voltage and battery state of charge - BMW F800 Riders Forum & Registry



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    voltage and battery state of charge

    7 Comments by Richard230 Published on 10-23-21 08:52 AM
    Here is a little chart that I was sent by Batterystuff.com which shows the relationship between measured voltage and the remaining level of charge of a typical lead-acid battery:

    State of Charge Voltage
    100% 12.7 - 13.2
    75% 12.4
    50% 12.1
    25% 11.7
    Discharged 0 - 11.6
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior.

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  3. #2
    notacop is offline The original Schwartz Wald Troll
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    That's reasonable but. I noticed my G650 was charging at 14. 4 volts on a run but when I attempted to start the bike after lunch it balked a little. i checked at home and the battery was down on fluid so I topped the battery off. 650 Forum guys blame the boiling over due to the battery location. Same place as on my F800ST and it never has a fluid loss.
    So voltage only won't necessarily tell you the whole truth of battery health.

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    Daboo's Avatar
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    I have read the forum posts that call for a certain amount of voltage and found I rarely get that. I think there are a lot of factors that play into this, like where you're measuring voltage.

    One of the features on my Uniden DFR9 radar detector is a voltage readout. Rarely does it read 14.0 or 14.1. I don't think I've ever seen it at 14.2. Where it is usually reading is in the mid-13s. Maybe because the battery is charged?

    Chris
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    Where are you pulling power for the detector from?

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    Kevin313's Avatar
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    Looks like a decent 'rule of thumb' for a battery at rest/ignition off (and at least a couple hours or so since charging).
    For the heck of it, just measured mine at 12.86V, ~ 1 year old battery, last ridden/charged 48 hrs ago.
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    N4HHE's Avatar
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    The chart is a good starting place but there are other complications. Voltage depends on temperature. Also there is a thing known as a “surface charge” which can result in 1,2V higher reading. There is relatively little power in the surface charge so it is easy to burn off by turning the headlights on for 30 seconds.

    Lead-acid batteries need 0.2V more to take a charge. 12.6V battery has to have at least 13.8V to charge to 12.6V. Higher voltage will pass more current which will charge faster, up to a point. As a result we commonlty see 14.2V on a battery being charged.
    2016 Yamaha FJR1300A; 2016 Beta 430RS; 2007 BMW F800S; 2009 Husaberg FE450; 2016 Subaru Outback; 2018 F150; 2013 Tesla Model S 85; 1983 Porsche 928S; 9 cats 

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    Quote Originally Posted by notacop View Post
    That's reasonable but. I noticed my G650 was charging at 14. 4 volts on a run but when I attempted to start the bike after lunch it balked a little. i checked at home and the battery was down on fluid so I topped the battery off. 650 Forum guys blame the boiling over due to the battery location. Same place as on my F800ST and it never has a fluid loss.
    So voltage only won't necessarily tell you the whole truth of battery health.
    Never add water to an AGM battery. Some require field activation (longer shelf life) but for that one application should never be serviced.

    My F800S battery lays at an angle no flooded lead-acid could function without spilling.
    2016 Yamaha FJR1300A; 2016 Beta 430RS; 2007 BMW F800S; 2009 Husaberg FE450; 2016 Subaru Outback; 2018 F150; 2013 Tesla Model S 85; 1983 Porsche 928S; 9 cats 

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    notacop is offline The original Schwartz Wald Troll
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    MN4, Mine is your average run of the mill lead acid battery. Dinosaur like me. I have some battery water I use to top it off.
    One of the newer designs would be a mo bettah thing but I just grabbed what was available at Auto Zone.

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