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748 Symptoms Of A Flat Battery?

Discussion in '748 / 916 / 996 / 998' started by West Cork Paul, Jan 17, 2019.

  1. EE8303C3-4068-48F4-89D2-A6F63A3E1D66.jpeg The bike’s in pieces and in the process of being stripped down further for a complete nut & bolt rebuild.

    She last ran about 2 weeks ago but is always on a trickle charger. I just went to warm her up so I could empty the oil before taking the crankcase covers off but no luck. :( As soon as the engine run button is engaged, there’s a lot of clicking from the area behind the tank and lights blinking but no fuel pump priming and no start.

    Disengaging the engine run button and trying any of the lights or horn just elicits a click and a feeble attempt at working.

    It’s as though the battery is almost dead and there’s not enough power to trigger the respective relays. However, when connected to the trickle charger there’s 14.5v there and when disconnected from the trickle charger there’s 11.7v from the battery; tested both across the terminals and from the +ve to an earth on the frame.

    I can’t upload the short vid which demonstrates what’s happening as it’s too large a file.

    Can anyone point me in the right direction please?

    TIA.
     
  2. New battery required.
    Halfords, AGM type... about £50 & use your discount card.


    Close thread.... problem solved.... Quick before it starts getting silly.
     
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  3. Ignore AC.

    But do what he said cos he's right.
     
  4. I had the same with a battery suddenly died, measured voltage ok but shorting the terminals together with a piece of wire wouldn’t even generate a little spark and voltage went......new battery from Halfords did the trick
     
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  5. 11.7 v is no good at all.
    Steve
     
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  6. He means a Yuasa form Halfords :bucktooth:
     
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  7. Don't copy this advice..... if the battery is ok, you are first going to get two burnt fingers and thumbs, followed by boiling acid all over the place, possibly an explosion. .... think breaking bad!
    I know someone who used a spanner as he couldn't find any wire......
    New desk, chair, carpet, jumper and hair cut required!
    Oh and a new battery, which was fine until he tested it!
     
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  8. To shed some more light (and I agree it might be the battery, but read on) I’ve got 11.7v from the battery when the ignition is off, but as soon as I turn the ignition on it drops to around 4v as measured across the terminals and 3.7v if measured battery +ve to frame. At that level it’s no wonder relays won’t fire.

    Not only that but I’ve taken it off the the trickle charger and put it on a battery charger which then indicates the battery is fully charged.

    BTW, the battery (Yuasa YB16AL-A2) was brand new in August last year, just 5mths ago. It couldn’t die a death that quickly could it?
     
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  9. Ok, a bit more info. When I connect the multimeter across the terminals it reads 13.8v, having had the proper charger on for a bit. However, as soon as I turn on the ignition it drops to 6 and then starts to count down, 5.99, 5.98, 5.97 etc. It seems to me there’s a massive drain occurring, but as nothing’s changed since 2 weeks ago I’m at a loss as to where that drain can be.
     
  10. It will be under warranty :thinkingface:
     
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  11. I've no idea what battery charger you have and how sophisticated it is with regards to testing.
    Try a new battery.... for £50 is it worth your time typing anymore questions ?
     
    • Agree Agree x 1
  12. It's possible for a battery to show a healthy voltage under zero-load but then drop down the fecking useless under load. This indicates that the battery is, technically speaking, fecked.

    Sorry to blind you with science here.
     
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  13. OK. .. there are loads of bare connections inside the petrol tank..... could something be shorted?
     
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  14. Take some wires and try the horn or a headlamp across the battery . This will allow you to test the battery separate to the bike
    ..... failing that buy a battery load (drop) tester.... see my battery advice threads.
     
    #14 AirCon, Jan 17, 2019
    Last edited by a moderator: Jan 17, 2019
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  15. Feck it, I'll park the issue for now, drop the oil out cold :confused: and continue the strip down. I'll get a spare battery and a new trickle charger and see what happens when I put it all back together.
    Thanks all for your advice.:upyeah:
     
  16. Once you found the issue.. come back and let us know. :bucktooth::upyeah:
     
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  17. what make of battery you eventually baught. yer battery is gubbed bud :upyeah:
     
  18. The battery has developed a high internal resistance and is drawing very little current, so the charging voltage remains at a high level and the charger thinks the battery is fully charged.
    The battery is knackered.
     
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  19. A bit more info. The battery was completely devoid of acid :confused:. How can that happen? It's not leaking. There's no acid destruction on the bike, the fairings or underneath on the floor where the bike has been standing. It's as though the acid has simply evaporated into the air :astonished:. Or maybe the leprechaun's drank it all, mistaking it for poitin?

    Has anyone had this happen to a battery before?
     
  20. I tend to agree (see the post above) could a shitty/dodgy trickle charger cause this?
     
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