Florida Joe

Will be going on 2 years of ownership in 4 months and just hit 4K miles and most of my driving is in stop and go traffic.


Any reason I should not be attaching a battery tender?


Thks

mercedes4ever

I run battery tenders / trickle chargers on everything, regardless of how often the cars get used. Batteries last twice as long.

Florida Joe

This is really dumb but where is the battery? My last SL had 2 batteries. Trunk & under the hood.


I opened up the hood to SL550 and it isn't readily visible. Is it in the trunk?

I feel dumb asking this and the manual isn't very clear.

California John

If my memory serves me correctly one of the batteries is in a compartment just behind the passenger seat. It is in the corresponding location to the storage area is behind the driver's seat. I opened up that compartment once to see what was in there. it is not difficult to put the cover back correctly. And I believe that the second batteri in the trunk, Again if I'm not mistaken.

BenzV12

There should be an extra hot spot area battery terminals for an easy access under hood so that you can connect battery tender's connectors to these .
I once hooked up my batter tender's w/o hassling car battery's terminals.Just pop up the hood and search + - .
I believe your manual should cover about it

mercedes4ever

I connect them directly [permanently] to the battery terminals, then run the cord to just inside the grill area & fix with a cable tie. This way, you don't need to lift the hood to connect it.

visionatsea

Referring back to the original question: I have about 2700 mi on my 2013 SL550 (will be on yo in June 2014) and left it alone for two of the coldest months this winter (Dec and Jan) without attaching a trickle charger. Before I did, like you, I was concerned about the at rest battery draw. Was told by dealer, at rest, the car draws about 15-19 miliamps per hour. The battery is 12V but I forgot how many amp hours it has. If you id the amp hours you can do the math to determine the at rest draw on the batter and how long it would take to draw down the battery to not less than 50% of it's total amp hours. The car has a huge alternator so the recharge time is minimal. With only a two year old battery I wouldn't be too concerned with battery deterioration. The battery is an AGM type (similar to wet cell), discharges at a slower rate and has a longer life.

Wolfman

I am in the other camp. I never use a battery tender. It's freezing cold in the winter; currently -6 F (feels like -16 F) as I write this with summers in the 90's.

Used to have our SL's parked for 4 months at a time and they always started fine. Batteries probably lasted 3 years or so.

My take is simple and it may sound a bit sarcastic. If a car can't sit in the garage for a month without being tended, it's really not a car I want.

mercedes4ever

AGM (Absorbed glass mat) is the best technology IMO.

Florida Joe

Thks for the responses.

I did hook up the battery tender to the battery in the trunk.


Took 48 hours to get a green light on the battery tender.

Will not keep the tender hooked permanently but thought it was good idea after almost 2 years with little use and mostly stop & go traffic.

Daytona-flyer

I kept a Battery Tender on my ol' '04 Z06. Without it the battery would be dead in two weeks. As I used the car only on the track, it did sit for long periods.

dave2001auto

Typical batteries for MBZ are 700 AH typical size car battery (size 37) or 900 to 1000 AH for the larger battery for the diesels (sizes H8 or 49). Just Google the model and brand of your batter to get its AH and CCA ratings. The AGM batteries with valve charge very quickly. It's the sealed gels that need a slow charge. Car batteries don't do well with deep discharge nor high temperatures, and IMHO the AH are either vastly over rated, under ideal situation and for a brand new fully charged battery.


MBZ has a warning not to charge the battery over 14.8V while connected to the car. Most battery chargers will go over 14.8V and some will go higher than 16V.

Lroten

Can anyone take a pic of the terminals under the hood to connect this charger to
I just am out of a Masersti that had a very simple hook up.
I really can't figure out where this is on the SL

jfcrabbit

I have 2013 SL550. Facing front of car, under the hood terminals are left side toward windshield. Turn and Press down red plastic cap to expose positive terminal. Negative is a few inches in front of it, silver stud exposed. Both batteries are in trunk under floor of trunk. No battery in engine compartment according to service manager. Battery terminals under hood are cabled to the battery in trunk. I also found out that you cannot trickle charge through cig. Lighter or 12 volt plugs because they ar switched with ignition. Hope this helps. The whole system is weird.

nycphotography

Only reason is because it's completely unneccessary.

As long as you drive it at least once every couple months, the car's charging system is all the battery tender it needs .

Mine sits for 2-3 months over the winter. Never had a problem. Motorcycles may discharge in that time, but a car battery is much larger and generally engineered for much colder climates than motorcycle batteries are.