Charging Battery in Car

[AussieZ3]

I use my Zed only on weekends and I recently purchased a C Tek MXS 5.0 automatic charger to keep the battery on trickle charge. The voltage applied by the C Tek charger varies from 14.7-15.8V during the charging cycle, which consists of 8 steps. The BMW TIS has a section titled "Charging Battery" which states that the charge current should drop exponentially when a voltage of 14.2 is reached. As the C Tek charger generates a voltage up to 15.8, I am concerned if the charger would damage the car's electronics.

I would like to hear from other Zed owners who have experience with C Tek chargers. - Kith

 

[Aceman]

I know many do use the CTek chargers and find them to be fine. I would imagine it would only charge at such high voltage if it was trying to recover a battery that was otherwise dead which these chargers can do. In raising the voltage the current will also be increased which can effectively clean the plates of any oxidisation and is usually a pulsed current.

I personally use a charger that I purchased from Aldi that is very similar to the CTek ones and only costs £15. I find it is a great charger for maintaining the battery whilst it is garaged and keeps the battery in tip top condition. I also have a lot more expensive "Ring" charger that has recovery mode for rejuvenating batteries that has worked well on other cars and can deliver upto 8 amps if required, again this is a pulsed type charger which seems to be the most effective way to recover a poor battery.

Ooh just realised do you have Aldi store in Australia ?

 

[roadvoyager1]

I bought a C-TEK MXS 5.0 last week to keep my battery healthy over the winter. I think you will find that 15.8V is only used in the RECON mode, which you can select or not. As my battery is fairly recent I just connected up, selected car mode and switched the charger on. It went to stage 4 (bulk charge) in a couple of hours and stayed on this stage for around 24hrs before progressing to stage 7 (float). If I understand the instruction booklet correctly it will now boost the battery every 10 days or when it detects a voltage drop. If you are concerned about the effect of the high voltage I would suggest that you disconnect the battery if you are going to use the RECON mode.

I sure others with far more experience will correct me if I am wrong and guide you in the right direction. By the way I also removed the interior light fuse and openned by boot lid whilst charging just in case there was any Hydrogen given off although I am not sure this was really necessary as mine is a sealed battery.

 

[AussieZ3]

Many thanks for the responses. Yes, we have Aldi stores here in Sydney and I have seen their battery chargers for sale at $29. I have no doubt the C Tek charger would apply a much lower voltage to maintain the battery but my concern is if any damage would occur to the electronics if the voltage exceeds 14.2 even in a short burst. I note that 14.2 is the voltage delivered by the alternator and posted below is the relevant page from the BMW TIS which has an issue date of 12/2007. Is there a later issue of this information from BMW?



The battery I have is a Varta Silver E38 which is an AGM battery and I hope to use the AGM mode on the C Tek charger which will ensure that the applied voltage would not exceed 14.7V. I hope to use the jump terminals under the bonnet to connect the charger rather than to use the battery terminals in the boot. I understand that the terminals under the bonnet are connected through the car electronics which monitors the voltage. Any comments would be appreciated.

 

[Fender2004]

I have used a ctek charger on my z3 for a number of years now, and have found no ill effects to the car in any way, even though the battery has been left in the car.

 

[vintage42]

I use a Battery Tender in winter, connecting it to the terminals in the engine compartment (battery in trunk). It senses the state of the battery and varies the charge from 1.25 amps down to a floating maintenance charge of milliamps. I rotate it between the Z3 and another car that is not used in winter.
http://www.amazon.com/Deltran-Batte...414762916&sr=8-1&keywords=battery+tender+plus

 

[TaffZee]

An Alernative to powered chargers:

http://www.ebay.co.uk/itm/10W-12V-s...71454905206?pt=UK_Gadgets&hash=item3f33f92376

I use this to keep my Caravan Battery topped up when not on the mains.

 

[vintage42]

I guess for winter storage of a Z3, the panel would be mounted on the roof of the garage with a cable going inside to the car. Looks like it would put out .57 amp on a sunny day.

 

[AussieZ3]

Thanks for your responses. I have searched the internet in using the terminals under the bonnet and found the following thread:

http://www.bimmerfest.com/forums/showthread.php?t=153381

The thread has two pictures suggesting locations to connect the charger. The B+ Terminal box has 5 cables connected to it and the thread suggests to use the connection below the jump cable connector. Does anyone know if the B+ Terminal box is just a junction box for the 5 cables or does it have any electronic circuits at the back?

The thread also suggests to use a different ground point for the negative terminal of the charger, not the recommended jump cable connecting point with large nut at the top of shockabsorber mount.

 

[vintage42]

It is not that complicated. Just use the same terminals you would use for connecting jumper cables. Positive to the big copper nut under the black plastic cover that has a big red + on it. Negative to the big nut on the strut tower a few inches forward.

 

[tower]

I guess for winter storage of a Z3, the panel would be mounted on the roof of the garage with a cable going inside to the car. Looks like it would put out .57 amp on a sunny day.

am using solar solution ,got it from Maplin (on offer too when i bought it....) attached it to south east facing garage window

 

[AussieZ3]

I know it's not complicated but I want to know more about the B+ Terminal box under the bonnet. The wiring diagram does not appear to provide much information. I hope to hard wire the charger cables and does it matter which terminal you connect the charger leads. There are 5 cables connected to the box.

 

[tower]

sorry can`t comment on that,just connect with the included alligator clips

 

[vintage42]

Same here.

 

[AussieZ3]

It turned out that C Tek MXS 5.0 is the charger recommended by BMW for use on the Z3. The BMW part number is 61432334070. I contacted BMW and they advised that the normal setting on the charger applies a voltage of 14.4V and this voltage will be suitable for the Z3.