Hi I have a Chrysler Grand Voyager 2006 2.8 it went into limp mode the other day I disconnected the battery and reset it was fine for about a mile then went back to limp mode after reading some forums I think the problem is the battery was put on the wrong way round and may have sorted something out can anyone help

 

Welcome to the forum. Modern cars are controlled by computers. There are computers for the engine and transmission, and for the body plus modules for seatbelts, airbags, air conditioning, anti-lock brakes, etc, etc.

When a computer detects something not working correctly, it will set a fault code that can be read with the proper diagnostic equipment. There is no point in guessing about what could be wrong since there are hundreds of possibilities. "Limp mode" is a symptom of a problem with the transmission. The transmission computer has detected some issue and has put the transmission in limp mode which allows you to drive it at moderate speeds to a facility where they can do the necessary diagnostic work to figure out what is wrong. This will involve connecting a code reader to the car's computers to see what fault code(s) may be stored there and possibly other work as well.
It is virtually impossible that your battery is connected backwards. The car wouldn't work at all if that were somehow the case.
Nobody here can read your cars computers to figure out what its problem is. Take it to a facility with equipment and expertise to diagnose it properly. Transmission issues are best dealt with by transmission specialists who do that work all day, every day rather than a general garage that rarely, if ever, does transmission work.