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Battery use for accessories

Discussion in 'Gen 2 Prius Audio and Electronics' started by oceansoul7, Aug 16, 2013.

  1. oceansoul7

    oceansoul7 Junior Member

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    I have a 2008 Prius that I'm taking to go car camping. I'd like to run an accessory (a CPAP for sleep apnea) that will consume about 12 amps per night. I'm camping for 5 nights and will be using an modified sine wave inverter to get from 12v to 110 v. Can I safely tap into my batteries and if so, how? I'm fairly sure simply using the battery under the hood is not an option. I'd prefer not to run my car simply to charge the batteries and will not have access to a battery charger. My other option is to buy a deep cycle marine battery, but I'd like to see if I can work with what I have first.
     
    #1 oceansoul7, Aug 16, 2013
  2. vskid3

    vskid3 Active Member

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    There is no battery under the hood. The 12v and HV battery are both in the trunk. The 12v is smaller than the one in most cars, though. I assume you meant 12Ah at 12v? That will probably be too much for the little battery. A bigger deep cycle would be the way to go, but you'll still need to charge it at least every other night, whether it be with the car or maybe solar panels.
     
    #2 vskid3, Aug 16, 2013
  3. bisco

    bisco cookie crumbler

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    you can run a 1000w inverter off the 12v, leave the car in ready and the hv battery will keep it charged and the ice will run when necessary to top up the hv battery. believe it or not, if you can find it, there's another thread here somewhere from someone else who wanted to camp and run a cpap. or else i have de javu!:p
     
    #3 bisco, Aug 16, 2013
  4. oceansoul7

    oceansoul7 Junior Member

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    Thank you. A few more questions in response:
    1) The accessory I'm running only needs a 150 w inverter and draws about 1.1 amps per hour, and I plan on using an inverter rated at 300w continuous use because that's what I have-should that be OK?
    2)Where is the best place to connect my inverter? I have both a cigarette lighter adaptor and alligator clamps.
    3) How do I engage my car in "ready"?
    4) Does this procedure make sense for 8 hours a night for 5 nights? Any sense of how often my car while need to start up and recharge given this electrical draw and how much gas it might burn? Obviously I don't want to jeopardize my car in any way, as I'll be far removed from any mechanic.
     
    #4 oceansoul7, Aug 17, 2013
  5. oceansoul7

    oceansoul7 Junior Member

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    What do you think of Bisco's response to my question:"
    you can run a 1000w inverter off the 12v, leave the car in ready and the hv battery will keep it charged and the ice will run when necessary to top up the hv battery. believe it or not, if you can find it, there's another thread here somewhere from someone else who wanted to camp and run a cpap. or else i have de javu!​
    :p​
    "

    reg. a deep cycle marine battery, my understanding is that I can safely draw 50-60% of it's capacity before recharging. Since I only need 44 amps total (1.1 amps per hour for 40 hours), wouldn't I be fine using a battery rated at around 100 amp hours without recharging?
    ​
     
    #5 oceansoul7, Aug 17, 2013
  6. bisco

    bisco cookie crumbler

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    sorry, i've run the limit of my expertise on inverters, i'v never used one myself. i'm sure you'll get more answers in due time. in the meantime, if you want to do some searching, there are a bunch of threads here on using prius as generator.
    i can tell you to make the car ready, you put your foot on the brake, and press the power button. same as starting it, makes the ready light come on as opposed to not putting your foot on the brake which is accessory mode and the ice won't fire. you won't hurt the car at all in ready mode, that's what it was designed for.
     
    #6 bisco, Aug 17, 2013
  7. ftl

    ftl Explicator

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    Your 1.1A draw at 120v is 11A at 12V (the power draw, amps times volts, has to be the same on both sides of the inverter; in fact you'll be pulling a bit more than that out of the battery because of losses on the inverter). So you'll quickly kill the 12V battery.

    As advised, just put the car in Ready mode so that the traction battery will keep the 12V battery charged. The engine will then come on for about half a minute or so every once in a while to top up the traction battery.
     
    #7 ftl, Aug 17, 2013
  8. vskid3

    vskid3 Active Member

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    I don't know how much gas you'll use leaving the car in "ready" all night, but I'm sure it would cost quite a bit less than such a large deep cycle. I would leave it in ready and hook up the inverter to the stock battery unless you'll already be at the limits for gas. Just be sure the exhaust is pointing away from wherever you'll be sleeping.
     
    #8 vskid3, Aug 18, 2013
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