[N8N]

Hi all,

reading some threads about battery replacement got me thinking. Last year I had to buy a new battery for my Jeep Cherokee and I got an Optima yellow top for it because I was just disgusted with the cleanup I had to do from the acid spill from the old parts store replacement battery that was in there. Jeep had only 81K miles but I had to replace both the battery cables because of acid damage, and luckily the intelligent design of the battery tray meant that I only had to replace the hold down and not the tray itself or worse yet the inner fender. (I bought it used, PO was not a "car person" and the battery still worked, so she didn't worry about it.) At the same time I got myself one of the fancy CTEK chargers to replace my aging one because of the good reviews and the fact that it had a charging mode for the gel cell type batteries.

Now I also have a recently purchased '09 335i which I believe still has its original battery. I've heard tell of batteries failing as soon as 4 years and my car is just coming up on its 4th birthday. I was wondering if it would be advisable to run it through the "recond" cycle on the CTEK charger to try to get some more life out of the battery, and if so are there any special instructions? I'm assuming that I should unhook the battery from the car when doing this, correct? Should I hook up a 12V power supply to the jump points to keep bad things from happening to the electronics while doing this (fortunately I have one, really intended for CB radio use, but I use it for electrolytic derusting mostly) or is that not necessary? What type battery do I have, anyway? Is it a wet battery, AGM, other? (real question is, what charging profile to use on it?)

Thanks for any advice!

[John 070]

imho the BMW battery lasts 6 years in service. I replaced mine at the 5 yr. mark to be proactive, and I paid the core and kept the old one. After thoroughly testing it, there's nothing wrong with the one that came out. If you go AGM it requires the car to be reprogrammed--at the time, the battery was only $80 more, but the labor was a couple hundred more. Not worth it, a battery, is a battery. There's nothing shabby about an OEM battery that lasts 6 years in the vehicle.

If your battery looks like this, it's lead acid (white).

[N8N]

I hope so... I'm just chea^H^H^H^Hfrugal and since I've already popped for the CTEK charger I figured I should try its capabilities. Is my stock battery AGM, and therefore it should be charged on the "snowflake/spiral" profile? Or is more info required? (09 335i) Also, I guess the important question is, should I unhook the battery to do this and if so what is the best/safest way to keep all my settings? I don't have a spare battery laying around but I do have a 12VDC benchtop power supply, so I was figuring on using that.

[John 070]

If the battery is white, it's lead acid, if it's black, it's AGM....I believe only M cars came with AGM...

[N8N]

ah, that's good to know. (runs outside to vehicle) yup, it's white. Actually I'm worried now as the magic eye looks black but then again it's dark out and I was looking at it with a flashlight. No apparent issues but it's just started to actually get cool at night, and I've only had the car for less than two months... battery looks like a minor PITA to disconnect too. Good news is that it's spankin' clean though, must be constructed with the quality. Any issues with just hooking up the charger at the jump points and letting it do its thing, or is that asking for trouble?

[John 070]

No worries, you should be able to hook up a battery tender to the terminals under the hood...I do in the winter when my car sits for a week or two....

[N8N]

OK I will probably do that on Saturday then just as a preventative measure. Been spending money like a drunken sailor on this thing (spare tire, misc. little tools, 17" wheels, Blizzaks, window tint, euro headlight switch, new Thule roof rack stuff, etc. etc. etc.) to get it into shape for road tripping so I'm going to try to do everything I can PM-wise to keep from having to do any repairs/replacements prematurely.

[N8N]

Well I wussed out... did it last night as I had to get firewood yesterday morning... I just put the charger on the regular desulphation/charging cycle rather than "recondition" when it's hooked up. Will do that out of the car, just too squirrely about the possibility of destroying sensitive electronics as I understand that the "recon" cycle involves an output of ~16VDC from the charger. Sometime when I have free time I'll hook up the 12V power supply to the jump points, remove the battery, and run it through the "recondition" cycle.

The thing that worries me is that I drove the car probably 150 miles or more yesterday and it took several hours for the charger to tell me that the battery was done (I actually left it on overnight as I put it on about 9 PM and I was very tired, at 11 PM it still was on the charge portion of the cycle) and since I had it out I figured I'd run the Jeep through a cycle as well this morning just for maintenance purposes. That one was as you'd expect, before I even turned around after plugging the charger in the charger was on the next to last light on the cycle (that is, it recognized the battery as being 80-90% charged already) and it'd gone into "float" mode within an hour. The Jeep is never driven but has about a year-old Optima yellow top. No real repairs/maintenance to the electrical system on that other than I replaced the battery and cables when I got it due to acid damage and flushed all the oil out of the starter with the CRC spray stuff due to a leaky valve cover. So you'd think of the two vehicles that the Jeep's battery would be at a lower state of charge due to sitting and parasitic drain and also a possible mismatch between a regulator designed for wet lead-acid batteries and having a spiral gel battery installed in its place... guess Bimmers are hard on batteries?

[sibhusky]

You can try to desulphate but ultimately it depends on the amount of sludge that has already accumulated, which is hard to say. The recondition method works by injecting current spikes/pulses into the battery in hopes of breaking off the sludge but it might not break it all off. Ive recovered 2 batteries this way but you also have to regularily do this to keep the sludge from forming or keep the battery charged up. Also set the charger to AGM when using the recondition feature as it will use a safer charging profile as to not overheat the battery while charging. AGM is actually a type of lead acid battery.

[N8N]

Do you mean to set the charger to AGM when reconditioning my Optima (which I would) or when reconditioning the conventional lead-acid battery in my 335i? My understanding is that the AGM setting (which is actually also referred to in the CTEK manual as to also be used in cold weather) is higher voltage than the regular wet lead acid setting, which I would think would be a Bad Thing... or does this actually help?

I'm really just trying to avoid having to prematurely buy an expensive battery (and if I were to buy a new one it probably would be AGM) and then have to pay to have my car coded for it... I guess that would be a pretty good excuse to install the factory alarm at the same time so I'd only have to pay for one coding session from the dealer.

[sibhusky]

Not familiar with your charger, but if your only reconditioning choices are gel or agm, then select agm for a lead acid battery at least thats what choices i have on my charger. You should also disconnect the battery from the car so the charger doesnt connect to the vehicle as there are always current/voltage pulses during reconditioning. A 12v battery can withstand much higher voltages but in short bursts which is what happens during the reconditioning mode, so your ok.

[NoTempoLimitN54]

In 2011 bought a NPower smart charger with 12V output at Northern when I was in FL. The NPower has 12V maximum output and desulphation. I needed to revive the battery in my wrecked 4Runner that had sat for 2 months without even a trickle charger, so I could sell the 4Runner. The charger resuscitated the 4Runner battery (which had been in service since 2007).

When I got back to LA I hooked up the NPower to my E39. Fortunately I have a garage with an electrical outlet. Prior to this, for five months the "DSC off" light had been permanently lit on my E39 (traction control off). ABS, speedometer and cruise control all worked. I did the diagnostics as suggested on bimmerforums and bimmerfest (very active E39 sections). I could not find anything wrong.

Then one day I noticed the DSC light was off... It fixed itself!

I believe that charging the battery fixed the DSC problem. It was just low battery voltage. Even though I drove my E39 every day and I even had a small charger on it for the two weeks I was in FL, it still wasn't bringing the battery up to full charge.

So I began a regimen of charging the battery once a week. The DSC problem never came back. I do the same thing with my E92. It's the easiest and cheapest way to avoid electrical problems.