not sure how it works, But if the unit 'absorbs' a surge. It effectively destroys itself. IE it is knackered
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ajlelectronics
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Sales talk. What they mean is that it has a tiny underspec Varistor which would get taken out by the pulse, along with anything else connected, if it actually did anything at all. I am still unconvinced that it is anything more than an "Elephant deterrent".
ajlelectronics
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Exactly. It will do nothing useful, just self destruct.
so the likes of us on here, could, theoretically dig the old diode out and replace it then?
ajlelectronics
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Nope, electricity travels far too fast for that. An overvoltage protection circuit would have an inline fuse before the Zener. Zener conducts and takes out the fuse by current flow, whilst the Zener briefly holds the voltage down.but by doing that, won't it absorb the 'spike'?
No fuse means that once the Zener blows apart (milliseconds), the overvoltage condition is probably still there.
Kram
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This sort of thing. 1.5kW peak disipation and 6.5w constant load. I'd suggest 17-20v as a good value for one - noting that a charged lithium jump starter may be as high as 16.8-17V and is quite realistic if it will be fitted to the car. I doubt any car electrics will suffer below 20v anyway.
The one in the previous pics above look bigger device than the one I found on farnell.
ajlelectronics
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Well you could, but you might as well just perform a magic spell to achieve the same thing. I *AM* open to be convinced by scientific explanation, I may well be forgetting more than I ever knew, but for now I am calling "Snake oil" just like welding "surge protectors".
Ubique
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It'll be an 'avalanche' diode.
Ubique
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Why bother? having the starter battery connected will protect connected systems better.
Farside
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It will detect the presence of snakes and warn you against their oil.Would something like this be much use?
Surge (ANTIZAP) Protector for Jump Leads
Surge Protector for Jump Leads (ANTIZAP) protects onboard electronics from voltage spikes. 12V & 24V systems - automotive, 4WD, commercial and marinecardno.co.uk
Ubique
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Starter battery - and if you're welding, put the ground clamp close to the welding area, other than that, on a 'this century' vehicle, there's nothing to worry about.
ETA:- where are these 'spikes' coming from? eliminate the source, eliminate the potential cause of problems....
ETA:- where are these 'spikes' coming from? eliminate the source, eliminate the potential cause of problems....
Kram
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Whatever device needs a connection on both cables. A starter battery gives some protection but wont respond/absorb extremely fast transients. A large electrolytic DC capacitor is also a good choice, that will have a very fast response. These TVS diode devices do work and are built into many electronics anyway.
It is something I wouldnt worry about, cars are designed for this stuff.
It is something I wouldnt worry about, cars are designed for this stuff.
ajlelectronics
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A fully charged battery.
Ubique
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Actually, a partially discharged starter battery will absorb spikes better
I agree leaving a good battery connected is one of the best protections.
But to answer the spikes question, when you're doing things that you shouldn't, you might end up with high voltage/high frequency transients/interference, which a battery won't absorb that well.
A clamping diode (aka zener) will short out and dissipate those spikes far quicker than the battery can absorb them.
The issue is that if you push the Zener diode too far, it'll just go pop.
In the OP's case, my guess is the combination of dead battery (with no/little capability to absorb charge, let alone any spikes), high voltage due to using a boost starter, combined with some high voltage spikes during the attempted starts, has pushed the alternator diodes over the edge.
JOEPRO
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I didn't get to this today but I will tomorrow evening. I suspect though it won't do much of anything without a battery/ load on it.
JOEPRO
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I have decided ill keep the Ring charger too 
Whilst it was no use as a jump starter it is a very good battery charger. Fan cooled so no worries in that regard and powerful. Alot of S classes have large batteries in their boot. And unfortunately my cars mostly live outside. So the example below shows where this Ring charger works very well
Close boot lid on cable and let the charger do its thing checking on it every few hours and never leaving on for more than a few hours at a time, when away or asleep.
Whilst it was no use as a jump starter it is a very good battery charger. Fan cooled so no worries in that regard and powerful. Alot of S classes have large batteries in their boot. And unfortunately my cars mostly live outside. So the example below shows where this Ring charger works very well
Close boot lid on cable and let the charger do its thing checking on it every few hours and never leaving on for more than a few hours at a time, when away or asleep.
