SV650.org - SV650 & Gladius 650 Forum - 12.4v at tickover, is reg rec knackered?

The battery will start to charge at anything over about 13.2V, give or take. They don't like being overcharged, so the reg/rec is intended to prevent the voltage rising above about 15V max.

What voltage you actually get from the charging system (alternator/(reg/rec)/battery) depends on a lot of things, engine speed, electrical load, age/condition/charge state of battery, voltage drop across wiring/connectors/fuses etc. Make sure all connections are clean.

Measuring the voltage on a battery without the engine running doesn't tell you very much, only really the state of charge, but not the capacity (i.e. the condition) of the battery. You really need to decide whether the battery will hold charge over a period of time, and whether it can deliver much current. Having said that, if the charging voltage looks reasonable and the battery won't start the bike reliably, it's probably heading for the paperweight store.