Battery troubleshooting guide
Much more needs to be written here, like how many charges each battery can take before it needs to be replaced.
Battery not charged
A obvious cause of low or slow performance is simply a low-level battery charge, even if the GREEN indicator light is illuminated. The YELLOW and RED leds do not light until the batter is almost completely discharged. You will notice significant degradation in performance long before that point.
Charger not working
Another cause is a poorly charged battery due to a malfunctioning battery charger. The battery charger has an automatic cut off mechanism to prevent overcharging. It seems that this mechanism can be affected by temperature, and the charger may not charge it too cold or plugged in in the wrong order. For further information see Battery charger information.
Temperature: The Motorboard and the battery must be between 60 Degrees F and 90 Degrees F to charge properly. If your battery charger lights blink red/green, most likely the temperature is out of range, and you should bring the Motorboard to room temperature before attempting to charge again.
Battery needs to be conditioned
Lastly Lead Acid and NiMH batteries need to be "conditioned" every ten charges. This involves completely draining and recharging the battery. LiIon batteries should NOT be conditioned.
Battery worn out
Under perfect conditions, Lead Acid and NiMH batteries are rated at only about 500 cycles, or 12 months (2 rides x 20 workdays x 12 months ) of daily use. LiIon batteries are rated at 2000 or more cycles or about 4 years of daily use. Another sources says "500 - 1,000 charge cycles (depending on use, this could be 2 - 5 years)".