The charging voltage of the 12V battery depends on the type of battery and the temperature. In more modern cars, the computer reads the temperature and manages the charging voltage via a regulator. The battery is close to the engine and gets very hot. The voltage value for a 100% full lead-acid battery is at least 13.9V and up to 14.3V at 20°C. As the temperature rises, the voltage for a full battery should drop by approx. 15mV/°C.

 

   On motorcycles, the battery heats up less because it is further away from the machine, and only the voltage regulator does the voltage regulation. The charging voltage is measured at half throttle, and at idle throttle it is not important. The value of the charging voltage for a 100% full 12V lead battery is a minimum of 13.9V and up to 14.5V at 20°C. A voltage closer to 13.9V gives a longer life, but slower charging. A voltage below 13.9V does not allow a 100% charged battery and after some time results in an empty battery and loss of capacit . This information has been verified from my own experience, and definitely the charging voltage of 13.5 to 13.8V is not enough.

 

   AGM batteries are charged at a voltage of 14.2V and up to 14.9V. The exact voltage depends on the battery manufacturer. If your AGM battery is not listed, the recommended charging voltage value is 14.5V at +25°C. If you are thinking of putting an AGM battery instead of a regular lead battery, check if your regulator provides sufficient charging voltage.

 

   Gel batteries are typically charged with a 0.2V lower voltage than regular lead batteries, but this also depends on the manufacturer.

 

   The most common causes of too low battery charging voltage on a motorcycle where the generator is excited by a magnet:

 

• breakdown of the stator (generator) on the housing - charging rarely exceeds 13V
• too low voltage from the stator - less than 15VAC between wires at idle without connected regulator
• defective stator - for example, the AC voltages between the wires are ok, but by measuring the short-circuit AC currents between the wires, significantly different currents are obtained
• break in one of the wires of the three-phase generator (stator)
• regulator breakdown on one of the input wires (from the stator) to the housing
• consumer overload or generator too weak
• the battery draws an unusually high charging current
• faulty voltage regulator - charging to a lower voltage or is very sensitive to voltage spikes
• bad connection of the voltage regulator to the battery - circuit from the plus of the regulator to the plus of the battery and the minus of the regulator to the minus of the battery dU1>0.26V or dU2>0.06V

   Detailed instructions for finding the fault can be found on the page "Troubleshooting".
   If it is determined that there are excessive voltage drops dU1 and dU2 in the circuit from the plus of the regulator to the plus of the battery and from the minus of the regulator to the minus of the battery, instead of searching for the location of the problem, it can be bridged with new wires. Example of instructions for a quick solution.

   In the season when the motorcycle is not ridden, it is recommended to store the charged battery at a temperature of up to 15°C. Best on concrete basement floor. Keeping the battery at room temperature leads to sulphation of the plates and aging, i.e. reduction of life. Research has shown that the colder the climate, the longer the batteries last. So, for example, in Canada the average battery life is significantly longer than in Florida.