If you own a motorcycle, you have probably dealt with a motorcycle battery charger that would not work because the battery voltage was too low. Most motorcycle battery chargers or motorcycle battery trickle chargers have this problem. Pulling the battery voltage down too low is easy to do. Just leave a load turned on your bike and come back in a few days and you have a low voltage battery.
If you have a severely discharged 12v battery (below 9v), you can begin to experience some problems with a motorcycle battery trickle charger. Most motorcycle battery chargers can only charge a 12v battery within a certain range, such as 7-13 volts for a 12v battery. If the voltage falls below 7 volts, the motorcycle battery charger cannot recognize the battery and cannot begin charging. In this situation, you would need to jump start the battery to increase the battery voltage to allow the motorcycle battery trickle charger to begin charging. This can be extremely frustrating. With you are looking for a new motorcycle battery charger; make sure you do some research on how low the battery charger can charge a 12v battery. Some of the high-end motorcycle battery chargers can charge down 2 volts.
It is not uncommon to pull a 12v battery down to 2-3 volts. Just stick a 12v DC light onto a battery and see how long the light will stay illuminated. I highly recommend the higher end motorcycle battery trickle chargers for this reason. Some of the higher end motorcycle battery chargers also have a supply mode. This is an awesome and useful charge mode because the battery charger does not care what the voltage of the battery is. This is one of those features that you do not realize how important it is until you have a severely discharged battery.