different module voltages

[Eros]

I have 4 modules wired in series of a common voltage and amperage. I want to add 2 additional modules in that series that are not the same voltage and amperage. What happens to my string , both the 4 mods and the 6 mods as a entire string ? Also, how will this work when terminating in a charge controller ?

 

[GoldDigger]

Having panels of different voltages in a series string is not normally a problem. Just make sure that the total Voc of the string in cold weather is not higher than the CC can withstand.
A difference of more than 5% in the current, Imp, can cause inefficiency or in the extreme case even lower total power output from the string than you get with only the original four panels.
Tell us more about the panel specs and the CC please.

 

[ggunn]

Having panels of different voltages in a series string is not normally a problem. Just make sure that the total Voc of the string in cold weather is not higher than the CC can withstand.
A difference of more than 5% in the current, Imp, can cause inefficiency or in the extreme case even lower total power output from the string than you get with only the original four panels.

To elaborate a little - basic electronics tells us that the current is the same everywhere in a series circuit, so if you have one module in a string which has a much lower current than the others, the current in all the other modules will be constrained to that amount.

 

[SolarPro]

Also, how will this work when terminating in a charge controller ?

It's entirely possible that the four modules you have now max out the (weather-adjusted) voltage to the charge controller. So even if you pass ggunn's current check, you could run into max voltage issues. Adding modules in series increases circuit voltage.

In order to put another source circuit in parallel with the existing one, you'd want to match the current and voltage characteristics as closely as possible, with an emphasis on voltage. Different current on parallel strings isn't a problem. But, ideally, both source circuits will have the same or very similar maximum power voltages.