Lithium Iron Phosphate Battery Charging Advice


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 email with “Keith’s Garage” as the subject.

Q: I have a 1966 BSA Lightning, a 1970 Honda CB750 and a 1974 Norton Commando that all use Podtronic or other aftermarket solid state rectifier/regulators for lead acid batteries. I would like to upgrade to lithium iron phosphate batteries and would like to know if I will be okay using the current voltage set points for lead acid batteries, or do I need to use rectifier/regulators specific for lithium batteries? Thank you for any help.

- Wayne Robertson/via email

A: My opinion for a long time has been that most of the older bikes don’t have the robust charging system necessary to keep a lithium iron phosphate (LiFe) battery fully charged. I recently spoke with Rick of Rick’s Motorsport Electrics to see if things had changed. He said that most LiFe batteries like the charging voltage to be 14.2 volts, and not much higher or lower than that. I don’t know what the charge cut-off point is for Podtronics, but the older Lucas Zener diode starts dumping voltage to ground in the 13-volt range. For the British bikes I’d stick with my usual recommendation of a good absorbed glass mat (AGM) battery for energy density and leak-proof design. Rick did say that he had a plug and play regulator rectifier for the CB750 that would work well with a LiFe battery. MC


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