CTEK Lithium XS Charging

[JSM2]

Since I haven't been driving my car much due to the weather, I bought a CTEK Lithium XS for the LIFEPO4 battery in my M3.

What I've noticed is that the charger seems to keep reverting back to Step 2 (and staying there), even if it has charged past that step in the profile already.

This has me worried that either the charger isn't working right, or that the car's battery charging circuits might be screwing with the charging profile when the car transitions to sleep mode. (My only other theory is that it has something to do with temperature, as my garage isn't heated.)

This charger was highly recommended on the forums, does anyone have any experience with how these chargers are supposed to progress through the charging steps?

Thanks!

[E90Fleet]

How are you connecting the charger?

Should be via the "jump" points under the hood

[hotrod2448]

I have about 10 of those chargers I use to maintain our batteries for the race cars. I have not seen any issues like what you are describing with them but, I'm charging batteries that are removed from the vehicle. I guess it's always possible that it's just a bad unit.

That said I think the idea of the car's electrical management doing something that makes the charger think the battery has been disconnected then reconnected and restart it's charging cycle is on the right track. I'm not sure what strategies BMW uses to shut power down through out the car and what type of cell balancing they use but, I'm sure there is a decent amount of residual current draw that may just be enough to keep the charger cycling through charging phases as well.

I would assume that post in the engine bay is direct to the battery with no type of power contactor in line to shut down but, I also remember there being a little magnetic tool to shut the battery power down for shipping on the E90 series so...

[mdefalco25]

I have one and have had it on for about a month now. I connected it to the terminals under the hood and notice that it will change b/t float and pulse. Only once had I seen it go down to step 2 but that was due to a power outage. I have a heated garage, however, from material I have read online, temperature shouldn't be an issue. Have you tried unplugging it for a little bit to reset it? Also, are you sure you don't have any doors open or keys nearby that would keep drawing power?

[JSM2]

The charging unit is connected to the jump points under the hood, and the battery is installed in the car.

I've reset/cycled power to it multiple times, I've also tried waking the car up (unlocking and opening the door) at the beginning of the charging profile.

The unit will usually go up to Stage 6, then drop back down to stage 2. Stage 2 is maximum charge, so I usually pull the unit when I see it do that as I don't want to overcharge the battery.

The keys are in the house while the car is in the garage, maybe 30 feet away, and 2 rooms over.

[mdefalco25]

You shouldn't need to unplug it. It's a set it/forget it type charger that is smart enough to not overcharge these batteries. Not sure what is going on in your situation

[DocOct]

I have that charger and it has been perfect so far. It just sits on the final stage long term. No issues at all with it. Not sure why your charger drops regularly.

[blschaefer1]

Originally Posted by DocOct

I have that charger and it has been perfect so far. It just sits on the final stage long term. No issues at all with it. Not sure why your charger drops regularly.

Same here. Mine works great.

[hotrod2448]

Originally Posted by JSM2

The charging unit is connected to the jump points under the hood, and the battery is installed in the car.

I've reset/cycled power to it multiple times, I've also tried waking the car up (unlocking and opening the door) at the beginning of the charging profile.

The unit will usually go up to Stage 6, then drop back down to stage 2. Stage 2 is maximum charge, so I usually pull the unit when I see it do that as I don't want to overcharge the battery.

The keys are in the house while the car is in the garage, maybe 30 feet away, and 2 rooms over.

What happens if you don't mess with the charger or the car and just leave alone for about 24 hours? Does it go back to stage 2? Max charge is still not a lot of amps on this charger.

[JSM2]

If I leave the charger alone, it usually takes 2 or 3 hours to get up to Stage 6, it will set there for a hour or two, then it will bounce down to stage 2. I usually don't let it stay on, after it bounces back to stage 2 for very long (maybe an hour or two), as I'm worried about it over-charging the battery if it isn't working right.

I will say the charger doesn't seem to be dissipating a ton of heat (I've read these chargers have a tendency to get warm), so I'm not convinced it's dumping a bunch of power into the battery when it is stuck on stage 2.

[aboulfad]

Although it may sound silly, did you contact the manufacturer? I have the other LifePO4 charger Optimate TM291 and their tech support was very helpful for tech questions.

If you are concerned about your battery or drain in your car, one way to figure out is to use ISTA/D and energy diagnosis procedure...

[shortseller]

Been using mine all of January, so far working as should, no problems of jumping up/down stages. Set it and forget it as intended. Sounds like your battery is not holding the charge or you are not properly hooked up or the unit is defective? Give the manufacturer a call if you have not done so yet.

[Fake News 2017]

Mine came with a 5 year warranty. Just call CTEK and get it fixed.

[sh55]

This isn't going to be very helpful but I had the same problem then one day it was no longer an issue. The only thing I did was disconnect the charger for >24 hours and I disconnected and reconnected the charging wire where it unclips, made sure the fuse was seated properly, and suddenly it worked properly.

No idea which of those things did the trick but I connected it to the car the exact same way (under the hood) and used the same plug in my garage.

[Agamemnon]

No problems with mine. Charge the car once a month and then put the charger away till next time. I use the alligator clips and connect to the posts under the hood. Usually takes a few hour before going through all the stages and then it is in float / trickle charge mode.