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Thread: Lightweight Battery Revisited

  1. #1
    enjoys driving fast Jack Olsen's Avatar
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    Default Lightweight Battery Revisited

    I've been using an 18-pound AGM wheelchair battery in my old Porsche for almost a decade, now. I've replaced it twice -- the last time when the price dropped to $30. More than anything, I'm a cheap bastard.

    Now, my garage recently won an award in the Classic Motorsports 'Show Us Your Shop' contest. The prizes for the contest ran the gamut of usefulness. I got a $500 worth of degreasers, brake cleaners and other chemicals from CRC. I got a (Chinese-made) TIG welder from Eastwood. And then… $500 worth of Battery Tender products. Now, I already own and use a battery tender. I like it. But once you've got one of those $30 beauties, you don't really benefit from having 15 more.

    But I looked up the company, and found out that they also have a line of lightweight LiFEPO4 (Lithium Iron Phosphate) batteries. The biggest one has 480 cold cranking amps and weighs 3-1/2 pounds.

    The last time I'd noticed this battery technology was when Porsche Motorsports offered it in a 12-pound version for $2,950.

    I don't know if it's because of laptops or all the Priuses out there or what. But now you can get a Lithium Iron Phosphate batteries pretty cheap. The Battery Tender one retails for $300, but can be bought from Amazon for under $200.

    So now I don't have 16 battery tenders. I've got one extra, a cool battery, and then a LiFEPO4-specific battery tender.

    Here's the new guy on the scale:



    And as you can see here, it's about the size of the popular 16-pound Odyssey battery. It's just that when you pick it up, it feels like they forgot to put the guts inside it. (It's actually less than 3-1/2 pounds.)



    I had to downsize the bracket I use in the car's smuggler's trunk. Normally in a 911, the batteries (yes, two) would have been up in the nose. For racing, you move them inboard. But repositioning the battery to this location really wouldn't be necessary if I'd started with a battery this light.



    And here's the old guy back on the scale, along with the portion of the tie-down I was able to chop out. My net weight savings was 14.7 pounds, and the cost to me (because of the contest, of course) was zero. That warms my thrifty heart.



    The Battery Tender LiFEPO4 battery can be got from Amazon for $185 and the LiFEPO4-specific charger/maintainer for it is $27. Here's a link, if you're interested.

    Now, that doesn't mean I'm not poor anymore. And it made me a little nuts to think about throwing out the old battery that still had a lot of life in it. But a little while back, we got a rainstorm here in California that delivered about an inch of rain per hour, and my driveway's drains backed up and I got about an inch of water in the pit I'd dug for my lift. So I created a low spot in the concrete and added a little 12V bilge pump for a boat. It shoots the water out through the access hole for the lift pretty effectively, and it's powered by my old car battery. I'll probably attach the old trickle charger as well. Although the way it's set up now is mostly for testing.





    Waste not, want not, flood not.

    And in case anyone here hasn't seen it, here's that goofy, award-winning garage with the (never-flood) lift in action:

    Last edited by Jack Olsen; 04-21-2015 at 10:25 PM.

  2. #2
    I wanna go fast! thepass's Avatar
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    +1 on the LiFEPO4. My battery was fading last fall, decided it was as good of an excuse as I would ever get to gamble a bit and try one of these. I got the slightly smaller model.

    CCA is surprisingly strong. From the info I turned up while researching these, the weakness of these batteries is capacity, and once they are below 80% they are toast. This just means you need to be conscious of not leaving a draw on the battery for a long time while the car is off. There are some things that draw power even when the car is off, so to be on the safe side I added a kill switch in-line with the battery cable to kill the circuit when the car is off.

    Have had the battery about 6 months now, no issues and works great. I accidentally left the kill switch in ON for a few days recently, and although I have a few LEDs and the ECU which draw a bit of power at all times, it started up fine today.



    Ryan Passey
    Singulär Motorsports | Goodwin Racing

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    "The sport dedicating to the spirits of time attacking motoring" -Emilio

  3. #3
    Not Certified Slow SDSUsnowboards's Avatar
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    Cool, Jack!that battery should be good for about one second at WSIR!

    Being poor, I use a Deka EXT9. it has 120 cranking amps, and goes flat if I leave it in the car for about 15 minutes. I think I go through two per year on average, because I'm dumb.

    Ryan, where did you get that switch? I've been thinking of the same.
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    Sir flink
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    I installed a 2.2lb Shorai LFX14A4-BS12 15 months ago. No issues so far. I'm pretty careful about keeping the kill switch off when the car isn't in use.

    OK, one slight issue: when the car is hot and I need to restart the engine (stupid clutch), it can barely crank the engine. Perhaps because the battery's a bit warm from being somewhat close to the exhaust. But it hasn't caused me any embarrassment yet.

  5. #5
    Senior Member TYP85's Avatar
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    Quote Originally Posted by flink View Post
    I installed a 2.2lb Shorai LFX14A4-BS12 15 months ago. No issues so far. I'm pretty careful about keeping the kill switch off when the car isn't in use.

    OK, one slight issue: when the car is hot and I need to restart the engine (stupid clutch), it can barely crank the engine. Perhaps because the battery's a bit warm from being somewhat close to the exhaust. But it hasn't caused me any embarrassment yet.
    Probably the starter, electric motors aren't as efficient ( max torque output) when really hot, the windings in the stator get hot and resistance goes up reducing the torque output of the motor....
    Batteries are also less efficient at temp extremes.

  6. #6
    Senior Member TYP85's Avatar
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    Quote Originally Posted by SDSUsnowboards View Post
    Cool, Jack!that battery should be good for about one second at WSIR!

    Being poor, I use a Deka EXT9. it has 120 cranking amps, and goes flat if I leave it in the car for about 15 minutes. I think I go through two per year on average, because I'm dumb.

    Ryan, where did you get that switch? I've been thinking of the same.
    You can strap two of them together and run them in "parallel": doubling the current output but keeping the same voltage. You have twice the weight and cost, but they might last alot longer.....

  7. #7
    I wanna go fast! thepass's Avatar
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    Quote Originally Posted by SDSUsnowboards View Post
    Ryan, where did you get that switch? I've been thinking of the same.
    Standard Longacre kill switch : Longacre Battery Disconnect Switch 45780

    -Ryan
    Ryan Passey
    Singulär Motorsports | Goodwin Racing

    #13 1990 Miata
    "The sport dedicating to the spirits of time attacking motoring" -Emilio

  8. #8
    Senior Member fatbillybob's Avatar
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    Hook that bilge pump up to your cool suit and drop a 20lb bag of ice in that hole and you can be cool while you work on your car.
    bawareca and billybobster like this.

  9. #9
    enjoys driving fast Jack Olsen's Avatar
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    Update: over a year now on the LiFeP04 battery. No problems at all.

  10. #10
    http://www.trackhq.com/Banners/yellowsitesponsor.gif emilio700's Avatar
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    We used Shorai LifePo4 batteries in our enduro cars back in 2012 IIRC. Like regular lithium batteries, they do not tolerate deep cycles. Not a problem if your car is healthy. If you have a short or current leak somewhere though, it can brick the battery. Any battery will suffer if deeply discharged like this but the LifePo4 batteries are particularly sensitive.
    But yes, they do have more than enough cranking power and are absurdly light.
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  11. #11
    JJ1
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    ^Do you guys have to trickle charge them?

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