If you charge at greater than 1C (IOW, charging a fully discharged battery in less than 1 hour), you're killing the battery. So, as far as I'm concerned, that "5 minutes for 8 hours of charge" is like the chain that used to be called "Nobody Beats the Wiz". It's an advertising slogan, not a fact. Run a charge app to see what the charge is. If it's greater than the battery capacity (IOW, if the battery is 3750mA and it's charging at 4000mA), the battery won't last very long (maybe 6 months to a year - and it should last for at least a few yeears).