APPENDIX P

BATTERY FLAME RETARDANT VENTING SYSTEM TEST

(Normative)

P1 SCOPE

This Appendix sets out a method for testing the ability of a battery’s venting system to retard effectively the propagation of an externally ignited flame of battery gas into the interior of the battery. Explosive mixtures of gas are usually present in the interior of a battery.

P2 PRINCIPLE

A spark is created in the gases emitted by a battery. The battery is observed to see whether gas ignition occurs within the battery.

P3 APPARATUS

P3.1 If the test is to be conducted on a battery

The following apparatus shall be provided—

• (a)an explosion chamber with an explosion-proof fan of adequate size to produce approximately one chamber volume change per minute, vented directly to the exterior of the building. (See Figure P1);
• (b)a battery charging source capable of constant voltage or constant current control, with at least 40 A output at 17.5 V;
• (c)a fully charged 12 V battery to serve as an ignition source. This battery shall be equipped with a functional flame retardant venting system;
• (d)the battery on which the test is to be performed;
• (e)wiring and fittings equivalent to those shown in Figures P2 and P3.

P3.2 If the test is to be conducted on a test fixture

The following apparatus shall be provided—

• (a)an explosion chamber with an explosion-proof exhaust fan of adequate size to produce a minimum of one chamber volume change per minute, vented directly to the exterior of the building. (See Figure P1);
• (b)a battery charging source capable of constant voltage or constant current control, with at least 40 A output at 17.5 V;
• (c)a fully charged 12 V battery to serve as an ignition source. This battery shall be equipped with a functional flame retardant venting system;
• (d)a second fully charged battery to serve as a gas mixture source. This battery shall be vented only through the test fixture or functional flame retardant venting system;
• (e)a test fixture. (See Figure P4);
• (f)tubing and fittings equivalent to those shown in Figure P5.

FIGURE P1 TEST CHAMBER

FIGURE P2 SCHEMATIC FOR TEST ON BATTERY

FIGURE P3 SCHEMATIC FOR TEST ON BATTERY

FIGURE P4 TEST FIXTURE

FIGURE P5 SCHEMATIC FOR TEST FIXTURE

P4 SAFETY PRECAUTIONS

Warning: Testing of a battery venting system can result in an explosion. Extreme caution must be exercised to avoid personal injury. Absolutely no testing shall be permitted where the prescribed safety precautions and procedures are not followed or exceeded.

The following safety precautions shall be taken—

• (a)all test apparatus, except the charging source, shall be fully contained in an externally vented explosion test chamber. (See Figure P1);
• (b)the charging source shall be conveniently placed outside the explosion test chamber for control by testing personnel. The charging circuit shall have 2 emergency disconnect switches placed—
  • (i)one near the charging source and conveniently placed for control by testing personnel; and
  • (ii)the other at a remote position at least 3 m from the explosion test chamber.

These disconnect switches are intended for emergency use only, since their use may damage some types of chargers;

• (c)a suitable test area shall be designated, eg 3 m² or more. Signs restricting unauthorised persons from this area shall be posted and observed while any electrical circuit in the explosion test chamber is or could be energised;
• (d)during testing, entry to the test area shall be clearly marked to restrict all persons not fully familiar with all safety requirements and not wearing full protection from the hazards to be encountered;
• (e)smoking, open flames, unprotected lights or other spark sources shall not be permitted in the area during testing;
• (f)full face protection devices shall be worn by all persons within the restricted area;
• (g)the battery spark source circuit shall have an emergency disconnect switch conveniently placed for control by testing personnel;
• (h)the exhaust fan of the explosion test chamber shall be operating during the entire spark test procedure. On completion of any test sequence, charging and sparking circuits into the explosion test chamber shall have been interrupted for at least 15 min with the exhaust fan operating before anyone is permitted access to the chamber. This time allows any hydrogen to be purged from the chamber to preclude the possibility of a delayed explosion occurring due to a sustained ‘hidden’ flame.

Warning: Hydrogen gas can burn without visible flame.

P5 PROCEDURE

P5. Arrangement of equipment

P5.1.1 Arrangement of equipment if the test is to be conducted on a battery

The equipment shall be arranged as follows—

• (a)arrange the test apparatus as shown in Figure P2 or alternatively as shown in Figure P3;
• (b)check the test battery system, other than the vent openings, for gas leakage, eg with a soap solution;
• (c)fully charge the spark source battery;
• (d)fully charge the battery to which the test vent is attached. The battery shall be gassing vigorously.

P5.1.2 Arrangement of equipment if the test is to be conducted on a test fixture

The equipment shall be arranged as follows—

• (a)arrange the test apparatus as shown in Figure P5. Place the gas inlet to the test fixture well below the water level as shown in Figure P4 to prevent ignited gases from entering the gas generating battery;
• (b)fill the test fixture with water to 3 mm below the underside of the top. Place the hold down frame over a one mil thickness of polyethylene film cut as shown in Figure P4. Place the frame, with film in place, over the 4 studs so that the film covers the open area between the fixture and the frame. Finger tighten the wing nuts to ensure a gas-tight seal around the gasket. Fit the vent system to be tested into the fixture;
• (c)check the test battery system, other than the vent openings, for gas leakage, eg with a soap solution;
• (d)fully charge the spark source battery;
• (e)fully charge the battery to which the test vent is attached. The battery shall be gassing vigorously.

P5.2 Preconditioning

P5.2.1 General

The venting system under test shall be preconditioned in accordance with paragraph P5.2.2 or with paragraph P5.2.3.

P5.2.2 Standard preconditioning

Subject the battery to which the venting system is attached to an overcharge of 2 to 4 A for 16 to 24 h. This will put the vent system in an acid moistened state as is typical of its in-service condition.

P5.2.3 Hot and cold cycle preconditioning (optional)

• (a)place the vent system in a cold box at –28.9°C for 16 h;
• (b)remove from cold box and place it in an oven at 71.1°C for 8 h;
• (c)repeat this sequence for 3 full cycles;
• (d)at the completion of the third full cycle, condition the vent system as in paragraph P5.2.2.

P5.3 Test procedure

The test procedure shall be as follows. The test shall be conducted within 1 h of completion of preconditioning in accordance with paragraph P5.2 above—

• (a)conduct the test at an ambient temperature of 25° ±5°C;
• (b)the battery temperature should be 27°C. If the battery temperature is above 27°C, a voltage correction of –0.038 V/°C for every degree above 27°C shall be used to guarantee an equivalent amount of gas generation;
• (c)when the test battery is gassing vigorously, charge the battery at a voltage of 2.92 V per cell. (Charging current shall not exceed 40 A);
• (d)allow the gas flow rate to stabilise. (gas flow should stabilise in 1 to 5 min);
• (e)create a spark of not less than 0.02 mJ of energy 13 mm from the test vent opening in the path of the gas flow;
• (f)repeat the spark at 10 s intervals for a minimum of 6 sparks per vent ensuring that evolved gases are ignited. If the ignited evolved gases ignite the battery, time must be allowed for the battery to self-extinguish or to ignite the gas within the battery.

NOTE: When all gas generated in the 12 V battery is passed into the (simulated 3 cell) test fixture, the effective gassing rate is twice that indicated by the charger current reading, for either single or gang vents.

P6 REPORTING OF RESULTS

The following shall be reported—

• (a)battery identification;
• (b)the preconditioning method (See paragraph P5.2);
• (c)whether ignition occurs within the battery or the test fixture.

P7 ACCEPTANCE CRITERIA

A battery shall be considered to have passed this test if ignition does not occur within the battery or the test fixture.