Battery Master Switch on K Series

[AlC]

Hi

 

While looking through various build diaries during my build I came across one that said it is preferable not to routinely use the battery isolator. The reason given was that the ECU used retains information on engine running etc, that is lost when power goes - so obviously in volatile memory. The upshot of this is that supposedly the engine wouldn't run quite so well for 30 miles or so afterwards while the ECU monitors the engine parameters.

 

I have 1.6 K series Supersport (135bhp) with whatever ECU Caterham supply. My question is to whether the above is true, and hence should I generally avoid using the isolator, or is it all rubbush and fine to use routinely?

 

Thanks

 

Al

[Mick Day]

Don't bother with a mechanical battery master unless you're prepared to replace it every year or so. Why? Most cause electrical problems which IMHO detract from the benefits.

 

Doesn't do anything to my ECU when I disconnect the battery.

[Wrightpayne]

Al,

 

I think this refers to using the master switch to kill the engine. If you turn off the engine using the ign switch first then turn off the master switch you'll be fine. You can even use the immobiliser and turn off the master switch.

 

 

Basically, only use the master switch to cut the power whilst the engine is running in an emergency. If you do then it will probably require an ecu reset - ign on engine not running and press accelerator 5 times (search archives).

 

 

Oh and despite the experience of others my master switch has been fine since new - 14 years!!

 

Ian

[AlC]

Thanks - seems I can use switch as planned

 

But I can still use immobiliser with battery switch? This suggests immobiliser not wired through battery switch. Makes sense I suppose, I'd just assumed battery switch killed everything.

 

Thanks

 

Al

[Nick Chan]

On my cars I always allow the immobiliser to set automatically and then turn the BMS off and that works fine. The BMS have been wired (correctly) to cut power off entirely to the rest of the car which includes the sidelights and hazards

 

BTW related to your original question and if you experience it in the future, if your battery is failing and doesn't hold decent charge, it can cause poor running as the ECU doesn't get decent voltage as everything else is kept running.

 

Nick

[Mr Locust]

From a security standpoint, and especially if your car has the ignition switch/button setup rather than key, set the immobiliser using the plipper (or time out until light flashes). Then kill the power.

 

Otherwise the the car is not immobilised when the red key is turned back on.

[jakeandlizzy]

The above answer is absolutely correct. It is the same concept that you would apply if you wanted to permanently disable the immobilizer, e.g. make sure it never has power when the key is not switched on.