Sunday, October 25, 2015

High Output Tow Vehicle Charging System

If you recall, my average estimated draw down of my battery system is 200ah - 50% of the 400ah capacity.  That's actually quite a bit of power and can run my HVAC for several hours.  My tow vehicle is a GMC Sierra 1500 with factory towing package, so it has a decent alternator on it already without going to a special high-output alternator.

The standard 7 Pin towing hookup does have a hot lead for charging an RV battery, but that is really only for keeping a small RV battery charged while driving - not for charging a high output system like this one.  The hot lead on a towing vehicle has a 12AWG wire and a 30 amp fuse.  This just isn't designed to handle the load of the large batteries I have, and the small wire size limits the current and takes too long to charge large batteries.

Another consideration for this setup is isolating the vehicle battery from the trailer batteries so you don't run the vehicle starting battery down while you're using your trailer on battery power.

In researching this topic, I came across the Hellroaring Battery Isolator and Combiner which not only is a great product, but they have some excellent Application Notes that explain how to design your charging system as well as excellent Technical Support to help you.  You can isolate your battery with a cheaper relay that are often used for cars with high output stereos or trucks with winches, but I would highly recommend spending the extra $ for a higher quality solid state system like the Hellroaring. 

 Using this description of the setup and I followed the recommendation from Hellroaring to use 25 feet of 8AWG wire.  The amount of wire highly influences the load on the charging system and I sketched my design and sent it to Hellroaring's technical support, and they were very helpful.  My setup should generate approximately 50 amps per hour which will charge up my 200ah of average daily use of my batteries in 4 hours of driving.    

I used a 60 amp fuse on each end of the positive wire, starting at the vehicle battery, and on the other end where I connect to the battery bank.  The red wire below shows the positive 8 AWG wire and fuse block at the battery:
   

I covered the wires with flexible conduit tubing before routing across the engine compartment and used zip ties liberally to hold the wires in place.  


I grounded the negative wire to the large strap that grounds the engine block to the vehicle body in the engine compartment (the yellow connector in the picture below).



I mounted the Hellroaring isolator in the engine compartment (the square block with fins below) and the positive goes into and out of the isolator, and then to the trailer.




Both positive and negative wires were then run along the frame to the rear of the truck and I mounted a standard 12v winch battery quick connect plug on the end.  Here it is below sitting on my rear bumper with the rubber plug cover:



I connected the same type of plug to the trailer batteries mounted on the tongue of the trailer so its a simple job to plug-in and hook up the trailer.  

7 comments:

  1. Hi Ron interesting set up on your truck / trailer battery charging. My 2 cents worth I would say use a number 6 or even better #4 marine stranded copper wire. Use metal zip ties as plastic breaks easy. Your wire run needs to be figured for + &- run, 25 ft is really 50 ft and I'd bet my life 50'#8 your getting 10% drop. Measure volts at your bumper plug vs at the battery. The fuses will cause additional % loss.if your alternator is doing 14.0 your rear plug might only get 13.2 volts. Not enough to charge your 400 ah battery. Also if your battery is down 200 ah - you need to charge in 260-280 ah as battery's are only 75% efficient.

    If you could get some lithium batteries 200-300 ah would kick the crap out of your current batteries. I wouldn't go back to roof ac or old sealed batteries if you put a gun to my head.if you could get about 750 watts solar on the roof , your set up would be kicken ass, I think it would run on a Maginum 1,000 psw inverter , which also has a 50 amp charger for 120 volts , run it with honda eu2000 as back up.

    Keep in touch
    Fahrensiemit@gmail.com

    Cheers OTTCT

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  2. Good feedback. I'll do some more measuring of my charging system. I'd love to go to lithium batteries - just can't quite get over the cost difference. Thanks.

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  3. Good feedback. I'll do some more measuring of my charging system. I'd love to go to lithium batteries - just can't quite get over the cost difference. Thanks.

    ReplyDelete
  4. Great effort that the amount of wire highly influences the load on the charging system and you sketched your design and sent it to Hellroaring's technical support, and they were very helpful. Thanks for sharing this lovely post.

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