In my cold environment,a Costco Group 41 (650 Cold cranking amp) and 2 previous ACDELCO batteries with the wasteful alarm system/short trips only lasts 1-2 yrs.Because of the generous warranty and declining prices,I pay less and less per year to get a replacement battery.I started with the 90 C$ ACdelco 6 yrs ago now I am using the fourth battery in 6 years at 65C$.ie I got 25 C$ back after spending 90C$ 6 yrs ago and got to use the 4th battery.Not bad but too troublesome to remmeber to get battery out and haul it back before minus 20 c with windchill hits.

I.ve checked the alternator output 14V steady,at idle 14.1 or 2 at 1500 rpm,2000 rpm.Not overcharging.

I've phoned Optima,they told me while no battery fits exactly, their group 75/35 redtop is the best bet.But this is only sl more CCA,While others has said on this site Group 34 RED top is the way to go.

Thanks for any comments from colder Us climes or Canada or other cold countries!

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Tom 2010 C250 4-matic Sport (Canada)

Price nonwithstanding, the Optima is the way to go.

The Optima can sustain far more charge/discharge cycles (something standard automotive batteries are not designed to do). So you should see a longer life with the Optima.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

Get the Optima Yellow-top or Blue-Top Deep-cycle battery (blue is marine version- supposedly more vibration-resistant).

Costco in the USA carriers the Blue-Top/Marine Optima. I have it installed in my 1988 300TE which has the same battery location & configuration. Just turn the Optima so the negative end (-) will meet with the negative/ground cable.

Also, get a Transpo adjustable voltage regulator and adjust so you have 14.2 VDC when you have your head-lights on.

A good automotive alternator rebuilder can get the Transpo (about $25).

:-) neil
1988 360TE AMG (OPTIMA blue battery)
1993 500E (stock MB battery)

If you buy a Transpo voltage regulator, I hope it fits your alternator as well as the Bosch voltage regulator.

My experience with the Transpo was not good - it didn't fit.

Others have had better luck I suppose.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

I have had very good luck with InterState batteries , have seven years on one in one of my Sd's still strong.........

William Rogers.......

My transpo fit perfectly on my W124 M103 alternator.

However, I needed more, so I installed a 150-amp alternator from a 1999 S430, just swapped pulleys.

:-) neil
1988 360TE AMG (150-amp alternator)
1993 500E (150-amp alternator)