Saturday, November 23, 2013
Another Battery Failure
For the last five years I've used a Deltran Battery Tender to help prevent sulfation and premature battery failure on the E46, which has spent most of its life asleep in the garage. Over the last few years I have been slowly replacing my Battery Tenders as they fail with a better solution** called the Battery Minder manufactured by VDC Electronics. I was at the garage to swap out the units last weekend when I noticed the Battery Tender was in an undocumented mode I'd seen before.
Normally, when the Battery Tender is in float mode, the red Charging indicator extinguishes and the green Storage indicator illuminates continuously. This time, however, I noticed the red Charging indicator was on continuously and the green Storage indicator was flashing. This mode fails to match the simple mode decoder label affixed to the unit and the documentation makes no mention of it either.
I naturally assumed the unit had failed so I tried to replaced it with a Battery Minder I had on hand, only to find that the Battery Minder refused to charge the battery. The Power indicator changed to red which, according to the documentation, translates to "battery is not fully charged and the unit has defaulted to float mode". I've seen this occur if the charge period times out, which occurs if I try to charge my large ampacity AGM battery bank at the lowest current setting of 2 amps, but this clearly was not the case here. The unit indicated the fault immediately upon attachment to the battery, which in itself is odd since most of these chargers need some time to detect the failure of the battery to meet the expected charge profile, but the unit reacted almost as if it detected a short.
At this point I figured that the battery had dropped a cell so I disconnected the charger and checked the battery with a VOM. The result? 11.9 volts. This is higher than the 10.5 volts typical of a battery with a reversed cell but clearly indicative of a fully discharged battery. At this point I glanced into the car to find various LED indicators flashing and the brightness of several incandescent bulbs wavering. I didn't need any additional evidence to point the finger at the battery so I decided to pull it out of the car.
Like most BMWs of this era more than one battery option exists. Cars with premium and cold weather packages (heated seats, mirrors, etc.) usually receive the largest battery (and a bigger alternator, incidentally) to compensate for the additional load presented by those options. Oddly, however, my more or less loaded E46 ZHP came with the 640AH part (61217586961) rather than the 720AH model. There is a cost premium of $40 and likely a few pound weight penalty for the larger battery so I had no incentive to order the larger unit. Incidentally, the ETK does not differentiate the parts based on VIN so I had to give the old part number to the parts department.
I recently learned through Mike Miller's column in Roundel that BMW is now once again advocating routine differential and transmission oil changes and has reduced their recommended engine oil change interval to 12000 miles (down from 15000). The intervals are still too high for many in the know, including me, but anything is better than their "lifetime fill" song and dance. So you can probably imagine why I grinned ear to ear when I took my first look at the new battery the parts guys put on the counter. Instead of a stupid label covering the battery cell closures, the closures are fully accessible so the battery can be routinely SERVICED. Has the pendulum started to swing back toward reality? Is BMW finally acknowledging that they're producing vehicles that are supposed to last 20+ years, not be thrown away after the warranty ends because they are uneconomical to repair due to a lack of routine maintenance? Maybe not, but it's a start.
I installed the battery today with no fanfare and the vehicle came back to life. I also plugged in the Battery Minder, selected a 2A charge rate, wet-cell charging mode, attached the clips to the battery and watched as the Battery Minder activated its charge cycle as expected. Mission accomplished.
** If you're wondering, there are several reasons I've migrated to the Battery Minder:
- AGM battery support. The Battery Tender Plus is only designed to charge traditional wet or "flooded" cells as provided on the E46 and earlier vehicles. The Battery Minder is able to charge wet cells, AGM batteries and GEL cells. If you happen to own a newer BMW the Battery Minder is your only choice. Because the charge profiles are different for AGM batteries, if you attempt to use a wet-cell charger on an AGM battery the battery will not be fully charged and sulfation will result -- which clearly defeats the purpose of a battery maintainer.
- Temperature Compensation. The optimum battery charge profile is affected by battery temperature. What works in the winter can be damaging in the summer. The Battery Minder will adjust the charge profile to accommodate changes in temperature. It does this through a thermocouple ring terminal. This terminal is normally expected to be attached to the negative battery post, which will cause the system to more closely track the battery temperature, but in my experience merely having the thermocouple attached and hanging free to measure ambient does the job. FYI, the optimum float mode charge voltages vary about 3 volts between 120F and 40F, so the feature is quite helpful in prolonging the life of batteries that see a wide range of temperatures in storage.
- Desulfator support. The unit's signature feature. The Battery Minder pulses the charge current in a way that can reduce or eliminate sulfation that has already occurred. To be honest I've never seen it bring a battery back from the edge and I tend to avoid to the extent possible the conditions that would normally cause sulfation in my batteries, but some people swear this works.
- Selectable charge rate (2, 4, 8 amps). I normally maintain batteries using the 2A setting since that's usually all the current required to get through the charging and absorption phases quickly enough on a fully charged battery. But there are times when I'm working with my AGM deep cycles that I need to increase the charge current enough to get the battery charge level up to a point that will not cause the charge cycle to timeout. What charge cycle timeout, you ask? The one that protects your batteries from overcharging, particularly in the case of a faulty battery.
- Better documentation.