OK thanks, maybe they changed the battery to a full sized one again? Actually i don?t even know if the voltage of the battery says much about it?s capacity... Does it?

[very, veeeeery off topic and nerdy!] You're right. I'm not an electrician, but I do remember some electricity lessons from high school. If the max voltage of the battery is 4 Volt, that means that when the battery is fully charged when it delivers 4 V. As time progresses the voltage of a battery decreases. The capacity of a battery is measured in mAh (mili Ampere hours = amount of charge expressed in Coulomb). The power is:

P = V*I [Watt]

I.e, Power = Voltage times Amperage at any given time, expressed in Watt. The work done [i.e. energy delivered in Joule] by the battery after an amount of time t is:

W = P*t [Joule]

So measuring the energy that a battery can deliver, I think, means measuring for a few seconds the current (in mA) and the voltage (in V). Multiplying those two produces the power P (in Watt) of the battery at that point in time. I think that may be number displayed in the "hidden" settings screen of the Dingoo. My Dingoo says "260000" when its fully charged. Now lets do some physics. Let's assume the unit of the "260000" is micro Watt (i.e. 10^-6 W = 260 mW = 0.26 W):

I = P/V = 0.26 W / 4 V = 65 mA (seems realistic)

So for snes9x. The number "4000" that it displays is the voltage I think. I read

here that the Dingoo battery delivers 3.7 V and 1700 mAh. Given that:

I = Coulomb per second = C/t => t = C/I = 1700 mAh / 65 mA = 1700/65 hours = about one day.

But given the fact that the voltage decreases in time, there will come a point in time that the Dingoo won't work anymore even though the battery can deliver some charge. I believe that's after 8 hours of work.