If I have first solar 15V and 10mA and the second solar 5V and 50mA, I connect it to series what is the output for the current?

 

Solar panel 1: 15x10mA = 150mW
Solar panel 2: 5x50mA = 250mW

I think that connecting mismatched solar panels is an unusual practice. If you connect them in series you would have about Vout = 20V and I = 10 mA. The power would be 20x10mA amps = 200 mW. But we expect a power of 150 + 250 = 400 mW. So, when you wire them in series, you limit the maximum current to the lowest value panel in this case is the 150 mW panel of 10mA.

A question for you.. what if you connect them in parallel?

 

Solar panel 1: 15x10mA = 150mW
Solar panel 2: 5x50mA = 250mW

I think that connecting mismatched solar panels is an unusual practice. If you connect them in series you would have about Vout = 20V and I = 10 mA. The power would be 20x10mA amps = 200 mW. But we expect a power of 150 + 250 = 400 mW. So, when you wire them in series, you limit the maximum current to the lowest value panel in this case is the 150 mW panel of 10mA.

A question for you.. what if you connect them in parallel?

If I connect it to parallel will be:
Solar panel 1: 15x10mA = 150mW
Solar panel 2: 5x50mA = 250mW

the output: 3.75V, 60mA and 225mW

 

If I connect it to parallel will be:
Solar panel 1: 15x10mA = 150mW
Solar panel 2: 5x50mA = 250mW

the output: 3.75V, 60mA and 225mW

Well, there's a kind of pattern here. In you connect them in parallel, you should expect now the overall voltage to be dragged down to 5V.
So, V=5V and I= 60mA, P=300mW. In both cases you can note a reduction in power output and therefore loss in system performance.

 

When you using different specification of solar as yours, please don't connect them in parallel or in series directly, when you in series then the one with 50 mA may destroy the one with 10 mA someday, the one with 10 mA will be become the load of the one with 50 mA, when you connect them in parallel then the one with 15V may destroy the one with 5V very soon, the one with 5V will be become the load of the one with 15V.

 

The circuit below is a possible method to do the in parallel with two Solars, if your are interested then you can try it, the VR1 that you can use is the normal potentiometer or SVR, I'm not sure the real voltages that the Solar1 could be, so you may need to adjust the values of R1.

 

The circuit below is a possible method to do the in series with two Solars, if your are interested then you can try it, the R2, SVR1,D1 is the load for 5V/50mA Solar2 and it is designed to draw as 40 mA to protects the 15V/10 mA Solar1, and the R2, SVR1, D1 can be design to power the LED or 5V/40 mA charger or some others.