[dginfw]

Not sure if its been posted before, (sorry to repeat if it has) but for those who have Battery Tender type chargers,  they offer a plug in meter that could help monitor battery condition (when parked) or charging voltage when running.  Not too pricey and easy to use.
http://www.amazon.com/gp/aw/d/B00DJ5KE9A?pc_redir=1409153472&robot_redir=1

[tresser4K]

You can also get a nifty usb adapter "insert".

[retrolynn]

Thanks! That looks like a great idea.    Lynn

[GSS]

Great find! I just bought one of each!

[High On Octane]

Wow that is slick, I NEED one of those!      I like how small it is.

[Bulletman]

Great..I just bought both....

[NorEaster]

Just got my USB insert today.
Rigging it up with these items to be able to run my phone as a GPS when needed and keep it charged as the GPS app drains the iphone battey quickly.
Rack for the tank: http://nfieldgear.com/enfield-store/tank-top-rack.html
Holder for the phone: http://www.walmart.com/ip/Sportline-Smart-Phone-Holder-Armband-Large-Black/27952797
USB plug: http://www.amazon.com/Battery-Tender-081-0158-Disconnect-Charger/dp/B00DJ5KEF4/ref=pd_bxgy_auto_img_y