flashing red just says turn it off because the battery is getting low. i guess thats cos it wont charge. wait 1 hour for temperature to become normal. wash filters and wait 24hrs til they are dry.check and clean battery contacts. those are the things the manuals list to try.
Even if i use mine 5 minutes I put mine on the charger and leave them there till i need to use again. Read your instructions on the box or instruction booklet and if it does not tell you otherwise. Just put it in and leave it. My tools have two batteries so i change mine in my charger twice a month.Been doing this for several years now.