rmorin49

I used a CTEK Battery Maintainer on my Corvette when it wasn't driven for a week or more. I plan to use it on our SL as well. Does anyone know if it will keep both batteries properly charged if the cables are connected to the terminals in the engine compartment?

threeMBs

Same effect as connecting directly to the main battery in the trunk.

rmorin49

What about the secondary battery behind the passenger seat? Is it on the same circuit?

threeMBs

My understanding is that only the main battery gets maintained (my CTEK is connected directly to the main battery). However, I'm far from the expert in the area.

tx170754

If it is like in the previous model, then I would connect the CTEK to the main battery. The R230 had a starting battery in the engine compartment, if that one was low on power then the car was switching to the one in the trunk. I have always stored the car during the winter and used the CTEK connected to the main battery in the trunk, I hope this helps.

rmorin49

Thanks. I'm going to ask a knowledgeable tech at my local MB dealer. I'm thinking that maybe the secondary battery might be responsible for opening and closing the roof. Sound plausible?

threeMBs

R231 has a completely different setup from R230.

threeMBs

No, second battery is responsible for, relatively speaking, minor functions like "hold", tpms plus few others. Starting, roof and all other main functions are performed by the main battery. One can not connect to (or at least its hard) aux battery in R231 because its a huge pain to get to (I tried, then took car to the dealer to replace aux battery).

rmorin49

Did a google search and watched a couple YouTube videos. Seems the "convenience" battery located behind the passenger seat may be on a separate circuit and thus would NOT be maintained by a maintainer connected to the main battery terminals under the hood. This is too bad as I agree it is a major pain to connect a maintainer to the other battery behind the passenger seat. I'm guessing these batteries are probably not good for more than 5 years so I will be looking into replacing mine in a year or so assuming my car, a 2015, still has the original batteries. Appreciate the feedback.

WN1X

That is one thing I asked the dealership regarding my SL550...what is the age of the main and convenience batteries? I haven't got an answer back from them.

Because the convenience battery is a pain to get to, I may make up a wiring harness to bring out a connection to a plug so I can easily connect it to a charger.

rmorin49

I may do the same thing when it cools off.

WN1X

I need to get my SL before I can start modding it

jetjok

Instead of all that work, just get a new SL every three or four years.