If you don't have a charger at least get a volt meter. After you take that ride don't restart it, put the meter on it and see what the voltage is. If it's over 12.6 to 12.7 or so it's fully charged. If it sits overnight measure again, if it's much less it's not holding a charge and will discharge itself. A bad cell will do that to a battery. If it drops under 12.4 or so over a week that also tells you its not holding a charge.
You can also put a meter on the posts with the motor running and you should see between14 and 15v, that will tell you the charging system is ok.
As mentioned, if the bike sat with a discharged battery at any time from factory to dealer floor, it can easily ruin the battery. If it's under warranty take it in to be tested and if found bad they will replace it. They can load test it and check the voltage. 12v batteries are easy to tell their charge state by the measured voltage in a given condition. Just after a charge session they will peak at over 13v but drop back to their full charge of 12.6 to 12.7 after a couple of hours. If they continue to drop they are defective.
IMHO a trickle charger without a charge sensor and auto-shut off will over charge a battery which is as bad as leaving them discharged.
Trust me, I have a doctorate in battery technology, having dealt with boats and RV's, RC's and electronics, for more than 30 years.
Here's a voltage vs charge state for 12v batteries:
12.65V 100%
12.45V 75%
12.24V 50%
12.06V 25%
11.89V or less Discharged
In real world use anything under 12V is worthless as a power source as the battery is virtually dead.
If you search you can also find self-discharge rates by battery type and temperature. Below 40 degrees the self discharge rate is practically nill. Over 80 it's much, much higher. Some battery technologies are more resistant to self discharge, like optima's and such. Most of those fancy batteries require different charging voltages and rates than standard lead-acid batteries like we have in our bikes.
