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Old 12-14-2016, 04:10 PM   #1
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alternator amperage

A tow package from an suv manufacturer includes a 180 amp alternator. If instead a vehicle without the tow package has it installed at the dealer, it is a 160 amp alternator. Is 160 amps sufficient for towing (to charge the battery and supply the trailer lights).

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Old 12-14-2016, 06:15 PM   #2
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There is no way for us to ascertain whether or not 160 amps will do the job. It depends what your suv draws on severe use.

Usually a high end SUV with a tow package has all the bells and whistles. so on a rainy day you have the wipers on, engine running, heater on, defroster for the front and rear windows and the mirror heaters. the seat warmers, the GPS and stereo systems and the fog lights. The kids rear videos screens and maybe a movie going and the cell phones charging. now you add a larger alternator to power trailer usage because of modern luxuries sucking up all the juice. The larger alternator is usually built more robust since they are pulling larger loads.

Now you ask if the 160 amp alternator can do the same job. that depends on what your also willing to give up. even on a square trade saying that the 160 amp alternator is pulling 70% duty all the time and the 180 amp alternator is only pulling 50-60 % duty it going to last allot longer. the SUV with a tow package also is usually using a bigger engine to pull the load of both the trailer and larger alternator.

Then it all gets down to how its actually wired to get the juice you need at the trailer. If the wiring is too small for the amp draw you need you wont get the power nor will the regulator for the alternator sense you need more power and open up the charge rate for the battery even if you have the biggest alternator available.

Is not a simple question if 160 amp or 180 amp alternator will work. Back in the old days we used 40 and 60 amp alternators and you really needed a 100 amp alternator when you added more amenities and fuel injection to the engines. Then it became an energy race to the top.

Just not a simple question to answer.
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Old 12-14-2016, 07:30 PM   #3
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Here is another approach to the problem:

If you:

- disconnect the trailer battery charging wire (reduce power demand to 0 amps)
- convert all trailer running lights to LED (reduce total power demand to 1 or 2 amps)

then the 160 amp hour alternator should be sufficient.

EDIT: On the other hand, IF you also have electric trailer brakes, also need to consider that load. As Steve said, may not be a simple answer. You may need to determine the total power load on the alternator, etc.
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Old 12-14-2016, 07:42 PM   #4
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10-inch brakes draw about 4 amps per wheel.
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Old 12-14-2016, 08:46 PM   #5
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Trailers haven't changed that much electrically in the last fifty years,but tow vehicles have . A little perspective...
In 1970 a base alternator was about 45A, heavy duty was 60A, a few trucks had 90A.
My 2001 Ranger has a 130A alternator, 95A was standard. some vehicles ran as low as 42A up into the 1990s.
Read post #2 again, stevebaz gave an excellent answer.
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Old 12-15-2016, 02:27 AM   #6
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Originally Posted by Ericpa3 View Post
A tow package from an suv manufacturer includes a 180 amp alternator. If instead a vehicle without the tow package has it installed at the dealer, it is a 160 amp alternator. Is 160 amps sufficient for towing (to charge the battery and supply the trailer lights).

thanks!
The 160 amp alternator will provide way more than the trailer will ever see through the trailer plug wiring from your TV. So, yes the smaller alternator you mentioned is "enough".

You probably won't see more than about 15 amps charging current getting to the trailer. The 160 amp alternator can charge the TV batteries at a high rate so you can have lots of power hungry options and charge while idling, but the trailer won't see it. The wire is not big enough to support that amount of power.

A large alternator is handy for running an electric winch for long periods at a time, or lots of auxiliary lights while idling at a job at night or for quickly re-charging dual batteries in diesel trucks, etc. But not for heavy trailer power draw.
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Old 12-15-2016, 09:46 PM   #7
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The 160 amp alternator will provide way more than the trailer will ever see through the trailer plug wiring from your TV. So, yes the smaller alternator you mentioned is "enough".



You probably won't see more than about 15 amps charging current getting to the trailer. The 160 amp alternator can charge the TV batteries at a high rate so you can have lots of power hungry options and charge while idling, but the trailer won't see it. The wire is not big enough to support that amount of power.



A large alternator is handy for running an electric winch for long periods at a time, or lots of auxiliary lights while idling at a job at night or for quickly re-charging dual batteries in diesel trucks, etc. But not for heavy trailer power draw.

I second the 160 amp will be more than enough.


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Old 12-16-2016, 08:30 AM   #8
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And, very little electricity is used during daytime travel.
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Old 12-16-2016, 12:13 PM   #9
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My 2016 Town & Country minivan has a 160 amp alternator with the towing package. The 2017 Pacifica replacement has a 220 amp alternator with the package.
I think 160 is enough myself.


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Old 12-16-2016, 12:28 PM   #10
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The size of the needed alternator is very dependent on the vehicle. My 2005 Dakota draws over 100 amps idling with very little on. That an 11 year old vehicle. New ones require more. The best be it to always go with the manufacturer's recommendations. I don't know of any automotive electrical engineers on the forum. So the information provided is by these folks is just a guess.
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Old 12-16-2016, 12:56 PM   #11
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If your goal is to charge your trailer batteries while traveling I would say forget it.
Wire gauge and distance are your nemesis in this situation.
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Old 12-16-2016, 01:11 PM   #12
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If your goal is to charge your trailer batteries while traveling I would say forget it.
Wire gauge and distance are your nemesis in this situation.
20'+ of gauge 10 wire gives me enough power to charge trailer battery and run Dometic 2193 refrigerator on 12V. Also I installed relay which turns on 12V power to the refrigerator only when TV's engine is on.
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Old 12-16-2016, 01:40 PM   #13
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Originally Posted by sokhapkin View Post
20'+ of gauge 10 wire gives me enough power to charge trailer battery and run Dometic 2193 refrigerator on 12V. Also I installed relay which turns on 12V power to the refrigerator only when TV's engine is on.
A larger dedicated charging wire is my thought as well. I'm getting ready to do just that. I question using only 10 gauge wire though. I'm thinking 2 gauge or larger. The easiest place for me to tie in would be at the battery terminal since the alternator is in an awkward place. I am planning on enlarging the ground from my battery to 2 gauge as well.
I want to use the "Battery Doctor 150 AMP 12 Volt Battery Isolator" to keep the vehicle battery from discharging when parked. Does anyone have any experience with these electronic controls vs using a solenoid or diodes?
I also don't see why I cannot just route the return to a good negative ground by the bumper of the tow vehicle instead of all the way back to the battery. Any thoughts on this would be appreciated.
And what kind of connections were used by those that went this route. I can't just use the terminal in the 7-pin round connector and don't want to screw it down on the battery either.
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Old 12-16-2016, 02:43 PM   #14
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On my T&C the OEM cable runs directly from the battery input to the fuse panel, but I added a cut off relay to break the power with the car engine off.
The odd thing is that the ground to the 7 pin plug is also run all the way to the ground on the firewall behind the battery almost doubling the voltage drop.
When I have time I am going to double the power wire using that ground wire and ground the 7 pin to the frame in the rear.
With the trailer hooked up the engine running the power meter in the trailer read 13.75 volts, but I did not measure the current being used or the voltage at the car battery.


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Old 12-16-2016, 06:35 PM   #15
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I'm thinking 2 gauge or larger.
Gauge 2 is overkill and waste of money. You need gauge 2 only if you need to run a winch or electric crane/wheel chair lift at the back of your TV. Run gauge 10 and use standard 7 pin connector to provide power to the trailer.
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