Battery - Acid ( Electrolyte) Precautions

Group 61
Electrical System



Bulletin Number
61 03 91 (3244)



Woodcliff Lake, NJ
April 1991
Service Engineering



SUBJECT:
Battery (Acid) Electrolyte

MODELS:
All

Situation:
1) ELECTROLYTE LEVEL

If the battery electrolyte level is allowed to drop substantially, the gas volume inside the battery grows proportionately resulting in an increased amount of flammable gas mixture. In addition, the plates are no longer covered by the electrolyte and may corrode. Any external or internal spark can potentially result in an oxyhydrogen explosion.

Corrective Action:
As described in S.I. 61 01 90 (3019), dated January 1991, the battery electrolyte level should be checked on every Inspection I and Inspection II on every vehicle. In addition, it should be checked whenever the vehicle is brought into the workshop if its battery is located in the engine compartment (325iC and 525i). A sufficiently high electrolyte level will prevent an oxyhydrogen explosion in the battery to occur.

Use only distilled water to top up batteries! No tap water nor electrolyte (dilute sulfuric acid) may be used to refill automobile batteries!

Situation:
2) NEUTRALIZING ELECTROLYTE (ACID)

Any leakage or spillage of battery (acid) electrolyte should be neutralized as soon as possible to prevent any damage to paint or body.

Corrective Action:
Depending on the amount of spillage, dilute some baking soda in water and apply to areas of the car that had been exposed to battery (acid) electrolyte. The neutralizing action will create some foaming in the area where the chemical reaction takes place. Flush with ample amounts of water once the chemical reaction has subsided.

Situation:
3) DARK STAINS ON INSIDE OF BATTERY PLUGS

In batteries with separate pockets (plates insulated by pockets), polyethylene film is used as separating material. During the initial charging process or when the batteries are subsequently charged, residual oil may be released by the separating material and be deposited on the underside of the battery cover and on the inside of the plugs. This oil is between dark grey and black in color. Sometimes, a very thin film can form on the surface of the electrolyte; however, the electrolyte itself does not change color or become cloudy.



Comment:
The residual oil is electrochemically neutral and does not affect the operation of the battery. As there are no adverse effects when this occurs, replacing the battery cannot be justified.