Battery cut off switches

[pereirac]

Hi

About the little 'screw' type battery disconnect switches you can buy, on an negative earth car would you connect it to the positive or negative terminal or does it even make a difference? I usually disconnect the positive terminal on my cars battery if I leave the car for a while but I have noticed that some connectors see designed to fit on the negative terminal of the battery?

Carl

[Quart Meg Miles]

It doesn't make a lot of difference on the Elans but on metal bodied cars disconnecting the ground side is always safer, allowing accidental connection to ground without sparks from either battery terminal.

[ElanSeries2]

I agree with Meg - however different people do it different ways. I think for race car cut-offs, its more common to put the switch in the +ve side, with secondary terminals (and a resistor) for alternator spike protection.

[holywood3645]

I put mine on the negitive (Ground) side, and accessable from inside car,
See Pics
James

[William2]

Also, a battery cut off switch acts as an anti theft deterent and therefore I would suggest connecting it to the battery positive feed.

[Quart Meg Miles]

Er, let's talk of ground and power sides rather than positive and negative. Gets confusing as half the Elans are positive earth.

Having said that, assuming you have Negative earth, William, why does your positive (power) cut-off help as an anti-theft deterrent better than ground side? Just interested in the reasoning.

[7skypilot]

Perhaps Carl is referring to the battery disconnect switch as shown here:

http://www.electricalcarservices.com/Ba ... 003-/p-895

rather than the FIA battery isolator cutoff switch pictured in James' photo.

I have the FIA switch on the 7 (it needs replacing regularly) and the much simpler and easy to fit disconnect switch on the Elan. The switch is on the earth terminal and very simple to fit. Turning and removing the large plastic-headed screw isolates the battery.

One note of caution however; it the disconnect screw is loosened by the tiniest amount (less that a quarter of a turn) it performs as advertised and 'isolates' the battery. I lost my lights (at night, of course) in France, on a 'gentle' rally, when luggage in the boot (trunk) loosened this screw - it resulted in an 'interesting' moment while I struggled to remember just where the road did go!

[jono]

Interesting thread as I'm just about to tackle this issue on my +2.

I am attracted to the idea of a remotely switched isolator which could be operated via a small micro switch concealed somewhere in the car.

My thoughts were to splice in the main solenoid switch within the rear quarter panel void and have the control switch under the dash or somewhere similarly concealed.

Has anyone done this and can you direct me to a source of a suitable switch?

Cheers

Jon

PS: hope this is not seen as a thread hijack

[tcsoar]

Hi Jono,

I fitted a remote relay to disconnect the battery, it was discussed on a this thread,
http://www.lotuselan.net/forums/elan-mods-f31/battery-cut-off-switch-t27407.html

It is quite a long thread, 5 pages, but I came in on page 3. Warning though, alot of what was discussed on this thread also appears here and it did get quite heated at times
Most of the info on my switch is on pages 4&5.

There are also some diagrams and pictures explaing what was done. If you want any more info you can pm me.

Chris.

[saildrive2001]

I installed a Battery ProgBrain remote unit in 2012 & have been very happy with the unit. See the web site http://shop.batteryprogbrain.com/ The unit also monitors the battery voltage & disconnects it if it falls below a pre set level (saves having to push start the car if you leave the lights on & the micro switches don't work) The unit can also be wired so that it senses when the engine is running so doesn't disconnect the battery even if the voltage drops. I had to purchase a vibration sensor to wire in for this purpose & I installed it in the trunk where the silencer hanger is bolted. The kit was very complete & well made. I purchased the Gold III model (I think this has been replaced with the T3) from Adventure RV Center in Sevierville TN 37876. 865 429 3698 http://www.adventurerv.net/battery-brai ... -4037.html

[stugilmour]

Jon, I also installed the Battery Brain Keith mentions above. Really like it. Great for doing repair jobs on the Plus 2, as I don't have to take the boot floor apart to disconnect the battery.

Remote control is on my key chain; push the button and everything disconnected. No need to run special wires to a relay trigger switch. Note this type of devise is connected to the power side of the battery so it always has a voltage supply to move the relay position. The main unit mounts directly to the battery terminal; no need for big cables to a remote mounted switch, although took a bit of jockeying to get it around the boot floor.

The actual relay is called a 'latching relay'; it only uses voltage to move the relay from off to on or on to off; it does not use a continuous voltage to stay in the on position so no battery drain sitting. The unit has a off / on button in addition to the remote, so no issue if the batteries in the remote control go flat. In the event of failure, the unit can be removed pretty easily with hand tools and battery connection returned to normal. My Battery Tender charging wires are below the unit so I can charge and maintain the battery with the entire electrical system isolated.

Only issue with this product might be retail availability. I had to wait quite a while to get mine thru a local retailer here. Here is a thread where I mentioned the product before. The UK link seems to still work OK. Looks like they have replaced the Type III Gold model I used, so assume the company is still active.

lotus-electrical-f38/alternator-fusible-link-t23176.html

http://www.batterybrain.co.uk/

These types of cut off devises make a lot of sense for our cars, but less so for a modern car. I was going to get one for my Esprit, but the advice was to leave the battery connected when storing as the ECU looses it's settings if all power is disconnected for winter storage.

To the original poster, if using a manual switch or screwed terminal lug for isolation, I would recommend connecting to the ground side of the battery as Meg mentions. This type of latching relay has to be connected to the power side, but does not require the big cables shown in some installs.

HTH

Stu

[pereirac]

Also, a battery cut off switch acts as an anti theft deterent and therefore I would suggest connecting it to the battery positive feed.

Does it make a difference which side you put the cut off switch, as long as the circuit is 'open' back to the battery the car will not start?

Carl

[stugilmour]

Carl, it makes no difference whether it is connected to the power or ground side. Of course, either switch position could be by-passed or jumpered pretty easily if you know where it is located.

HTH

Stu

[billwill]

Carl, it makes no difference whether it is connected to the power or ground side. Of course, either switch position could be by-passed or jumpered pretty easily if you know where it is located.

HTH

Stu

It does make a difference if the switch is in the boot with the terminals exposed as in the photo above. In this case it is MUCH SAFER if the isolator is in the ground lead. When you are driving the isolator is closed so those contacts are at ground potential, so if a metal tool or lifting jack etc rattle around in the boot, there is no harm done if the tool touches the terminals.

On the other hand if the isolator is in the live wire, then a tool might bridge from a live terminal to a chassis nut and cause a molten tool and a fire in the compartment right next to the fuel tank!!!

[Quart Meg Miles]

On the other hand if the isolator is in the live wire, then a tool might bridge from a live terminal to a chassis nut and cause a molten tool and a fire in the compartment right next to the fuel tank!!!

Ja woel, und wit der prize urv tools dese dias yu carnot offord dat!