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Bit of Advice on Battery Cut Off Switches


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I have two new cut off switches to fit. Where do i put them? I know i could isolate the earth with one leaving both batteries disconnected or should i put one on each pos?

The real question is where do i mount them? Photos or advice on the physical location would be good. I can't think of anywhere they won't get in the way and will still be handy.

and

your feelings of how best to isolate the two batteries, pos or earth?

top switch this page

Thanks

Neill

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Ralph...."she" doesn't like that idea.....although i do as its very easy to do / install !

I already have a 2kg Powder Fire Extinguisher in that footwell against the box so mounting them nearer the gearbox tunnel might be almost out of the way.

Lets see if anyone else has some novel positions.....for the switch,,not the wife. :P

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First question is what are they for - if memory serves you're building an expedition truck not a challenge vehicle so it doesn't have to pass scrutineering but it may need to be securely immobilised or disabled whilst leaving accessories like a fridge etc. running from the 2nd battery.

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I know you have purchased the battery isolators but when I bought my 90 it had these fitted along the top side of the battery box next to the passenger seat on the door side. I didnt like it and replaced with these http://cgi.ebay.co.uk/REMOVABLE-KEY-BATTERY-ISOLATOR-SWITCH-250AMP-24V-060550-/310145023234?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item4836157d02 then moved them to the front of the battery box in the foot well but in fairness they fitted very well and were also out of the way as they can be installed as far back as you like.

Just another option for you, hope its of help.

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@Fridge. Correct, Thats why i thought of doing it for both pos feeds and bought two. Do you think that will be OK?

@outdoor i saw those but they were a bit pricey. I also looked at tthe ones with keys and the one with an ignition wire. I decided to keep it simple and install a fuel shut off somewhere else and put the fuse in for the radio to leak enough current for the radio codes and clock.

So it looks like footwell is the easy choice or run a massive cable and put them on the dash....since i need to remove the dash soon i might just go the whole hog.

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or run a massive cable and put them on the dash....since i need to remove the dash soon i might just go the whole hog.

This suggestion is rather ironic. in trying to add isolators to potentially make the electical system on the vehicle safer, you are adding metres of extra cable, half of which is connected straight to the battery, unfused and unswitched!

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Any suggestions welcomed. What switch do you think Fridge? I have to one with a metal pin.

Luke i'm pretty much in aggrement as to running large and long cables. Rest assured they would be fused with Mega Fuses. Already running 150Amp Mega's in the Split charge system. All the large fuses will be in the box and before the cable goes anywhere. They go up to 400Amp continuous draw @ 800amp blow and i;ve seen some 500's on some sites. If i get a short liike i did previously my fuse should blow first. I'm carefully sizing them all and buying plenty of spares. I'm still in the process of fine tuning the charge and power setup so the fuses may be lowered from 150 to 100. 100's blow at 200amp so i'll need a larger one for the winch circuit but i don't thing the charge cct needs to be more than 100.

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Neill,

I know we're all on tight budget's at times mate but seriously do yourself a big favour and spend the money on the heavy duty ones you see in the above post as I've managed to break for a better word 3 of the cheap plastic ones with the red key's in the last 6 months I've now gone for a heavy duty one as i know it'll do the job and it's made i think by hella anyway so that to me says a lot about the quality of it

HTH

John

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Thanks for that.

Nice to see some visuals. Cheers.

so now the position ideas are in what about pos or neg placement ? I have a dual battery setup.

I'd go for positive, mainly because it makes it simpler to bypass the switch for specific circuits such as radio memory and clocks. If you isolate the positive you can run the feed through a small fuse just to those items whereas isolating the earth and putting a fused bypass in allows you to forget to turn the isolator switch on and blow the bypass fuse when you turn the ignition on.

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I have the same issue and though long and hard. I put in a single isolator like this http://www.vehicle-wiring-products.eu/VWP-onlinestore/battconns/battisol.php Ref 60550 in the front face of the passenger seat box.

Mine is fitted so that when switched on the key points downwards and the end of the key brushes the floor carpet so it cannot snag shoes or bits and pieces in the passenger side floor.

The switch is quite a bit bigger than it looks in the picture. I also went for this one, as mine isolated both vehicle and leisure batteries from all earth, so the vehicle is completely dead when the key is removed. Since I have a winch, whose current goes through this, and a 2kW inverter, it copes with large battery cables.

On race cars, the required practice is to mark the earth cable which is the one the marshals cut if you have a prang, so I have put mine on the earth side too. It is still easy to rig up a separate battery for safeguarding a radio etc.

It is not wise to make these any longer than necessary anyway, and they are a b****r to route neatly (though if you used welding cable rather than battery cable, you get much more flexibility).

Regards

Richard

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PS

I have a separate winch isolator switch from Vehicle Wiring Products Ref MBS4.. It is near the top of the passendger side seatbox next the tunnel, which has also proved to be sufficiently out of the way. My winch switch is in series with the isolator, so both need to be on for the winch to work.

PPS I have no relationship with Vehicle Wiring Products, but have bought loads from them and it has always been top notch stuff. I am wary of buying mission-critical stuff from eBay as iwhat arrives is often not quite what you expected especially in regard to build quality.

Regards

Richard

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Cutting battery either pos or earth off with the engine running isn't a good idea as the alternator is still connected ignition-side and they can "free run" up to 110v which doesn't do anything any good.

It's not MSA-compliant and not completely super-safe but if you route the alternator feed cable (big one) to the battery + side of the isolator switch then the alt is always connected but killing the switch will kill everything else whilst protecting the alt. The only risk doing it this way is if the alternator or its cable is damaged/on fire etc. then the isolator switch won't stop it. For your purposes though, this seems like the best option as I've not found any quality isolators for sensible money which have a separate ignition cutoff a-la the plastic "FIA" ones.

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If the isolator cuts off all earths, when switched off on a 300TDi, it will close the fuel solenoid valve on the fuel pump and stop the engine. However, this is may not be good for the alternator.

I wouldn't expect it to, the alternator and the stop solenoid are both earthed to the block, and the alternator can provide charge to the solenoid without a battery connected.

It doesn't do the alternator much good though!!

An FIA approved switch has the auxiliary contacts to both disconnect the fuel solenoid directly from its supply, and discharge the alternator through a resistor.

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