A Permanent CTEK Battery Charger/Maintainer Install

[DrGER]

Back in early 2019 after our first polar vortex in NW OH, I took a look at setting up a battery maintainer in our detached/unheated garage for our '14 A4q that was only being driven a few minutes weekdays at the time.

I found that Audi offered a battery charger/maintainer (PN 420093050D) that appears to be a rebranded CTEK MXS 5.0. Since the cost of the original CTEK is less than half of the rebranded charger, I went with one of those:

CTEK MXS 5.0 Charger (40-206): https://www.amazon.com/CTEK-40-206-5.../dp/B00CD44RQO

CTEK sells a set of accessories for their chargers, including a charge indicator quick connect for attaching directly to a battery:

CTEK Indicator Eyelet (56-382): https://www.amazon.com/CTEK-56-382-C.../dp/B002MT8S7E

and an extension cable, also with their standard quick connects:

CTEK Extension Cable (56-304): https://www.amazon.com/CTEK-56-304-C.../dp/B00ADIHUVG

The battery positive terminal control module, also called Fuse Panel A (8J0915459), had an open threaded terminal for attaching the positive lead of the charger, though I needed to replace the eye terminal on the positive wire so that it would fit properly inside the control module:



The negative wire on the quick connect cable fit on the port (left) side grounding post directly after re-installing the foam tool kit carrier:



With the car battery connection done, I mounted the charger to the the garage wall:



and routed the extension cable into the boot, thus:



We're coming up on two years with this set up, and so far, so good.

When we got this A4 in July 2017, I had a 100+ mile daily commute. After changing jobs in June 2018, it might take me 3+ weeks to put on 100 miles some months, and with work-from-home mostly for the past year, we might not take this car out much more than once or twice a month.

Having the battery maintainer fitted like this has worked out well, IMO.

Looking at this again now, I think I might add a proper fusible link to the battery control module and move the charger positive connection to the outside terminal (upper left threaded post in the first image, above). That will be an early spring project, at this point... --g

Updated 13 Apr 2024 with new Google Drive image links. --g

[A4B8 2.0tfsi]

RTFM and you'll see that you shouldn't direct charge your battery. Just do your connection in the engine bay, on + and - charging terminals, as per the manual, and it works as intended and by Audi recommended.

[eljay]

Thanks for sharing, but as stated above, you should be charging the battery through the terminals in the engine bay so that the battery management system takes care of charging at correct voltage and the various modules around the car are kept happy.

[Theiceman]

I'm not so sure about all this. If you had a dead battery. There would be no " battery management system "
Also I'm not sure what battery management system is active with the car shut down and sleeping..
I'll have a read over the manual but Im thinking the positive post on that battery and the positive in the engine bay are electrically the same place.
Physically separated so a spark can't do bad things in an enclosed trunck around battery charging funes.

I think it's worth further discussion as im likely totally wrong

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[DrGER]

Thanks for your comments & concern.

Inspection of wiring diagram No. 119 for the 2.0L gasoline engine (including CAED), shows us that Battery -A- positive terminal is connected directly to the engine bay Battery jump start terminal -U6- through the Battery interrupt igniter -N253- (which is actuated by the Airbag control module -J234-). The negative terminal, however, connects to common ground through the Battery monitoring control module -J367-. Hence, we connect the charger/maintainer negative terminal to the available body ground point in the spare tire well rather than to the Battery -A- negative terminal directly, which is effectively equivalent to using the charging posts in the engine bay.

Battery, Fuse Panel A, Battery monitoring control module:


Battery interrupt igniter (part of Fuse Panel A):


Battery jump start terminal:


Updated 13 Apr 2024 with new Google Drive image links. --g

[Theiceman]

Thanks for your comments & concern.

Inspection of wiring diagram No. 119 for the 2.0L gasoline engine (including CAED), shows us that Battery -A- positive terminal is connected directly to the engine bay Battery jump start terminal -U6- through the Battery interrupt igniter -N253- (which is actuated by the Airbag control module -J234-). The negative terminal, however, connects to common ground through the Battery monitoring control module -J367-. Hence, we connect the charger/maintainer negative terminal to the available body ground point in the spare tire well rather than to the Battery -A- negative terminal directly, which is effectively equivalent to using the charging posts in the engine bay.

Battery, Fuse Panel A, Battery monitoring control module:


Battery interrupt igniter (part of Fuse Panel A):


Battery jump start terminal:

Yeah I had a feeling this would be the case.

Btw where is the ground lug in the engine bay ?

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[DrGER]

Yeah I had a feeling this would be the case.

Btw where is the ground lug in the engine bay ?

Left (driver) side (2 in diagram):

[AOW162435]

I just did something similar to our 2014 A4, using CTEK components as well (MXS 5.0 maintainer and Comfort Connect panel mount: 56-531).

My connection is in the grille. I routed the cable into the engine bay on the passenger side, then under the air filter housing and finally into the firewall area. I took care to neatly zip tie the cable as I went, making the bulk of the install completely hidden.





Andreas

[Theiceman]

Left (driver) side (2 in diagram):

I don't remember seeing that...now I gotta check lol.

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[DrGER]

I just did something similar to our 2014 A4, using CTEK components as well (MXS 5.0 maintainer and Comfort Connect panel mount).

My connection is in the grille. I routed the cable into the engine bay on the passenger side, then under the air filter housing and finally into the firewall area. I took care to neatly zip tie the cable as I went, making the bulk of the install completely hidden.

Thanks for sharing this. I'll be interested in knowing how your panel mount holds up to the outside elements (rain, snow, road dirt, etc.) in that location over time.

I don't remember looking at the indicator panel mount when I did this two years ago. Since we park hood-in in our early 20th century garage (built in '27) and it's a tight fit as it is, this solution is not practical for us -- but I suspect the panel mount would fit in the trunk liner just above the port (left) side access panel door for a cleaner installation. Another potential spring project (given that we're likely to keep this 6MT for a while longer)...

[AOW162435]

Thanks for sharing this. I'll be interested in knowing how your panel mount holds up to the outside elements (rain, snow, road dirt, etc.) in that location over time.

I don't remember looking at the indicator panel mount when I did this two years ago. Since we park hood-in in our early 20th century garage (built in '27) and it's a tight fit as it is, this solution is not practical for us -- but I suspect the panel mount would fit in the trunk liner just above the port (left) side access panel door for a cleaner installation. Another potential spring project (given that we're likely to keep this 6MT for a while longer)...

Absolutely. No different in size than a typical fog light switch. The same 'panel' mount is also sold by itself, without the 10' of cable (56-562). May be a better option for your application.

The connector housing had a few small gaps in the rear which I sealed properly. The supplied rubber plug has a nice snug fit so I'm not too worried about the location. For now. :)



Andreas

[DrGER]

Our last day of Feb was spring-like today, with the temperature outside near 15C, so I took a look at installing the CTEK Comfort Indicator Panel (56-531) in the luggage compartment liner, and cleaning up the charger cable connection on Fuse Panel A at the battery positive terminal.

The CTEK panel comes in three flavors: shorter cable (56-380), longer cable (56-531), and no cable (56-562). I ordered the shorter cable (1.5 m) model from an eBay seller in OH for a fair price, who sent the version with the longer (3.3 m) cable; not bad. To clean up the charger cable connection on fuse panel A, I added a new 150A strip fuse to the open terminals on the port (driver) side of the fuse panel. The threaded posts here use an M6 nut and washer.

Inspection of the space behind the luggage compartment trim above and behind the port side access panel door shows ample room for the CTEK panel. I chose to mount the panel vertically with the top edge parallel (more-or-less) to the trim panel edge; better to keep it as far aft as possible to avoid interference with the trunk lid hinge mechanism. While the panel comes with a small template sticker for cutting the opening, I chose to use a bit of blue painters tape for this (to improve visibilty while cutting the trim panel with a sharp box cutter knife):


With panel hole cut, the cable gets routed through and the panel snaps right in:


To avoid having the charging cable get pinched on trim panels, I removed the lock carrier trim panel:


and pulled the charging cable through to the battery well along the existing negative cable here:


The excess charging cable got tied off here:


And on to the positive connection point on Fuse Panel A and the port side body ground point:


At Fuse Panel A, the port side strip fuse was not installed; adding this with 6 mm stainless steel hardware gives us access to the proper connection point for the (fused) charging cable:


With proper connections at the battery and body ground, we can put everything back together again:


And the cleaner, final result:


Updated 13 Apr 2024 with new Google Drive image links. --g

[AOW162435]

^ Nice clean install.



Andreas

[sc117]

Super clean install. I might do the same. Thanks for sharing!