Dead...

Having Problems with your BMW R1200RT/R1250RT? or have some Maintenance and Service questions?
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Sacowan
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Location: NorBay, NorCal
Bike Model and Year: 2020/RT
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United States of America

Dead...

Post by Sacowan »

The bike, 2020 1250RT, has a lithium-ion battery less than one year old.

I changed out my exhaust system a couple weeks ago, which requires disconnecting/connecting O2 sensors.

Since, I have had the bike out twice for a couple hours each with no problems at all.

Day before yesterday, tried to start the bike and nothing. Nothing lit up, gauges, lights, nothing. Check the battery and it showed .4 volts.

Pulled the battery, hooked up the charger. Let it sit overnight. Charged back up to 12.5.

Installed the battery. Pushed the "on" button and everything lit as usual. Brought up the voltmeter in the dashboard. Battery read 12.4 volts. Hit the start button, dash went dark. Pushed the "on" button again and watched the voltmeter go down from about 10v to 4v and dash went dark again.

Made no changes to the bike other than the exhaust.

Any ideas as to where I should start looking for the problem?
Ain’t no right way to do the wrong thing.
JoeInTUS
Posts: 2
Joined: Sun Jun 08, 2025 3:25 pm
Bike Model and Year: 2017 R1200RT
United States of America

Re: Dead...

Post by JoeInTUS »

12.5 volts seems very low for a lithium ion battery. I would start with the battery. Here is Shorai’s charge vs voltage chart.
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IMG_0433.png (370.58 KiB) Viewed 833 times
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Stu
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Re: Dead...

Post by Stu »

Sounds like the battery is knackered
Mark S.
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Bike Model and Year: RT1250RT 2021
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Re: Dead...

Post by Mark S. »

Many li-ion batteries have a built-in battery management system (BMS) to prevent over charging/discharging. The BMS can tell you if there is an issue with the battery. I would track down the manual for the battery and look for clues there.
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