E55AMG05

What type Is the auxiliary battery(NOT the one in the TRUNK!!!!!) A STD(standard), AGM, or GEL?
My car is a 2005 E55 AMG. The battery auxiliary model number is A211 541 00 01 12V 12Ah 170A(EN). I need to know what battery type it is

Shadow5501

It's an AGM. It's a standard motorcycle/powersports battery. Widely available at auto parts stores and mail order for less than $100. You can search up part numbers in other threads discussing the aux batter.

E55AMG05

Thanks. Now one last thing. The voltage that shows on my speedo. What should the normal voltage reading be. And does that voltage come together from both auxiliary battery and the big trunk battery? It would be really helpful

Shadow5501

The display is just the main battery. I don't know of a way to see the aux battery voltage on the display. I just got out my digital voltmeter to verify the aux battery was low and was causing the red battery light upon starting the car.

E55AMG05

Wow so there separate on the display only maim battery shows hmm interesting. And even if the small aux battery fails the red light will turn on. I plugged mine to a voltage meter and My aux battery is showing 11.6 volts that's without being charged and with car sitting in the garage for a cold month while i was on vacation. 11.6 volts is not that bad if I turn the car on the alternator should be able to charge it np right

Shadow5501

11.6 is pretty low, essentially flat. Fully charged is at or near 13.0 volts, and AGM batteries don't self discharge as much as conventional batteries. The car will charge it for 20 minutes after every start. It may take a couple of days driving to fully charge it. I'd drive and see if it will hold a full charge before replacing it.

E55AMG05

Your right alternator can charge that sucker good. My auxiliary battery is at 12.5V that should be fair right?

Shadow5501

Yeah, that should be enough to avoid the warning.

CharlyE500

Has anyone use this AUX battery ?

Interstate Batteries CYTX14-BS 12V 12Ah Powersports Battery Cycle-Tron Rechargeable Replacement AGM

https://www.amazon.com/Interstate-Batteries-Cycle-Tron-Powersports-Rechargeable/dp/B08W2H7S4W