Charging Question - Battery

[Skywagon]

The battery is about 2.5 years old.  Friday I was fiddling around with the bike with key on several times and probably not more that about 15-20 minutes total, if that. I got all suited up Saturday to ride, hit the starter, and boop...it spun about a half turn and got the dreaded solenoid click of a dead battery.  My digital meter said 12.4 V direct on battery.  I put the deltran agm charger on it for about 30 minutes and it still wasn't enough.  I decided to take the battery out of the bike, check for corrosion (there wasn't any), and charge the battery overnight.  Even though the terminals and cables were clean, I cleaned them and applied my usual dose of dielectric grease.  I put the battery in and it spun like crazy.  I put my meter on the terminals and it looks like the alternator was putting out between 14.1 and 14.2

 

I took off for a 200 miles country jaunt.  I never shut off the bike.  I changed the display from tire monitor to voltage monitor.  For the whole time I was riding the display showed 14.1 or 14.2.  It never dropped to a lower voltage.  This is my question and request.  If some of you could set your monitor to voltage and let me know what you see for voltage on your ride I would appreciate it.  I've never monitored it while riding so don't know if this is normal or an indication of the battery or something else.  Everything else I owned or have owned cuts back on charge after a while.  My car will start at about 14.5 charge and then drop back to 12.4....same on everything I own.

 

After the battery has sat overnight the meter shows at rest voltage of 13.8 and the bike spins over just fine

[szurszewski]

The only BMW I ran a volt meter on while riding usually hung out at about 13.6v - that was a K1200LT, and it was a very cheap cigarette lighter plug meter. 

[Rinkydink]

My 17 RT runs 14.1 per the display while riding. 

[dirtrider]

3 hours ago, Skywagon said:

The battery is about 2.5 years old.  Friday I was fiddling around with the bike with key on several times and probably not more that about 15-20 minutes total, if that. I got all suited up Saturday to ride, hit the starter, and boop...it spun about a half turn and got the dreaded solenoid click of a dead battery.  My digital meter said 12.4 V direct on battery.  I put the deltran agm charger on it for about 30 minutes and it still wasn't enough.  I decided to take the battery out of the bike, check for corrosion (there wasn't any), and charge the battery overnight.  Even though the terminals and cables were clean, I cleaned them and applied my usual dose of dielectric grease.  I put the battery in and it spun like crazy.  I put my meter on the terminals and it looks like the alternator was putting out between 14.1 and 14.2

 

I took off for a 200 miles country jaunt.  I never shut off the bike.  I changed the display from tire monitor to voltage monitor.  For the whole time I was riding the display showed 14.1 or 14.2.  It never dropped to a lower voltage.  This is my question and request.  If some of you could set your monitor to voltage and let me know what you see for voltage on your ride I would appreciate it.  I've never monitored it while riding so don't know if this is normal or an indication of the battery or something else.  Everything else I owned or have owned cuts back on charge after a while.  My car will start at about 14.5 charge and then drop back to 12.4....same on everything I own.

 

After the battery has sat overnight the meter shows at rest voltage of 13.8 and the bike spins over just fine

Afternoon David

 

Your 1200 wethead isn't like most modern automobiles. Your wethead has an internal alternator with an external voltage regulator so there are no alternator brushes & no excitable (variable) rotor magnetic field. For the most part it is constant (full) output alternator with the rectifier/regulator dumping the unused current into heat. 

 

Depending on the battery temperature that 14.1-14.2 volts should be pretty close to what is needed to keep your AGM battery charged.  Most auto/light trucks/BMW 1100/1150   use an external alternator with a current adjustable rotor (alternator only puts out what is needed to charge battery & run vehicle electrics. In a lot of modern automobiles the alternator output is actually computer controlled to more closely match the vehicles electrical requirements & lower alternator load for improved fuel economy.

 

The  newer BMW 1200 wetheads use an AGM battery & those require slightly higher charging voltage to keep properly charged.

 

 When getting charging voltages from others you need to be aware of WHERE they are getting the voltage readings from (ie system voltage or battery post voltage). If from a very similar motorcycle in similar ambient temperatures using the same dash readings then it is comparable. If from a different motorcycle brand, or different model,  or  an earlier year with an external alternator, or OEM GEL battery,  then possibly not comparable. 

 

 

[Skywagon]

Thanks DR.  That is just what I needed to know.  14.1- 14.2 full time on the BMW display is normal per your explanation.  I was afraid something was haywire.  

[Skywagon]

Thanks Rinkydink....with your view and DR's explanation sounds like all normal.  I never felt the need to monitor it before but guess I will occasionally now.

[realshelby]

David, mine runs 14.0 almost always with the current battery. It ran 14.0 - 14.1 most of the time on the OEM installed battery. I may have seen 14.2 once or twice over the years.....

[Bernie]

22 minutes ago, realshelby said:

David, mine runs 14.0 almost always with the current battery. It ran 14.0 - 14.1 most of the time on the OEM installed battery. I may have seen 14.2 once or twice over the years.....

 

I have the same reading on the dashboard on my 2018 R1200RT-LC.

The only time it drops, is if I turn on heated jacket, gloves, grips and seat and then switch my Clearwater lights to his beam (100%). 

It will then drop low enough to give me a warning. So I just switch the lights too low beam. LOL

 

[LAF]

Yes on the GS I see 14.1 consistent. 

 

As others, if I run the grips or heated clothing I can see 13.8 - 14.0 easy.

 

It is really hard to see a full 14.2 on a bike as it needs a decent amount of electric to just run all it's electronics.

[Skywagon]

ok...sounds like the 14ish number is normal.  Thanks all.  I am so glad to hear this as any thoughts of an alternator issue on my wethead would have made me ill.

By the way when I was looking in the manual, I found the following paragraph.  I know I've seen a few questions hear about parasitic drag.  It's actually in the manual

 

If the battery is not disconnected, the onboard electronics (clock etc.) will drain the battery. This can cause the battery to run flat. If this happens, warranty claims will not be accepted. During driving breaks of more than 4 weeks, a trickle-charger should be connected to the battery.

 

Page 132 in my manual