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Thread: 12v motorbike/jetski battery duration

  1. #1

    12v motorbike/jetski battery duration

    Hi again, Has anyone played around with a motorbike/jet ski 12 v batteries? Im sick of lugging a heavy big deep cycle car 1 with me just to run my stereo and sounder. As my motor is not electric start anyway. And they are half the size and weight. I am trying to way up the math for how long it will last before going flat. I dont mind recharging it the night before a days fishing. But will it last a day running only these 2 items?? Any help....
    BD

  2. #2

    Re: 12v motorbike/jetski battery duration

    You can buy motorbike size batteries from some boating stores, I know that BCF sell them. They tell me that the plates in them are a bigger size so that they don't shatter with the wave motion. I don't if this is true or not. A smallish battery ($30) only my sounder I am told gives approx 20hrs of sounder (its a real cheapy) Oh definitely make sure you get one thats a sealed cell, should be a bit cleaner.


    Cheers

    Rob

  3. #3

    Re: 12v motorbike/jetski battery duration

    All reports ive got is that they are tuff as aswell. I mean if it can handle a jetski then they must be robust. But i want to find out how long it will run for before i buy 1. I used to know all this stuff, but now im confused after learning about generators and fridges and sign waves etc... etc... But my stereo runs a 10 amp fuse and my sounder runs a 2 amp fuse. So it cant be drawing anymore than that. Any maths wiz's here??
    BD

  4. #4

    Re: 12v motorbike/jetski battery duration

    First you need a few numbers.

    You need ampere/hour rating of the battery and you need the current draw of the radio and sounder.

    So if you have 14A/hr battery and your radio draws 20W and your sounder draws 10W.
    The total current draw would be 30W.
    To covert this to current (A) simply divide by the value of the supply voltage (in this case 12).
    So you have a total current drain of ....30/12=2.5A.
    Now... the time (hr) the battery will last is battery rating (A/hr) divided by the current you put on it (A)
    Therefore time in this case would be 14A/hr divided by 2.5A=5.6hrs or thereabouts....

    In the scenario you've given above with the 10A and 2A then a 14A/hr battery will last a tad more then an hour.

    Sounders draw stuff all usually. Radios draw a bit as they have amplifiers to power. See if you can find what current the radio draws and you'll be home and hosed.
    Hope that helps
    Last edited by finga; 15-06-2007 at 06:36 AM.
    I intend on living for-ever....so far so good


  5. #5

    Re: 12v motorbike/jetski battery duration

    Wow finga nice work mate.. Thanks. But i will find out what the radio and sounder draws and find out the battery etc.. And can you work it out for me before i go wasteing more money. Because 1 hour doesnt sound too good to me.

  6. #6

    Re: 12v motorbike/jetski battery duration

    Mate, the sounder will not draw 2A.
    It'll be more like 1/2A for the sounder so the radio would be the deciding factor as a lot of the doof doof radios do draw 10A.
    What radio is it??
    If there's a reasonably big sparky contractor near you go and see them and ask about the batteries out of the emergency signs/lighting and battery backups.
    Or the all day, all night electric wheelchair, mobility scooter fixer-upperer.
    They're usually gell batteries and better in the boat.
    Last edited by finga; 15-06-2007 at 08:43 AM.
    I intend on living for-ever....so far so good


  7. #7

    Re: 12v motorbike/jetski battery duration

    I just looked right through the book and nothing. Even on the box it says nothing. Its a supercheap special mate.. . It a superworks marine cd player that i use for basically the radio only. How much does a normal head unit use??
    Thanks bd

  8. #8

    Re: 12v motorbike/jetski battery duration

    being a "supercheap" special, it will probably be made to a price and as such, will draw more than a "good" unit, BUT at most only about 1 Amp or so, I have used a motor bike battery for Prawning when doing early season "looking" and with an underwater light (fairly high current drain) it lasts for well over 4 hours, so I'm sort of guessing that just a radio and sounder, if used as needed would last 3 or 4 times longer than that (maybe) also, why do you have to carry the battery anywhere? can't you just mount it in a box in the boat?? then just take it out IF it is not needed.

  9. #9

    Re: 12v motorbike/jetski battery duration

    Noelm i only have a smallish boat and i have made a realy cool box for the stereo/sounder and battery that i remove and sometimes i like the extra space so i take it out. But the battery weighs so much i cant lift the whole thing on my own!!! So i want to down size it. I just rang bcf and they have battery for $79 that is a marine grade jetski 1 and is 17 amp hours. How does that sound??
    ps. even supercheap cant find the amp hours the cd player draws either. i just annoyed them... and to answer your question the battery is not holding charge anymore anyway... It sat for a few months without being used or recharged.
    Last edited by BenDover; 15-06-2007 at 09:04 AM.

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