Electric fence circuit with common ground or similar circuit?

Thread Starter

Ball-unique-username

Joined Mar 9, 2021
3
Hi. I'm looking for a product or schematic of an electric fence circuit or similar deterrent with a common ground.

Purpose: I'm sometimes in bear country and in some places like Whitney Portal a tiny population of 22 bears cause literally hundreds of thousands of dollars in damage a year. The official regulation of scrubbing a vehicle of all food, cosmetics, etc. is impractical and often doesn't work. I have a 12v solar setup that can indefinitely power something with a reasonable draw and the vehicle has metal fenders all around. The idea is to steak in a ground and electrify the chassis. The problem is the chassis is also the 12v ground. I did obtain and take apart an old commercial 12v electric fence module (with a broken case so it didn't cost much) but there was no common ground (battery is isolated). To use this I would have to somehow provide an isolated 12v source. I considered using an inverter and transformer but there might be feedback to the inverter which could fry it which is a fire hazard.

Any suggestions?

Edit: I probably threw out that commercial circuit because it didn't fit my needs.
 

crutschow

Joined Mar 14, 2008
27,709
I'm a little confused, as you seem to be talking about two different 12V sources: the car battery and the 12V solar setup.
The car battery obviously can't be used, since it is connected to the chassis, as you noted.

The isolated source could be a small rechargeable battery, charged by the solar cell.
The hot of the electric fencer goes to the metal on the car, and a small ground rod will provide the ground.

Are you sure one of the fencer battery connections isn't connected to the fencer common?
 

Thread Starter

Ball-unique-username

Joined Mar 9, 2021
3
I'm a little confused, as you seem to be talking about two different 12V sources: the car battery and the 12V solar setup.
The car battery obviously can't be used, since it is connected to the chassis, as you noted.

The isolated source could be a small rechargeable battery, charged by the solar cell.
The hot of the electric fencer goes to the metal on the car, and a small ground rod will provide the ground.

Are you sure one of the fencer battery connections isn't connected to the fencer common?
The solar system powers a lot of the stuff in the vehicle and has a common ground with the starter battery so they can be bridged while charging. This is how every 12v solar setup I've seen (several hundred?) is implemented or else they would use something more efficient like 48v.

The one I took apart definitely did not have a common ground. I have no idea about any others.
 

crutschow

Joined Mar 14, 2008
27,709
The one I took apart definitely did not have a common ground. I have no idea about any others
How do you now that?
Did you measure the resistance between the battery ground to the fencer ground?

So, if you want to power the fencer from the vehicle battery, then you need a fencer with the fencer battery negative connected to the fencer common.
You then would connect the fencer hot to the earth ground rod.
That may seem in reverse, but the electricity doesn't care which end goes to earth ground.

There are many fencer circuits out there, most using ignition coils so, if you want to roll your own, you can try one of those.
All the ones I've seen have the battery negative as circuit common.
 
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