What voltage should the alternator pump out on 1200gs

stephinson

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What voltage should the alternator pump out on 1200gs

I keep getting a flat battery when riding

I have put a voltmeter on and its hitting 14.3 volts at tick over but does not rise when revved

Is this correct or do I need a new battery
 
Hi :)

Voltage sounds about right. What happens to it when you turn on load devices, eg servo brakes if fitted, main beam, brake lights etc?

Just a thought, checked the battery connections are good and tight, and does the battery loose its charge when not in use?
 
Yes sorry

did 300 miles on sunday

got it out wednesday for a ride
started fine

got to petrol station
started fine

After an hours ride when we stopped
came to start and it just clicked

Got it bump started (blumin hard)

put it on charge
next day started no problem

Voltage stays at 14.3 when I turn heated grips on
 
Resting voltage

Yes sorry

did 300 miles on sunday

got it out wednesday for a ride
started fine

got to petrol station
started fine

After an hours ride when we stopped
came to start and it just clicked

Got it bump started (blumin hard)

put it on charge
next day started no problem

Voltage stays at 14.3 when I turn heated grips on

To diagnose the problem a little further: My 2p would be to measure (preferably the resting) voltage of your battery (hours) after charging it and then again (hours) after each trip. The easiest may be measuring the voltage before you start (use any el power).
 
I checked it after I had charged it and resting it was 12.3

tested it again this morning and its still 12.3

I have used optimate and that does not show any problems

if its getting 14.3 volts when riding them its got to be the battery I would guess if 14.3 is correct, but I think optimate only pumps out 14.3 when it charges
 
It sounds to me more like a duff connection somewhere. Or the starter relay. Battery sounds ok, alternator sounds ok, so I'd check elsewhere before shelling out on a new battery
 
I checked it after I had charged it and resting it was 12.3

tested it again this morning and its still 12.3

I have used optimate and that does not show any problems

Did you you the Optimate between the two readings? If you did, you need to repeat the excercise without hooking it up to the Optimate between readings.

A good test of a fully charged battery is to measure the voltage when it's been doing nothing for a while. You say 12.3v - fine. Keep the voltmeter connected turn the ignition and headlight on (don't start the bike) and leave it switched on for 2 minutes. Check and record the voltage drop over this period. What is the voltage after 2 minutes? If it still 11+ volts, this would suggest that your battery is OK. If it's dropped much more than this, it suggested that the battery is dud.

It's worth noting that a battery only really deteriorates when it is less than fully charged. For long battery life, avoid leaving the bike with a battery that is less than fully charged. The rate of sulphation of the plates is exponentially accelerated the more a battery is discharged. Don't turn the engine off with the kill switch and leave the lights on for any time.

Greg
 
you need to do a load test on the battery.


just measuring the volts on a battery with no load won't tell you much.
 
you need to do a load test on the battery.

just measuring the volts on a battery with no load won't tell you much.

Told a lot on Tim Cullis's out in Morocco. And most battery load testers I've seen are more car battery capacity friendly :(

BTW IIRC it was on dynamos that the voltage raised with increased revs and you needed about 3000 rpm to actually charge the battery :(
 
Told a lot on Tim Cullis's out in Morocco. And most battery load testers I've seen are more car battery capacity friendly :(

BTW IIRC it was on dynamos that the voltage raised with increased revs and you needed about 3000 rpm to actually charge the battery :(

good for checking voltage rise when when it's connected and revving the engine, but i've seen loads of batteries read 12+v but be totally shagged. it's their performance under load that is important.

i use a drop tester built for cars, i just read a little further down the dial ;)

airheads need about 3k revs to get into positive equity with the charging. they have alternators, just poor ones compared to the car type fitted to the oilheads.
 
Load testing and more

I checked it after I had charged it and resting it was 12.3 - tested it again this morning and its still 12.3 ...

Okey, batteries are a little sience and a little art, but to try to stick with the basic principles eg KISS. Most people have or are easibly able to get hold of and use a basic a voltmeter. So if you check the resting voltage (over night a good start point, or allow 4-8 hour of rest after charge or discharge dependend of amount charge/discharge of the battery) at room temperature you should get:

12.65V 100%
12.45V 75%
12.24V 50%
12.06V 25%
11.89V or less Discharged

(Some small variations between different battery types and size - and if temp below 77F/room temp expect less). So 12,3 VDC sounds low if this is after a proper full charge unless (outside) in "low temp". If the battery can not be charged to a resting voltage of about 12,7 VDC - no need to look any further you have a weak battery that need to be changed. Why that happened is an other story. With a new battery keep an eye on it to see if the bike is able to keep it charged and fit. If not, time for more investigation...

As for charging voltage of 14,3 VDC - it sounds about right, but several factors are influencing this...

So KISS and Best of luck
 
The alternator gets up to about 14.5 v tyo charge the battery and when it is charged the alternator drops back to 13.4 or thereabouts. That voltage counteracts the natural slow internal discharge of any battery - itts the float voltage. The battery itself should be about 12.7 when fully charged though immediately after charging it will be higher than this so you have to wait a while to test.

There are all sorts of issues that could cause the problem you describe but basiocally they come down to two groups. Either your charging system is not getting the amps through or your battery capacity is poor. To deal with the former check all the connections, particularly those from alternator to the frame. Are they clean and greased or are they cruddy and dirty? Are they tight? Cos if your alternator is getting up to 14.5v then the problem must be high resistance in the circuit.

Do that first cos thats the least expoensive option. If they are ok then I suggest you take the battery off the bike and charge it with a battery charger. Will it charge up to 12.7? Will it hold that charge over 48 hours? If you put a 12v 50 w bulb across it, how long does it take to get from 12.7 (full) to 12.2 (half empty). Multiply the time in hours by 8 and that will give you the capacity of the battery to compare with the rated figure.

Or alternatively, if you're bored and felling flush, just replace the battery cos thats by far the most likely culprit.
 


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