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Charging my RV battery

Discussion in 'Towing' started by Isthatahemi, Apr 7, 2010.

  1. Isthatahemi

    Isthatahemi [OP] Well-Known Member

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    I'm going to be doing a lot of dry camping this year with my pop-up camper. I will be using the truck to charge the batteries, and run the fridge while en route. When I am stopped, I am thinking I won't get more than 2 days out of my battery, less if my wife is using her hairdryer. I have 2 methods available to recharge the batteries...
    1. Plug the 120V / 120V converter into the 120V inverter power in the box of the truck, idle the truck. (converter draws 360w max)
    2. Plug the 7 pin wire harness, and idle the truck.

    I think that method 1 will charge the battery quicker, and to a much higher level. Mostly because all voltages are regulated up this way. Method 2 is more conventional, but at idle, I doubt the alternator will produce enough voltage to charge the battery fully. I think the combination of voltage drop, and the alternator not cranking out full voltage, will be slow, and not terribly effective.
    Any thoughts?
     
  2. TimS

    TimS Well-Known Member

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    The most important thing is to unplug your trailer from the truck so you don't discharge your truck battery. There are dual battery systems out there that have automatic seperation from the 2 batteries once the truck is shut off. I decided to just unplug my pop-up. I also have a fridge and a couple of lights and thats it.
    We just recieved from Northern Tools a solar battery maintainer. $150.00. I plan to hook that up during the day to maintain the trailer battery. I hope to try it this weekend if I get some time.
     
  3. Isthatahemi

    Isthatahemi [OP] Well-Known Member

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    The Tacoma has a relay that disconnects the charging circuit when the key is removed.
     
  4. TimS

    TimS Well-Known Member

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    You must have the factory tow package. I installed mine with stuff from e-trailer. There is constant 12v power to the plug on the truck.
     
  5. Isthatahemi

    Isthatahemi [OP] Well-Known Member

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    I think you may have missed the point of this thread......
     
  6. Isthatahemi

    Isthatahemi [OP] Well-Known Member

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    Yes, as in plugging the 120/240 plug from the camper's charger / converter unit into the back of the truck.

    On my truck with the scangauge, and using a voltage tester, I found out that the max voltage at the trailer battery after driving for 2 hours was 12.4 volts, (13.3@ on the scangauge) is not sufficient to charge the RV battery, (13.6 would be required to fully charge it). This is probably due to the undersized wire on the tow package, leading to a large voltage drop. This was also while running the fridge on 12v, as it would be while traveling. So I have now determined that the only way to get a full charge in a reasonable amount of time is to plug in the converter. It kicked out of bulk charge mode after about an hour. So the efficiency of the regulated 120v inverter to 120v converter is the only way to go. Not to mention, while running the inverter to charge, the truck was only consuming <2 liters of fuel per hour. Revving the engine did not noticeably change the voltage at either end.
     
  7. Isthatahemi

    Isthatahemi [OP] Well-Known Member

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    I should note as well that I was able to get a good charge just by using the inverter / converter combo without starting the truck. My Tacoma has a large enough battery (160 mins reserve capacity), that it should be able to safely run the inverter for an hour without having to start the truck>
     
  8. MJonAgs32

    MJonAgs32 asphinctersayswhat?

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    Look into getting an oscillator. Either that or generator is the best route.
     
  9. maju

    maju Well-Known Member

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    I would think that you should be able to use a solar charger its not like your going to use the electric all day while camping. Youcould get a second battery and have one on the solar charger and one in use. and just swap them out periodically.

    http://www.batterystuff.com/solar-chargers/
     
  10. Isthatahemi

    Isthatahemi [OP] Well-Known Member

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  11. Isthatahemi

    Isthatahemi [OP] Well-Known Member

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    Why would I buy a generator, when the truck charges it just fine,:confused: the fuel consumption per amp / hour is also very reasonable.......
     
  12. Isthatahemi

    Isthatahemi [OP] Well-Known Member

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    I was meaning to say that the point of the thread was about using the truck to charge, and avoiding the generator, solar or what ever other methods are available, given that the truck has ample charging capacity, I see no reason to lug around extra equipment, that's all.

    Anyhow, our camper has a shower, furnace, interior / exterior lights, 1500 watt inverter, ventilation fan, etc.. We rarely stay in one spot for more than 3 days, so we will be charging through the 7pin while towing, and through the inverter when needed while stopped. I
     
  13. Isthatahemi

    Isthatahemi [OP] Well-Known Member

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    Dry camped for 2 weeks, used the inverter plug in the box to charge the battery for appoximately 4 hours a day. I would charge in the morning for 1 hour idleing, one hour truck turned off. Same in the evening.
    I should note the my Tacoma sucks for charging while towing, I always arrived with a cold fridge, and a almost completely dead battery. Stupid truck only sends 13.4 volts to the charging pin on the 7 pin. Useless. 14 volts is the minimum required at the connector to have adequate supply, very disapointing considering the cost of the towing package. I understand the battery will not fully charge this was, but after 14 hours of continuous driving, the battery should be higher than 11.7 volts (dead).
     
  14. Isthatahemi

    Isthatahemi [OP] Well-Known Member

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  15. skytower

    skytower Well-Known Member

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    Sounds to me like you need a stronger alternator, or a second one. It's quite alot to ask from a alternator to run that much equipment.
    If you're not getting the right voltage at the trailer, you may need a larger gauge of wire.
    As for the booster, I would think that it will put an even larger load on your alternator. Usually those are for protecting sensitive electronics, right?
     
  16. genxer36

    genxer36 Lord of Tomfoolery

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  17. Isthatahemi

    Isthatahemi [OP] Well-Known Member

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    Tha Tacoma only puts out around 13.4 volts under normal conditions. Not enough to supply a fridge and charge the battery at the same time. Heavier gauge wiring will help, but the dc dc booster will solve the issue completely, whereas thicker wire only helps a little, again because the Taco runs 13.3ish, as opposed to every other vehicle I have worked on that runs 13.6 - 14.4.
     
  18. skytower

    skytower Well-Known Member

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    The voltage is only half the equation. Your alternator can only push so many amps at its rated voltage. Try to pull more and it will eventually fry.
    The fact that your battery is dead after driving with all the accessories attached is enough evidence for me to say you're overloading the alternator.
     
  19. wiscdave

    wiscdave Lets Do It!

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    mod the rear outlet to run 400w all the time as found here on this great forum and you wouldn't have wasted your gas idling for an hour.. LOL
     
  20. Isthatahemi

    Isthatahemi [OP] Well-Known Member

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    The alternator is not even straining to provide the power, it is just loafing along. I have the towing package with the big alternator, and it is completely normal to run a 12v fridge and charge the rv battery while towing. The problem is twofold, voltage drop from to the 7 pin, and low voltage from the alternator. The alternator is controlled by the ECU, so there is no changing that.


    That is one common use for them. And yes it will put a load on the alternator, but that is the idea. There is still the main fuse, and the charging line fuse protecting the electrical system on the truck. Basically I am just going to regulate the voltage to around 14.4 volts, as that is what is necessary to charge a deep cycle battery fully, while powering the fridge.
    I will likely be using it to charge the battery while dry camping as well if it works well, as opposed the plugging the trailer converter / charger into the inverter plug in the box.
     
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