20 AMP load on 12VDC system an issue?

Discussion in 'Prius v Technical Discussion' started by Paul Anderegg, Sep 7, 2013.

  1. Paul Anderegg

    Paul Anderegg Junior Member

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    I am in need of some technical information regarding the Prius v's 12 volt electrical system, hopefully with some official reference links.

    I work at a television news station, and we are looking into the feasability of using a Prius v as a news gathering vehicle. The reason I selected the v was due to the fact that it can "take" a full length 30 inch radio console between the seats, after removing the factory console and relocating the button cluster of course. Also a big deal is 40MPG vs 15MPG for a standard large SUV, which is what most TV stations run in the field.

    My chief engineer has requested some specifics about what type of current draw my 12v components draw, as well as current draw for such things as headlights and A/C system. We so far have hooked up the current vehicle used for this task, and the total 12v draw from the 9 scanners/radios as well as the 800 watt power inverter charging a laptop is around 10 AMPS. One of the radios transmits once in a while in short bursts, tacking on an aditional 10-13 AMPS during those brief periods.

    The car will be run 100% out in the field at night, with the full volley of radios receiving for a 9 hour shift. Currently, the longest "inactive" periods I see sitting in the vehicle would be about 1 hour, and passing an hour and a half my power inverter starts to squel a low voltage warning, at which point I must run the engine for a while to charge things up. With the heat lately, I have also found myself running the engine to keep the AC going. Another common thing would be to be out on a scene for 30+ minutes with the vehicles parking lights and radios left on, like at a freeway traffic fatality scene. We use Optima Yellowtop batteries in many of our vehicles, and the version in my current CR-V is very small.

    So, those are the facts. Here is what we really need to know.

    Can the 12v charging system handle a 10 AMP constant load if I am sitting in the car all night in "ready"? Will the engine just kick on every now and then, or is there some sort of relay that activates a charging mechanism from the drive batteries? Next, is there any concern hitting the car with that extra 10 AMPS on top of the steady 10 AMP when the two-way radio transmits? Also, where can I find the official Toyota technical specs for these systems, so that my chief engineer can see these first hand?

    Any quality links you might be able to share to posts discussing any of the specific aspects of the Prius electrical system would be greatly appreciated! :)
     
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    I know that there is a 100 amp fuse between the 12 volt battery and the Inverter, so that is the upper limit for sustained current draw.

    TIS

    Is the portal to Toyota wiring diagrams.
     
  3. Flying White Dutchman

    Flying White Dutchman Senior Member

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    it would be smart to put a exatr battery in the car to have longer 12 volt running when on acc. mode.
    of course for this the HSD is perfect it wil only start the ICE when the HV battery starts to run down ) the 12 volt will never run down when the car is ON.
    so when you put it in acc. mode you have a fully charged 12 volt batterys(s)
    but again the prius battery is small so you need some more for that.
    better to put a relay between the extra battery and the 12 volt prius battery
    when that extra battery runs down you start the prius and the relay will close again starting to charge the extra batter with a max 100 amps.!
     
  4. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Stay in Ready.
     
  5. Flying White Dutchman

    Flying White Dutchman Senior Member

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    so they can drive of in your car when you filming?
     
  6. rdgrimes

    rdgrimes Senior Member

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    The car is fully capable of handing those loads as long as the hybrid system is on and in "ready" mode. However if you shut it off the smallish 12v batt will drain quickly.

    There are several extensive threads here about using Prius as an emergency generator which might provide you with the technical info you need. But my recollection is that you can expect the 12v system to deliver 1000w continuous load, maybe more if long cables are not involved. Peak or surge loads can be a lot higher. Your 800w inverter is certainly no problem, people are using 1500w inverters to power their homes. There are higher power alternatives that involve tying directly to the traction battery (240v) but this involves extensive modification and expertise.

    The key to all this is, of course, having the car "running". The ICE will cycle on and off as needed to maintain the traction battery, probably a few minutes on and a few minutes off. No question that the gas savings will be substantial compared to your SUV alternative, which no doubt would be left idling.

    Security: With the smart key system there are special considerations if the system is left running and you need to leave the vehicle. The only way to lock it while running is with the mechanical key.
     
  7. Paul Anderegg

    Paul Anderegg Junior Member

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    Thanks for the replies guys!

    I have read a bit regarding the use of Prii as generators, but I was under the impression these were plug in electric versions, and not normal hybrids?

    SO, here is what I am thinking, correct me if I misunderstand anything. If I am in the car and have everything turned on, with the vehicle in "ready", the drive system batteries will charge the 12V battery, and the engine will kick in from time to time to replenish the drive system batteries which are being used to juice the 12V one? And the drive system batteries are referred to as "HV", high voltage?

    My plan may be to install a relay and switch, so that I can "kill" the entire console/inverter with one flip of a switch when I leave the car for any significant length of time. Would the kill switch be a better and simpler option than installing a second battery? My current CR-V has a physically small, like 450CCA Yellowtop battery, which can take the 10 AMP draw for about an hour and half before succumbing to the drain, but if the Prii is always providing 1000watts while in ready, then I think this will work! :)
     
  8. rdgrimes

    rdgrimes Senior Member

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    There are threads for both types of systems. The only difference would be when you're tapping the hybrid battery directly, which you're not doing. For 12v taps, no difference.

    Semi-correct. When the hybrid system is on, you're drawing power from that. There's no charging of the 12v batt unless you've previously discharged it. The hybrid system is high voltage, but the car is running on 12v. Just think of the hybrid system like an alternator on any other car, only huge.

    I'll refer you back to the dedicated threads for Prius as generator. People have come up with different methods of disconnect for the inverter. I think you can draw more than 1000w, that's just a number that's been suggested for longer runs of cable. With 6ga wire in short runs you should be able to pull even more. You'd also want to place a fuse in the hot lead from the battery. I think it has a 80 amp fuse already for the battery, but adding a smaller one for your inverter is prudent. In my reading of those threads I also noted the recommendation for using the more expensive "sine wave" inverter to avoid issues than inverters tend to introduce. I'd also suggest an inverter that offers a readout of voltage, load, etc, so you can track what your drain actually is. If everything is shut off and no drain on the inverter, a disconnect or off switch is purely a safety.

    I don't see any need for a second battery, what with all the issues that brings, unless you need to run things with the hybrid system off. Go for a larger 1500w inverter too, and you'll be set if you ever lose power at your home for 3 days. ;)
     
  9. rdgrimes

    rdgrimes Senior Member

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  10. ChapmanF

    ChapmanF Senior Member

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    I can't think of any compelling reason to add more battery. It would only make sense if you wanted to run stuff a lot with the hybrid system off. As long as the car is in ready, you've got all the capacity you need, and the engine will only cycle on when needed. It's really quite slick for the sort of thing you're considering.

    Instead of a dumb switch, you might look into an InPower VCM-06 module, which only needs connection to the battery and will turn on when you put the car in ready. (It doesn't need any other connection to the ignition, etc., because it can detect the hybrid system is on by watching the 12V battery voltage.)

    You can set it to turn off right away when it detects you've turned the car off, or set a time delay. In the time delay it also watches battery voltage and will always turn off before leaving your battery discharged.

    It should run maybe $60-ish. It can handle a load up to 15 amps directly. For a larger load, you can add a relay and use the VCM-06 to switch it.

    -Chap
     
  11. CrazyLee

    CrazyLee Member

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    I have a Gen2. I run a cooler that draws 3.75 amps. = 45 watts.

    On a long trip the 12v battery would slowly draw down and that forced the engine to work harder to keep the 12 v power up. My fuel mileage went down because of that. I don't remember exactly, but it was small, maybe 5 mpg. I cycled the cooler power after that.

    You probably see more drain with more drain.
    I accidentally blew the under dash 15 amp fuse for the cigar lighter. The 400 watt inverter power wire came off and shorted. It took a while to find and replace the fuse.
     
  12. bat4255

    bat4255 2017 Prius v #2 and 2008 Gen II #2

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    For budgeting purposes, I would assume 30-35 mpg's and not 40. Whith the extra load you plan on, it will be tough to even get 35 mpg average.
     
  13. D_n_D

    D_n_D Junior Member

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    I have a 2013 v3 and when mostly flat roads avg 48mg. Carrying about 400lbs usually.
    now that most of my trips are up/down hilly roads I avg 36-38.

    I would love to see news use a prius v. I hate news vans/suvs they rarely pay attention.

    Posted via the PriusChat mobile app.
     
  14. bwilson4web

    bwilson4web BMW i3 and Model 3

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    My experience with both the 2001-03 and 2010-2015 was ~75A was the maximum draw, lights and other accessories off, before the charging voltage sagged. My interest was emergency house power so after conversion, no more than 1 kW usable: Prius - UPS Project

    You have a similar requirement that taxi companies face. You might approach the dealer and/or Toyota directly to explain you have a variation of a taxi electrical configuration.

    I would consider using a Schottky diode setup with a 'jump' battery. It would take a charge but should the voltage go too low, the diode protects the jump battery so it can jump the car. Alternatively (and more desirable) would be 12V cut-off relay for the load (check with RV suppliers) that can isolate the extra load if the 12V bus falls below a fixed cutoff, ~12.2 VDC.

    Having run over four days during an extended power outage, just keep the car in READY and make sure there is gas in the tank. Unlike ordinary car, 12V systems, the engine will cycle while you still have the full, 12V capacity.

    GOOD LUCK! (sounds like a great project!)
    Bob Wilson
     
    #14 bwilson4web, Jan 18, 2017
    Last edited: Jan 18, 2017
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  15. Yaesu

    Yaesu Member

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    Based on the responses and additional reading, it appears that under typical driving conditions (no high speed fan, rear window defroster, headlights, windshield wipers) it appears that there is sufficient charging power from the drive battery to charge the 12-volt battery to run the cooler. I will install a digital volt meter for a while to monitor the 12-volt battery.
     
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  16. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Better still, a Scangauge II. <GRINS>

    Bob Wilson
     
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