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Battery keeps going flat

Discussion in 'Technical and Troubleshooting Torque' started by Murphy, Oct 22, 2012.

  1. I am relatively new. I ride most weekends but I often find that, in that short time between rides, the battery goes flat. I have had a couple of new batteries but they still go flat within 1 to 2 weeks? I am told this is not normal. It is a 2007 CBF250.
    Any ideas? Thanks in advance

  2. Put a multimeter across the terminals when it is running and see if the charging system is working.

    Though maybe it is murphys law.
  3. what he said!!
  4. No, that's definitely not normal. Your bike should charge your battery while you ride, but it sounds like it's not and something is not working right in your electrical system. I mean, assuming when you "ride most weekends" it's more than a km or two.

    It sounds to me as though you're not hugely confident with testing your bike's electrical system, so I'd whip it down to the local dealership/mechanic and see what the problem is. Most likely it's something simple.
  5. Does it have a puncture?

    Sounds like it's going to ground somewhere while stationary. Normally that would play havoc with how it rides. I would think it's charging fine or you would have known about it by now.
  6. Please introduce yourself first in the welcome forums as it is playing havoc with our spam detection.
  7. Also a cbf 250 being a honda may have an issue with the regulator/rectifier if it has one. Normal problem.
  8. Are you using a sealed battery or one of the older style varieties (which usually have a white case). If it is the older style then check to see if the fluid level in the battery is where it's supposed to be (should be high and low markings on the case).

    Well looked after a battery can easily last more than 5 years (my '07 bike is still on its original battery) - so definitely something wrong with yours. As mentioned above, definitely worth checking the charging circuit - use a multimeter set to 20v DC and put one electrode on each of the battery terminals with the engine running. You should get a reading around 14-15v, too high or too low and you definitely have a problem.
  9. Sounds like a faulty regulator/rectifier or alternator.

    Easiest fix would be to charge a battery and ride it to an automotive electrician to fix.
    • Like Like x 1
  10. Another thing to check is whether a particular system is draining the battery while the bike is off. Try checking the voltage across the battery terminals while removing fuses. If the voltage goes up when you remove one then something is draining the battery. It may only be tenths of a volt.
  11. Sounds like something either has a high resistance short, or something is staying on, IE. park lights, instrument lights, some other accessory circuit?
  12. Multimeter inline on one removed terminal while key is off
    N out will show any current flow - )

    If that doesnt make sense its cool to ask for details
  13. Do you have an aftermarket alarm or GPS tracker etc? I have a tracker in mine which seems to take enough out of the battery over about a week that the bike won't start until I charge it up again - even though it's supposedly in "long term deep sleep power saving mode" after 15 minutes with the ignition off.
  14. Simple way to eliminate accessories being left on....disconnect the battery.

    If when you come back in a week or 2's time and reconnect the battery it has held its charge, then, you can start looking for which actual device is causing the drain.

    If the battery is flat again, then the culprit could be in the charge ( or lack of ) circuit.
  15. You can get a free battery test and charge output check at Batteryworld.