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Battery Charge

Discussion in 'General Motorcycling Discussion' at netrider.net.au started by Disco_Dave, May 17, 2011.

  1. I accidentally ran my battery down the other day on my bike by leaving the keys in the on position. After jumping the bike and riding it for about 30 mins yesterday i measured the voltage (bike off) to be 12.1V.

    I tried to start it again tonight (cold start) and it wouldnt so i push started it and took it for another 30 min ride. After riding i measured the battery at 12.2V

    1) Does anyone know what the correct battery voltage would be?

    I am hoping my alternator isnt stuffed as i hear they are really expensive.

    2)Any idea what an alternator would set me back if i needed to replace it (for a gs500F suzuki).

    3) Also, if i need to buy a new battery does anyone have any idea where i can get a decent battery from in melbourne?

  2. I would expect a reading of around 12V to 12.5V. Before investing in alternators and batteries I would look at giving it a good charge with a battery charger. The alternator in a gs500 is not that big, and a half an hour of riding will not fully charge your battery.
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  4. (Nerd hat on)
    Voltage isn't a good indicator of battery charge but if that's all you have:
    - You should only measure the voltage after the battery has rested (no discharge or charge) for a few hours.
    - 12.6 is considered tip-top full for a wet cell battery

    If you measure while charging from an alternator, engine spinning faster than idle, I'd expect to see 13.8 - 14.4 volts. As a guide my VTR250 doesn't really charge much until over 3000 RPM and tends to hold the battery at around 14.2 volts above that (depending on how much current it's being asked to provide).

    You may want to invest in a CTEK charger or similar which performs some basic tests on your battery before and after charging and can have some limited effect in removing dendrites from between the cells (when on recondition cycle).

    Otherwise, your average wet cell battery (sealed or vented) can be expected to last between 2 and 5 years depending on how it is looked after.

    Furthermore, most car/bike charging systems tend to be of the 'aim for 14 volts' type which only ever charges a battery to about 80% of full capacity. In order to properly charge a wet cell battery the charger needs to watch current and temperature; the voltage is much less important.

    Discharging a wet cell battery below 60% charge (when measuring charge by specific gravity) accelerates damage to the cells so your average battery can only ever deliver 20% of it's capacity (80% -> 60%) which for a bike is usually somewhere around 1.5AH (20% * 7.2Ah), or running your headlight for about 20 mins before you go below the 60% figure.
  5. Firstly, this should be posted in "Troubleshooting" .

    The voltage reading is low. 13.2 would be better, but it is the available amperage that spins the Starter Motor against Engine Compression.

    Charge the Battery fully, overnight on a decent Charger, then give it a crack.

    it will either work or it won't.

    "Battery World" is a good place to buy any battery.