mb1000

It's time to replace the auxiliary battery in the trunk.

1. Bought "AutoCraft Platinum AGM Battery, Group Size H8, 900 CCA" from advance auto parts online. This is the exact matching AGM battery with OEM

2. Asked store to test and all good with 1000CCA

3. To keep electricity on while doing replacement, I use jump start cable to connect auxiliary battery with another car. This way you don't have to reset anything


4. Take out a floor board that close to the vertical board in the trunk.


5. Pulling the left lower bottom the vertical board and take out the board from left side. You will see the battery on the right.


6. Making sure to attach an air hose on the right top on the battery and plug the left air hole on battery.


7. The rest is the same as to replace any battery. Took me 30min. to complete.


Done.

mercedesbenzs55

Is your S the preface model or post? The auxillery H8 battery is in the trunk.

DaveW68

No need to hook up a battery charger or tender when you replace the aux battery. You don't lose any of the presets or other settings in the car when you replace it. Those will maintain power off the starter battery when you're replacing the aux.

mb1000

yes pre face lift. 07 to 09 MY has 2 batteries I think. One more small one in the car for seurity

mb1000

good to know. Next time


Dave, do you know where soes the transmission get the power, from start battery or consumer battery?
After replaced the consumer battery, shifts seem to be better.


thanks