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Old 10-12-2020, 09:30 AM   #1
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Improving trailer charging while driving

I have a 2003 Chevy Duramax. It is equipped with a single alternator. It has the mount for a second one, but I suspicion there is more to the electronics than simply adding another generator. My problem is simply, the truck does a very poor job of recharging the trailer batteries while driving. Alternator output is fine. I believe it's a 120 amp alternator. Truck batteries are new. Battery cables are in good shape. I have power at the plug, just doesn't seem to ad much even on long hauls. I have checked all fusing. Wiring seems to be fairly small, and that is an easy change, but not convinced that is the issue. Has 14 gauge running to the back. My question to you all is what have you done to improve the charging? I have 4 golf carts in the trailer. Thanks in advance for your responses.
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Old 10-12-2020, 12:11 PM   #2
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check trailer charge fuse in fuse box under hood. 30 amp and pink in color.
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Old 10-12-2020, 12:14 PM   #3
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turn on parking lights check at trailer pos. terminal , cable off of battery. lights off voltage,, lights on voltage
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Old 10-12-2020, 12:29 PM   #4
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The wiring is small as you mentioned. I’ve read on here where people ran bigger wiring to improve it. I can also add another alternator but will likely just install a larger aftermarket alternator eventually. I’m a big fan of solar panels and that does a great job of keeping the battery topped up.
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Old 10-12-2020, 01:21 PM   #5
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If you are charging trailer batteries through the stock TV wiring "not much" would be a good description of charging current.. Especially through ~20 odd feet of wire.

I would consider a DC-DC charger like the Renogy DCC 12-20 with the 120 amp alternator. Disconnect the charge wire at your TT's junction box and use it as a control wire for the DC-DC charger, turning it on and off as engine is on or off. For the actual Charging Current run a duplex #8 ga wire ( I used marine type) from battery terminals back to the rear bumper trailer connector. Terminate the truck segment with an andersen connector (I used 50 amp size) Use some of the Duplex wire to continue on to the DC-DC charger mounted near the batteries.

The DC-DC charger will take whatever voltage the alternator decides to put out and boost it to the proper charge voltage, depending on whether batteries in TT need Bulk, Absorb, or Float voltage. The DC-DC charger is also a battery isolator, controlled by the original charge wire, so your TV battery doesn't run the TT batteries down when engine is off. No more need to disconnect trailer connector wire when stopped or while camping and still hitched.

The DC-DC charger will actually solve your problem for less money than an extra alternator that you just feed the output into either existing or upsized wire. The issue is that the starting battery gets charged sooner than the TT batteries and alternator (or alternators) will be regulated down to a lower voltage.

The DC-DC charger is a multi-stage charger that just needs to be programed (simplly done with DIP switches) for the proper battery type. Even works on LiFePo4 batteries (which I use).

$127 for the DC-DC charger from Renogy and the rest is about 25' of duplex wire and a pair of Andersen Connectors. Probably cheaper than a High Output or second Alternator.

My unit sends a continuous 20 amp charge to my Battleborn batteries until they're fully charged. If your alternator is larger you might be able to use their 40 amp unit.
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Old 10-12-2020, 01:27 PM   #6
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I ran a dedicated 4AWG circuit from one of the batteries back to the hitch, where I mounted a 150A Anderson plug.

Installed a Victron Orion 12/12-18 DC-DC charger, which delivers a little over 25A to our LiFePO4 batteries. I have it set up to automatically turns on/off with the engine while in use.

The factory charge wire on our 2017 2500HD was only 12AWG.....









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Old 10-12-2020, 02:03 PM   #7
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01Tundra--

Looks good. I like the Victron products a lot but I found the Renogy unit to be less expensive and still have bluetooth monitoring capability through my BMV.

In the end we both got to the same destination.
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Old 10-12-2020, 10:59 PM   #8
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In a GM, running in tow/haul OR having your lights on boosts the alternator voltage a bit (a couple of volts?). That'll help the charge current. Other than that, yeah, it's wire size.

I've seen 13A in a stock setup to FLA batteries.

I put my $ into solar, instead... but the engineer in me loves these solutions.
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Old 10-13-2020, 10:06 AM   #9
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I am set up with a solar suitcase which works great when we are sitting for a couple of days. That type of system doesn't lend itself well to moving from place to place everyday. I know a roof system would solve it, but I should be able to recharge while driving. The DC to DC charger looks to be a solution. How difficult is it to wire up, and what other components are needed for installation? Does the charger go in the Tow Vehicle, or is it installed in the trailer and connected to the tow vehicle through wiring?
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Old 10-13-2020, 10:38 AM   #10
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The biggest questions I see with installing one of these is, where do you mount the unit in the truck? What gauge wire do you run to and from the unit? How do you transition from the truck to the trailer? It looks, by Renogy's diagram that the system is simply protected by ANL fuses, and I like the idea of a simple toggle type switch for on/off as opposed to connecting to the ignition. I agree with you Mike, looks to be a lot cheaper than the other alternatives.
Went back and reread your post Mike, and you explain most of this. I'm now starting to understand the layout. Thanks.
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Old 10-13-2020, 02:12 PM   #11
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Improving Trailer Charging

Comanchecreek

Here is another idea. Put a 25 amp 3 stage automotive battery charger in the trailer. In the truck, mount a 500w inverter (real sine wave if possible)in a convenient place. Now rub a 14 gauge wire to the charger location using standard AC connectors and wiring.

The current between the inverter and the charger is probably around 3 amps hence the 14 gauge wire. If the charger is the "smart" type, it will deliver the full 25 amps until the batteries reach 80% charge. Remember, the charger current at 119V is one tenth of the charger current at 12V.

This may be an easier, cheaper route and you may already have the portable charger.

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Old 10-14-2020, 05:47 AM   #12
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Your truck came with the ability to have 12 volts at the 7 pin plug but it was intentionally not connected by the factory. You can verify this by checking the Top Right pin (12 volt hot) pin to the Bottom Left pin (ground) as you look at the 7 pin receptacle. You will have no voltage.

Directly below your master cylinder, taped to the wire harness but clearly visible is a red wire with a terminal end. This is the wire for the 12 Volt trailer receptacle.

Now remove the cover of your fuse box underneath the hood. On the outside of the box you will see two posts, both are hot. Put the terminal end over the #2 pose (closest to the fender) and secure with a nut.

Voila, one and done, you now have constant power to the 12 volt pin in the trailer receptacle.

A word of Caution.......this power is not constant, it Is NOT controlled by a solenoid so if you leave ur trailer connected to ur camper you will drain your truck batteries, possibly to the point of not being able to start it.

You could easily get a 12 volt continuous rated solenoid and wire that into the mix to allow power when running the truck but no power when the ignition is off.

To get even more detailed information for your truck Go here:

https://www.gmupfitter.com/pdflists/view/6

and download the Electrical manual for your year and model. This will give you the best information available about the wiring of your truck.
Attached Files
File Type: pdf Camper Vehicle side 7-Way.pdf (1.42 MB, 44 views)
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Old 10-14-2020, 09:46 AM   #13
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I have the correct fuse at stud one. I checked the fuse and it is good. My problem isn't "no" charging, just weak output. My thought is that with the computer controlled voltage regulator, after the truck batteries are fully charged, the regulator cuts back on the alternator output, which doesn't help my trailer batteries recharge. I have 4 golf carts in the trailer, and I need more output to get them up to snuff. I've decided to go with the DC to DC charger that TitanMike referred to. I can run the 8 gauge wire from the batteries to the bed of the truck, (I have a fifth wheel), and install a plug in the bed next to my regular 7 pin plug. I'll use an inline fuse to protect the wire. I'll then rewire the trailer to use the original skimpy wire to function as an on off switch for the charger. Most of the change will happen in the trailer, so if I pull other trailers, my connector will act normally. The second connector will only be involved when I tow the fifth wheel. All makes sense to me now, I'll have to let you know how it goes.
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Old 10-14-2020, 10:08 AM   #14
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Quote:
Originally Posted by Comanchecreek View Post
I am set up with a solar suitcase which works great when we are sitting for a couple of days. That type of system doesn't lend itself well to moving from place to place everyday. I know a roof system would solve it, but I should be able to recharge while driving. The DC to DC charger looks to be a solution. How difficult is it to wire up, and what other components are needed for installation? Does the charger go in the Tow Vehicle, or is it installed in the trailer and connected to the tow vehicle through wiring?
My entire setup took maybe two hours total. Charger is next to batteries in my setup. Running the larger wire from batteries to charger took longest (because I wanted it neat). Duplex #8 marine type stranded wire (looks like Romex but a more finely stranded wire conductor) running from TV battery terminals, an underhood fuse (I used ANL type) and Andersen Connectors at hitch for quick disconnect. Wire in TV runs along the same wire loom that goes from under hood to the trailer connector, fastened to it with lots of zip ties.

Same on trailer cord, zip ties every 8-10 inches and then to the Charger.

Initially I tried to use the existing charge wire to supply the charger in the trailer but i was only able to get about 75% of the rated output into my Battleborn batteries so I added the #8 awg wiring.


The Lithium batteries in my setup suck up all the power going into them and they charge quick. For those charging lead/acid batteries I see an even larger benefit. The DC-DC charger will be able to maintain a higher bulk rate without being hampered by the charging system in the Tow Vehicle wanting to switch to a lower rate because of the voltage drop over the distance.

Some pictures of my setup:





Note: First pic shows a circuit breaker instead of fuse. Found that under hood heat "de-rated" the circuit breaker greatly so I either had to put a breaker in that was twice the size or just replace with a fuse. I put an 50 amp ANL fuse inline whch is more proper for the #8 wire.
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Old 10-14-2020, 02:05 PM   #15
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TitanMike have you had any problems with that type of circuit breaker? I like them but they get some bad reviews. I intend to follow your installation procedure as it make complete sense, and should work well for what I want to do.
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Old 10-14-2020, 02:47 PM   #16
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So it appears my Chevy does not have a battery isolator on it. The charging plug on the 7 prong is always hot. I want the DC to DC charger to shut off when the key is off. Any suggestions on battery isolation for that circuit, or an alternative to make the charger shut off when parked?
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Old 10-14-2020, 04:33 PM   #17
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Originally Posted by Comanchecreek View Post
So it appears my Chevy does not have a battery isolator on it. The charging plug on the 7 prong is always hot. I want the DC to DC charger to shut off when the key is off. Any suggestions on battery isolation for that circuit, or an alternative to make the charger shut off when parked?

Just run a small gauge wire from the "ACC" bus in the fuse panel. A circuit that is only hot when key is on. A simple add a circuit fuse connection will work.

This wire should then go to the connection on the DC-DC charger. THIS wire only carries a couple milliamps of current so it doesn't need to be very large at all. 16 ga stranded would be overkill but that's as small as I'd go just for physical strength.
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Old 10-14-2020, 05:13 PM   #18
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Quote:
Originally Posted by Comanchecreek View Post
So it appears my Chevy does not have a battery isolator on it. The charging plug on the 7 prong is always hot. I want the DC to DC charger to shut off when the key is off. Any suggestions on battery isolation for that circuit, or an alternative to make the charger shut off when parked?
An easy way to do that would be to use the solenoid here under the hood:

https://www.ebay.com/itm/Starter-Sol...gAAOSw0e9UuHjc

As Mike stated an add a fuse to an ACC circuit in the fuse box activates the solenoid when the ignition switch is turned on. It deactivates it when the ignition is turned off.

You can get this at any auto parts house:

https://www.ebay.com/itm/Lumision-16...Cclp%3A2334524

This eliminates running a 16 gauge wire all the way from under your hood back to the camper where the DC-DC charger is located.

You just need two terminal ends to run to the 12 Volt charge wire where you mount the solenoid under the hood, and a short 16 gauge to activate the solenoid.

Easy Peasy
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Old 10-14-2020, 05:30 PM   #19
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An easy way to do that would be to use the solenoid here under the hood:

https://www.ebay.com/itm/Starter-Sol...gAAOSw0e9UuHjc

As Mike stated an add a fuse to an ACC circuit in the fuse box activates the solenoid when the ignition switch is turned on. It deactivates it when the ignition is turned off.

You can get this at any auto parts house:

https://www.ebay.com/itm/Lumision-16...Cclp%3A2334524

This eliminates running a 16 gauge wire all the way from under your hood back to the camper where the DC-DC charger is located.

You just need two terminal ends to run to the 12 Volt charge wire where you mount the solenoid under the hood, and a short 16 gauge to activate the solenoid.

Easy Peasy
Can't dispute your suggestion. I just hate using relays for anything other than low current applications (10 amp or less). The higher current ones have to be continuous duty and are even then a failure point. Continuous duty relays are more expensive than most so chances are one won't be carrying a spare.

For this application one can't just add a cheap starter relay.
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Old 10-14-2020, 05:35 PM   #20
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TitanMike have you had any problems with that type of circuit breaker? I like them but they get some bad reviews. I intend to follow your installation procedure as it make complete sense, and should work well for what I want to do.
I noted I had problems from the get-go due to under hood heat.

When looking at the spec's I found I had neglected to de-rate it due to the high ambient temp. Current installation has an ANL fuse in place of the C/B.

Nice thing about ANL fuses, just about every auto parts store keeps them in stock. They're widely used by those with monster sound systems in their cars.'

If the circuit breaker is mounted in a cooler environment than properly sized they should work just fine. I'm currently using the old C/B on my power panel in my TT for another purpose and no issues. They do make good shutoff switches too.
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