deep cycle battery to jump start car?

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cizzi
cizzi Solar Expert Posts: 109 ✭✭✭✭
I have a spare 8GU1 deka 36AH battery laying around the house.. can I leave it in my car trunk and use it to jump start my car battery in the event I would need it? or is this not recommended?

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,502 admin
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    Re: deep cycle battery to jump start car?

    My wife always liked the idea of those "little" emergency starting boxes (with the attached cables). She bought a couple for me over the years...

    My experience. If the car does not start on the first revolution, it will not start because the small battery cannot supply enough current.

    If you try to continue to crank--the small battery is permanently killed.

    You might try connecting the battery for 5 minutes to "quick charge" the car battery a little bit--and then you may be lucky.

    And the hassles of keeping the jumper battery charged (connect it to the car's electrical system?).

    Then, the issue I have seen (this is normal weather--we don't have freezing weather hear)--if the battery is dead enough to not start the car (lights left on, somebody cranked and cranked trying to get gas to the injectors after refilling the tank, etc.)--if the battery is a couple years old--even if the battery is recharged and seems to start the car fine--in the next several weeks to months--the car's battery will fail to start the car with no warning at all.

    So, for me, after I notice the car battery starts to weaken (engine cranks slower, starting with headlights on gets really dim, etc.), or if the battery has gone dead once (and it is more than 1 year old)--I just replace the car battery immediately... Knowing that there is only months (or even weeks) left of useful life.

    Then I am left with the problem of leaving the lights on--don't do it :roll:, and carry a set of jumper cables (at least in urban areas, it is not hard to get a jump).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • landyacht.318
    landyacht.318 Solar Expert Posts: 82 ✭✭✭✭
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    Re: deep cycle battery to jump start car?

    I have a 12 a/h sealed battery from a jumperpack. It as at least 9 years old now, and recently would not help to start a 4 cylinder car that was just barely able to turn over on it's own. I use it to power my 9.6 volt drill, or portable tv or some fans, but it is now worthless in terms of cranking amps. It will hold it's 12.8 voltage for weeks sitting unused, but has no real capacity left.

    When it was newer it would start my 318 when the starting battery had enough juice to only make the relay click. It saved me about 2 dozen times when I only had the one starting battery and no solar.

    As BB said once you have abused a flooded starting battery by draining it to the point where it can't start the vehicle, it never really recovers.

    But if you have the battery in your trunk and it keeps you from having to ask for a jump then it's worth it. Just charge it monthly if not used, and asap if it is.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: deep cycle battery to jump start car?

    that small battery being put up against a nearly dead starting battery will cause the small battery to be sucked down almost instantly because it'll try to recharge the starting battery as best as it can before both equalize. as bill said it may be enough to help the starting battery kick over the car or whatever, but then again it may not be enough even if nothing else is wrong. too many people also needlessly have headlights, radios, etc on while trying to start a vehicle. even if it becomes switched out of circuit (not all are) it further drains the battery before even trying to start the vehicle. a short usage is sometimes employed in cold climates to warm a battery in order to gain back a bit of capacity, but with a dead or a nearly dead battery even this is useless.
    imho, a small maintainer pv can do wonders at preventing the need to backup the battery with an undersized battery.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: deep cycle battery to jump start car?

    The idea of trucking around a "extra" battery to jump my car once every ten years seems pretty silly when every other car in the parking lot can jump you,, so carrying around a set of jumper cables makes way better sense.

    Failing that,, a CAA/AAA membership makes a jump only a call away.

    Having said that,, if you are WAY out in the boonies and you have a funky car maybe it makes sense. When we park at -40 for several weeks,, we have been know to carry a warm battery down to the car for a jump,, since the car battery doesn't have much reserve since it is so cold.

    Tony
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: deep cycle battery to jump start car?

    those are also good alternatives that make sense. 90% of the times i ever had battery troubles was during the cold of winter and that small battery being left in the car remains just as cold as the starting battery and is slowly depleting its power during storage while at least the starting battery gets rejuvenated with the car's alternator. it's possible and is very probable your reserve battery will fail before the starting battery fails.:roll:
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: deep cycle battery to jump start car?

    Just thought I'd mention that jump-starting cars, from whatever source, is not the simple thing it once was. Among today's vehicles there are those that will crank but not start because the voltage is too low to satisfy the computer's needs. I can name two from experience: Jeep Cherokee/Comanche and Pontiac Sunbird.

    Having lived in frozen wasteland climates all my life, I can tell you that for the most part your car will start in any sort of weather if it has been properly maintained and no one has left the lights on. For those rare instances that come up, jumper cables and a helpful fellow motorist is the best answer. Not worth lugging a spare battery around and trying to keep it maintained as others have mentioned.

    I've had good luck with the booster packs, but they have to be kept charged too and won't work for a completely dead battery.

    An ounce of maintenance is worth 20 lbs. of battery in the trunk.:D

    Oh: diesels are another story.:p
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: deep cycle battery to jump start car?

    Modern fuel injection, coupled with modern electronic ignition makes not starting so much less of an issue. Assuming you have kept you battery in good shape,, and every once in a while put spark plugs in and a fuel filter,,,(routine "tune ups", points, plugs condensers, chokes, carb adjustments have all gone away) it will fire up even at -40. Sure clanks for a few seconds,,, even with 0w/15 synthetic oil!

    I change the battery out of our winter vehicle after about 4 years, since we are 150 km from town,,, not starting is not an option. I keep the old battery for various uses,, turn the oldest one in for the core. (I always have one lying around from something,,).

    Tony
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: deep cycle battery to jump start car?

    And here's my 2 cents:

    Buy good THICK jumper cables!

    Cheap thin ones don't work very well at all - you may have to let the jumping vehicle run for a while and "charge" your dead battery before the engine will even crank over - while with thick cables you can usually just hook them up and go. Sometimes with a cheap set of cables, you never can get the engine to crank over unless you double up and parallel TWO sets.

    A vehicle I bought a long time ago came with a home made set of jumper cables made out of 2/0 welding cable and I have held onto that set of jumper cables with a death grip ever since. They are horribly heavy - just picking them up feels like I'm hefting a battery, but they are SO worth it.

    I am so totally spoiled by these fat jumpers!
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
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    Re: deep cycle battery to jump start car?
    dwh wrote: »
    A vehicle I bought a long time ago came with a home made set of jumper cables made out of 2/0 welding cable and I have held onto that set of jumper cables with a death grip ever since.

    Heh heh... I just happen to have a couple 15 foot runs of 500MCM I have no idea what to do with... What would someone think if I pulled those out for a jump?!? :p:D

    The welding cable would be beautiful, though. I have a couple pieces of 1/0 laying around, that might be a very good idea...!
  • vcallaway
    vcallaway Solar Expert Posts: 157 ✭✭✭✭✭
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    Re: deep cycle battery to jump start car?

    AAA = Best investment EVER.

    Only drawback is 2hr response time is typical. Wife has a bad habit of locking keys in the car.

    I've had a couple of those portable jump starters. After a few uses they tend to not work so well. Biggest problem is remembering to charge them back up.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: deep cycle battery to jump start car?

    Hide-a-Key,,,, and even better investment!

    Tony
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: deep cycle battery to jump start car?

    you know tony i did one better than that during one point of my life as i carried 2 sets of keys and kept them in different pockets. this saved me some embarrassment and inconvenience a couple of times. i carried 2 sets because i thought hiding a key was risky.
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: deep cycle battery to jump start car?
    niel wrote: »
    you know tony i did one better than that during one point of my life as i carried 2 sets of keys and kept them in different pockets. this saved me some embarrassment and inconvenience a couple of times. i carried 2 sets because i thought hiding a key was risky.

    I usually put my hide-a-key up on the frame somewhere around where the transmission crossmount meets the frame.

    Good luck finding it without *some* idea where to look...
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: deep cycle battery to jump start car?
    RandomJoe wrote: »
    Heh heh... I just happen to have a couple 15 foot runs of 500MCM I have no idea what to do with... What would someone think if I pulled those out for a jump?!? :p:D

    The welding cable would be beautiful, though. I have a couple pieces of 1/0 laying around, that might be a very good idea...!


    I used to have a piece of 500 MCM under the seat of my truck for a billy club. I can just see you asking a few friends to drop by and help you lift 30' of that stuff so you can jump some little old lady's car. :D

    1/0 would probably be just as good as my cables, and a lot less weight. Mine have clamps like these:

    http://www.grainger.com/Grainger/items/2FGD1
  • Ralph Day
    Ralph Day Solar Expert Posts: 1,019 ✭✭✭✭
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    Re: deep cycle battery to jump start car?

    Hi Tony
    Hide-a-Key's are great. I once got to town and found I'd left the car keys in the house door (ignition key was worn and could be removed while car was running). Went for the hide a key and found the magnet only...the rivet had rusted off and the box dissapeared. My neighbour went to my house and brought the keys to town for me:blush:

    I always rust proof the key and now the rivet or metal parts on the hide a key box, once bitten twice shy.

    Ralph
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: deep cycle battery to jump start car?

    I often never take keys out of cars! Some times I'll stash the key behind a mud flap or something so that when we are in town either one of us can get into or drive the car.

    My sister keeps a hide-a-key with a $20 bill in it,, just for emergencies,,, also not a bad idea.

    Tony