With the other battery thread slowing down, I'd like to start a new thread with a more specific question. What models of Optima Red Top will fit the MCS? I've done the searches and found a few old threads on the subject but info is still a bit lacking. It seems the 34/78 or 75/25 work but they also make the 34R which has the reverse post location like the MCS needs. Who is running an Optima and what size is it? Also, (if needed) what modifications need to be made to hold it down properly?

 

I've had 2 optima red tops in the past... Each one didn't last very long and they don't seem to have as much output as conventional batteries..

 

I've had a Red top Optima in my old Forester for about 4 years. It's been great. Like many good things every once in a while one isn't so good. I'd buy another when the time comes.

 

bought red top at costco 74-35 i believe been in for 6 months in my 03 mcs, straight replacement no fitment issues. They also have yellow top not sure if one costco carries fits. Believe MINI is grp size 47.

 

Thanks bgrpph. Are you sure it's a 74-35 and not a 75-35? They don't list your size on their site.

The stock battery is a group 47 and from another thread: length=242mm, width=179mm, height-190mm. The 75-35 nearly matches everything except it's about 10mm taller (.3in).

The best battery for the application seems to be the 34R that has reverse terminals that nearly match the locations on the stock battery. http://www.1st-optima-batteries.com/schema_34R.asp .

 

I now figure the Optima 35 is the best choice as it has the same dimensions as yours. The terminals also match up.

Now the plot thickens... when I take my multimeter to it, I get 12.4V in the low sensitivity setting and ~12.53V on high sensitivity. Also, the indicator on the battery is still green. My car is a 6/02 build so the battery has had a long life (in Florida, no less). I have also noticed the buzzing speedo needle on startup that people get prior to their battery dying. I just can't understand how it still has over 12.5V in it. Any tech savvy person around to explain it? Tomorrow, I'll bring the battery up to NAPA to get it tested but it appears to be a gonner (except for the voltage confusion).

 

No expert but the battery may not be putting that amount of voltage out under a load. Are you measuring output while cranking or unloaded?

 

I had two yellow top Optimas in my first MINI... I dont know if it was the car... but it did not want to communicate with my alternator :(

(both worked by themselves, but not together)

 

I tested it with the car off. When I first attepted to start it, I took the key to position 2 for a few seconds to let the electronics get started like I always do. They seemed to work fine I then turned it to the start position and it made one fire then absolutely nothing. All warning lights except the seatbelt light and interior lights were out...and the seatbelt light was flickering. The A/C was making a clicking noise until I turned it off and the windows don't work. It wouldn't even lock with the key until I let it sit for a few minutes. I'm thinking along the same line as you in that it has nothing left under load; or voltage is fine and amps are near zero.

(either that or my starter died and fried all the electronics )

Now that's just weird

 

Sorry battery # is 75-35. check search for costco part #, i previously posted this awhile back when i had receipt handy.

 

I called my local Costco and was told they don't have any Optima batteries. I ended up going to Sears and getting one there. It was the Red Top 35 model. Fits fine without any modification but there is a good size gap on top to the hold down clamp. I might try to come up with something to put in there.

When I started the car up after putting the battery in, the SES light stayed on. I've taken it through a couple on/off cycles and it's still on. I don't see how the new battery would cause anything as that light is for emissions related stuff. We'll see how it goes over the next couple days.

 

Well the SES light went off today at startup so all is good. Here's some pics...