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Just bought a CTEK MUS4.3 to charge up my 2020 S, which mode should I use? Snow flake or regular battery mode?
I connect it directly to the charging posts under the hood. When I selected battery mode, stage 4 lights up, when I used Snow flake mode, stage 6 lights up.
 
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Discussion starter · #23 ·
Correction made to OP. I assumed that MXS 5.0 meant 5 Amp. It does not. It is 4.3 with more features. CT5 is 5 amps.
 
I plugged in the CTEK 4.3 on my 2020 S for more than 10 hours, it is still on stage 6 this morning. Can’t believe 3 months old battery can be running this low. Make me wonder if it is really working on newer model?
 
I plugged in the CTEK 4.3 on my 2020 S for more than 10 hours, it is still on stage 6 this morning. Can’t believe 3 months old battery can be running this low. Make me wonder if it is really working on newer model?
Last night I plugged in my MXS 5.0 on my 2015 SD and it reached stage 7 in a couple of hours!
 
Discussion starter · #26 ·
My knowledge of the CTEKs is definitely old. :rolleyes: I haven't bought one in five years and even then, I just got a new 4.3 to replace the old one I broke. So I looked closely at the offerings and the 4.3 is gone. The cheapest one now is the MXS 5.0. This is still 4.3 Amps but gives you new features like some kind of "enhanced flood batteries" plus recondition AGM. With a price increase, of course.

Next up is the Polar 4.3, also 4.3 Amps, good to -22F vs -4F. Looks the AGM is charging at 15.0 vs 14.7

Moving up is the CT5 that is 5 Amps. It shows you, roughly, the hours to finish charging but know what step you are in.

Then paying more money gets you the 4.3 Test & Charge, 4.3 Amps, Looks like it also charging at 15.0 vs 14.7

And finally the 7002, 7 Amps, but gets you the benefit of acting as a power supply as needed.

If I did not have one, the cheapest way to go is MXS 5.0 but the 7002 has to be faster, but I think its the oldest one among them. IOW, no new fancy things like an alternator tester.
 
In another thread, it was mentioned that if you select alternator voltage as one of your MFD main screen choices, you can see the actual battery voltage, in addition to the alternator charging voltage.

Later, this was further explained. You must not start the car to see battery V, just turn ignition to the on position. If you start the car it just reads Alternator charging V. This turn out to be true. However, is the battery voltage resign on the MFD accurate?

I tested.
Short answer...NO!

I had just driven my Macan the day b4 & checked MFD battery V. Showed 11.6 V or only ~ 20% charged! How is this possible? I was sure my battery was good. Yes, it is 4+ years old but, I had topped off the charge a month ago & CTEK MUS 4.3 said fully charged & my multimeter had read 12.56 V right after. So, not perfect 12.7 100% but, ~ 95% which is not bad. I checked @ under hood jump start terminals.

So I decided to test the accuracy of the MFD battery V readout, with a fully charged battery, using my CTEK to top off.
Procedure:
Pop/unlock hood
Roll R window down 1” & remove Rear 12V socket plug (do not lose)
Plug in 12V CTEK adapter wi red adapter, + extension cord—flashes red
Connect to charger but do not plug into outlet yet
Turn ignition to On & then to off
Plug CTEK into power outlet
12V adapter now flashes green as car battery begins to charge
Verify CTEK set to Snowflake/Cold/AGM
Lock car -shuts off accessories & interior lights

I checked b4 I went to bed last night & step 4, today < 12 hrs. later it was step 7... done!
I unplug CTEK from power outlet
W/o opening car door to wake computers, I opened the hood... which I had popped/unlocked last night b4 charging.
MM = 12.59 V or ~ 95% charged!
{Note: I had charged to 12.77 V, 3+ years ago when battery/car only 1 year old.}
I suspect 95% vs. 100 % charge due to battery being > 4 years old.

I then check MFD battery V reading & shows 12.1V…~ 50%! Clearly this MFD display of battery voltage is way off! Significantly underestimates true battery voltage.
 
I checked my battery on the display at 12.1v too. Maybe it’s under partial load.
 
Here is my CTEK MUS 4.3 charging procedure on my MY2016 Turbo:

Pop/unlock hood
Roll R window down 1” & remove Rear 12V socket plug (do not lose)
Plug in 12V CTEK adapter wi red adapter, + extension cord—flashes red
Connect to charger but do not plug into outlet yet
Turn ignition to On & then to off
Plug CTEK into power outlet
12V adapter now flashes green as car battery begins to charge
Verify CTEK set to Snowflake/Cold/AGM
Lock car -shuts off accessories & interior lights



I have a garage. I bought the CTEK extension to attach to the 12V adapter so I can have the (HOT) CTEK charger outside the car.

This procedure probably will work regardless of which 12V outlet used.

I pop hood 1st so when charging complete I can ck V with multimeter from underhood jump start terminals w/o having to open door to pop hood & wake up computer & put more load onto the battery drain it a bit.
 
I finally figured out how to make it worked. I was in test mode all the time that's why it stayed at stage 6 for 10 hours. You need to push the mode button for 2 seconds to get into the charge mode. After that, I used the snowflake mode to charge my battery, 6 hours later, it's green light and fully charged.
 
Discussion starter · #31 ·
... You must not start the car to see battery V, just turn ignition to the on position. If you start the car it just reads Alternator charging V. This turn out to be true. However, is the battery voltage resign on the MFD accurate?

I tested.
Short answer...NO! ...

W/o opening car door to wake computers, I opened the hood... which I had popped/unlocked last night b4 charging.
MM = 12.59 V or ~ 95% charged!
{Note: I had charged to 12.77 V, 3+ years ago when battery/car only 1 year old.}
I suspect 95% vs. 100 % charge due to battery being > 4 years old.

I then check MFD battery V reading & shows 12.1V…~ 50%! Clearly this MFD display of battery voltage is way off! Significantly underestimates true battery voltage.
How did you check the MFD? You had to open the driver door, which wakes up some things, alarm off, things come to life, then turn the key to the accessory position and all kinds of things wake up. You can actually here pumps moving, fans or something. Does not the PCM turn on regardless of whether the radio sound is on? And the idiot lights on the dash? They are testing something. If you have the lights on auto, the lights will turn on? Did you completely shut the door so the interior lights are off? Etc.

I don't think its as simple as it sounds. 12.1 could be correct if something is drawing current. I don't think there is anyway to determine anything from the MFD UNLESS the car is running and then you know its the alternator doing its thing.
 
Yes, I woke the computer up to check the MFD, as described after I charged battery & checked battery V using MM under hood w/o waking you car. No way is my battery V going to drop from 95% to only 50% charged by simply turning key to on. I don't buy it.

Someone (not me) Can test this by checking battery V @ jump start or actual battery terminals & then with MM still connected, open door & turn ignition to On & check MFD battery V. If they read 12.1 & then the MM, which 2 minutes b4 had read 12.7, now DROPS to 12.1... agreeing with the MFD, I will be astounded.
 
How did you check the MFD? You had to open the driver door, which wakes up some things, alarm off, things come to life, then turn the key to the accessory position and all kinds of things wake up. You can actually here pumps moving, fans or something. Does not the PCM turn on regardless of whether the radio sound is on? And the idiot lights on the dash? They are testing something. If you have the lights on auto, the lights will turn on? Did you completely shut the door so the interior lights are off? Etc.

I don't think its as simple as it sounds. 12.1 could be correct if something is drawing current. I don't think there is anyway to determine anything from the MFD UNLESS the car is running and then you know its the alternator doing its thing.
You are correct. Just measuring voltage is very limited in assessing a battery’s state of charge. This link below is to a marine focused website but the guy who writes the articles really knows his stuff When it comes to electrical systems. The link is to an article about programming a battery monitor on a boat but it does give you a sense of how complicated it is to properly assess a battery’s condition or state of charge.

 
I think the MFD shows the alternator voltage not the battery voltage. I used to see 14.5V on MFD while driving, after I fully charged the battery this weekend, today on my way to work, it showed 12.1V all the way. Looks like the system detects the battery status and sets the alternator to the lower voltage to avoid over-charged the battery.
 
Discussion starter · #35 ·
I think the MFD shows the alternator voltage not the battery voltage. I used to see 14.5V on MFD while driving, after I fully charged the battery this weekend, today on my way to work, it showed 12.1V all the way. Looks like the system detects the battery status and sets the alternator to the lower voltage to avoid over-charged the battery.
We’re talking with the engine off, key in acc position.
 
We’re talking with the engine off, key in acc position.
Yes, I'm aware of that. Just put the key in ACC position, it still showed 12.1V as when I turned off the car, then I started the engine, it gradually moved up to 14.7.V. When I start driving the car, it slowly moved down to 13.2V as the alternator voltage. I know my battery is close to 98% full so the alternator voltage is lower.
 
Yes, I'm aware of that. Just put the key in ACC position, it still showed 12.1V as when I turned off the car, then I started the engine, it gradually moved up to 14.7.V. When I start driving the car, it slowly moved down to 13.2V as the alternator voltage. I know my battery is close to 98% full so the alternator voltage is lower.
The alternator voltage should be regulated and would decrease as the battery reaches full charge.
 
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MFD with ignition on but car not started is NOT the alternator Voltage. Explained several times above in this thread.

Re MFD display of battery V...I wonder if it will typically show ~ 12.1V (50% charged) when you have a fully charged battery?

In any event, I think MFD display of battery voltage is wrong & therefore completely useless.

One caveat, I don't think checking battery voltage, via MFD, is listed in any Porsche owner manual. Maybe we are wrong & it is NOT intended to show battery V with ignition set to on but car not started. We are assuming this is true.
 
Discussion starter · #39 ·
How long does it take to charge the car?

I know it depends on many things, just wondering. And with which charger, 4.3 or 7 amps?
 
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One caveat, I don't think checking battery voltage, via MFD, is listed in any Porsche owner manual. Maybe we are wrong & it is NOT intended to show battery V with ignition set to on but car not started. We are assuming this is true.
Let me put it this way (and this is not meant in a rhetorical or smartaleck vein): where do you think the MFD comes up with that number -- 12.1, 11.9, pick a number, any number -- when you turn the key to the accessory position?

I'm asserting that it's not a random number, i.e., the MFD is reading some voltage. That it doesn't match what you -- a bit earlier -- measured at, say, the jumper posts does not surprise me. Of course, there will be slight discrepancies based on the accuracy of any voltage reading device, but more importantly you've also fired up the inside or outside lights and who knows what else, when turning on the car. I've done this -- accessory only -- and watched the MFD readout drop a bit, as the seconds go by.

What I think you should do is connect a volt meter to the posts with long leads, so you can watch, from inside the car, what the meter's readout is saying, while also watching the MFD readout in the accessory position. Maybe I need to do this myself, with a little GoPro action, as another one of my Macan-based science projects.
 
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