Technical Article |
By James Williams
Racer/Technician
Advantage BMW
Being a technician at a major dealership is somewhat like being a nurse or doctor assigned to ER. You get to see good, bad and ugly, like it or not. Worse-case scenarios are drugs in the front door on a near daily basis. Bent suspension and holes in the oil pans are also frequent horrible sights. Most can be fixed without drama, but some require more cure than usual.
Ever seen an exploded battery? Not what you might expect; it really doesn't look that bad at first, but proper response, like first aid, makes all the difference in the world. An E-30 came into my care one day with the repair order stating "Customer tried to start car, heard loud bang in trunk, all lights went off." Quite a mess awaited me. The top of the battery was blown away exposing all six cells. The cover over the battery that holds the lug wrench and other goodies was shrapnel as well. The long tie bolt and clamp that holds the rearmost foot of the battery in place was blasted out of the battery tray. The worst part was all this debris was blown all over this poor customer's belongings: golf shoes, bag and clubs, umbrella, jumper cables, kids' toys, whatever happened to be in the wrong place at the wrong time. What a mess!
It had happened that very morning, so I made a bucket of water with baking soda stirred in. The more soda to water ratio, the better to neutralize the acid. I put on Latex gloves and tried to be very conscious of where I touched the car and the car touched me. I removed all the personal affects and placed them in garbage bags. All carpets, trim panels, spare, jack and tool kit were removed. Small parts and pieces were thrown in the bucket to soak while the cloth-based trim parts were scrubbed with the water and baking soda. More water with the soda was poured in the trunk to drain out. I also wiped the entire inside of the painted surfaces with a cloth soaked with the neutralizer, then wiped the entire trunk out with a cloth and clean water. This prevents leaving a white crust after the baking soda dries. After the trim pieces were washed and rinsed, I hung them on the fence in the sun to dry. Do not lean them against the wall to dry or they will dry in a curve and will not want to fit properly anymore. A new battery and tray were installed with new tie-downs and all electrical systems were checked. Voltage spikes can kill control units, fuses and in some cases, the instrument cluster. Today, however, all systems were go and this 325i lived to tell its tale of woe to other BMWs in parking lots for some time to come.
So, the question remains: How did this happen to begin with? Well friends, the answer is simple. Lack of maintenance. Many conditions must exist at the same time for this to occur. Low fluid level is the biggest culprit. Each battery is filled leaving a small air space at the top, about 15% of the volume of the battery case. Without proper maintenance, meaning adding distilled water to the proper level, the ratio of fluid to air space becomes inverted. This means the battery case is filled with a highly explosive gas, with acid filling the remaining volume.
Then one day, you get in your car and hit the key, just like any other day. The engine might start to crank over slowly, an indication of low amperage. This causes a buildup of resistance and heat within the battery itself. If there is a crack in one of the contact bars connecting one cell to the next or the battery plates are warped from heat and age, a spark occurs. The rest, as they say, is history.
Keeping the battery filled with distilled water to its proper level should keep this from happening. Also make sure battery cables are clean at both the cable ends for the battery and the body ground connections and the hot lead connections. Fear not when you turn the key and go forth!