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Discussion Starter #1
I havent posted about it much but I am building a range extending trailer. I purchased an inertia switch as a safety feature. When it is tripped, it cuts all power to the heating/cooling system, bms and everything else.

The problem is that twice today I hit bumps and it killed power. I was worried about this happening but I tried it anyway. I guess my concerns were valid.

I would like to have a safety in place in case of a bad accident. Is there a better option than an inertia switch out there?

Thanks!
 

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I have a 4x4 EV conversion & had to put an inertia switch to make it legal, I bought a "First" switch from eBay and yep, it tripped over every bump.

I then bought one from a Ford Escape being from a 4x4 car I thought it should be ok , ( its also a "First " brand but the difference in quality is immediately obvious.) Installed that and it has not tripped a single time .
 

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Definitely trying a higher quality unit and different orientation would be my first steps.

You could use an Arduino with an accelerometer. Then go drive around on really bumpy roads to find out what values the sensor experiences. Then have it kill the 12v with a relay if acceleration is above a certain value.

This is nearly everything you need. Not much more needed than the example code, just a value and set a pin high.

https://www.arduino.cc/en/Tutorial/ADXL3xx
 

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Discussion Starter #4
I wonder if there really is a difference of if you just got lucky.

I just looked and mine is from a Ford Focus.
 

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I have a 4x4 EV conversion & had to put an inertia switch to make it legal, I bought a "First" switch from eBay and yep, it tripped over every bump.

I then bought one from a Ford Escape being from a 4x4 car I thought it should be ok , ( its also a "First " brand but the difference in quality is immediately obvious.) Installed that and it has not tripped a single time .
I'm sure Ford doesn't expect Escape owners to actually drive over anything more adventurous than an occasional gravel driveway; urban potholes or accidentally hit curbs are the most likely severe bump sources for any "crossover" style family wagon like this. While these two units had different sensitivity, it wasn't likely due to the intended use of the vehicles for which they were built.
 

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Install a switch on the back of your sun visor and leave it in the down position. If/when you have an accident (possibly because of the reduced visibility caused by having the visor down) the switch will be triggered by your forehead and will cut the power from your system. Problem solved.......You're welcome.
 

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Discussion Starter #7
Install a switch on the back of your sun visor and leave it in the down position. If/when you have an accident (possibly because of the reduced visibility caused by having the visor down) the switch will be triggered by your forehead and will cut the power from your system. Problem solved.......You're welcome.
Id like to avoid running a wire from the trailer to the drivers area for a switch but thank you.
 

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Id like to avoid running a wire from the trailer to the drivers area for a switch but thank you.

I think galderdi is joking with you. These switches are position sensitive. What is the switch orientation? Does your trailer have some kind of spring suspension? It usually takes a lot of force to trip these switches. I would be concerned about the forces on the other components on the trailer.


Also, if the trailer is treated as a lever arm, rotating about the ball hitch, the forces can be considerable higher the farther away from the hitch.
 

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Discussion Starter #9
I think galderdi is joking with you. These switches are position sensitive. What is the switch orientation? Does your trailer have some kind of spring suspension? It usually takes a lot of force to trip these switches. I would be concerned about the forces on the other components on the trailer.


Also, if the trailer is treated as a lever arm, rotating about the ball hitch, the forces can be considerable higher the farther away from the hitch.
I have the switch mounted securely pretty close to the ball, within 3 feet. I think it was just 2 monster pot holes that triggered it but I cant be pulling over each time I hit a pot hole to check. I might have to take it out...
 

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Good question, I have heard of the sensitive being an issue with these switches but do think they are important for our homemade cars.
 

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Just a thought.

There has been recent UK publicity about problems with BMW cars loosing all power.

A couple were killed when they ran into a car that lost all power and stopped in the dark with no lights.

So inertia switches should NEVER be wired in a way that disrupts lights

Pete
 
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