I need a new battery for my R class. Dealer try to kill me... $870 Australian dollars plus 3 hours of work. ($220 Australian per hour)
I called up to a local battery shop, they offer me $500 for a OEM battery, free install.
if disconnect and reconnect a battery, does the car need to connect to a computer? or reset anything? What I worry is after they replace a battery, the car cant start up and need to tow to dealer. it happened in my friend BMW335i.
Anyone did it before?

Kevin

 

Just did both in my 2010 R350 Bluetec. Nothing happened and the clocks even reset themselves when I turned the car on. Paid $300 for the big battery and $16 for the little one. Canadian funds.

 

No reset required for a simple battery change.

 

sound easy.
Does it carry 2 batteries?

 

A big one and a small aux. one under the pass. front floor. It powers the gear shift in case of a main battery failure.

 

I replaced my battery just a week ago!.
the battery is a standard Group 49 AGM. European designation is H8
You really must use an AGM since in case of severe accident you dont want battery acid leaking in passengers.
You can get them from many sources should not be that expensive. Check on line.

The official procedure is to remove some trim , move seat forward and peel away the carpet from between the rails. Older R class you had to cut the first time, I think newer cars have precut carpet.
For DIY dont bother removing sill or pilar trim, just unbolt the seat and tilt it forward giving very good access. peal back the carpet. There is one thick cable harness.. DO NOT DISCONNECT AS IT MAY GIVE YOU AN SRS WARNING AND YOU HAVE TO BRING IT TO DEALER OR INDY WITH TOOLS TO RESET.
Then remove the plastic battery cover and its easy going from now on. There is clear pvc vent pipe on one side and a red cap on the other that you will have to remove from the old battery and place on the new one,. When I changed the battery, I connected a spare battery to the jump start terminals. so no module was reset. The formal procedure calls for doing standard reset of doors, steering, sliding roof etc if you disconnect the battery. You may not have to. I have had dead battery in my R class before and did not have to do any resets. Make sure all accessories are off! key out of range of car!
If you do connect a jump battery then be careful not to short the battery compartment Positive cable anywhere! It is live! I wrapped it in plastic.

The other battery is a small sealed lead acid( could be agm) battery under the passenger seat foot well. You have to remove more trim to peel forward the carpet, and a carbon fiber plate to access it.The battery dimension is 4" x 2" x 2". The closest repalcement is . CA1212, or UB1213. However the replacement battery is about 1/8 inch narrower so you may have to put in some foam padding. Also the terminals are different. The OEM has 0.25 and 0.187 inch terminals while replacements I have seen are both 0.25 inch. The battery store I went to had adaptors. In the end I did not buy it. I was a made in china house brand. too narrow, wrong connectors. To many strikes.. I put the original one back. It tested fine under 2 amp load. It does minimal duty.

have fun.

 

I have read elsewhere that if the aux. battery fails, you can have electrical problems. When you are halfway there and it is a minimal cost, why not replace both?

 

Most techs remove the right front seat on the R class to get at the battery, it's just easier. Not the most convenient place to put a battery.

 

That's how I did it. Just do not disconnect the wiring harness to the seat.