I need to replace my H8 (49) battery for the 240d soon. Local Costco sells the Interstate AGM variety. Would an AGM battery provide any advantages (or disadvantages) for this type of vehicle?

Not really, especially from Costco where the Interstate batteries are more expensive and have a significantly worse warranty than the Kirkland batteries.

Kirkland batteries are an incredible deal IMO and put out serious CCA. I have some of their small automotive sized batteries in my tractors, I threw the first one in because it was kicking around but was impressed with the performance, they have been starting 150HP+ diesels for years with no issues.

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1993 300D 2.5L Turbo

I'd stay with flooded lead acid technology, that is what the charging system was designed to work with. Make sure the battery is well vented to prevent corrosion.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

You need to know the charging rate of your alternator. Meaning find out what charging rate the battery needs to charge properly.

Get the info of the battery you and go to the makers website and or ask the tech department.

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84 300D, 82 Volvo 244Gl Diesel

Don't try to save money when replacing battery. Get the best, highest quality battery you can afford.

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Jim

The gel battery in my 39 Studebaker is going out. Its about 7 years old. Should I get another gel or go conventional.

I would rather not use a vented battery if possible.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

excellence answer.

Unless the alternator has been upgraded, agm isnt going to be happy.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

So what I read long ago is you needed 13.7 volts to charge an AMG batter. In my case that is what my alternator put out at idle when I got the 84 300D.

Some people change their regulators and get more voltage from the newer regulator. (I got more voltage after replacing the negative batter cable and later when I found my positive cable was corroded inside where the cable went into the positive clamp. After the fix I ended up with 14.5 volts at idle.)

"That's why the recommended corrective maintenance charge voltage (when charging a single 12-volt AGM battery) should be between 14.4 to 15.0 VDC, and the preventive maintenance charge voltage should be between 13.5 to 14.1 VDC. Never use a recharge voltage less than 13.50 VDC on AGM batteries…you'll regret it."

I think that if a new voltage regulator boosts you up to the 14.5 volts at idle that should be sufficient to charge an agm battery. Especially if you drive the car daily.

I kind of sluff off. I manly pay attention to the cold cranking amps or in the old days the amp hours of the batter and don't worry much about the interior construction of the battery.

My issue with batteries tends to be me leaving the head lights on by mistake or even the parking lights on by accident.

https://hawkerbattery.com/wp-content/uploads/2022/07/Hawker-Headlines-Summer-2022.pdf

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84 300D, 82 Volvo 244Gl Diesel

Another issue with AGMs is that they can't be topped up with water. So while they need a high charge voltage, charging current needs to be carefully limited to avoid boiling. If you boil off the water from an AGM then it's basically toast.

That's why I have a bank of AGM batteries attached to my solar system in the house, with an expensive multi-stage charger, and don't recommend them for an automotive application. Especially with an older car with a basic regulator.

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1993 300D 2.5L Turbo

So my gel battery is acting dead or worn out in my 39 studebaker truck...you guys think an old wet style will work better?

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

@t w, Yes especially if it is still a gen.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

It has the 83 Mercedes 300 turbo motor and is stock for that car, a bosch alternator.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

@ t w, I'd stay with a flooded lead acid battery that is properly vented. Spoke to our local alternator, starter and generator rebuilder about this a while back. His position was to stay with the battery technology that the charging system had installed at the factory. Our Bosch alternators from that era are low IMO on voltage for an AGM.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Thanks sugar bear!

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.