When I bought the converter I was told I could use the boost button to speed up the charge by forcing it to 14.4 v and people on here say you can do that. I have said it and done it too but this is what the owners manual says:
In the first line it says
BOOST MODE- Indicated by green LED remaining on. The output voltage is 14.4 vdc to rapidly recharge the battery up to 90% of full charge.
Further down the page it says
WIZARD MODE BUTTON- The manual button has been provided to allow the operator to temporarily override the converter (NOT RECOMMENDED) or to verify the converter is operating properly. For manual operation, press and hold the button. The indicator light will soon remain "ON" indicating Boost Mode. Continue to hold the button and the light will blink rapidly indicating the converter is in the Normal Mode.