Not real sure what your question is but the following is a link to two different shorty packs carried by SMC. One is a 2S which is 7.4 volts and the other is a 4S which is 14.8 volts. The 4S has a higher mah rating which denotes capacity, and it has a higher C rating which indicates it can deliver higher amperage. You need to select the battery first by how many cells are required for the voltage needed for your car, each cell carries 3.7 volts, that's why the 2S is 7.4 and the 4S is 14.8, the S stands for series so you have 2 cells in series for 7.4 volts. One more thing, a shorty is physically a smaller battery, it is shorter than the normal batteries.
Hope this helped, if you let people know what you are trying to power I am sure you will get battery suggestions.