E92 M3 Voltage on ctek 5.0

[bosse92m3]

E92 M3 voltage and ctek 5.0 question

Hey guys so trying to get my hand around this.

I drive the m3 on weekends and have it sitting during the week.
A Few weeks back I got the " very low change" message on idrive.

After this is decided to get a ctek mxs 5.0 battery tender.

I put the m3 on the tender but before hand measured the voltage at the jump start points in the engine bay.
Voltage was 12.1v

After having the charger on it for an hour it showed that it was past 80% full and the took 4-5 hours to get to 100% full.
This didn't sound right to me as it seemed to fast for a battery that was at 12.1v.

I measured the voltage an hour after the ctek had been unplugged and it showed 12.2 -12.3v.
Not much of an improvement even through the ctek said 100% charged an hour ago.

I decide to plug in the ctek again and monitor the voltage.
This is how it went:
Plugged in and it went straight to light 3.
It slowly increased the voltage to 14.4v and after 20 minutes went to light 4. It stayed on light 4 for 1.30 minutes again at 14.4v.
Light 5 went on for 3 minutes and showed 13.2v
And maintained 13.8v.

Again after this I unplugged the ctek and checked the voltage a few hours later. It now shows 12.5v but as soon as I unlock or lock the car it drops quickly to 12.1v and slowly creeps up to 12.5v.
When I turn accessories on and the car is off it drops to 11.9v

This may sound a little confusing if your not familiar with the ctek charger but hopefully someone can help out and let me know if this sounds correct.

My question is, are these voltages correct?
And why did the ctek show 100% charge when the battery was at only 12.2v.

I should also add the the battery is only 1 year old bmw battery, non agm.

Thankyou in advance

[Helmsman]

Hi Bosse,

I've found the voltage drop to maybe 12.4V even on a assumingly fully charged and fresh/replaced changed soon as you unlock, clearly a lot of current drain from various electronics. Same thing when the CTEK is plugged in, the 5A isn't enough to keep up the voltage.
When fully charged (very little current required) it should go close to max voltage ~14.5V, where after it goes down into maintenance mode (just under 14V). Soon as you "wake up" by opening door or turn ignition on, car electronics will force the CTEK voltage down again.

12.1V does sound low though, and 11.9V even more so when fully charged. Sounds like time to check for a new battery?

[dparm]

These symptoms sound like that of a worn-out battery. Most auto parts stores in the US do free battery testing; I suggest you do that before you get stranded somewhere.

Also, check what the voltage is when the car is running -- easy way to validate the alternator is charging it.

[pjk380]

As mentioned these cars draw a lot of current from the electronics. I believe your description during the charge cycle with the Ctek sounds about right. I too use a Ctek charger. If the battery voltage is 12.1 V, you need to charge it. Charge it all day or all weekend, it wont hurt the battery. The Ctek will monitor the battery and provide the correct voltage for what the battery needs.

I too noticed the car voltage can be all over the place especially when you unlock or lock the car. Lights come on, go out, inside lights are on, dash lights on, etc. I think the voltages you are seeing are not that unusual.

You mentioned your battery is a 1 year old non agm BMW battery. It may still be a little discharged or it could have a bad cell. It will take a lot longer to get to fully charged than it takes to get to 70%-80%. A 1 year old battery should not have a bad cell, but it is not unheard of. I would keep it on the charger for as long as you can and monitor the voltage.

If you are concerned and want to monitor the battery, Ctek has the Ctek CTX battery sense & monitor App. I’ve had it for over a year now and I can see my battery voltage and the battery charge level. I think it’s a pretty neat tool to check battery voltage and health right from your phone.

[bosse92m3]

Originally Posted by Helmsman

Hi Bosse,

I've found the voltage drop to maybe 12.4V even on a assumingly fully charged and fresh/replaced changed soon as you unlock, clearly a lot of current drain from various electronics. Same thing when the CTEK is plugged in, the 5A isn't enough to keep up the voltage.
When fully charged (very little current required) it should go close to max voltage ~14.5V, where after it goes down into maintenance mode (just under 14V). Soon as you "wake up" by opening door or turn ignition on, car electronics will force the CTEK voltage down again.

12.1V does sound low though, and 11.9V even more so when fully charged. Sounds like time to check for a new battery?

Thankyou for the reply, after a little more investigating I believe your correct, Theo seems to be about right. Only thing that's still abit weird is how it drops to 11.9 v sometimes when I use accessories, but I ll always seems to climb back up.
Thanks again

[bosse92m3]

Originally Posted by pjk380

As mentioned these cars draw a lot of current from the electronics. I believe your description during the charge cycle with the Ctek sounds about right. I too use a Ctek charger. If the battery voltage is 12.1 V, you need to charge it. Charge it all day or all weekend, it wont hurt the battery. The Ctek will monitor the battery and provide the correct voltage for what the battery needs.

I too noticed the car voltage can be all over the place especially when you unlock or lock the car. Lights come on, go out, inside lights are on, dash lights on, etc. I think the voltages you are seeing are not that unusual.

You mentioned your battery is a 1 year old non agm BMW battery. It may still be a little discharged or it could have a bad cell. It will take a lot longer to get to fully charged than it takes to get to 70%-80%. A 1 year old battery should not have a bad cell, but it is not unheard of. I would keep it on the charger for as long as you can and monitor the voltage.

If you are concerned and want to monitor the battery, Ctek has the Ctek CTX battery sense & monitor App. I’ve had it for over a year now and I can see my battery voltage and the battery charge level. I think it’s a pretty neat tool to check battery voltage and health right from your phone.

Thanks for reply, yes I have been monitoring the battery with a multimeter, but have been looking into the ctek momtior app, i might have to get one as it would be so much easier

[bosse92m3]

Originally Posted by dparm

These symptoms sound like that of a worn-out battery. Most auto parts stores in the US do free battery testing; I suggest you do that before you get stranded somewhere.

Also, check what the voltage is when the car is running -- easy way to validate the alternator is charging it.

Cheers mate, yes I checked with the alternator running and it sits at about 14.7 so seems good