Car battery replacement ?

[drummerdimitri]

So my car's battery is dying (6 years old) and I would like to replace it.

It's a Varta 80 Ah AGM model that costs 230$ to replace however since I'm looking to save up some cash would I be fine using a 74 Ah lead acid Varta instead?

The later is 100$ so huge price difference and I wonder if it would be worth the savings 

The car is a 2012 mercedes C300 4matic blueefficiency without engine start/stop feature.

[Gyro]

If it hasn't got fancy start-stop features, then any battery with sufficient capacity and CCA (Cold Cranking Amps) rating will work fine. Not that cold cranking is likely to be a problem in the Lebanon. 

[sokoloff]

I'm a big fan of the AGM batteries, particularly in underseat installations where acid leakage can go undetected much longer and rust out the car.

Things to check:

• Will it fit? It looks like the 74Ah lead-acid is smaller than the stock AGM battery. That's usually OK, as long as whatever holds the battery in the car can still work.
• Are the terminals the same type (side vs top post)?
• Are the terminals on the same side as original? (some batteries have positive and negative on the "other" side from each other)

Electrically, it'll be "mostly fine". AGM and lead-acid batteries chemistry is slightly different and the charging targets are different. It's possible that the car is targeting the charge profile for AGM which will slightly overcharge the lead-acid, leading to a lower battery life and higher likelihood of leakage. For a 7-year old car, you have to decide if that's worth it or not. (I'm generally one to keep cars 15-20 years, so 7 year old car isn't getting into the "clunker; who cares?" territory for me.)

I'd replace with another AGM, but I realize that's not financially equal decision.

The lead acid substitute will "work".