Yamaha Mio Newer Battery Always Dead

[Rice_King]

The title basically says it all. I have a 2006 Yamaha Mio (bought new by me) with a new battery that will not keep a charge.

This Mio had not given me any problems until about a year ago when the original battery would no longer stay charged. The battery (and bike) was 5 years old then and I just assumed the battery had gone bad, so I replaced it with a new one at the local Yamaha shop. About 1-2 weeks after the battery replacement, it was dead again. That episode just keeps repeating. Within a week (or two) of having it charged in the shop, I wind up having to kick-start it. I have had it back in the shop more times than I can count because of this battery issue. Meanwhile, the shop doesn't seem to think anything is wrong. The mechanics seem content to keep charging it for me -- happy to say at no additional cost to me (other than my time).

I have limited knowledge of these bikes. I know that automobiles have a charging system that keeps their batteries charged. Wouldn't my Mio have a similar setup? It is my wife and mine only motor vehicle so, as you might imagine, it is ridden a minimum 10-15 km per day.

What would prevent the battery from keeping a charge? Or why isn't it getting charged by our daily use?

[Kwasaki]

I think you were lucky to get 5 years, I find batteries a bit like a lottery the sealed ones on bikes seemed to last the best.

The Mrs Mio is 2005 first battery lasted nearly 2 yrs, told that 's about it so bought the same and the next was gone just over a year, sourced and bought a sealed one called a G-max and it's readings are still good as of today.

[karlos]

If the new battery isn't holding a charge you'll need to look into the charging circuit a little further, seems like a bad earth, Stator or maybe something has melted from the stator to the battery.

Best thing to do is to try and get it running again, kick start or charge the battery, then check to see what voltage is running to the battery with the engine running, best to have it on it's center stand and bring the bike up to what would be around 5kmh, as these bikes seems to idle too low to generate the 14.7v charge you are looking for

I'm fairly certain that your bike will register less than 14.7v perhaps just the batteries output of 12v will show, you'll then have to chase down the problem:-

1. Starting by cleaning all battery contacts
   
2. Clean the engines earth and it's contact point on the chassis
   
3. Trace the positive cable from the battery to it's stator (alternator) checking for and cleaning any bad contacts along the way
   
4. There might also be a heavy fuse somewhere along this cable, check to see if that's not blown
   
5. Check and clean all contacts on the bike's regulator / rectifier
   
6. Aside from the above you'll need to dismantle the bike's charger (Stator / alternator) and check for resistance and continuity there
   

[Rice_King]

Thanks Karlos. Good info!

I attached my multi-meter to the battery leads and revved the engine to a respectable RPM. I saw the numbers fluctuation between 13.2 at idle and 14.8 at high RPM. It was difficult getting a solid reading doing it on the bike's main stand due to it vibrating and attempting to slide sideways. It was also very hard to keep the engine speed at a steady RPM so I cannot put much faith in the results I got. I will need to get the shop to test the voltage in a more professional manner.

[Kwasaki]

Thanks Karlos. Good info!

I attached my multi-meter to the battery leads and revved the engine to a respectable RPM. I saw the numbers fluctuation between 13.2 at idle and 14.8 at high RPM. It was difficult getting a solid reading doing it on the bike's main stand due to it vibrating and attempting to slide sideways. It was also very hard to keep the engine speed at a steady RPM so I cannot put much faith in the results I got. I will need to get the shop to test the voltage in a more professional manner.

Although from a car question post just some more info.

An alternator fault.

Dirty terminals and connections or corrosion.

A loose belt.

A voltage regulator fault.

The alternator getting too hot.

I would of thought 14.1 if you checked with a voltage meter would be OK anymore than 14.2 I was always told is cooking the battery and shortens battery life.

Shouldn't be less than 13.8.

[karlos]

Thanks Karlos. Good info!

I attached my multi-meter to the battery leads and revved the engine to a respectable RPM. I saw the numbers fluctuation between 13.2 at idle and 14.8 at high RPM. It was difficult getting a solid reading doing it on the bike's main stand due to it vibrating and attempting to slide sideways. It was also very hard to keep the engine speed at a steady RPM so I cannot put much faith in the results I got. I will need to get the shop to test the voltage in a more professional manner.

14.8 is a little higher than the 14.7v max, but the full 14.7(ish) volts should be produced at low rpms (what would get you and your bike to 5kmh) and high rpms, sounds to me like the stator needs checking and the regulator too.