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Thread: Dual Battery Woes

  1. #1
    Newbie BigRedBee's Avatar
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    Dual Battery Woes

    I've got two batteries in my car, connected together with a Hellroaring battery isolator. One battery is a standard car battery. The other, isolated battery is an Optima Yellowtop. While the car is running, the alternator both batteries and all the loads are all tied together. When the car is off, the isolator seperates the deep cycle battery and carputer from the car's starting batter.

    My carputer is in standby mode most of the time, except while driving, and perhaps 20 minutes each day when it's running off of the isolated battery.

    My problem: After about 4-5 months of operation, the Yellowtop has a dramatically reduced capacity, and drops below 11 volts after just a short time (20 minutes) of use with the car off.

    Any ideas on my problem? I've actually had this problem occur twice now. The first time I thought it was just a bad battery.
    VIA EPIA M10000 | 7" Lilliput Touch VGA | PW70 | 256 Meg RAM | 20 Gig 2.5" drive
    Dual Battery with Optima Yellowtop | Hellroaring Battery Isolater
    ICOM 2720A| Delorme Earthmate GPS | Tiny Track APRS
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  2. #2
    Constant Bitrate spectrrr's Avatar
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    hmmm.... I'd love to hear thoughts on this too... i'm prettymuch doing the same exact thing as you, although my second battery is a used Optima truck battery. (found the hellroaring units to be a tad pricy, going to make my own).... anyway, if theres gonna be problems, I'd be interested in hearing too this one too =)
    2000 Jeep Cherokee
    -CarPC: [_____]50% complete
    -planning done, still need a few parts
    -In-dash motorized VGA is finally out, need $$$
    -Need to replace factory HU

  3. #3
    Newbie BigRedBee's Avatar
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    I found this in the FAQ on the Optima web-site. I certainly don't have independant charging circuits, HOWEVER, I believe that the Hellroaring isolator does not result in much of a voltage drop. Could my problem be related to lack of independant charging ciruits?

    Q: Can I use an isolator with an OPTIMA?
    Yes, most any type of battery separator or solenoid can be used with an OPTIMA. The important thing to remember is that the charging voltage must be within the limits suggested by OPTIMA Batteries. If you are using an OPTIMA and a conventional battery, your system must charge each battery independently. Remember, some isolators cause a voltage drop, make sure your charging voltage AT THE BATTERY is sufficient. Continued undercharging of a battery will lead to premature failure and a drop in capacity.
    VIA EPIA M10000 | 7" Lilliput Touch VGA | PW70 | 256 Meg RAM | 20 Gig 2.5" drive
    Dual Battery with Optima Yellowtop | Hellroaring Battery Isolater
    ICOM 2720A| Delorme Earthmate GPS | Tiny Track APRS
    Survives Crank

  4. #4
    Constant Bitrate spectrrr's Avatar
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    nice find.... gotta make sure i check that in my circuit....

    do you have a multimeter handy that you can check that with?
    2000 Jeep Cherokee
    -CarPC: [_____]50% complete
    -planning done, still need a few parts
    -In-dash motorized VGA is finally out, need $$$
    -Need to replace factory HU

  5. #5
    Newbie BigRedBee's Avatar
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    Multi-meter? yes. I've actually got a digital volt meter hardwired to the aux battery. It looks perfectly 'normal'. I'm more concerned about the 'independant charging circuit' comment.
    VIA EPIA M10000 | 7" Lilliput Touch VGA | PW70 | 256 Meg RAM | 20 Gig 2.5" drive
    Dual Battery with Optima Yellowtop | Hellroaring Battery Isolater
    ICOM 2720A| Delorme Earthmate GPS | Tiny Track APRS
    Survives Crank

  6. #6
    Newbie openminds's Avatar
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    The Optima Yellow top battery is a Deep Cycle battery. These batteries are designed to be charged then discharged. These batteries use a thinker plate and thinner Active Paste layer than your standard automotive Optima. Each time you charge the battery, you consume some of the paste.

    Now, in a situation like a camper or other system where the battery is fully charged than used as a power reservoir, you consume a small amount of this paste during your charge cycle and a little during your discharge. Usually this is done "not so often" so this paste lasts a decent amount of time.

    In a car, your battery is in charge mode whenever your car is running. I know there are regulators and what not, but trust me, your car is constantly charging your batteries. During this charge cycle, you are consuming this paste layer. And since this paste layer is much thinner (with thicker plates) than the standard automotive Optima, you have a much shorter life cycle with your battery.

    Sure, the capacity is attractive, but you will suffer with a shorter life. I have always ran standard automotive optimas and never had a problem. If you do want some extra capacity, use the Blue Top Optima. It is designed better for continous charging.

  7. #7
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    maybe

    maybe it is that the batteries (since they are different types) have different internal resistances, so they don't charge equally. Hence the need to charge each battery independently.

    ---- just my $0.02

  8. #8
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    this issue has been asked in one of my car audio magazines and what OpenMind said is almost exactly like what they said. their suggestion was to use a normal car battery and mount, vent it correctly. I think stinger makes a series of sealed batteries that are not deep cycle batteries.

    Optima batteries are usually used in race vehicles w/out an alternator, the battery will last long enough to run a race. In the car world, they are used to power systems during shows and while the vehicle is off.

  9. #9
    Newbie BigRedBee's Avatar
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    Thanks, Openminds, for the post. That explains why both times the battery has died shortly after a really long trip. I've just returned and gotten my third, new, optima yellowtop. Perhaps I'll return it in exchange for a bluetop.
    VIA EPIA M10000 | 7" Lilliput Touch VGA | PW70 | 256 Meg RAM | 20 Gig 2.5" drive
    Dual Battery with Optima Yellowtop | Hellroaring Battery Isolater
    ICOM 2720A| Delorme Earthmate GPS | Tiny Track APRS
    Survives Crank

  10. #10
    Constant Bitrate
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    I've used an Optima Yellow Top as my car's starter battery for over a year now. (90A max alternator output).

    No failure and voltages are correct.

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