does anyone know why they at dodge put a passengers side battery in these trucks my truck one day in the cold would not start so i put a brand new battery on the left side now it starts no matter how cold, but when i unhook the left battery it will only turn over slow but will not start even when it is hot i put a volt meter on it and it reads about 12.75 volts and i tested the left battery it reads about the same and when i unhook the left one my clock goes dead and i have to reset it. does the right side battery do anything or just help?even when i unhook the left battery and test the volts through the cable to the other side it still tests 12.7 volts thanks

 

Firstly, you should always replace BOTH batteries at the same time - even if just 1 is bad.

Secondly, you cant just take a meter and measure a battery - that doesnt really tell you much at all about the condition. You must test the battery with a load on it. This will tell you how much amperage the battery can put out as well as general battery health.

These trucks have 2 batteries wired in parallel. They supply 12V and LOTS of current for both turning the engine over and powering the grid heaters (which draw a lot of amps).

Why the need for two batteries??? Big Motor, Big starter, high compression, relatively thick oil, variable operating climates.

Hope this answers a few questions.

 

There are 2 batteries because of the high amperage drain when starting and when the grid heater is running.

If you check the voltage under a LOAD test you will probably find the old battery is failing.

Replacing just one battery makes the pair only as good as the weakest one. You should always replace in pairs...

 

Several guys have had good luck going back to one big battery. I personally would not do it. The right battery has always gone bad in the two trucks I've owned with dual batteries. I don't know if it does not get a full charge due to the wiring set up or does not get full load or whatever. I took both batteries out of my truck two years ago and replaced them with NAPA Legends. The right one went stone dead and the left one is in my sons old truck still working fine. I did power both my stereo amps off the right battery this time. Not sure if it will do any good or not.