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Battery fuese/trips

SamW

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Jun 26, 2016
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What amp do people recommend for a fuse/trip on the main starting batteries as im not to sure what they draw when cranking the engine over

Thanks sam
 
In general there is no fuse on the main cable, but if you want one use watts divided by volts to get the amperage drawn.

A petrol 80 will be different to a diesel, and whether you have a 12v or 24v system.

For example the hdj80 stock starter is 4.5kw but at 24v the fuse would be different ftom the 12v starter which is 2.5kw

Regards

Dave
 
Why would you do that Sam? I don't think that running the starter through a fuse is either necessary nor a good idea.
 
I have to agree. There really is no point fitting a fuse but I am curious as to what your reasons are. I suspect Byron’s sad fire that destroyed his cruiser may have something to do with this. Here’s a bit of info that may help.

The starter cables are never fused. Why?
  1. Because they are sized to retain the integrity of their insulation for as long as the battery is delivering the short circuit current. In other words, the energy input from the batteries would be depleted before serious harm could be done to the cable insulation.
  2. Because there would be insufficient current delivered by the batteries over and above what is needed for the starter to cause a fuse to blow which does not blow during very cold max load starting. Ok, perhaps ordinarily you don’t need this, what if for some reason you had to operate the starter for a long period (fuses have a time characteristic as well as current) or to crank a dead engined truck out of harms way? You could well blow the fuse.
  3. A fuse on the battery would be so big as to not protect anything but the starter cables, which are designed not to burn anyway (see 1).
Still interested in your thinking though. :)
 
Byrons fire is the exact reason why just wanted something im place that could blow or trip if there was a major electrical issue
 
If your that concerned abbot the fire risk you're far better off fitting an accessible battery isolator switch of the type that boats must have. There are resettable circuit breakers available for marine use but the biggest I've seen are 300A which may do for a quick easy hot start but from cold it'd be marginal. No,idea what duty cycle they are at that sort of size either but, again, I don't think they could handle a prolonged bout of engine cranking, especially with the glow plugs lit if it's a diesel.
 
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Just use a cut off switch like they do on race/rally cars Sam
 
Byron's fire was a most unfortunate event and something that hopefully none of us will ever suffer. But car fires are relatively rare and I'd think that messing around with the wiring would only be set to increase the likelihood of a problem. A total cut off switch is a better idea than a fuse for sure. But you'll have to put everything through that and as with race cars, have it mounted on the outside of the vehicle. Fires can start from small cables too not just the big ones. Every time it gets switched off (by idiots nicking the key) you'll have to reset your clock, radio, cb etc etc. A small price maybe.

I realise that the camp is divided on this one, but I'd really leave it alone. If there was evidence that this was a common issue with Landcruisers I might be swayed; like it was with Reliant Scimitars. I'd just make sure that the wiring I did have was in really good order. I don't think there ever was a definitive answer to the cause of Byron's fire - unless I missed it, but cars only do this when there is a fault. I'd focus on that rather than fitting something that 'normal' vehicles don't have from the factory.

Fitting a decent cut off wouldn't be hard. However, you really do need to find a top quality cut off as many of the autoshop £6.99 ones are utter rubbish and more likely to fail or cause a fire.
 
Use a good quality FIA cutoff switch. Tried and tested in lots of vehicles. The key doesn’t need to be exposed so interfering g kids can play with it just somewhere where you can get to it when needed.

If we could have cut the power from the batteries and opened the bonnet we could probably have got the fire out.

Car fires are luckily rare. Out of all the Car sites I’ve used over the years I don’t recall any reported fires from the members. Here there have been 2 or 3 members if I remember who have had fires. Bad luck or coincidence it doesn’t really matter but having been there with Byron I’ve made some changes to mine.
 
The main thing here Sam is to make absolutely certain your wiring is protected and fused to suit the cabling at the point it gets thinner. I.e. going from battery to LED light bar cable for example. The use of ribbed conduit and keeping things tidy so they don’t get chafed or otherwise caught is a must with the vibration. You can always PM me photos if you’re unsure.

One thing as Mark said, if you can get the bonnet open you’re pretty much going to save the vehicle. The bonnet cable passes right by where Byron’s fire started in the front right corner and has a plastic outer that will simply squidge when it gets pulled hot. If you’re concerned, and I think this is a good mod, I would put an additional release somewhere with a solid wire or metal outer Bowden cable to operate your bonnet catch. I have some ideas on this as Byron’s fire got me thinking too. They’re not quite formed yet though.
 
I have one of these cut out switches to fit. It is half for convenience (because when I am doing E.g welding or work on the electrics I won't have to remove the battery terminal) and half because I am adding a lot of wiring to my truck and even though I am doing it as carefully as I can, it still could fail.

I won't connect the isolater into the starter cable though as the starter has a nice big solenoid as an isolator.

The isolator switches are only rated at 100A continuous and 500A for 5 seconds. My neighbour has one in his kit car in the starter cable and it gets very hot if you keep cranking the car over trying to get it started. Bypass it and the car cranks over much better.

I read the very sad story of what happened to Byrons truck, although my experience wasn't anywhere near as bad, I had a fire on a Peugeot 306, I had a minor crash in the snow and the next day, when the snow had melted some wiring in the bumper had shorted out and gone on fire. It was about 6.30 am and my neighbour had knocked on my door and told me, I tried to tip washing up bowls of water on it because I didn't realise at first it was electrical, then realised but I didn't have any tools to disconnect the battery they were all at work. So had to use some old pliers to break the terminal off. Luckily the fire didn't catch but it was a lesson learnt for me - when there is a fire you can't think straight, and it may not happen at a convinient time!

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£16 posted from rally design. I will put the T pull behind the rubber flap in the inner wing. If I want to use it for security I will put a small fuse holder bypass on it to save the clock time etc.
 
I have one of these cut out switches to fit. It is half for convenience (because when I am doing E.g welding or work on the electrics I won't have to remove the battery terminal) and half because I am adding a lot of wiring to my truck and even though I am doing it as carefully as I can, it still could fail.

I won't connect the isolater into the starter cable though as the starter has a nice big solenoid as an isolator.

The isolator switches are only rated at 100A continuous and 500A for 5 seconds. My neighbour has one in his kit car in the starter cable and it gets very hot if you keep cranking the car over trying to get it started. Bypass it and the car cranks over much better.

I read the very sad story of what happened to Byrons truck, although my experience wasn't anywhere near as bad, I had a fire on a Peugeot 306, I had a minor crash in the snow and the next day, when the snow had melted some wiring in the bumper had shorted out and gone on fire. It was about 6.30 am and my neighbour had knocked on my door and told me, I tried to tip washing up bowls of water on it because I didn't realise at first it was electrical, then realised but I didn't have any tools to disconnect the battery they were all at work. So had to use some old pliers to break the terminal off. Luckily the fire didn't catch but it was a lesson learnt for me - when there is a fire you can't think straight, and it may not happen at a convinient time!

View attachment 140810

£16 posted from rally design. I will put the T pull behind the rubber flap in the inner wing. If I want to use it for security I will put a small fuse holder bypass on it to save the clock time etc.
It makes sense what you are doing. Those isolators have their place and that is certainly not in the starter cables of an 80 though starting current is low at 187.5A as said they’re not really man enough. Don’t be deceived though, the starter cable to the starter motor is live all the time at 12v except for starting when it’s at 24V. Many of us will have experienced a stuck solenoid on these trucks when the contacts are on their way out so neither solenoid will isolate the starter if things go wrong with it. Ask me how I know!
With both batteries feeding into a fault there’s twice the current available for starting available to feed into a short circuit.

Does that Bowden cable have a metal outer Rich?
 
As I have run my (12v) cabling under the slam panel, I have fitted cube fuses at the battery terminals.

I cannot remember how long ago I fitted them but the reason was simply to protect against a fire in a frontal collision, they would fail if the starter cable shorted but TBH, there is more chance of a fire being started by an unfused aftermarket accessory cable shorting out.

https://www.12voltplanet.co.uk/battery-terminal-cube-fuses.html

Neat and tidy, I did purchase some spares but have yet to have an issue :doh:..........me and my big mouth!

Regards

Dave
 
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Like others have said, I personally would go with a battery isolator switch. The company I work for manufacturer large mining equipment, all the excavators they manufacture have fused starter motor cables. The fuse idea is great in theory, but due to low battery charge / high current draw at times can cause a fuse to blow...... when normally the engine would normally otherwise start.
 
Thanks for all your input guys its ot that i just want to fuse the starter cables i just assumed that the starter would draw the highest amps so if i was to fuse it all i wouldn't want it to blow a fuse or trip every time i went to start it if thats makes sense im not great at explaning things. Its things like what happened to byron that get you thinking what could you do to help save the truck if that was to happen
 
It makes sense what you are doing. Those isolators have their place and that is certainly not in the starter cables of an 80 though starting current is low at 187.5A as said they’re not really man enough. Don’t be deceived though, the starter cable to the starter motor is live all the time at 12v except for starting when it’s at 24V. Many of us will have experienced a stuck solenoid on these trucks when the contacts are on their way out so neither solenoid will isolate the starter if things go wrong with it. Ask me how I know!
With both batteries feeding into a fault there’s twice the current available for starting available to feed into a short circuit.

Does that Bowden cable have a metal outer Rich?

Yes it has a metal coil with thin plastic outer sleeve and plastic liner. All the metal seems to be steel not stainless though.

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It comes with a bulkhead mounting end, so could be used instead as a bonnet release cable in tandem with the standard cable at the catch, if an extra hole was drilled into the catch housing and latch (If I remember correctly from repairing my catch the other week).

20180222_080952.jpg


The pull handle is plastic, it is a hard plastic not sure of the heat resistance, although a penny washer could be used instead if it was mounted in an area where it could get on fire.
 
You’re right, I was thinking of using it as a bonnet release. A stainless one would be better it’s true as you want it to work when you really need it.

Food for thought.
 
What amp do people recommend for a fuse/trip on the main starting batteries as im not to sure what they draw when cranking the engine over

Thanks sam

Hi @SamW

As well as carrying fire fighting gear I think the most important things one can do to be able to deal with an electrical fire are:
  • Install emergency cut-off switches for each battery that can easily be accessed in an emergency
  • Have a secondary method of opening the bonnet should the standard system fail.
I am still fiddling around with secondary bonnet release mechanism but am very pleased with the cut-off switches I have fitted to my UK 80 and plan to do exactly the same to the 80 I am outfitting in Cape Town.

I have just posted up some more information on the cut off switches I installed. The link below should take you right to the post so that you dont have to wade through all my previous ramblings on the thread:

https://www.landcruiserclub.net/community/threads/electrical-upgrades.148514/#post-1476701

You will see I also fused the starter cable with a 250A fuse - remember my car is 12v start. I agree this is not strictly necessary but it does no harm and could do some good by cutting power if the starter and or cable is compromised in a smash. Very cheap 'belt and braces' if you like.
 
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The problem with vehicle fires is the battery is quite happy to keep throwing out hundreds of amps through shorted cables, once cable insulation has melted, an extinguished fire is almost certainly going to reignite, so shutting off the current at the battery or batteries is the first priority, this being my justification for fuses at the actual terminals.

Often by the time the bonnet has been opened (assuming you still can) and the batteries disconnected, the damage is already done and your vehicle may be a write off, fuses are quick and decisive IMO.

Whilst on the subject, given engines and gearboxes and so forth are isolated from the body to offer insulation from vibration ect, the main path for earth is the heavy cable from engine to body or battery. The importance of this cable must never be underestimated, without it the earth return is going to be via a throttle or bonnet release cable.

Regards

Dave
 
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Wise stuff Dave.

Since this all raised its head, I have bought another extinguisher, checked all my connections and installed a set of very sharp cable cutters in the cabin. I have not gone down the route of adding more fuses, cut offs etc as to be brutally honest, my view is that there is the potential to introduce more problems than solutions. As horrible as it was it is very rare and I think that adding more components might actually increase the chances of problems developing. Not fire maybe, but not starting, battery drain, breakdown and so on. The fact that the bonnet couldn't be opened on this occasion doesn't mean that it will be the case in every emergency. If you see or small smoke then the first thing to do is hit the release. And pull up sharpish. I don't want to be rummaging around for a second bonnet release somewhere.

I was heartbroken when I read of this and genuinely whilst I wouldn't wish this on anyone (OK OK so I can think of one guy) I cannot think of a nicer guy than Byron and it was a cruel blow. But I still don't think that it demands any unnecessary fitting of additional countermeasures.
 
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