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Tech Corner

Technical Q and A for classic motorcycle maintenance and repair.


Lithium Batteries and Chargers

Motorcycle Classics tech expert Keith Fellenstein 

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Lithium batteries and chargers

Q: In your January/February 2017 column you mention that lithium batteries last longer maintained by special lithium chargers. Why? If special chargers are needed, maybe lithium batteries are not viable in our bikes with their non-specialized charging systems? And what is the life expectancy of the lithium battery? — Cliff Elkins/via email

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A: The chargers are designed to meet the requirements of lithium batteries. A single lead-acid cell develops higher resistance as it charges, while a lithium cell develops lower resistance as it charges. Lead-acid batteries self balance as each cell reaches capacity, while lithium batteries trend toward short circuit. A battery management system reads the individual cell charge state and directs charging voltage to the cells at a lower charge state. If your charging system produces between 14 and 15 volts at running rpms and if your battery has a built-in management system, a lithium battery should be fine. Battery chargers that have de-sulphation circuits should never be used with lithium batteries. Modern lead-acid battery chargers can be used, but should be monitored and disconnected once they indicate the battery is charged. Shorai says that their batteries have the same charging requirements as AGM batteries, but recommend their charger for the reasons laid out above. Shorai warrants their batteries for 5 years.