Laptop dies at 19% without a 'low battery' warning. Help?

[EscapeToNowhere]

Hi, well i really dont know anything about computers what so ever, but for a few days now, my Acer Laptop has been shutting down when theres 19% left of the battery, or 20 minutes without warning. Usually it gives me a low battery warning when theres 13 minutes left, then a critical battery waning at 7-8 minutes left.
(copied off from the sticker on the bottom right)
-Windows 7
-AMD Athion II X2 processor P340
-ATI Mobility Radeion Hd 4250

I hope those ^^ help, thanks.

ps. ive only had it for about 3 months, well since christmas

 

[nismo91]

click start / windows
type power options and select it
select change plan settings on your current power plan
click change advanced power settings
go to battery
check the low and critical battery level and actions.

if those aren't set in 20% it probably means your battery is out of calibration.

 

[EscapeToNowhere]

Thank you so much for a quick response, but it did not work.

"click start / windows Check
type power options and select it Check
select change plan settings on your current power plan Check
click change advanced power settings ] cannot find
go to battery ]- cannot find.
check the low and critical battery level and actions." ] cannot find

Is there any other way ?

 

[nismo91]

after you click change power settings for current plan, left bottom, change advanced power settings

 

[EscapeToNowhere]

i dont know what happened. maybe it worked, but everythings back to normal now. thank you so very much,