Hi all, 

What sort of tests would one do when buying used/ secondhand lithium battery other than measuring the voltage? Most lithium batteries have smart parameters, so believe it will be possible to read the number of cycles and SOC status? Some people have issues handing out original invoices because they claim it contains their personal details, but I find it strange because you will already know their first names, probably last names via TrueCaller if you have their number, and invoices rarely have customer address; so that claim doesn't hold water. I would personally ask for the original invoice if the battery is new/ or few months old just to satisfy myself that it's not old, to verify the serial number and probably for warranty purposes. Speaking of warranties, is it transferable from one person to another? Is it possible to claim for warranty without an original invoice? Your inputs are welcome on this subject. 

This will probably be dependent on the brand and original seller. I would suggest to find out the place of purchase and speak to them, if they are going to honor the warranty when the battery is sold to someone else. Also, contact the manufacturer and ask the same, in case the reseller does not exist anymore by the time you need to put a warranty claim.

In regards of testing, there should be some information from the BMS for State of Health (SOH) of the battery, which is an indication of the usable life left on the battery.

The ideal, would be to perform a full capacity test but that requires additional equipment and time, and it's not practical when buying second hand batteries.

Someone else, might be able to better advise how to test properly second hand lithium batteries.

@PowerUser thanks, I've sent emails to the battery manufacturer (Blue Nova) and store that sold it (ACDC). My logic tells me the warranty should follow a product and not a person.