[Kevinl]

My 335i does not get driven much mainly weekends the battery has been replaced but some times when I turn on the car the A/c will kind of blow weak for a little while than start blowing hard. I think the battery is draining somewhat and the car wont let the blower fan run at full speed till it has charged up.

I was thinking of getting a battery maintainer like a ctek to keep the battery topped off during the week when the car is sitting is that a good idea or will it cause problems with the electrical system

[Boland01]

I use a battery maintainer on our 535i as it can sit a week or two in between using the car. Hasn't hurt anything.

[dmatre]

Connect at the terminals under the hood rather that at the battery itself, and you'll have no problems.

Since inheriting a Volvo (now my DD), the BMW has become a garage queen.

When I first got the battery tender, I connected direct to the battery. Maybe it's related, maybe not, but 2 months after starting to use it, the battery bought the farm.

With the new battery I moved to the under-hood connections and it's been > 1 year now without issues.

[roadkillrob]

I have the plug hooked directly the the battery on mine, I just open the trunk and plug it in, it is a battery tender brand. I have used it anytime the car would sit for more than a week without being driven. I also have a dashcam in it that is powered all the time, so that also adds some drain when it sits too long. Car is an E93 and also sits all winter here in the north east (I only have 20k miles on it since new)

I got the car in January of 2008 and have used the tender since then - I put a new battery in it this year when the battery was 7.5 years old and it had not had a single issue, but figured it was due some love and put a new one in it.

[Boland01]

I also connect to the terminals under the hood. Simple and quick to do.

[Wilt]

Originally Posted by roadkillrob

I have the plug hooked directly the the battery on mine, I just open the trunk and plug it in, it is a battery tender brand.

When I first purchased my maintainer, I did the same. Then I realized that it is NOT a good idea!!!

The IBS keeps track of battery status, the amount of drain and the amount going back in from the alternator. Hooking maintainer directly to the battery terminals bypasses the IBS, so what it thinks is nowhere like reality.

[Meeni]

Originally Posted by Kevinl

when I turn on the car the A/c will kind of blow weak for a little while than start blowing hard.

You may need a slow charger for your usage pattern, and you have received advice on that already. However, this is not a bug, it is a feature. The blower in auto mode does not run at full tilt until the computer is satisfied that it's going to blow the air at the right temperature to help reach target (so in hot weather, it waits until the compressor has generated enough cold, and in winter until the heater has enough warm air). It's a nice feature that prevents the ugly blow of death with superheated air everytime you turn on the car.

[Kevinl]

Went to the dealer and bought the Bmw Branded yes I know its a ctek charger/maintainer the car had practically no airflow again so I am just gonna leave this hooked up during the week when the car is sitting

hopefully the battery is ok like I said it has been replaced

[SpeedBuggy]

I use the BMW (Re-branded Deltran) Advanced Battery Charging System with the Alligator Clips. Works great, I have a '06 on the original battery and use this same unit.

Car has become a garage queen as of late and is stored during the winter months and I use this all time to keep the battery fully charged. It is typically connected anytime it is sitting.

Always connected to the access points under the hood. I do wait until the engine compartment has cooled off before connecting. Be careful of routing the cables under the hood as not to get the caught or pinched by the hood, latches or other body components.

[jwalker87]

I use a Battery Tender (HERE) with an extension cable hard-wired to the underhood connections (there's an available nut near the post), so its super convenient to plug in and out. Here are some pics of the install.

[ctuna]

Eclectically if you hook to any 12 volt line it still goes to the battery so
I don't see how you could bypass the IBS without unplugging the
IBS.