridge in a pop up. They can't vent out the top for obvious reasons. And when the temps get to 100 like now the gassers struggle to keep 50°. My beer is icy cold at 34°.

I did change out my battery. Had a new Trojan 31 AGM. Put in a new Trojan 31 wet cell which increased the amp hours by 30. One trip to town and the wet cell is all ready fully charged. I think something is wrong with the AGM.

Thanks everyone for your input. If this doesn't work well with the new battery I will put in a bigger charge line.

~DJ~ wrote:
It is my understanding that the amount of charge going to the truck camper battery is determined by how much the alternator needs to send to the truck battery. So if the truck battery is nearly full the camper battery gets very little charge.

Not like that. Alternator just provides a voltage. Alternator does not know where the power goes or how full any battery is.

Alternator generally does start a bit high in the mid 14 volt range and as the alternator warms up along with the entire engine compartment the voltage usually drops to the mid to high 13s. The alternator holds this voltage continuously while running.

Yes the engine battery seems to charge first and long before the house battery. This effect is mostly because the charging cables are not balanced, not even close. The connection to the start battery is short and fat. The connection to the TC house battery is long and thin. And the start battery is only discharged a small amount vs. the house battery.

To get more charge in the house battery you need some big fat wire to equalize the voltage. Also the house battery will take several hours to charge and the alternator may not hold voltage up in the 14s for the entire time causing the time to charge to be extended.

Alternators don't push amperage, batteries and other loads suck amperage.

Because of resistance you aren't allowing enough amperage to reach the TC battery. The likely culprits in order of possibility are;
small wire gauge,
corrosion,
loose connections,
or a failing alternator.