Do I need to use a battery tender to Change out my battery on my 2006 Honda Odyssey,the parts house said I would short out my electrical system/ navigation/ onboard computer?

 

Idle speed, transmission shift points, and convenience features(power windows, entertainmaint..etc) will be affected.

You will not likley "short out" anything,but you will be inconvenienced until things return to normal on their own,or in some cases are reset to normal.



So yes,use a battery tender.

 

I think your best bet is to use a memory saver cable that runs from a 12v source (like a jump starter) to your OBD2 port.

Example of jump starter with a 12v outlet:

I've tried the 9v memory savers without any success. The above works in my experience.