Battery Safety Terminal Blew, While Driving

[1er_vert]

Wife was driving along and suddenly heard a deafening POP. It startled her and she pulled over car still running, to see if she struck anything. Nothing looked amiss and she continued driving another mile and parked at home.

She later told me about the incident. I went out and attempted to start her e86 Coupe and got x-mas lights on the dash. Nothing turned over. A USB charger/voltmeter connected to her cigarette lighter read 12.3v.... easily enough to start, but zero. I hooked up my CTEK charger/maintainer and it showed errors and completely drained. This was not true, after seeing the voltmeter.

I went back to inspect the 730CCA wet cell battery. It appeared swollen. I started to remove mounting brackets in searing, 116F heat. As I was moving the battery to retrieve a dropped bolt I hear another POP as a red positive cable unfurled out of a black box and a stub touched the positive battery lead. Ugh. I disconnected the negative ground and yanked to Interstate battery out. I realized the BST ignited earlier. But how? no crash occurred and no SRS Airbags deployed. Did intense ambient heat boil the battery acid up to send a surge that signaled the BST to ignite itself?

Upon removal of the BST box, the plastic housing was severely deformed by the small explosion. The red cabled stub that blew out basically disconnected all power to critical modules and starter, I believe.

Big question - can heat play a part? Did a seat belt tensioner trigger the disconnect? I'm currently waiting for BST parts to arrive and I just got her a new, equivalent spec AGM battery. I hate wet-cell, sloshing bombs inside the car.

[chickdr]

I have both AGM and non AGM in mine over the years. No notable difference other than the higher cost of an AGM. Hope you get it sorted quickly.

[1er_vert]

Originally Posted by chickdr

I have both AGM and non AGM in mine over the years. No notable difference other than the higher cost of an AGM. Hope you get it sorted quickly.

I also had both types of batteries before. A swollen battery casing is not a good sign. It needed to be replaced.

[cbpip]

Swollen battery is an indication of a bad regulator and over charging and or alternator. Regulator can be changed as a part of the alternator.

[KevinC]

My BST blew in my old '08 on a fairly hot day (90's) a few years ago. I parked the car, and right about as I was pulling the key, POP!! The battery was fine (nearly-new AGM). Basically no explanation for how/why the thing would have given out. What a PITA. And an expensive one.

[1er_vert]

Originally Posted by KevinC

My BST blew in my old '08 on a fairly hot day (90's) a few years ago. I parked the car, and right about as I was pulling the key, POP!! The battery was fine (nearly-new AGM). Basically no explanation for how/why the thing would have given out. What a PITA. And an expensive one.

Did the car restart, after replacing the BST? No dash errors?

[KevinC]

Originally Posted by 1er_vert

Did the car restart, after replacing the BST? No dash errors?

Managed to push-start it, limped it home 20 miles, dying as I pulled into the driveway. Towed to my mechanic 80 miles away the next day (I live in the sticks) after preliminary diagnosis was the BST being blown. Turned out to be correct. 3 week wait to get the part. I was livid - stupid "safety" feature almost stranded me, then out of service almost a month, plus big bill to fix. Still no idea what set the stupid thing off.

[1er_vert]

Originally Posted by KevinC

Managed to push-start it, limped it home 20 miles, dying as I pulled into the driveway. Towed to my mechanic 80 miles away the next day (I live in the sticks) after preliminary diagnosis was the BST being blown. Turned out to be correct. 3 week wait to get the part. I was livid - stupid "safety" feature almost stranded me, then out of service almost a month, plus big bill to fix. Still no idea what set the stupid thing off.

I did some extensive research on this anomaly. It appears sensitive body control modules and sensors are prone to triggering the BST off. I do recall under-estimating the Z4 nose and crawled over a parking curb once. I saw what I did and corrected the breach, as the front bumper slowly grinded back out over the curb. Two days later - the BST ignites.

The wet cell battery was swollen and a possible under-voltage condition is potentially suspect(DTC codes: 93B2, 2E98, SDF4). I simply replaced it with AGM, just to rule out any further possibility of BST blowing out again. Once the new B+ cable and AGM battery was installed and the SRS Airbag light was reset - all has been good, so far.

I'll continue to monitor the condition periodically...

[XMetal]

If you got a swollen battery, it a good chance that's been overcharged or over voltage. I would put one of those cigarette lighter voltmeter on the car and monitor the alternator output while you drive.

[elerner61]

Every 4-5 years replace battery.
At 70,000 miles replace voltage regulator.
https://www.ebay.com/itm/22237535128...0AAOSwnHZYdwNy

Best way to keep the electronic gremlins at bay.