# Safety interlocks



## skooler (Mar 26, 2011)

Jamie EV said:


> So I put this in controllers for lack of a better area....if there's another thread about this, I apologize.
> 
> What are the key safety systems that you would include in your EV electrical system?
> 
> ...


A few ideas from the top of my head...


A fuse in each battery box
A main pack fuse (near the controller) - rated slightly higher than the other fuses (you want the fuse for the battery box to blow first)
A main contactor to disconnect the controller (and maybe DCDC converter) using the ignition- if its not already built in.
A manual disconnect for maintenance / last resort - an Anderson connector attached to a lever is quite popular.
A clutch allows for a mechanical disconnect but almost certain motor death in the event of a runaway.
A circuit breker could replace the main pack fuse.
Use a propper throttle with 3 wires not 2.
Only do things you are confortable with, dont skimp on safety, outsource jobs where required.
Anyone else wish to add anything?


Cheers,


Mike


----------



## Jamie EV (Oct 3, 2012)

Really good stuff, Thanks!


----------



## Jamie EV (Oct 3, 2012)

Can yhou elaborate on the three-wire throttle?


----------



## skooler (Mar 26, 2011)

Jamie EV said:


> Can yhou elaborate on the three-wire throttle?


Yep, quite simple, 2 wires is often a variable resistor that may wear out or fail (jamming the throttle open or closed or leaving deadspots in the throttle travel).

3 wires is usually a hall effect pedal or potentiometer. These have a kind of error checking built in.

A Hall effect pedal will have much less wear as there is no electro-mechanical connection.

My advice would be to use a hall effect pedal (HEPA) from an existing car as it will already be suitable for automotive use.

Cheers,

Mike

P.S. Feel free to correct me if I'm wrong.


----------



## Ziggythewiz (May 16, 2010)

We had this discussion about 6 months ago, but I can't find it right away, so oh well.

Mike's covered most of it, a few other items: 
Most people probably grossly oversize fuses. Most of them are rated to pass current at their rating for a long time. Stick a 400A fuse on a 400A system and it will pass 1000A for much longer than you want it to. You have to check the datasheet for your fuse type and pick something not too far over your average usage to get any decent protection.

Two contactors is best, one on each leg. The emergency disconnect is usually just a button that removes power from both of these.

A collision switch should also remove power from the contactors in case you can't.

Charging interlock: You should have a mechanism to prevent the car from moving while charging. I used to make fun of people dumb enough to drive off while plugged in, but one day I managed to forget half a dozen things I was supposed to do before leaving for work. Luckily at the time my charger was connected via plugs that pulled away no different by car force than by hand.

Battery terminals or boxes should be covered to prevent anything from falling, or bumping onto the contacts while driving or performing maintenance.

Tools MUST be insulated to prevent shorting while performing maintenance. Before any tool touches your car, cover that handle!


----------



## Jamie EV (Oct 3, 2012)

skooler said:


> Yep, quite simple, 2 wires is often a variable resistor that may wear out or fail (jamming the throttle open or closed or leaving deadspots in the throttle travel).
> 
> 3 wires is usually a hall effect pedal or potentiometer. These have a kind of error checking built in.
> 
> ...


I see.

Is a HEPA the same ohmic resistance as a pot? Most PWM use a three wire pot , don't they?

I like the idea of using the existing "drice by wire" device from the OEM. Very reliable...so long as it's not a Toyota...


----------



## Ziggythewiz (May 16, 2010)

Jamie EV said:


> Very reliable...so long as it's not a Toyota...


A toyota's wire is far more reliable than the American meatsack with their foot stuck on the pedal. The only flaw the toyotas ever had was bad carpeting.


----------



## Jamie EV (Oct 3, 2012)

Ziggythewiz said:


> A toyota's wire is far more reliable than the American meatsack with their foot stuck on the pedal. The only flaw the toyotas ever had was bad carpeting.


I agree. I was only kidding. They sure took a drubbing over that throttle thing....when clearly American cars had much worse issues.


----------



## mk4gti (May 6, 2011)

Another point is choosing a controller that has built in safety aspects (such as overspeed protection).


----------



## Ziggythewiz (May 16, 2010)

Jamie EV said:


> I agree. I was only kidding. They sure took a drubbing over that throttle thing....when clearly American cars had much worse issues.


Yeah, it was funny how many American recalls got swept under the rug those years...all to support the auto bailout for old dinosar companies that couldn't innovate to save themselves.


----------



## Nabla_Operator (Aug 5, 2011)

add:

Inertia switch in the circuit breaker (contactor) circuit
red mushroom button (emergency switch) in the same circuit

.


----------



## skooler (Mar 26, 2011)

Jamie EV said:


> I see.
> 
> Is a HEPA the same ohmic resistance as a pot? Most PWM use a three wire pot , don't they?
> 
> I like the idea of using the existing "drice by wire" device from the OEM. Very reliable...so long as it's not a Toyota...


What do you mean by PWM? I dont see what pulse width modulation has to do with an analogue signal developed by a pedal!? Do you mean "controllers" rather than "PWM"?

If that is the question then my answer is any controller worth its salt will have 3 wires, but can be driven off 2.

I imagine you can get them in a variety of flavours! Typically they use 2 values between 0-5v as an example, my RX8 HEPA uses 3.2 - 4.3V (from memory). 

It actually has 2 sensors inside, reading in the opposite direction (one with values between 0-5v and another with values between 5-0v).

So the pedal itself has 6 wires, I only use 3 of them.

There's some pictures and description of the problems I encountered from post 105 in my build thread:

http://www.diyelectriccar.com/forum...nversion-formally-good-motoriii-61556p11.html

Cheers,

Mike


----------



## Jamie EV (Oct 3, 2012)

Ziggythewiz said:


> Yeah, it was funny how many American recalls got swept under the rug those years...all to support the auto bailout for old dinosar companies that couldn't innovate to save themselves.


Oh come on Zig...that debates in Chitchat...


----------



## dtbaker (Jan 5, 2008)

back on topic. 

- big fuse between battery boxes, boxes either non-conductive, or plenty of non-conductive material near terminals

- big main circuit breaker WITH manual pull cable running to somewhere near driver's knee, red, labelled for both driver and hopefully visible for Emergency Responders reaching in driver's window.

- inertia switch interlock inline with the key-on 12v power to main contactor.

- double return springs on accelerator

- clutched design tranny adaptor


----------



## Jamie EV (Oct 3, 2012)

I meant controller not PWM sorry.


----------

