Try installing a new coin cell battery first. That a cheap one dollar fix available in any store that sells batteries. See the manual- Dell Latitude E7470 Owner's Manual

Remove or disconnect the battery and the power supply.  Remove the memory module(s).  Then try powering on -- you should hear two beeps.  If you do, then put the modules back one at a time in each socket until the system fails POST.  If one module fails in both sockets, it's bad;  if both modules fail in one socket, the socket is bad.

If you do not hear a two-beep sequence when you try to boot the system with no memory aboard, the mainboard is bad.

Now it switch on after trying to remove battery, leave it disconnected, connected again several times, tried to remove and put memories, but says that windows 10 cannot start. Starts windows recovery tool and it says it is not possible to recover. Tried advanced options with no results.....

Probably PC has bitlocker, it request me the recovery key for starting in safe mode. I put the recovery key. It says it is correct and restart but again the step start from beginning 

Run a full diagnostic, particularly on the hard drive or SSD (f12 at powerup).

Done. No problem found. But os doesn't start. Probably due to bitlocker. Even if I have the recovery key. What should I try before reinstalling os ? 

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Having Same Problem. Strange behaviour on this laptop. I've set all power options to never sleep or hibernate. Yet the laptop goes to sleep. But when sleeping, if I press the power button or any other key, it simply won't wake up. The keyboard backlights come on, but nothing will wake it up. I have to press the power button to reboot.                                                                 

. TOS76>

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Having Same issue. Today I wanted to use my laptop and I pushed power button, but nothing happened. Since it was not connected to the power and battery won't hold as it used to I shrugged, plugged in power cable and pushed power button again. Nothing. Only battery charging light was on. Ok, maybe it needs few seconds. I waited, tried again, nothing, waited some more, still nothing.

Then I got suspicious, maybe my battery is dead. So I opened back cover and to my horror looked at swollen battery. I quickly disconnected, took it out of laptop and put into safer place.

Now I tried to turn on the laptop with only power cable, and absolutely nothing. Even battery charging light turned on only for a 2-3 seconds when I plugged in cable and nothing else.

I don't know what to do. Is my laptop dead? From what? Nothing happened to it.