TheSaint

I have long been thinking of installing a tricle charger in my 2003 SL, R230
So today i bought a CTEK MXS 5.0 trickle charger.which is one of the better battery chargers/trickle chargers here in northern Europe. It is also good for AGM batterys which i have in my car

When i hook up the trickle charger to the battery located in the trunk i will use the wire harness that bolts on the battry terminals
The positve wire from the trickle charger to the positive battery terminal
The negative wire from the trickle charger to the negative battery terminal

When read the instructions that came with this CTEK trickle charger it says that i should wire the positive wire from the trickle charger to the positive battery terminal
but the negative wire from the trickle charger should be connected to a grounding point in the trunk and not be connected to the negative battery terminal. Why i do not know,

I find this strange since the negative battery terminal comes from a grounding point anyway?

I spoke to mechanics at the Mercedes dealrship / repair shop i use and they told me that when they installed a trickle charger they wired the positive and negaive wirs from the trickle charger to the battery poles

Should i connect it direct to the battery poles or should i run the ground wire to grounding point in the trunk?

Here is a picture of the trickle charger: CTEK MXS 5.0 Battery Charger with Automatic Temperature Compensation

keitheva

I have the same charger and I connected the dongle directly to the battery poles. It hasn't exploded yet!

kbdixon

I Use the same model on my 2008 sl550 and it works fine over the last two years wired to battery poles. No issues at all

funymuny

I use several CTEK chargers/maintainers...not the exact model but recent, similar...have always attached to both battery poles. No issues. Must be rooted in the issue of battery gases and sparking. Get the spark as far away from the battery as possible? Otherwise, the point is to complete the circuit which begins and ends with the battery.

gocargo

I agree that the manufacturer is trying to mitigate a potential spark from igniting any escaping hydrogen gas from the battery.

I always use both battery terminals to connect to my chargers BUT I always open the hood or trunk for 5 or 10 minutes prior to hooking up the charger in order to allow any concentrated hydrogen gas (under the hood/trunk) to dissipate.

good success and Merry Christmas.

TheSaint

Thanks a lot for all of your help Now i know i can put the positive wire from the charger to the positive pole on the battery and the negative wire from the charger to the negative pole on the battery
They want you to wire the negative wire from the chatger to the ground because that minimize of any chance that the battery might explode


I sent an email to CTEK support in Sweden and below is their answer:
We recommend that you connect the red terminal to positive and the black to the chassis, even though direct connection to the battery is also possible. I will try to explain why we recommend as we do.
Lead / acid batteries deliver more or less always liiite explosive gases both when discharging and charging.
Valve regulated (VRL) types of lead acid batteries can keep the internal gas and recombine to liquid. Such batteries have a minimal gas outlet but they have a safety valve that can release excess gas.
By first connecting the plus pole to the battery and then the minus pole a bit away from the chassis - it is not possible to ignite the potentially explosive gas that may be located near the battery by ignition.
In addition, many cars today are equipped with BMS (Battery Monitoring System) or other monitoring systems, and then it's important that the charger's negative pole is properly connected, "outside", so that BMS can read incoming charging.
IF BMS can not read incoming charge, it may include cause problems in the start / stop system.

When connecting permanent ring cable shoes, the charger is usually not connected via the quick connector to the ring cable cases at the time of installation, and when the charger is switched on, it takes place via the quick connector and the spark plug is minimized. Then, of course, it is safer in all ways to connect directly to the poles.
The ring cables should of course also be installed on the "right" side of BMS.

funymuny

That sounds to me like CTEK's risk management (aka legal team) group helped to craft that response. As gocargo stated...open the hood for a few minutes. Heck, use a fan or leaf blower to air out the area surrounding the battery, then connect to the battery. Do not construe my response to in any way condone any action related to any activity related to your vehicle, and specifically, your battery or CTEK charger/maintainer. You should consult a professional mechanic experienced in automotive electrical systems before proceeding. I make no guarantee or warranty with respect to my comments herein.

TheSaint

I agree in what funymuny said that this is CTEK`s legal team speaking

I will hook up the positive wire from the charger to the positive battery terminal, and the negative wire from the charger to the negative battery terminal as i think most of us do :-)

Also if i where to connect the negative wire from the charger to a grounding point in the trunk of my car i would have to lengthen the negative wire from the charger when using the eyelet wire
There is also a grounding point that sits a bit off from where the battery is located and i can wire the negative wire from the charger to this ground point on my car :-)
Doing it this way i will follow the instructions from the battery charger

Note that this thread is just how i am thinking of doing the wireing and i advice everybody that are going to hook up a CTEK charger to do this according to the instructions that comes with the CTEK chargers

As i said this is for my car and i am not responsible if any connect the charger as descibed here they do it at their own risk..

I advice all who plan to put a battery charger in their car to follow the instructions that comes with the battery charger!

Looking at the picture the eyelet wire looks to be made to be connected to the positive and negative battery terminals if you ask me :-)

And the legal disclaimer.
If any wire their battery charger from what they have read here in this thread they are doing it on their own risk and i am not responsible for any faults or problems!

funymuny

Agree. But you left off your legal disclaimer :-)

TheSaint

There is a legal dislaimer now funymuny

if any connect their charger as descibed in this thread they are doing this at their own risk and i am not responsible for any problems that might happen
I advice all who plans to install a battery charger to follow the instructions that comes with the battery charger!

funymuny

Good one.

Cashwowud

I have a question which I was going to post on a new thread but is relevent to The Saints' post. I have not used my 2005 350 for a couple of months and when I started it I have the message "Convenience functions not available" which in the past has been cured after a short run. This didn't happen and so I connected a charger up overnight. I should have followed one of my mottos which is "if in doubt - read the instructions" because now I have the red message "Battery Visit Workshop". In the manual it states that this can happen if you connect a charger and so do you guys not get this when you connect a trickle charger?

cashwowud

next2pool

Many chargers and even some trickle chargers will not work if a battery is totally drained. I would check the battery voltage with the engine off and the charger disconnected. It should read about 12.6 V if it is fully charged. I would take it for a drive and re check it. The message may also disappear after a few restarts.

TheSaint

I had a battery that would not take any charging and i know that there is nothing wrog with this battery

On my regular battery charger there is a boost" option. So what i did was to give the battery a little boost a few seconds and then put the charger on, but on low amps

The battery astarted to charge at once. The reason i had to give the battery a little boost was because the battery was total drained for power

Note that when i did this i had the battery out of the car and i would never had done this with the battery hooked up in the car.

TheSaint

Since the instructions for the CTEK battery chagers / trickle chargers says not to use the negative battery pole to wire the negative wire from the charger you can use the grounding point shown on the picture with a red arrow
Well, this is the grounding point for the negative battery cable so....
The picture is not of my SL, R230 but a picture i found on the net
It might be a bit close to the battery but the eyelet wires that comes with the chargers are short so if you do not want to splice the wire to get it longer..