2 days after charging the battery indicator stops at app 40 per cent for several hours until the "battery almost drained" message appears and the phone switches off. Any idea where is the problem and what to do? Also, the 2500 battery takes too much time to charge (from 40 to 100 per cent no less than 4 hours - is that normal or different charger could be quicker? (I am using a 5V 1000 mA plug.)
I know this isn't what you want to hear, but I have a Doogee DG350 that does close to the same thing.
It has become painfully apparent that Doogee has some hardware issues (much like iNew).
After flashing, formatting, multiple ROMs, different chargers with different charge rates from 1 to 2.1, and no help from Doogee, my only viable solution to keep this older device as a 4th backup was to buy extra batteries with external charger.
Fortunately, this is the only bug I have and otherwise the phone is exactly what I expected. The only inconvenience is not to forget to charge every third day regardless what the indicator says so I can live with it.
It sounds as if you may benefit from the many apps to re-calibrate the battery like "Battery Calibration" while following the instructions. An alternative is to do it manually if the app doesn't work:
Full battery charge with phone on, then turn it off. Full battery charge with phone off. Turn phone on. Under settings, "wipe battery stats". Drain battery until phone shuts itself off. Plug it back in while off and allow a last full charge that will hopefully give you an accurate reading.
It also wouldn't be a bad idea to physically inspect the battery for the usual telltale signs that it is defective or damaged (bulging, warped, etc), but I assume you already did this.
Also, thanks for the opinion/info on the 580. Any reviews, observations, problems, or positives are always appreciated!