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Old 08-26-2019, 02:42 PM   #1
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Alternator Charging

Is it possible to wire a second alternator in a pickup to a battery charger in a 5th wheel?

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Old 08-26-2019, 02:51 PM   #2
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Of course it's possible (as long as you have room for a second alternator) but why not run a circuit from you pickup battery to the 5th wheel.
You can install a Victron Battery Protect to make sure that this circuit does not drain you battery. It is an automated cut-off switch with cut-off presets with min and max settings.

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Old 08-26-2019, 03:05 PM   #3
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Originally Posted by ja_landry View Post
Is it possible to wire a second alternator in a pickup to a battery charger in a 5th wheel?
It is possible. Does your pickup have a place to mount a second alternator?

There may also be a higher capacity alternator available to replace the one you have.

1) Heavy gage positive cable to TT connector. Heavy gage ground form TT connector to pickup ground. Circuit breaker near new alternator.

This usually provides mediocre TT battery bank charging do to line and connector voltage losses. Paying careful attention to causes of loss can get usable results.

2) Install a battery to battery charger system. The booster charger raises the voltage output at the TT battery to fast charging voltage even when there is significant line loss back to the tow vehicle.

This usually provides good charging from the tow vehicle. It may provide all the extra charging you need without a second alternator. A higher capacity alternator replacing your current alternator would be a good feed for this system. Short periods of travel often don't provide a charge for long enough to fully charge a lead acid battery (14 to 18 hours required). However substantial charging of deeply discharge batteries is certainly possible.

An analysis of your current system capacity and loads can help make a good choice.
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Old 08-26-2019, 03:26 PM   #4
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Many trucks come with options for bigger and/or second alternators. Finding the parts should be easy enough. Itís probably easier, and maybe about the same price, to just install a solar panel on the roof of the fiver.
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Old 08-26-2019, 05:28 PM   #5
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Most alternators have the capacity to charge additional batteries...
The problem is that the engine ECM now controls the charging voltage... this is now much lower today than it was say 10 years ago... this lower charging voltage means that the battery in the vehicle no longer gasses off and is brought to a full charge based on the temperature of the battery.... while the trailer batteries 25 ft away on small 14 or 16 gauge wire never have the ability to take on a full charge...
The lack of gassing means that a car battery goes from cradle to grave without ever having the cells opened and serviced with distilled water added.
There are several companies that offer a booster.. .that installs at the rear of the truck... it uses battery voltage and boosts the voltage to a number you can preset... and will supply that voltage at 25 amps... more than enough to recharge batteries with a few hours of drive time....
One of the manufactures is Redarc, its model # BCDC1240D
Hope this helps..
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Old 08-28-2019, 11:55 AM   #6
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Thank you for yout input. I have homework to do.
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Old 08-28-2019, 12:05 PM   #7
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What you want is the DC to DC charger Jelag refers to, or a similar device from another make. The problem in alternator charging is the distance from the engine bay to the trailer batteries causes voltage loss.

These devices are made for precisely the need you have, to charge secondary batteries from a potentially lower voltage primary battery.
Been through all the continental states and provinces. Loving life on the road.
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Old 08-28-2019, 07:09 PM   #8
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Why? A high capacity alternator into a properly wired 7 pin and you charge the RV battery while driving.
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Old 08-29-2019, 07:57 AM   #9
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I looked at adding the 2nd alternator on my Duramax. It's a factory option if ordering and there are several aftermarket kits but very pricey. I decided didn't need it as we don't have a residential fridge.

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alternator, charging

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