Battery Isolation Switch and Alternator Wiring??
Discussion
Whilst in the process removing my engine, I found that the 12v supply from the alternator was wired directly (well, via a fuse) to the battery and wasn't interupted by the Battery Isolation switch. So, as it is at the moment, if I turn off the switch there will still be a 12v "live wire" (and potential for sparks) between the battery and the alternator.
This doesn't seem quite right to me. Can somebody confirm if this is correct or not?
The isolation switch is a single pole unit and looks similar to a mains circuit breaker (if that makes sense?)
This doesn't seem quite right to me. Can somebody confirm if this is correct or not?
The isolation switch is a single pole unit and looks similar to a mains circuit breaker (if that makes sense?)
If its a single pole unit, this will be the only way it will work.
not sure if its allowed, but it was how my old single pole unit was connected also.
If you have it at the other end your battery will be isoloated but the alt. will still be connected to the ignition and this will keep the engine going even on cut-out.
I you have a double pole this is fine as you cut the ignition as well as the battery feed.
If you not sure get a FIA double pole unit, they are < £20. IIRC.
not sure if its allowed, but it was how my old single pole unit was connected also.
If you have it at the other end your battery will be isoloated but the alt. will still be connected to the ignition and this will keep the engine going even on cut-out.
I you have a double pole this is fine as you cut the ignition as well as the battery feed.
If you not sure get a FIA double pole unit, they are < £20. IIRC.
For the Sagaris I started with a Cartek solid state isolator which switched the alt output as well as the main battery cables. Unfortunately the peak power draw when starting the AJP caused it to trip - the power rating was too low so it was not going to work. I replaced it with an Armtech unit which did a similar job but via a solenoid. It worked perfectly for our first meeting but was completely dead when we got home.
The supplier insisted it had to be sent off for inspection. Given the next meeting was only a week or two away, I bought an ETA 911 isolator in the interim. Armtech some time later returned their unit, saying there was evidence that it had got wet and a circuit had burnt out as a result but they had repaired it FoC. All a bit odd, as there was no way it could possibly have got wet given where it was located in the car the car itself had not got wet in its one and only outing. But anyway, fully working unit, purchased by Mr Bunce.
The ETA 911 isolator looks a bit similar to a circuit breaker in a household fuse board. It is small, cheap compatred to the Armtech/Cartek, has the facility for remote trip switches but is single pole. I have one trip button on the outside for the marshals and one on the dash cowling right next to the steering wheel where it is easy to get at in the event of disaster such as throttle sticking open.
The battery wiring is as follows: live cable to the back of the isolator, which then feeds every circuit including ignition. In addition, cables direct to the starter motor feed and the alternator output - these are not switched and are therefore permanently live.
www.e-t-a.com/uk_high_performance_cb+M5e5d1cde27c....
The 911 isolator is very commonly used. A double and even triple pole version is available, but whatever you do are going to have some live cabling in the car somewhere. I simply made sure that the connections on the alternator and starter are well insulated.
You could wire the starter and alt feeds using the second pole on a 912 isolator. The disadvantage is that the power from the alt has nowhere to discharge to when you hit the rip and over time it will damage the alt. The 912 is more bulky than the 911.
The supplier insisted it had to be sent off for inspection. Given the next meeting was only a week or two away, I bought an ETA 911 isolator in the interim. Armtech some time later returned their unit, saying there was evidence that it had got wet and a circuit had burnt out as a result but they had repaired it FoC. All a bit odd, as there was no way it could possibly have got wet given where it was located in the car the car itself had not got wet in its one and only outing. But anyway, fully working unit, purchased by Mr Bunce.
The ETA 911 isolator looks a bit similar to a circuit breaker in a household fuse board. It is small, cheap compatred to the Armtech/Cartek, has the facility for remote trip switches but is single pole. I have one trip button on the outside for the marshals and one on the dash cowling right next to the steering wheel where it is easy to get at in the event of disaster such as throttle sticking open.
The battery wiring is as follows: live cable to the back of the isolator, which then feeds every circuit including ignition. In addition, cables direct to the starter motor feed and the alternator output - these are not switched and are therefore permanently live.
www.e-t-a.com/uk_high_performance_cb+M5e5d1cde27c....
The 911 isolator is very commonly used. A double and even triple pole version is available, but whatever you do are going to have some live cabling in the car somewhere. I simply made sure that the connections on the alternator and starter are well insulated.
You could wire the starter and alt feeds using the second pole on a 912 isolator. The disadvantage is that the power from the alt has nowhere to discharge to when you hit the rip and over time it will damage the alt. The 912 is more bulky than the 911.
teamHOLDENracing said:
For the Sagaris I started with a Cartek solid state isolator which switched the alt output as well as the main battery cables. Unfortunately the peak power draw when starting the AJP caused it to trip - the power rating was too low so it was not going to work.
Andy were you using the standard or GT spec? I was looking at running the Cartek unit.Regards
Iain
i keep looking at these and struggling to see the advantage in an electronic one at 200 quid over the manual thing or 20 odd.. I assume Im missing the point here but what is it :-) ok the packaging is better, and fitting remote switches is easier, and possibly less likely to cause a spark, but they are much heavier and lots more expensive ?
G
G
GreenV8S said:
I think if you have an alternator you want to have something to pull the alternator output down through a resistance rather than just isolate it, otherwise the alternator electronics get upset.
There is a resistor in the alternator side of the manual switch. I have had one manual switch fail on one circuit in 7 years, and that was the one on the tuscan so I've no idea how old it was. other than that no probs. Im genuinely interested in the advantages of the electronic one :-)G
For me the advantages would be:
Reliability (as previously stated); solid state potted electronics over mechanical contacts
Packaging; two sets of low current wires tied in with the rest of the loom over pull wires or looping the high current circuit through the car.
Security; thieving feckers cant run off with a switch like they can a key. That happened to me on a car I was spannering last season, we missed a race becasue someone thought they'd like a souvenir...a bit like cigar lighters at motorshows.
Disadvantage: Cost.
Regards
Iain
Reliability (as previously stated); solid state potted electronics over mechanical contacts
Packaging; two sets of low current wires tied in with the rest of the loom over pull wires or looping the high current circuit through the car.
Security; thieving feckers cant run off with a switch like they can a key. That happened to me on a car I was spannering last season, we missed a race becasue someone thought they'd like a souvenir...a bit like cigar lighters at motorshows.
Disadvantage: Cost.
Regards
Iain
It was packaging, reliability and number/location of cut out switches for me.
The manual contacts do wear out - I had one go on your car Graham when I had it. They are very cheap though.
I hate the pull cables turning a plastic key, it seems a very unelegant solution to me
The electronic version gives me a master switch, external cut out switch and and another cut out right next to the steering wheel.
The Cartek one is a tiny little unit, very light. The downside to it is it needs to be bolted down to an earth.
The ETA one is cheaper, but not nearly as cheap as the manual plastic key type
The manual contacts do wear out - I had one go on your car Graham when I had it. They are very cheap though.
I hate the pull cables turning a plastic key, it seems a very unelegant solution to me
The electronic version gives me a master switch, external cut out switch and and another cut out right next to the steering wheel.
The Cartek one is a tiny little unit, very light. The downside to it is it needs to be bolted down to an earth.
The ETA one is cheaper, but not nearly as cheap as the manual plastic key type
This ETA one, how does it work? I'm just looking at it on Demon Tweeks and it just looks like a household breaker to me... Where do the other push button switches attach? How does it reset? How do you get around the alternator discharging problem?
I'm just trying to see which one to put on mine, I would like to replace the rather crude pull cable with something a little neater, but the Cartek GT one just looks like a rip off at around £250. Is this a realistic alternative? If not I'll just put a normal cable type one on...
http://www.demon-tweeks.co.uk/products/ProductDeta...
I'm just trying to see which one to put on mine, I would like to replace the rather crude pull cable with something a little neater, but the Cartek GT one just looks like a rip off at around £250. Is this a realistic alternative? If not I'll just put a normal cable type one on...
http://www.demon-tweeks.co.uk/products/ProductDeta...
I have a kill button next to the steering wheel and another outside on the windscreen scuttle. Hit either of the kill buttons and it trips the master switch (just like an RCD). You reset by switching the master back on, so you do need to mount the master where you can reach it when strapped in.
Gassing Station | General Motorsport | Top of Page | What's New | My Stuff