I would be checking the starter. That is to much of a voltage drop. It shouldn't drop off much under 10v.

 

Talked to the shop yesterday. They told me the battery was bad - I knew that. Said they put their battery into it and let it sit over the weekend and no problem, so no voltage drain. Knew that too, but good to have someone else check. They checked the AC systems and voltage regulator - no issues there. They couldn't find any shorts to ground or broken wires. Not sure where they're going from here, but what are the chances I got 2 bad batteries in a row?

 

It doesn't take much to knock the magnets loose from the rotor, after putting a bike down and corresponding charging system problems, could be worth a look. Do you know if they did an AC voltage output test ( stator output ) for sure?
Certainly easy to check a battery, charge it, load test it, that's it.

Your bike runs fine on a fully charged battery which is to be expected, if your charging system doesn't produce enough amperage to meet the draw while your bike is running, it will run on the battery until it's weak enough to kill the bike.

 

Picked up the bike yesterday. Guys said my battery had a bad cell - 2 bad barrteries in a row is pretty unlikely. They said they checked everything out:

- checked and charged battery
- checked for shorts and drains
- checked wires at starter, battery and lights
- disassembled primary and checked rotor and stator

Said they found nothing. I am still suspicious. We'll see what happens to the new battery. I'm now $460 into this problem. Hope its solved.

 

Hello voodo. I know it is 5 years later, but i bought a brand new street bob 2015 with 1200 miles on it and i'm at my second battery too. Dealer did all the tests like your and found nothing wrong, they put a 3rd battery in there and told me my batteries was 100cca and completly dead.


Did the new battery fixed your problem ?


Thansk alot
David

 

Sorry, David. I just saw your post.

If I rememeber right, the little red rubber boot that covers the positive battery terminal wasn't sitting on correctly. So, when riding, the batery would short against the inside of the battery box cover. We could tell because the paint was melted on the cover inside where it lines ups with the positive post.

I made sure the boot would sit on correctly. I also painted the inside of the battery box cover where it lines up wiht the positive batter terminal with a good spot of Liquid Electrical Tape.