Anyone had problems with voltage spikes caused by battery isolator kill switches?

[RIP]

There's a lot of FIA "type" (ie fake) battery isolators on eBay for around £15, so I bought one for my 4x4 buggy. It has three circuits: isolating the battery, cutting off the engine, and activating a resistor circuit to drain any remaining voltage from the power lines to protect the components. However, I've noticed that the resistor circuit only activates an 1/8th turn after the battery is isolated, leaving a big window for voltage spikes.

Has anyone experienced issues because of this? Or maybe this standard behaviour for all battery isolators?

 

[daleyd]

If the battery was still connected while the resistor was connected wouldn't it dump a load of amps through it (the resistor that is)? I would think the battery needs to be disconnected first, then the resistor connected, so sounds deliberate to me (I don't know if that's the case I'm just musing....)

 

[RIP]

If the battery was still connected while the resistor was connected wouldn't it dump a load of amps through it (the resistor that is)? I would think the battery needs to be disconnected first, then the resistor connected, so sounds deliberate to me (I don't know if that's the case I'm just musing....)

I did think about that. The resistor is 3 ohm, so it would draw 4 amps, so not much at all.

 

[daleyd]

I did think about that. The resistor is 3 ohm, so it would draw 4 amps, so not much at all.

At 48W I suppose it depends on the power rating of the resistor - if it’s a small 1/2w thing then it may be an issue. If it’s a big chunky one not so much.

But I can theoretically see why they would break the circuit before it’s connected, especially if the resistor used is quite weedy.

 

[RIP]

I'm just going to leave it then. I'm not spending £50 on a FIA isolator which as you say, may work the same.