95% of the usage is to and from work, a 10 minute 4.5 mile ride. I would hope this is enough to keep the battery up, but maybe not. The battery in my ZR-7 (same battery, also 2 years old) was better, but not by much.
It takes more than a 4.5 mile ride to keep the battery up. It will fade from full charge over some time as the battery gets a little more depleted after each run.
The price is right, and I can wire it into a battery tender extension. At least I know all the cars in the parking lot have cigarette lighter sockets
It would make more sense to use an automatic battery tender at home, if the bike is kept in a garage. The tender can then be plugged in after each run or once a week. My keyless ignition draws a tiny current even with the bike switched off, and this will flatten the battery in about two weeks of being stored, so I have fitted the Powerlet socket to the bike and modified the battery tender cable by swapping the battery connectors for a Powerlet plug. The bike gets plugged in if its going to lay idle for more than 2 days. Of course there's no need for you to do that, battery tenders come with a tail that attaches to the battery with a small connector so you can just plug right in, but the Powerlet socket has a few advantages for me.
There is also a couple of things you can do to preserve battery power so that the battery stays up for longer:
Change all lighting for LED, including the headlamp - especially the headlamp.
Fit a MOSFET regulator for more efficient charging.
Set the engine idle speed to 1100rpm so that the bike gets some charge at idle.
Fit a headlight control module, to keep the headlamp off until the engine has started.
You can also bypass the ECU low voltage threshold. Personally I'm not a fan of doing this but many people have done it without issue. The ECU provides the ground to the starter relay, and if the battery voltage falls below the threshold the ECU refuses to provide the ground and disables the starter. All that is needed is to disconnect the Yellow/Brown wire from the starter relay and replace it with a wire going straight to ground.
also came up with a great solution with no need to play with wiring, just a hole drilled into the starter relay and a button installed, to manually force the relay contacts together for 'emergency' starting.