I use a trickle charger that puts a measly 20 milli-amps (20/1000) into my battery all the time my bike is standing. I have one battery that is over 20 years old and still good.
That's very good life from a battery. Tell me, is this battery used in a vehicle with an electric starter?
The trickle charger is excellent for keeping the battery out of sulfation.
However, when a battery discharges from use, metal is moved from one plate to the other. Recharging puts it back, but seldom in the same place it came from. That's nearly random, affected to some degree by plate separator technology. Repeated charge/discharge cycles can leave plates with huge holes in them. And, the reduced plate area means that the original storage capacity is reduced. While such batteries still have storage capability and read full voltage, they don't store the power needed to drive a starter motor.
But, then there are times when all the angels dance only on the left side of the head of a pin.
In the past, I have used a battery in my 74 CB550 for about nine years. But, the last three or four was kick start only, with the headlight off most all the time. It still read full voltage after charge when I retired it. But, it wouldn't light a 23 Watt bulb for more than 5-10 minutes before going flat and needing recharge.
I guess I was just unlucky.
