Charging Issue

Ok friends, need a little help on an ongoing problem...first some background information...the bike is a 2013 Roadster with 17,000 miles on it. It hasn't been ridden much of late as I have three others that need exercise. The last time I rode it (a couple months ago) I suspected a charging issue as it nearly stranded me in downtown New Orleans...very slow turn over, but eventually started. This after about an hours ride from the north shore. Charged it overnight and took a short ride the next day but not long enough to fully discharge a hot battery if the charging system wasn't working.

I just got the chance to do some diagnostics. Battery has been on 1.25 amp Delran "Battery Tender Plus" trickle charger for a few days and is showing "green" which supposedly means fully charged. When checked with a multi meter directly across the battery terminals it reads 9.8 volts which seems exceptionally low for a "fully charged" battery. I would have expected something more in the 11 - 12 volt range. Start the bike and let it warm up for a minute...voltage never goes over 10 volts. Run it up to 2500 rpms and the voltage reads 10.2 volts across the terminals. Again...would have expected it to be higher at 2500 rpms...somewhere in the 14.5 volt range since I should be reading the charging system at this point and not the battery state.

So my question...bad battery? change the regulator out or some deeper problem? BTW...this is the bike I refer to as my Redheaded Slut...and she has to participate in a bike show and then lead a ride in a couple of weeks. Would be exceptionally embarrassing if she strands me on the side of the road since her presence was specifically requested.

I plan to change the battery anyway just to eliminate an easily replaced problem.

take the battery down to your local Auto Zone and let them test it, not heard of the voltage reg going bad on a Rocket but you never know four year old bike about time for a new battery anyway

I would expect a bad battery had to replace Wendy battery on her bike it went dead at a gas station after a 2 hr ride lukey that they was a parts store across the street to get it jumped got home tested the battery showed good went out the next day and it was dead so I changed it to full power and then loaded tested it and it went to bad

Battery is about a year old...should have mentioned that

R3Tex said:

Battery is about a year old...should have mentioned that

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Is it a Motobat by chance?

Nope garden variety yuasa

Bike WONT turn over at 9 volts I don’t think.
Disconnect the battery entirely that jump the bike off car battery check voltage first then check again once started. When running remove one the positive jump lead - if motor continues to run at least it’s holding its own voltage. I don’t know if this is safe to do electronically tho

Check connections at the starter motor including earth lead

R3Tex said:

Nope garden variety yuasa

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Had 2 Motobat $hit the bed on me - never another.
Shocked it's a you-assa, my preferred choice.
Suck it up and get another - one that you must activate.
I replace every 2 years as mine seems to eat em up.

My 2014 Roadster is still on the stock battery no issues, as mentioned earlier I’d take it in to have it tested, you can measure across the terminals, that will tell you the stored voltage but you need a load on the battery in order to test the battery properly.

As for the voltage you measured across the battery while the bike was running it should be at the opperating voltage of the bike, over 12volts. Not much different than testing the alternator on a car, for example, if the battery is at 10volts, start the car and measure again. If the voltage accross the battery measures aprox 13 volts, the alternator seems to be working. Then while the car is running turn everything on, lights, fan, radio etc...measure again and the output should still be close to 13 volts give or take, depends on the output capacity of the alternator. If it’s around 13 volts under load the alternator is good. If after a good run the battery is still at 9-10 volts then the battery isn’t taking a charge.

If you want to load test the battery yourself then do the same thing without starting the vehicle, measure the voltage of the battery with everything off (disconnect the ground and then measure the voltage). Once you have your reading, re-connect the ground then turn everything on, lights on high beam, driving lights, whatever you got. Don’t start the bike, the battery should drop a little, maybe 11.5volts or higher. If the voltage takes a nose dive then the battery isn’t holding a charge...bad / dead cells probably...change the battery.