Well, it's more complicated than that. I'm sorry this is wordy but I'm trying to work out multiple problems and trying to provide lots of info and pictures.
The last two batteries I've had in my BMW E39 have been Interstate MTP-93s, based on glowing recommendations from other owners. The first, bought in 2003, dumped enough acid in my trunk to run down into the spare tire well stripping paint along the way, eventually drying up around one of the drain plugs.
The second was supplied in 2005 as a warranty replacement for that first one from a supplier 50miles from the first who happens to be my indy shop of choice when I can't do a job myself. After body shop repairs, I've tried to protect the battery area including the application of battery mat material. I've posted in a number of threads, including here, about how the original battery leaked and how this new one still continues to show signs of oozing from the caps.
I generally remove and check the battery no less than once a year. I check fluid levels and test the electrolyte in each cell with a hydrometer. I have never had to add a drop of water to this batteyr and the hydrometer indicates 100% after an overnight rest. I sometimes use a desulfating battery tender over one night every 1-3 weeks to make sure it's topped up and get some desulfating action. A fair weather car I used to have was on this tender 24/7/365 unless I was on the road with it and there were no issues with it.
Every time I look at this battery I see something like this:
Just for kicks, the last time I did this (Sept 2010) I reinstalled the caps, covered with foil tape (as per someone's suggestion here) and then covered that with clear duct tape as an insulator:
A full album of everything I observed that day is here
A couple of weeks ago I noticed that the car was cranking slowly but figured it must be my imagination. A couple of days later I figured it was definitely slow so I brought up a reasonably accurate voltmeter function on my instrument cluster. It was definitely weak, with the cluster completely shutting down during cranking. Charging voltage was/is 13.8-14.0, just like it has always been for the 9.5 years I've had this car. After about 30 mins of driving I put it on a charger capable of 10A when I got home and it charged for only around 15mins before showing ~14.4V. The temp was just below freezing around this time. I had not used the tender in 3 weeks or so.
I thought that it might have been short trips, or maybe the kids left a reading light on one time, combined with the temps etc... I put my tender on for the rest of the day and overnight. The tender was in charge mode for many hours before kicking to desulfate mode. I've generaly used the cluster voltmeter, but I measured "idle" voltage (still a draw of more than 3A with trunk lighting and various computers awake) of 12.2V at the battery, which according to my reading is expected for "fully charged" at 0C.
The fact that the battery takes days to weaken, still starts the car even when cold and weak and indicates 100% on the hydrometer has me puzzled. Other batteries I've had show declining hydrometer readings over the service life and have always ended up dying in the end with the characteristic 10.4V and no-start condition from a sulfation cell short. I thought my desulfating charger habits were seriously extending the service life.
Well, it got weak again after a week although I didn't let it get nearly as low as before. No slow cranking was observed but measurements indicated lower than normal terminal voltage when turning on the ignition but before starting. I performed a test on the car to check the current draw when the car is in "sleep" mode. That passed just fine at 24 mA - right on spec. So the charging system is OK, and there are no abnormal draws to run the battery down while parked so the problem must be the battery, or the battery has been unable to deep charge due to temperatures which have been well below freezing since this started (sometimes closer to 0F). I thought again I'd recharge with the tender and observe, just in case the full reboot of the car (caused by disconnecting the battery to do the drain test) had actually fixed a module that was maybe staying awake. I never had any perception of battery issues in the spring/summer/fall.
Yesterday I observed that voltages according to the cluster were on the weaker side again. Today I brought the battery inside to warm up to room temperature. I was then going to do a fairly extended bench charge with the 10A charger intending to do cell equalization and make sure that a full, deep charge was achieved with 100% certainty.
On getting the battery to the bench, I found under the foil tape a significant build up of white crystals from the battery still oozing from the caps since September. Why does this keep happening with charging voltage being in proper range and, if anything, the battery is certainly not being overcharged considering what's happening to me now? This battery is remote vented - why would enough pressure build up to cause oozing past the caps instead of venting gases out the vent?
One thing I've always wondered is if the battery is overfilled. I see the fluid top is "fish eyeing" in cell but I measure that the fluid level is over 1" above the top of the plates. I've tried to capture the fluid level in a couple of pictures, enhancing brightness to try to see into the cells:
All of my pictures from today are here
As I said, if they are overfilled then that is two completely separate vendors, in two different years (2003 and 2005) which have sold me overfilled Interstate batteries. I'm seriously considering removing some electrolyte, even though this is generally a bad idea, to see if they stop oozing all over the place.
Of course if I can't get it to perform properly, that may be academic because I need a replacement anyways. I don't have a lot of options in group 49/93 available to me locally and I wouldn't want to throw in another Interstate/JCI just to have it keep leaking, and JCI is my number one choice. 5 years of service life is pretty good, but based on the hydrometer reading of 100% and my use of a desulfating battery tender I thought there was still plenty of life left...
I appreciate any comments on both the oozing and the charge retention issues.
The last two batteries I've had in my BMW E39 have been Interstate MTP-93s, based on glowing recommendations from other owners. The first, bought in 2003, dumped enough acid in my trunk to run down into the spare tire well stripping paint along the way, eventually drying up around one of the drain plugs.
The second was supplied in 2005 as a warranty replacement for that first one from a supplier 50miles from the first who happens to be my indy shop of choice when I can't do a job myself. After body shop repairs, I've tried to protect the battery area including the application of battery mat material. I've posted in a number of threads, including here, about how the original battery leaked and how this new one still continues to show signs of oozing from the caps.
I generally remove and check the battery no less than once a year. I check fluid levels and test the electrolyte in each cell with a hydrometer. I have never had to add a drop of water to this batteyr and the hydrometer indicates 100% after an overnight rest. I sometimes use a desulfating battery tender over one night every 1-3 weeks to make sure it's topped up and get some desulfating action. A fair weather car I used to have was on this tender 24/7/365 unless I was on the road with it and there were no issues with it.
Every time I look at this battery I see something like this:
Just for kicks, the last time I did this (Sept 2010) I reinstalled the caps, covered with foil tape (as per someone's suggestion here) and then covered that with clear duct tape as an insulator:
A full album of everything I observed that day is here
A couple of weeks ago I noticed that the car was cranking slowly but figured it must be my imagination. A couple of days later I figured it was definitely slow so I brought up a reasonably accurate voltmeter function on my instrument cluster. It was definitely weak, with the cluster completely shutting down during cranking. Charging voltage was/is 13.8-14.0, just like it has always been for the 9.5 years I've had this car. After about 30 mins of driving I put it on a charger capable of 10A when I got home and it charged for only around 15mins before showing ~14.4V. The temp was just below freezing around this time. I had not used the tender in 3 weeks or so.
I thought that it might have been short trips, or maybe the kids left a reading light on one time, combined with the temps etc... I put my tender on for the rest of the day and overnight. The tender was in charge mode for many hours before kicking to desulfate mode. I've generaly used the cluster voltmeter, but I measured "idle" voltage (still a draw of more than 3A with trunk lighting and various computers awake) of 12.2V at the battery, which according to my reading is expected for "fully charged" at 0C.
The fact that the battery takes days to weaken, still starts the car even when cold and weak and indicates 100% on the hydrometer has me puzzled. Other batteries I've had show declining hydrometer readings over the service life and have always ended up dying in the end with the characteristic 10.4V and no-start condition from a sulfation cell short. I thought my desulfating charger habits were seriously extending the service life.
Well, it got weak again after a week although I didn't let it get nearly as low as before. No slow cranking was observed but measurements indicated lower than normal terminal voltage when turning on the ignition but before starting. I performed a test on the car to check the current draw when the car is in "sleep" mode. That passed just fine at 24 mA - right on spec. So the charging system is OK, and there are no abnormal draws to run the battery down while parked so the problem must be the battery, or the battery has been unable to deep charge due to temperatures which have been well below freezing since this started (sometimes closer to 0F). I thought again I'd recharge with the tender and observe, just in case the full reboot of the car (caused by disconnecting the battery to do the drain test) had actually fixed a module that was maybe staying awake. I never had any perception of battery issues in the spring/summer/fall.
Yesterday I observed that voltages according to the cluster were on the weaker side again. Today I brought the battery inside to warm up to room temperature. I was then going to do a fairly extended bench charge with the 10A charger intending to do cell equalization and make sure that a full, deep charge was achieved with 100% certainty.
On getting the battery to the bench, I found under the foil tape a significant build up of white crystals from the battery still oozing from the caps since September. Why does this keep happening with charging voltage being in proper range and, if anything, the battery is certainly not being overcharged considering what's happening to me now? This battery is remote vented - why would enough pressure build up to cause oozing past the caps instead of venting gases out the vent?
One thing I've always wondered is if the battery is overfilled. I see the fluid top is "fish eyeing" in cell but I measure that the fluid level is over 1" above the top of the plates. I've tried to capture the fluid level in a couple of pictures, enhancing brightness to try to see into the cells:
All of my pictures from today are here
As I said, if they are overfilled then that is two completely separate vendors, in two different years (2003 and 2005) which have sold me overfilled Interstate batteries. I'm seriously considering removing some electrolyte, even though this is generally a bad idea, to see if they stop oozing all over the place.
Of course if I can't get it to perform properly, that may be academic because I need a replacement anyways. I don't have a lot of options in group 49/93 available to me locally and I wouldn't want to throw in another Interstate/JCI just to have it keep leaking, and JCI is my number one choice. 5 years of service life is pretty good, but based on the hydrometer reading of 100% and my use of a desulfating battery tender I thought there was still plenty of life left...
I appreciate any comments on both the oozing and the charge retention issues.
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