Battery Woes

[akbeemer]

Annie’s F800GS, went for a ride of about 60 miles. Bike started normally at our place and after one stop during the ride. Got home and cut off the engine and shortly thereafter tried to start without success. Put a meter on the battery and it was at 11.4 volts. Charged it overnight and it was at 13.2 volts. Reconnected battery and started the bike. The battery dropped to 11.4 volts under load. Bike was charging at 14.2 volts at idle. The battery was at 13 volts after shutting off the engine.

About 8 years ago we had a battery that would preform normally for awhile and then seem to lose enough charge to start the bike. We were on a ten day trip and I had to jump her bike once or twice a day. I was told that AGM batteries can have a connection between cells fail, thus reducing the charge available, and then the break can temporarily weld itself when the battery is under load. This explanation seems to describe what happened.

So, is there another plausible explanation for what is happening now? That being, a battery that was under charged after a ride on a bike with a functioning charging system, but took and is now holding a charge. Anyone else have an intermittent failure on a battery?

 

[tsconver]

That 13 volts is a surface charge. If it is dipping to 11.4 when cranking you need a new battery.

 

[Omega Man]

Sure-

I can’t say I have had a battery fail and come back to life unless it was a really fresh battery and I left something on.

My battery died yesterday...

My battery died yesterday, and it went down with a vengeance. :banghead I have a lot of experience with batteries-probably have 17 in service at the present time, but this experience was new. I rode the 2009 F800GS the 3.5 miles to the Post Office, was in and out in 2 minutes and it was over. I...

forums.bmwmoa.org

They ask a lot out these small batteries.

How old is the battery? It sounds like AGM?

Barring it not be a loose wire on a terminal, it sounds like battery time.
OM

 

[lee]

Charged it overnight and it was at 13.2 volts

How long did you wait to test it after disconnecting the charger?

 

[akbeemer]

Well, Lee you have identified the key flaw in my testing. I load tested it again after turning on the ignition and high beam until the charge on the battery was 12.7 v with the ignition off. Tested it again under starting load and it dropped to 9.9 v. So, new battery it is.

 

[98lee]

This test is best done with the battery disconnected from the bike, but it’s not absolutely necessary.
Fully charge the battery.
Disconnect charge and wait an hour. Test voltage.
Wait a day. Test voltage.
Wait another day. Test voltage.
Keep repeating for 3-5 days and noting voltage.

If the voltage continues to drop each day and continues to drop below 12v, you either have a bad cell in the battery or, if you left the battery connected to the bike, a drain from something on the bike. Repeat test with battery disconnected from bike to determine which one. Or save yourself some time and just do the test with the battery disconnected in the first place.

It's probably a bad cell. A bad cell will cause a battery to rapidly self discharge or “not hold a charge”.

 

[EUGENE]

I ran across a battery system lately that was 6volt with a positive ground. Odd, but was a 1955 tractor. I did get it running.

 

[bobs_one]

Older French and English cars (and some motorcycles) used to be positive ground in an attempt to provide Cathodic Protection from corrosion. Not sure if it worked on the cars and bikes of not, but it is commonly used on oil drilling platforms and bridges, etc. I suspect that it takes more than 6V to make it work, so that may have been the problem.

 

[mikegalbicka]

My 62 Mark II Jaguar had positive ground with a dynamo instead of an alternator.

 

[brownie0486]

That 13 volts is a surface charge. If it is dipping to 11.4 when cranking you need a new battery.

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Think of the cranking-volts test as a compression-test for your battery. Anything under 9.6 volts means the battery is worn out. This battery rates well with 10.48 volts.

I've seen 9.9 a few times, usually 10.4-10.6 while cranking it over on the 11RT. That was the older battery I replaced last fall because I didn't know how old it was and I'd had it two years [ as a preemptive to failure on a trip ]. The new battery is showing the same results from new.

On a trip when it's not on a tender, I see the same results [ but the bike is being ridden every day ]. I've seen many questions and answers on batte3ry health, none have stated unde4r 11.44 cranking is an issue.

 

[akbeemer]

When I did the initial load test and the battery dropped to 11.4v during startup I viewed that as good. Then I realized (with prodding from Lee) that I load tested too soon after taking the battery off of the charger; was at 13.2v with surface charge. When I tested the battery again while it was at 12.7v and it dropped to 9.9v I realized I had a battery issue.

 

[Omega Man]

When the starter and or related accessories pull voltage on the start cycle lower than 9.2 volts, it’s pretty iffy if the bike will start. The computer isn’t tap-dancing happy down in the 9.2 range.
OM

 

[pglaves]

Here is an interesting note from models past -even antique K75 bikes. The ignition trigger cuts out about somewhere near the 10 volt range while the Motronic will still fire the injectors somewhere down in the 9.5 volt range. So with a run down battery, cranking will cause the ignition spark to cut off but the injectors to still squirt. Then, even if you attach jumper cables or charge the battery the fuel fouled spark plugs are useless. That is why every K75 we have ever owned - maybe 8 or 9 or so - all always had three new or re-cleaned spark plugs in the tail cone.

 

[brownie0486]

Here's another set of volt numbers I keep on my phone found somewhere.

Key off 12.7-12.8
key on 12.2-12.3,
cranking should be 11 or close, anything under 10 battery may need to be replaced
idling 13.6-14.2

2011rt
key off reads 12.7
key on reads 12.3 no accessories on [ I turned the denali d2's on and it dropped .1 volts to 12.2 volts ]
cranking reads anywhere from 9.9 - 11

This is with keeping it off the charger for 20 hours [ yesterday afternoon to 10am this morning ] I saw 9.9 starting it this morning off the tender for that time. Next time I started it after a 5 mile ride to meet some of the guys for coffee, 10.4 while cranking. Fueled up, next start showed 10.8.

This is a new Yuasa equivalent to the oem battery that was installed 8 months ago. Thing is, I replaced it simply because I didn't know how old the batt was when I bought it. Even more telling for me, the old battery numbers were exactly what the new battery numbers were today. Did I have to replace the one that came with the bike? Unlikely at best.

 

[pglaves]

The RT is now 13 years old. How many miles? I suspect it is possible that there is a little abnormal starter drag drawing the cranking voltage lower than typical.

 

[brownie0486]

The RT is now 13 years old. How many miles? I suspect it is possible that there is a little abnormal starter drag drawing the cranking voltage lower than typical.

37K. The 16RS has 35K and runs pretty much the same numbers posted. Interesting, thanks

 

[brownie0486]

The RT is now 13 years old. How many miles? I suspect it is possible that there is a little abnormal starter drag drawing the cranking voltage lower than typical.

Paul, I'm correcting the post remark about the 16RS having the same starting volts after rechecking it yesterday. The RS turns over with 11-11.3 volts cranking unlike the RT's numbers listed.

Your suggestion it may be drag on the starter for some reason on the RT will be checked by my mechanic next service. Thanks for the suggestion

 

[globalrider]

That 13 volts is a surface charge. If it is dipping to 11.4 when cranking you need a new battery.

Or it could be a starter drawing far more current than normal which draws down the battery voltage.



A thorough cleaning of the starter, armature and segments along with a new brush plate and the starter ran like new. Prior to that, it sounded like the battery was dead.