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Re: [ST] Flat Battery



Chris,

You are correct that I errored in confusing cold cranking amps with amperage in an automotive battery.

The point remains that an automotive charging system is capable of producing many more amps than a motorcycle electrical system can handle.  The result is damaged components, typically the regulator rectifier is the first to fail.

Rick

 

-----Original Message-----
>From: Chris Harwood <Chris@xxxxxxxxxxxxxxxxxx>
>Sent: Mar 7, 2007 7:48 PM
>To: ST@xxxxxxxxxxxxxx
>Subject: Re: [ST] Flat Battery
>
>Rick
>
>I've studied electricity for over 40 years including at university and some of your comments there make me cringe.  You could connect a billion-amp charger to your battery and the charging current will be determined by the battery's internal resistance and the difference in voltage between the open-circuit battery and the open-circuit charger.  That could be milliamps.
>
>Incidentally, we dispensed with amp-hours over here some years ago and we rate lead/acid car batteries in cranking amps now.  It's all part of progress and we are clearly more advanced than the rest of the world (not).
>
>Chris Harwood
>00 RS UK
>
>>>> drbrant@xxxxxxxxxxxxxx 08/03/2007 00:05:06 >>>
>Neil,
>
>Actually Kevin explanation is a rather good.  As a basic rule you can divided a batteries amp hours, the rating on the battery, by the charging amps to determine the maximum total time to charge the battery.  Note typical car batteries range from 500 amp hours to 800 amp hours.  Most motorcycle batteries are in the 10-20 amp hours range.  I think the amp the middle numbers on a Yuasa Battery.
>
>The major risk associated with using an running automobile to charge a motorcycle battery is too many amps over heating the electrical system and damaging components.  I sold a GS650 to an in-law many years ago who was an automotive mechanic.  He attempted to charge the battery with an 8-0 amp hour automotive charger and destroyed the regulator rectified in the bike.  An alternator in a car will produce similar results.  It is also possible to short a battery out by exposing it to too many amps. 
>
>If you don't believe us you can either study electricity some or go and hook a high amperage charger to you motorcycles electrical system.
>
>Rick B
>Pfafftown, NC
>-----Original Message-----
>>From: Neil Lindsey <Neil.Lindsey@xxxxxxx>
>>Sent: Mar 7, 2007 6:42 PM
>>To: ST@xxxxxxxxxxxxxx 
>>Subject: Re: [ST] Flat Battery
>>
>>Kevin -- 
>>
>>sorry, but you have no idea what you are talking about
>>
>>----- Original Message ----- 
>>From: "Kevin Dicks" <kdicks@xxxxxxxxxx>
>>To: <ST@xxxxxxxxxxxxxx>
>>Sent: Wednesday, March 07, 2007 12:14 PM
>>Subject: Re: [ST] Flat Battery
>>
>>
>>> Agreed.  What I should have said is that a car battery needs more current 
>>> to
>>> charge it compared to a bike battery given the same time period - another
>>> effect of this is, as you point out, it has a higher AH.  If you leave a
>>> battery on a 20mA charger for long enough, given the correct voltage, it
>>> will probably eventually charge (as long as the battery is in good 
>>> condition
>>> etc).  The point I was trying to make was that even though a car battery 
>>> and
>>> a bike battery have the same voltage, they are very different when it 
>>> comes
>>> to current (and therefore the AH each can provide).  Given this 
>>> difference,
>>> the charging system of a car can (because it has to) provide far more 
>>> power
>>> (Volts *  Current) than a bike charging system can.  Given that,
>>> jump-starting a bike from a car with the car engine running, 'may' lead to
>>> problems with the bike due to the higher current the car charging system
>>> provides.
>>>
>>> -----Original Message-----
>>> From: st-bounces@xxxxxxxxxxxxxxxxxxxx 
>>> [mailto:st-bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf Of Eoin Kirwan
>>> Sent: Wednesday, March 07, 2007 3:08 PM
>>> To: ST@xxxxxxxxxxxxxx 
>>> Subject: Re: [ST] Flat Battery
>>>
>>>
>>> On Wednesday 07 March 2007 03:23, Kevin Dicks wrote:
>>>> Current is not the same as Voltage. Just look at the size of a car's
>>>> battery in comparison to a bike's.
>>>
>>> But it's the same voltage. The larger size means more amp-hours, so it can
>>> power a given load for a longer time - or a larger load for the same 
>>> length
>>> of time - before it becomes discharged.
>>>
>>>> The car battery needs more current to
>>>> charge it - even though the voltage is the same as the bike's (give or
>>>> take).
>>>
>>> It doesn't need more current to charge it, it needs more amp-hours to 
>>> charge
>>>
>>> it. Whether you do that by using a larger charge current in the same time,
>>> or
>>> use the same charging current for a longer time, is up to you. The 
>>> *maximum*
>>>
>>> recommended charging current will be larger, but you don't have to charge 
>>> it
>>>
>>> at the maximum rate, it'll just take longer.
>>>
>>>
>>> Eoin
>>>
>>> '04 ST955i
>>>
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>>
>>
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