Z4-forum.com

Hi!
My Z4 is in storage because of winther.
I have the oem AGM battery.
What is the max charge voltage, 14,4 or 14,7?

14.7v would be the boost charge voltage setting for agm but for storage over winter you would either be wanting a float charge of 13.5v (constant) or pulse charge.

I use CTEK Ready to go.
It has a Normal and a AGM mode.
AGM gives max 14,7 and Normal 14,4..
CTEK tells me to ask BMW. Bmw sends me on a trip around.... =nowbody knows.

I’ve noticed that BMW now sell a re-badged CTEK battery charger https://shop.bmw.co.uk/bmw-uk/en_GB/p/g ... PID_91584/ and out of interest I entered the VIN of my 2015 35iS to check compatibility. Was surprised to see it appears to be incompatible - anyone have any idea why?

Dont fit mine either, incompatible..

Just plug the ctek in on std not cold setting and it'll be fine.

Mike

Ducklakeview wrote: ↑Mon Dec 11, 2017 12:32 pm Just plug the ctek in on std not cold setting and it'll be fine.

Mike

Ok, il try that, thanks

Ok!
I had my Ctek on Normal and mostly plugged in all last winther, and the battery have been working fine all sumner, 10 000 km, so Normal on the charger seems to worke fine! (not the AGM mode).
Its now time again to store my very nice Z4. Its been a fine summer!

I had been running my original BMW battery on a BMW branded CTEK (older model than the one in that link) for 5 years with no problems. Only replaced the battery earlier this month as I ran it dead flat (for the second time) by leaving ignition on accessories position overnight. Thought it was about time to replace the original battery anyway as it was 10yrs old.
As DLV mentioned, just run it on the normal setting, not the cold setting.

I'm pretty sure all the CTEK models enter a pulse charging mode after the battery has reached capacity anyway so the voltage is largely irrelevant when you have it connected for long term storage.