The same situation for me since many years on manu mikes. Never seen something like blown rectifiers (that is what they're afraid of).http://www.powerletproducts.com/product/battery-tender-yuasa-charging-cable/261
This plugs in to the power outlet under the left side of your seat (assuming your riding an ST) and will trickle charge your battery. I've used it for the past three years. Maintaining battery charge couldn't be easier with this adapter.