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Discussion Starter · #1 ·
Been in the hospital for a few days now resting up at home. Everything is ok but once again I go out to try and start my slk and nothing happens battery is dead... The last time it happen when I left my slk sitting for about 3-5 days without starting it or driving it. When AAA came all it needed was a hot shot..
No problem with the battery took a full charge batter is only 2 1/2 years old.
AAA said alternator charger and all were ok. So if I don't start it up and or drive it every day this is what happens? Is there a easy fix to this problem?
Is there some thing like a battery tender? Something I can hook up to my battery to keep it charge or when it run down from just no driving it the tender or what ever it is called can just be plug into a outlet and onto my battery to keep it charge and turn itself off and on when needed. to always have a charge in the battery charged up. at all times Where could I buy one and about how much are they and will this solve my problem. Thanks for your input and answer to help me out.. Also sorry this may have been posted before a few months ago...

jnc 1948...
 

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There are a few threads on here for battery tenders, those who have them should chime in shortly with some answers..

You should be able to leave your car 1-2 weeks without a problem, if the battery is tested ok, you've got a drain somewhere!
I'd suggest rather than just sticking a tender on it, try and find the cause by pulling fuses one by one using a multi meter :

How to Find and Stop Car Battery Drains ? DIY Car Battery Drain
 

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Registered 2000 SLK320
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Just a couple of questions, when you go to the car is there enough power for the fobs to open the doors and turn off the alarm.
When you put the key in the ignition and turn do all the idiot lights come on or is everything dead.
Have you tested the battery voltage on the non start occasions to check that the battery is actually discharged or is there another problem.

Regards Stuart.
 

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Discussion Starter · #5 ·
when I get it charged AAA says alternator, started and all are aok... So when it sits a few days why does it go dead? and bettery
is all most fully charged.... What could be making the batter go weak and or dying ??


Thanks again

John
 

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Registered 1999 SLK230
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As “curro101” said above - “you’ve got a drain somewhere”. Meaning that some electrical component is drawing power {current from the battery} - when it is not supposed to. This is quite common in cars loaded with electronics

a trunk or glove box light?
a failure in a power amp or radio
an alarm system malfunction
a bad window switch
a bad power/heated mirror
a bad switch in the anti-lock brake system
and several other possibilities….

To track it down you have to find which electrical circuit is drawing power with the ignition turned off.

To run a fully charge battery down within a 48 hour period - the draw should be significant.

How to Find and Stop Car Battery Drains ? DIY Car Battery Drain

Carl B.
 

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2008 SLK55 AMG
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Discussion Starter · #8 ·
Battery update Triple AAA came out and charged my battery up and said I had a bad cell in it... everything else was ok... So I brought a new battery from them AMG type for 179.00 So I guess it is still a good thing to get the battery tender and put it on the new battery with me not driving it every day correct? When I put the better tender on the slk will I be able to close the hood?

Thanks again

jnc1948 (John)
 

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I use etyu's attachment method (quick connect) and I close my hood when charging. Got to keep cleaning you know :D
 

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* Founding Member #2
2008 SLK55 AMG
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Battery update Triple AAA came out and charged my battery up and said I had a bad cell in it... everything else was ok... So I brought a new battery from them AMG type for 179.00 So I guess it is still a good thing to get the battery tender and put it on the new battery with me not driving it every day correct? When I put the better tender on the slk will I be able to close the hood?

Thanks again

jnc1948 (John)
You mean AGM (Absorbent Glass Mat).
All the more reason to use CTEK "smart" battery trickle charger as they have a setting for AGM car battery.

I usually leave my hood open as a reminder that the trickle charger is still connected.

I've accidentally tried to reverse vehicle with the tickle charger still connected:
First time, it separated from the connector (Battery Tender type), fortunately the connector is a staight one without a locking tab (unlike the one on CTEK). I noticed it in time.

Second time, the connection was firm and it pulled the Battery Tender Plus off the shelf causing it to fall and causing a small dent on the metal casing (minimal damage).

If I'm in the process of cleaning the vehicle with the trickle charger connected, I now lower the hood temporarily and raise it up as soon as cleaning is done. Although I only clean maybe once every 2 weeks or longer, because of the drought in California.
 

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Registered 1999 SLK230
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A few thoughts:

Had to buy a couple new Starting Batteries myself this past month. Having not purchased any in the past four or five years - I was SHOCKED at the price of Batteries now. The last Optima {about 7 years ago} had a retail price of $129.00, and I bought it on sale for $99.95. I thought that was a lot then. Now they are like $249.00

Thought I was getting a good deal for an AGM type at Sam's Club for $159.00. Just had to replace the battery in our 2009 E350. M/B Road Service brought it out and installed a new M/B replacement for $179.00. No service charge as the car was serviced at the M/B Dealer since new.

If there is no drain on the battery - with a new AGM - you should be able to let the car sit for more than a couple weeks, without the battery going dead. I have a now 7 year old Optima in one car - that sits for more than a month sometimes - always starts right up. Other cars less frequently driven - I keep on battery tenders.

I know we sometimes use the term "Trickle Charger" in an interchangeable way with the almost generic term "battery tenders". Just want to keep in mind that there is a difference between an actual Trickle Charger and a Float Charger like the computer controlled battery tenders.

A Trickle Charger will supply a relatively small amp charge to a battery until the battery is fully charged - and then shut off to prevent overcharging. A Float Charger will monitor the state of charge in the battery, turn on if it needs to bring the battery back up to full charge - then turn off again. Most of the battery tender types - are float chargers, and most of the newer ones offer programing for AGM type batteries as well. {but always good to read the specifications before you buy.}

FWIW,
Carl B.
 
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