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Supplemental battery power

Discussion in 'Gen 2 Prius Technical Discussion' started by retired prof, Aug 29, 2022.

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  1. retired prof

    retired prof New Member

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    I need expert technical advice, so I'm including what I think are relevant details...

    A few weeks ago I brought my 2005 Prius with 60,000 miles in for normal service. I may only drive 10 miles, once a week on average. As part of the paperwork, I got the printout of the general health of my car.

    Because this question is concerning the battery, I will say that the battery check came back as green...no problems or concerns. A few days later, I added a Compustar alarm system that completely drained my battery in 2.5 days.
    I jumped the car and brought it back to the dealership to ask about the health of the battery. They rechecked the battery and even though the battery checked out as normal voltage, even under load (green), I decided to install a new battery because the one that died was 10 years old.

    So, here's the question; Can I attach a device such as a lithium jump starter to the 12-volt battery to increase the length of time between my driving the car and the inevitable discharge of the battery. Because this would be like adding a second 12-volt battery (I'm thinking this would be attached creating a series circuit), will this device:
    1) add excessive amperage to the electrical system, therefore risking the onboard computer system.
    2) overheat the existing battery since the add-on device is acting as a trickle charger
    3) Do I need to attach the device to the 12-volt battery (in the hatchback) or can I use the jumper terminals
    located under the hood. Would it be possible to use the cigarette lighter as an electrical port for this device.

    I plan on disconnecting the device BEFORE I drive.

    Just FYI, Compustar has been uncooperative in this matter saying that this amount of draw is NORMAL and won't run any diagnostics to see if the device is faulty and will not divulge any data about the device's electrical needs. I will not bring my car back to the installer because I question his competence and his ego will not allow him to admit an error.
     
    #1 retired prof, Aug 29, 2022
  2. Tombukt2

    Tombukt2 Senior Member

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    I mean you could put your test meter on the hot lead that feeds that alarm system. And see what kind of draw you have just sitting there leave the flukey plugged up all night whatever I don't think my GB70 noco will keep my 12 volt in the back up if I turn it on and it's cycling the meter's running back and forth chasing they call it it will only do that until it establishes that it's connected and then it will turn full green ready for somebody to start the car if somebody doesn't do that starting the car that is the noco will turn off. I don't know about other branded starters lithium thing he's minus the noko 2000 GB 70. I mean if you're willing to do all that why don't you just have the standard two prong battery tender leads connected to your 12 volt when you park your car you crack the hatch drop the mail part of the plug in the trunk and plug it up close the trunk it will lock with the cord sticking out it's thin Don't get it in the lock and your tender can sit there for months long as it's plugged in in the power doesn't go out. If you absolutely have to do it up front same business you can still close your hood and be connected to the fuse box jumper points just realize that if somebody pulls on the wire or something that mess will come off up there easier than it will at the battery if you have the tender leads at the battery when it's plugged up you're not going to easily unplug it by fooling with the cable with the trunk closed.
     
    #2 Tombukt2, Aug 29, 2022
  3. mr_guy_mann

    mr_guy_mann Senior Member

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    You need to measure what the draw on the battery is. Normal draw on a Prius is under 20mA.

    You can live with up to 50 mA IF you drive an hour or more every day. If the car sits, then get a trickle charger for it, or remove the alarm.

    Booster packs do not have high reserve capacity- they are designed to put out a large current for a very short time. Not a "small" current over days. Some units will "turn off" after a while.

    Posted via the PriusChat mobile app.
     
    #3 mr_guy_mann, Aug 30, 2022
    Last edited: Aug 30, 2022
  4. bisco

    bisco cookie crumbler

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    there are threads here where people add another 12v lead acid for audio accessories, etc. and it seems to work well. i would search them for advice and hook ups.
     
    #4 bisco, Aug 30, 2022
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