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Dumb news, good news, bad news - but how bad?

Discussion in 'Technical and Troubleshooting Torque' started by Bravus, Apr 21, 2011.

  1. As some may know, my bike key is on a soft koala keyring and lives inside my glove (left or right, he's ambidextrous) inside my helmet when not in use. He's ridden there safely for years.

    Today I was carrying a lot of other crap, so the helmet was at all sorts of angles and I thought he'd fallen out. Looked everywhere, couldn't find him. Somewhat panicked, I then thought I might have left the key in the bike.

    I had, and the good news is that it was still there at the end of the day.

    The bad news is that it was in the 'On' position. Must have got distracted... hey, there are a *lot* of cute girls on campus!

    Battery was dead flat - so flat the bike wouldn't start in second down a long hill.

    I'll bus home, drive the cage in with tools, pull the battery out and take it home to charge overnight.

    My question is, might there be something worse than a flat battery. I'd heard that with bad luck leaving the ignition on could burn out the coil.

    I guess it's a testable question when I get back with a charged battery.
  2. i left mine on for a few days (was in pieces so no lights) didn't hurt coil but sulphated the battery.
    don't think yours will be that bad
  3. A dead flat no-maintenance battery won't even allow the bike to be roll started - the bike simply won't run, and won't stay running even if jumped. I had my own experience with this just the other day.

    New battery, or take the battery to an auto elec to get some magic battery CPR conducted.
  4. If it's an AGM type sealed motorcycle battery, as long as you get it onto a proper charger within 24 hours you shouldn't have too much trouble bringing it back to life.

    After 24 hours, chemical things start to impair the batteries ability to be a battery again.

    Good luck

    Also, don't just charge it once and when the light goes green throw it back in.

    Use some old headlights or a 12v work light to run it low again (not dead flat) and recharge again.

    After two or three cycles, it should be good to go.
  5. ps. Bet you wont do that again in a hurry. :)
  6. I did the exact same thing a couple of weekends ago, I jumped on my mates bike and started riding a 250 ninja and I forgot that I didn't turn my lights off, end result battery was flat.

    I couldn't roll start it, and eventually headlights went very dim, I got a lift back home and came back with tools (and luckily riding gear was still in the back of the car) and it took me three goes to roll start it but it worked so I was pretty thankful of the motorcycling gods that night as I absolutely hate public transport.
  7. Took a suspect old battery I had lying around in with me, just on spec, and it lit up the lights on the dash (and the headlight - this is one of those times having no headlight switch really kills ya) dimly but didn't have enough to turn it over, or to start with a push. So I brought the proper battery home and it's on the charger now.

    The charger is notionally 5.4 A, though it's not a well known brand so that number should be taken with a large grain of salt. I'll check that the battery is not too hot before I go to bed anyway, because the web suggests bike batteries are happier with 2 amps or so.

    Opinion seems varied on whether and to what extent batteries can be revived. I'm fairly hopeful, but it may have shortened it's life a bit.

    Pretty expensive moment of distraction... more so if it's completely dead.
  8. if its only been on for half a day it should be completely fine.
  9. Just to round out the saga, took the charged battery back this morning and the bike started immediately.
  10. Used to be a real risk with old, mechanical points based systems. I'm pretty confident it's unlikely to happen with an electronic set up.

    You should be OK. I had a battery once that had been boiled dry twice (gotta love old Suzukis :D), refilled with tapwater 'cos I didn't have/couldn't afford acid, had been flat on half a dozen occasions and was still starting the bike reliably as long as you didn't leave it longer than 48 hours.

    As for charging, I've got an old, largely unregulated car charger and have never used anything else. A biggish bike battery is fine on it overnight. Dunno what currrent it chucks out, but I'd guess about 10A initially if the battery's flat, reducing over time to a couple of amps trickle as the battery recovers. It will also charge stuff that will make a smart-charger throw up its little electronic hands in horrified defeat. Lead-acid batteries have significant ability to do their own charge current regulation.

    Something that's worth remembering is that most vehicle charging systems are capable of whacking a whole lot more current through a battery than any charger you're likely to encounter. Most people would be quite shocked if they had an ammeter on their dash. I've seen car systems that would jam the needle of a 30A ammeter against its upper stop if the battery was a bit low and 15A was normal following a protracted cold start or a troubleshooting session so 5A-10A into a bike battery doesn't scare me in the least.

    Oh, and my batteries last a loooong time :D.