[dgiraldi]

Doing some research on changing the batteries out on my 2004 E500.

1 – Is it worth taking to dealer to just get batteries changed out?
2 – looking for DIY battery changes…any tips?

My battery light comes on and tells me to take to shop, I'm thinking I will need to change out the batteries?

 

[drivbiwire]

Get an MCR check before replacing the battery(s). You may have a faulty charging system.

The MCR will tell you the condition of the cells, if you have a bad battery replace it. I would urge you to stick with the OEM battery (AGM) since these will be of the proper Ah rating for your car. Ah is a big deal on these vehicles more so than CCA's which is borderline meaningless.

 

[lippens]

If you're battery light comes up, it might be that your alternator is failed. You would then have 20 minutes or so worth of electrical lifetime. Hurry to a workshop, or check the charging voltage:

Turn the key to position 1
Set the instrument cluster to the odometer menu
Press the reset button briefly 3 times
The voltage will be displayed
Start the engine

Make sure you read 13.0V or plus. If you do, then the alternator is fine. If you're reading below 12V, then you have minutes worth of driving time since you're running on the battery.