Capacitor Drain Time
Received this question from an Ohio fire officer seeking clarification on one element of the Phases of Rescue drill. The four-part Phases Drill to address NFPA 1670 Ops-level competencies has been presented in the University of Extrication column.
I am using the University of Extrication's "Phases of Rescue" drill to determine my department's capabilities. I have one question though. In Phase 1, one of the steps is to "document capacitor drain time". What exactly is meant by this, and how is this done?
During the Phases drill, this benchmark can be accomplished by the OIC making a statement out loud so the crew members can hear. "Battery shutdown now, capacitor is draining" or something to that effect.
What this refers to is a physical action that can be documented during the drill showing several key training points;
- that the crew is aware of the status of the vehicle's airbag electrical system,
- that the crew is aware of what an airbag capacitor does,
- that the crew is aware that the power has to be shut down to begin to make things safer, and
- that the crew is aware that even with the power shut down at the battery, the airbags are still a potential deployment concern.
I'd recommend in your real-world operations, that the OIC actually make a radio transmission to your dispatcher when the battery of the crashed vehicle has been shut down. We do this now at structure fires; under control, loss stopped, we have PAR, etc. This new idea is a real-world way of documenting that the electrical system has been dealt with at a crash scene, and that the crew at the crash scene knows that fact and is aware that the capacitor is now draining down. Every second that the battery is shut off and the capacitor is draining is making things a little better for the operating crews.
Bottom line: an undeployed airbag is ALWAYS to be considered a deployment potential and treated with great respect even with the battery gone and the capacitor completely drained!
Ron, On capacitor drain times, do you have one yet for the Honda Element. I heard they are stating 30 minutes. Could this be ?
On Wednesday, May 18th, I will contact American Honda through their Corporate Communications division. I will ask about the drain time and post theirreply as soon as I get an answer.
In the meantime, the following info is what is posted on their media site under the Element's safety features. Note what they say about the hidden B-pillar and the use of a Slim Jim-type tool.
Element is expected to meet or exceed the highest rankings possible for government front and side impact safety tests (five stars) and Insurance Institute for Highway Safety frontal offset crash tests (good performance). To accomplish this, a smart-linked unibody structure is used that is designed to progressively absorb energy and isolate the passenger cabin from forces. The lack of a B-pillar is compensated for by a network of cross members, door braces and the use of high-tensile steel, and a hook and catcher system to protect the cabin just as well as if it had a B-pillar.
Inside, the supplemental restraint system features standard dual-stage driver's and passenger's front airbags, available side airbags with Occupant Position Detection System, and the LATCH system for installing child seats. Front seat belts feature dual pre-tensioners that pull the lap and shoulder belts toward the occupant in the event of a collision.
Theft Deterrent Measures
Immobilizer System (if incorrect key is used)
Flush mounted door lock knobs
Wave Key (difficult to copy)
Available Keyless Entry with "copy protection"
Internal covers that prevent "slim jim" lock deactivation
We are using Air Bag nets on the steering wheel. With luck we will never hve to find out if they work. Has any one used these and had a bag deploy.:)
Have you heard anything from Honda on the Element, regarding the drain time.
Despite three direct contacts with the airbag technical people at Honda, and despite three promises to "get back to you", I still do not have an answer to the Element's 30 minute drain time rumor.
From the UK, and we have had a few lines of thought on this one in the last few years. Started off with the 30 minutes, went to crossing the battery connections to short the circuit.
But the last one that we recieved from Rover Motor Group was that it may take in fact up to and over 3 hours for the capacitor to drain. Therefor our line of training is to stay out of the airbags way whenever possible when it has not gone off even after 30 mins or more.
I think you should send cowboy54 the article you forwarded to me regarding the "shorting out the circuit" routine.
NOT a good idea.
Steve,I think what cowboy meant was unhooking both battery leads from the battery and hooking them together.A lot of people think of that as "shorting"when all you are really doing is grounding both circuits.If indeed you do hook up the leads as described above,I would be curious as to how a circuit capacitor could hold a charge for 30 min.Should render them discharged in under 3 min.I'll be following this closely to see what develops.T.C.