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Flat Battery Means Replace?!

Discussion in 'Technical and Troubleshooting Torque' started by Bravus, Aug 14, 2012.

  1. So, I left the key in and the bike on last night... dumb me, picked up the mail and messed up when I stopped. Killed the motor by putting the stand down, and then the *usual* procedure is to turn off the key, pull it out and drop it in my glove. Forgot, and the battery was dead flat this morning... couldn't even roll-start it.

    (The issue was exacerbated by the fact I had 98 octane fuel in an old Bandit, which meant it needed choke to start.)

    Got a lift in to work, and when I got home this evening jump started it (easily and quickly) with the car and then went for a long ride. Used up the last of the 98 and filled up with 91, and it started fine at the servo. Was *very* careful to get the key out when I got home!

    I was happy to leave it at that, but checked a couple of old threads here to see whether it was dumb to jump start a bike (old, carburetted) with a car. Didn't find anything on that, but found lots of opinions that once a battery has been flat it's stuffed and should be replaced.

    Doesn't seem to make sense to me: it's not an old battery and it was perfect before my stuffup. Guess I'll see how it travels over the next few days and see what's up.
  2. Do that. It's probably alright but batteries do have a finite lifespan.
  3. jumped old bikes a million times with a car. I don't know if it makes a difference but I was told years ago to just make sure the car's not running

    if you've only drained the battery once and for a shor time it's probbly okay - but if it's not you may have a long walk ahead of you some day. Most here will probably tell you to change it. Me - I'd take a chance
  4. When you drain a battery the lead goes from metal to a dissolved aqueous form - recharging reverses the process.

    The problem with letting the battery go completely dead therefore is that it increases the likelihood of the metal depositing in just one place, which can cause two of the lead plates to touch and short out - thereby reducing the overall capacity of the battery (it's why older books suggest tapping batteries with a mallet to break up some of these dendritic growths).

    Modern batteries have a lot of features now to reduce the occurrence of this, but really the only way to tell if it's still good is to just see how it goes.
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  5. you should be ok to jump a bike with a car, as for the battery if it is old then the flattening would have taken a toll on it. you may have to invest in a trickle charger for future purchases.
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  6. It will probably need a recharge with a battery charger......if it been dead flat just riding it wont give it a decent recharge especially if youre only going short distances.

    If its more than a few years old it could be worth getting a new one,if its a yum cha special.....if its a good quality then it should have a better life span.

    Have u checked the fluid level? (if its an acid battery)

    If u dont have a charger take it to a battery place (like Century) and Im sure they will check it and charge it if its still ok for not much cost

    If u can charge it at home,do it out of the bike,in the open with the caps off and overnight.......and top up the fluid with distilled water beforehand.
  7. Jump it off a car and then go for a good long ride to charge it. You'll have shortened its life by a smidge but it'll be fine in the short/medium term.

    Flattening a battery won't kill it. Leaving it flat for weeks will.
  8. I've heard of people using the side stand or the kill switch to stop before. Always seemed a bad habit for this very reason.
  9. First time it's bitten me in 6 years. ;-)

    Think there's even an ancient thread about it...
  10. I don't know why so many people here believe a flat battery means it's ruined forever. When I say otherwise a thousand people cry foul and make personal attacks, then don't even have the decency to apologise when I end up right. My battery used to die every couple days, for months, until it finally started holding it's charge properly. Piece of junk Indian battery but it came right in the end. Buy a trickle charger off ebay and just keep it nearby, just in case
  11. How long can bikes be left for without have to trickle charge? I am going overseas for 2 weeks and am wondering if I should get a trickle charger and take the battery out... My bike is under a carport so I will need to take the battery out to trickle charge.
  12. 2 weeks wont be a problem with a good battery. My backup bike only gets a riding every now and then.3 months sitting she started straight up
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  13. Started cold with no trouble this morning. Will report back in a week or so, but the signs are good so far.
  14. It should be fine.....if its a good battery and not too old.
    Just disconnect it ....but 2 weeks is bugger all

    I left my car battery disconnected and went OS for 7 months and it started first go when I returned.

    My other vehicle that had a blinking light for the alarm I left for 2 months another time and it was fine also...obviously with the batt connected to have the alarm set.

    Both vehicles had good quality Century batteries.
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  15. Just a note on "Trickle Chargers." A Trickle Charger just trickles a constant current into the battery, whether it needs it or not. A better solution these days is to use an intelligent charger, which will not only charge the battery faster, or have the option to do so, but will also condition and maintain the battery if it is left connected to the charger. They may even recover an older battery from being run completely flat. However in my experience once an old battery is run flat it is close to end of life, even if it takes charge and starts the vehicle easily.

    Intelligent chargers cost a bit more, but they are worth the investment.
  16. If you have an alarm, then you will be slowly drawing down on the battery. Whether you flatten and damage it during the unridden period, depends on a bunch of factors. Trickle chargers for the win.
  17. +1 the intelligent chargers allow the battery to drop charge every so often then recharge them which is much better for it than constantly feeding charge to a fully charged battery. Standard trickle chargers are best just for keeping dead batteries going with a bit of a boost between rides.

    I can't see on overnight mistake being an issue on a fairly new battery as it shouldn't have gone completely flat in that time (although if the battery was old then maybe). If it has gone completely flat and is more than 2 years old then my experience has shown anywhere between 1 week and 6 months before it becomes apparent that the battery is dead.

    My wife had worst case scenario after her last trip to the Superbikes. She left her heated handgrips on for 2 nights after arriving home and the 5yr old battery went dead. Charged it over night then went for a ride the next day with the battery performing perfectly. Went to fire it up for another ride a few days later and it had nothing left.

    It's not always that quick and after your description of events, I'd guess it didn't go flat enough to kill it anyway, but a trip to Battery World for a free load test is the safest way to find out for sure. :)
  18. All good so far... guess if I get around to it I could get it tested, but so far it's pretty happy.