Car Batteries, and How Low Can I Go? - The Odyssey PC680

Discussion in 'Tech Articles, How-To's & Write Ups' started by mcglsr2, Aug 15, 2016.

  1. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Hey everyone. Recently, I did a pretty massive re-wire on my 95 Mustang. Without getting into the details, suffice it to say it involved a battery relocate. For various reasons, I became interested in the Odyssey PC680 - which is technically a motorcycle battery.

    SUPER MEGA IMPORTANT UPDATE: The PC680 IS NOT ENOUGH. The car eventually stalled and would not re-start, and would not take a jump. Hooked up the original battery temporarily, and the car started up just fine. So, I'm leaving the rest of the post for posterity and informational purposes, but understand: the PC680 DID NOT WORK FOR ME. It was just too small of a battery to work consistently and reliably.


    The PC680

    The big question I had (and struggled to find an answer online) was: Will this battery reliably and repeatedly crank my Mustang?

    The answer so far: It would seem so. The tests:

    • Battery fully charged, start the car: Car Started, Yay!
    • Idle the car for 10 min, turn it off, start the car: Pending...
    • Idle the car for 20 min, turn it off, start the car: Pending...
    • Drive the car for 5 min, turn it off, start the car: Pending...
    • Drive the car for 20 min, turn it off, start the car: Pending...
    • Battery fully charged, start the car, idle for 10 seconds, turn it off, start the car, idle for 10 seconds, turn it off, etc. (repeat until car won't start): Pending...
    • Let the car sit for 5 days off the trickle charger, start the car: Car Started, Yay!
    • Let the car sit for 7 days off the trickle charger, start the car: Pending...


    I Will Elaborate

    I haven't driven the car much yet with this battery. I'm taking it slow as I don't trust it yet, and don't want to get stranded somewhere. What I've noticed, though, is that when the battery has a full charge, it cranks my car with no problem (see details on my car below, as your car and thus experience may be different). After driving the car for a bit, and then parking it, and then trying to start it again, the starter *does* drag. However, the car still started. I did this about 5 or 6 times in a row - started the car, ran it for a couple seconds, turned it off, started it again, etc. Each time it did start. And each time, the starter dragged.

    So it's not a failure. It does work. I'm currently building up my confidence in it. There's a series of tests that I will run it through and report my findings on once I've completed them. I will update this thread as I complete those tests.

    Another thing to keep in mind is that I live in Florida, so it doesn't really get that cold here. I have yet to try the battery in "winter" but I expect it's performance to be a little worse. Having said that, it won't be as cold as it could be for some people reading this, so keep that in mind. The colder it is, the harder it will be for this battery to start the car.


    Battery Maintenance

    The downside to this battery, because of it's size, is that it doesn't have a lot of reserve. So if the car sits for any length of time, with the computer and alarm stuffs putting a constant (though very small) drain on it, it will eventually fall below cranking voltage. So I put the car on a battery tender every now and then to make sure the battery stays fully up.

    Also, because I don't trust the battery yet, I carry with me a portable battery jumper - just in case the battery, for some reason, doesn't quite have enough oomph to kick the car over.


    The Future

    So the jury is still out on this battery. It seems to mostly work, and I'm working on figuring out when it won't work. If, at any point, I decide that this battery just isn't big enough, then I will step up to the slightly larger Odyssey PC925 which I feel confident will have no issues starting this car.


    Specifics on My Car

    Whether this battery will work for you or not depends on your car, the size of the motor/compression ratio, the amount of amp draw all the electronic stuffs pulls, etc. For me, in my car, it's a stock 5.0L motor with currently stock compression, about 9.2:1. I am not running anything super power hungry like amps, though I do have an aftermarket radio, aftermarket gauges and stuff like that. I would say my power draw is fairly low for a car that still has most of it's creature comforts (radio, A/C, power door locks/power windows, etc.). I also have an aluminum flywheel, so it's a bit lighter than the stocker.

    If your car has more compression, this battery might not work for you. It depends on your compression ratio and how hard it is to turn over. Also if you are running a bunch of amps and stuff, this battery is probably too small, unless you have other batteries that the amps are using. But then, if you are running a bunch of amps, you probably aren't concerned with weight, so you'd be better off using a larger battery anyway.

    Here's a shot of the PC680 (with the red cap) sitting on top of the stock battery. Note the size difference:

    [​IMG]



    Battery deets:

    [TABLE="class: grid, width: 500"]
    [TR]
    [TD][/TD]
    [TD]PHCA[/TD]
    [TD]CCA[/TD]
    [TD]HCA[/TD]
    [TD]MCA/CA[/TD]
    [TD]Weight[/TD]
    [/TR]
    [TR]
    [TD]PC680[/TD]
    [TD]520[/TD]
    [TD]170[/TD]
    [TD]350[/TD]
    [TD]280[/TD]
    [TD]15.4 lbs[/TD]
    [/TR]
    [TR]
    [TD]PC925[/TD]
    [TD]900[/TD]
    [TD]330[/TD]
    [TD]610[/TD]
    [TD]480[/TD]
    [TD]26 lbs[/TD]
    [/TR]
    [TR]
    [TD]Stock Battery[/TD]
    [TD][/TD]
    [TD]550[/TD]
    [TD][/TD]
    [TD][/TD]
    [TD]32 lbs[/TD]
    [/TR]
    [/TABLE]


    PHCA: Pulse Hot Cranking Amps - the number of amps the battery can deliver for 3-5 seconds at 80 deg F
    CCA: Cold Cranking Amps - the number of amps the battery can deliver for 30 seconds at 0 deg F
    HCA: Hot Cranking Amps - the number of amps the battery can deliver for 30 seconds at 80 deg F
    MCA/CA: Marine Cranking Amps (or Cranking Amps) - the number of amps the battery can deliver for 30 seconds at 32 deg F

    More about PHCA: this is an Odyssey term, rather than an "industry standard." Essentially, Odyssey feels that people aren't going to be cranking their cars for 30 seconds, so the CCA, HCA, etc. that use 30 seconds for duration is a bit unrealistic. Instead, people will crank for 3-5 seconds. If that doesn't work, they'll crank again for 3-5 seconds, and so on - sort of like a pulse. Odyssey feels this value is more indicative of how the battery will perform rather than CCA/HCA as this simulates a more realistic scenario. And if you think about it, looking at the stock battery CCA and the PHCA of the PC680, and the fact that the PC680 *does* crank the car, maybe Odyssey is on to something there...
     
  2. ttocs

    ttocs Legend

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    looks similar to the starter battery I use but only in support of the larger battery that powers everything else. The idea was I could play off the large battery and even if it was dead still start the car. The small battery had similar results to what you describe but I included a switch that I could flip if I needed to use the large battery to crank in case the small was dead and the big was good.
     
  3. Frank.JD.Perez

    Frank.JD.Perez Well-Known Member

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    OMG MCGLSR2 THANK YOU I've been wanting to relocate my battery to the back and tuck it away where the spare goes
     
  4. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Interesting - why separate out the big one from starting the car? Were you worried about it hurting some audio gear?

    Sure thing. I did a write up on my battery relocate - I ended up putting mine not in the trunk as that wasn't ideal for how I use my car. But it would probably apply. I don't know if you have seen the write up, it's part of a larger project but there's a "section" on the battery relocate, link here.
     
  5. ttocs

    ttocs Legend

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    no mine was designed around being able to play the stereo with the motor off and even if the big one was dead it would still start.
     
  6. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Ah, gotcha.
     
  7. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Updated. The PC680 did not work for me. It just barely worked most of the time. And when the car stalled and died, it eventually would not restart, and flipped out when I tried to jump it.

    So, I have concluded that PC680 is just too small. It *might* work if you have a racecar and disconnect the battery when it sits. *Might* work. For a normal Mustang, it won't work. So, on to a battery the next size up...
     
  8. ttocs

    ttocs Legend

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    that was my experience with the same size kinetic battery. It had the juice to kick it when its fresh but a little low and I have to kick the switch to use the 2nd one. You could always add a 2nd small battery with the isolator to help but not sure you are really gaining much then.