Kremmen
Registered user
Alternators ain't like dynamos they put out a good charge even at tick over.
How many miles to recharge battery after starting the engine?
- Thread starter FatBob
- Start date
AAMOI i can tell you now, that when the charge light on an airhead goes out just over tickover, the battery is still very much in negative equity. charge doesn't gain on the current draw until about 3000rpm 
modern charging system should be way better than that.
modern charging system should be way better than that.
Just done it myself on my 1150;
The voltage is clearly regulated to 14.0v max and it is giving some charge at tickover but nowhere near its maximum.
Greg
- 13.3v at tickover with dip h/lamp on
- 14.0v at 2,000 rpm and above
The voltage is clearly regulated to 14.0v max and it is giving some charge at tickover but nowhere near its maximum.
Greg
You need to know what amps is is generating also - they all regulate to approx 14v otherwise the battery would get damaged
E. Buygum
Registered user
Alternator on '08 GS is rated at 720W which is plenty to run lights, other equipment and have a surplus to charge battery. Limiting factor on charge rate is probably not the alternator's ability to deliver voltage but the lead acid battery's ability to quickly recharge. I think most car batteries can usefully handle about 1A to recharge...not sure if motorbike battery is any different. If 1A is about right, then, given the the starter motor takes around 90A, it will take 90x as long to recharge as start. So if it takes 5s to turn over engine to start, a battery in good condition should have recovered in under 10 minutes.
RPilot
Guest
.
Yes modern AGM batteries have an improved abilility for quicker recharge.
But loading balance requires basically higher average revs.
At idle generator regulator provides sufficient energy to supply ignition, fuel pump and headlight.
Break even for additional load will be a minimum rev of about 2800 to 3000 revs, which e.g. may not increased constantly under stop and go conditions in the city traffic.
Hence max power potential of 720 W will be not available under most realistic circumstances.
Consequently switched heating grips, wests and foglights may cause to drop voltage below 14 Volts.
In some cases a constant voltage control can be usefull to see what happens.
Best
ok, not very scientific test completed.
my 1200GSA
battery resting voltage as found: 12.6v
started and measured at ECU controlled fast idle: 14.6v
after the idle has settled to normal and battery has recovered a bit from the shock of starting for the first time in 2 months: 14.6v
rev to 4000: 14.6v
i don't have spots, but i plugged in 2 x EXO heated vests and the voltage dropped slightly to 14.47 (1 jacket) and 14.36v (two jackets). i can't remember if these garments are 3 amp or 5 amp.
in short, i don't think OP will have any bother on his commute.
my 1200GSA
battery resting voltage as found: 12.6v
started and measured at ECU controlled fast idle: 14.6v
after the idle has settled to normal and battery has recovered a bit from the shock of starting for the first time in 2 months: 14.6v
rev to 4000: 14.6v
i don't have spots, but i plugged in 2 x EXO heated vests and the voltage dropped slightly to 14.47 (1 jacket) and 14.36v (two jackets). i can't remember if these garments are 3 amp or 5 amp.
in short, i don't think OP will have any bother on his commute.
Info is for a 100GS but it gives some idea on how much you're asking of your charging system / battery with lots of electrical accessories:
http://www.gunsmoke.com/motorcycling/r100gs/charge_diagnostics/index.html
http://www.gunsmoke.com/motorcycling/r100gs/charge_diagnostics/index.html
State of charge can, to a degree,be determined by battery voltage, so:
a) measure battery voltage in morning before starting
b) measure battery voltage when you arrive (leave to cool for a few hrs), even better the next morning after 2 journeys and an overnight rest.
if b is less than a, you'll need to charge the battery on occaision.
a) measure battery voltage in morning before starting
b) measure battery voltage when you arrive (leave to cool for a few hrs), even better the next morning after 2 journeys and an overnight rest.
if b is less than a, you'll need to charge the battery on occaision.
GSband
Registered user
This post adds the info that R12GS alternators have 600W output from MY 2004 upto 2007. Alternators on facelifted R12GS's (MY 2008 and onwards) have 720W output. 
chrismartink6
Guest
This happened to my friends bike. He's Bike had been stand still for about a month then he started it to warm it up a little on the centre stand. After five minutes he turn the bike engine off and moved the bike out of the garage and placed it on it's side stand.
When we decided to leave for an afternoon's riding the bike would not start again, and the engine warning light came on. We called BMW in Dorchester and they explained that they was probably enough juice to start it, but not the second time. Once started the first time we should have kept the engine running and take it for at least a 10 mile run to recharge the battery.
When we decided to leave for an afternoon's riding the bike would not start again, and the engine warning light came on. We called BMW in Dorchester and they explained that they was probably enough juice to start it, but not the second time. Once started the first time we should have kept the engine running and take it for at least a 10 mile run to recharge the battery.
