Cutting the battery. Not as important?

[GPM1230]

I had a conversation with a firefighter the other day and he tells me that cutting the battery power is not as important as it used to be, due to capicators that hold charge long after the power is cut. He also says it's ok to leave the battery power on while you lower windows, move electric seats and so on. I'm all for that, but I thought we cut the power before we start cutting. Are there some new developments on this?

[Bones42]

If anything, capacitor storage times have gotten shorter.

We still remove power from the vehicle.

[LeeJunkins]

Manufacturers believe it is important enough that some have added a quick release handle to allow quick disconnection, without destroying the cable. Simply move the handle a quarter turn and lift the cable off. This came out on the GM Hybrids but many are starting to use it.

[LeeJunkins]

With the exotic electronics of today’s vehicles manufacturers are now marking the battery cables, showing emergency workers were to cut.

[LeeJunkins]

This procedure is so vitally important to both the victim and the rescuer’s safety that many manufacturers are now insuring that electrical shut down is accomplished immediately.

Pyrotechnic battery cable ends are now connected to the airbag control module. If an airbag is deployed the battery cable will internally explode, disconnecting the electrical system.

With manufacturers being in bankruptcy they would not spend this kind of money if they did not think it is vitally important

[Rescue101]

Lee,can i get that for the passenger seat? A launcher that is? T.C.

[LeeJunkins]

Lee,can i get that for the passenger seat? A launcher that is? T.C.

Sure can, talk to Lockheed Martin Aerospace. My son works for them, I can have him find out.

[JorgHeck]

There is one important thing to know about the (pyrotechnic) safety battery terminals used to disconnect battery cables in crashes. In all vehicles I know that have these terminals, they do ONLY disconnect power to the generator to reduce the risk of post-crash fires. (For the same reason a lot of OEMs turn of the fuel pump on airbag activation). All safety systems and the other vehicle electrics will still be energized after a safety battery terminal activation.

Regarding the question about the need for electrical shutdown I also think it's important to disconnect the battery as soon as battery power is no longer needed or not working anyway. One of the main reasons for electrical shutdown is to avoid post-crash fires and this is more serious with more electrics in the vehicle.

[firedog7]

This is correct,
There is a second cable that allows power to remain to the lights, windows, doors, cell phone, On Star system etc, The doors will unlock and the interior lights will come on.
This cable will have to be disconnected in order to shut down the power

[LeeJunkins]

Jorg and Firedog7

Like you I believe we need to disconnect all battery cable for airbag and fire safety.

But, you guys have got me wondering now about the actual operation of the BDSD, this is the info I got from Delphi.

Activated during a collision event, the Battery Disconnect Safety Device is designed to help prevent potential short circuits, providing circuit protection for the cables connecting the battery to the vehicle's starter, alternator and electrical centers. It performs this through the utilization of a small pyrotechnic charge that quickly and safely disconnects protected circuits.

Operation of Delphi's Battery Disconnect Safety Device begins with the triggering of the unit by the Electronic Control Unit (ECU), which receives information from sensors in the vehicle and determines whether to send electronic signals to the airbags and/or the Battery Disconnect system. At the heart of the Battery Disconnect unit is a specially configured high-current conductor; in the Audi A6 application, for example, it is housed in a small fuse center near the vehicle's trunk-mounted battery. The pyrotechnic pressure drives a piston that cuts the conductor in less than a millisecond after activation occurs, disconnecting un-fused cables from the battery before collision-induced damage can cause a short circuit.

Delphi’s BDSD is also available with a safe engine restart option, that allows drivers to restart their vehicles following a collision if there are no electrical hazards. This feature enhances safety by enabling drivers to move their vehicles off the road, preventing the occurrence of a possible second collision.
The safe engine restart option incorporates a standard fuse that is mounted parallel to the BDSD. After the BDSD is triggered, severing the current, this fuse allows for a warm-engine restart providing the event that triggered the BDSD did not cause a short circuit. If the crash did result in a short circuit, this fuse blows immediately, preventing an unsafe restart.

According to the engineer I talked to this safe engine restart option is were the windows, door locks, lights and etc. get their power. Without this secondary wire or if the crash was sever enough to blow its fuse. The BDSD cutting the main cable to the starter would cut all power.

[JorgHeck]

Hi Lee!

The pyrotechnic pressure drives a piston that cuts the conductor in less than a millisecond after activation occurs, disconnecting un-fused cables from the battery before collision-induced damage can cause a short circuit.

I think the term 'un-fused' cables is the important part in the product information you posted. I think that the Delphi device is therefore also only for the cable running to the engine compartment (un-fused).

If necessary I can send you parts from the german ERGs of BMW, Audi and VW (I worked together with VW and Audi on their latest one) to proof this.

[nameless]

these pyrotechnic devices seem great, but do they do the disconnect inside of the device casing or will you be able to visually verify that the system has successfully operated and power has indeed been cut?

call me skeptical, but I wouldn't trust this device after its ridden around in a car for 5, 10, even 15 or 20 years.

[firedog7]

Lee,
I responded to a couple of BMW crashes with the system described in the above posts,
When we arrived, the damage to the vehicle was not very sever but enough to set the drivers airbag off. The doors where unlocked and interior lights were on
Tried to move the vehicle off the road and as I expected the starter would not engage because the power lead to it was no longer intact. here is a pic of a power cable with the pyrotechnic device from a 2009 BMW. The red positive lead remains intact and the other cable leading out of the black plastic blows off and cuts power to the started and fuel system. I'm not sure what other companies manufacture these types of disconnects, but this has been my experience with them.

[nmfire]

Here's my opinion on the subject.

- We don't know if the car has this thing
- We don't know if it worked
- Even if has one and worked, there can still be power flowing.
- So cut the damn thing every time.

[LeeJunkins]

Thanks guys,

The main thing with me is that people come to me for answers and I want to be positively sure that what I tell them is accurate. I have found that through our discussions and sharing experiences we many times end up with more accurate answers than the info we get from some engineers.

I was in a conference call for about 30 minutes last week with three corporate engineers trying to find some info and they all had their computer diagrams in front of them but, they could not answer my question. I went to the dealership and myself and a tech actually put the car on the rack and found the answer in about ten minutes.

Jorg, I would appreciate any info you could send me on these.

Firedog7, Can I use this picture?

[DeathValleyCap]

If I'm the first arriving officer, and most of the time am, I make decsion if we need to move seats, if not the cables get cut. We have a great tool to roll down windows, it's been in the fire service for years and my FF know not to get off the engine without it. You guess it, it's the Halligon/Hollagon however you want to spell it in your neck of the woods.

[firedog7]

Lee,
Yes you can use the picture, I have more pics of some batteries I'll send you
Firedog7

[firedog7]

Here is a picture of a Door interlock on a few new BMWs
This hook will lock and hold into the vehicle body near the lower B-pillar
It is to keep the doors from coming open in severe frontal crashes
If you find that the door is not opening after you have used your spreader on the latch area move down to the lower corner to force the hook out of the vehicle body.
Firedog7

[domi411]

wow very interesting these photos of the battery connector

For the photo of the door, gm use something look like that.

The GM guy told me if was for lateral impact

I can send you the photo i have if you want

[firedog7]

Please post it