A fuse is a safety device consisting of a strip of wire that melts and breaks an electric circuit if the current exceeds a safe level.

So what is it protecting?
Well it’s not the faulty equipment that caused the problem,
or the nail going through the hidden cable, it’s not even you!
It’s actual job to cut off the electrical current before it fries the wiring and literally causes a fire.

Not protecting me?
Nope, it takes very little current across the chest to stop the heart.
Typically 30 mA (0.030 A) worth of AC (mains) to 300-500 mA (0.3-0.5 A) DC can cause your heart to “quiver” aka fibrillation aka not pump correctly.

Incidentally it’s harder to “let go” of what is killing you when frying on DC than on Mains. Grabbing a DC wire your hand clenches HARD round it and will not let go. AC and your muscles are “quivering” it is sometimes possible to let go.

Now think about your hairdryer with it’s 3 amp (3000 mA) fuse in it.
Hows about your electric kettle with it’s 13 amp (13000 mA) fuse!

Still think a fuse is there to save you? I think not.

Protection devices like RCD (residual current devices)
aka residual-current circuit breaker (RCCB), Ground Fault Circuit Interrupter (GFCI), Ground Fault Interrupter (GFI) or an Appliance Leakage Current Interrupter (ALCI). are there to try to protect humans.

They work differently from fuses as they look at what’s going on down the supply lead i.e. When something is working properly the electrical flowing in and out (live and neutral) are the same. If a fault occurs and some of the current flows to EARTH (or if you’re the unlucky person, through you) and that’s an imbalance. Once that current exceeds a set level it simply turns off the supply.

Before someone asks, yes they work on both AC and DC systems.

And back to fuses.
Meet the idiots way of working round a constantly blowing fuse.
Yep, there are idiots who put nails in fuse holders as a “temporary fix” to allow them to get home. There again if they did that in their homes?

Nothing quite like coming how to a real fire is there?

I’m not really interested in what your country uses in households or industry. The variations are numerous, all have their particular quirks, identification, voltage ratings, etc. All I’m interested in is automotive blade fuses because (strangely enough) that’s what I come across everyday when on the boat and fixing vehicles. (Pic borrowed from Wiki)

I wrote about the different colors used in fuses in the post 12 v systems.
It also contained the MAXIMUM current rating for wire.
So does a 5 amp rated fuse go “pop” at 5 amps?
I wish it did and yet so many people think that’s the case.

Fuses are supplied as having TWO ratings, continuous and their Blow rating.

  • Continuous means it will work (not happily) at this maximum amount of current. Some “experts” say you should never run a fuse at more than 70% of it’s rating. I’m kinda in agreement there.
  • Blow means it literally vaporizes, melts, and breaks the circuit.
    Typical for automotive fuses that’s TWICE the fuse rating.
    Ouch, a 5 amp cable sits there with 10 amps going through it before it blows? In a way yes.

Electrical circuits occasionally “surge” i.e. want a hell of a lot more current when starting up or in a certain “mode” than when operating quietly. It’s not a long “surge” so the wiring can take it. Thus it’s good the fuse doesn’t blow quickly or at it’s rated (continuous) current.


A fault is a disastrous long-term failure.
LOADS OF CURRENT gets pulled (hopefully) and the fuse just gives in.

The worse faults are those where something fails gently i.e. pulls more and more current until the fuse blows or typically you start smelling VERY HOT WIRING.

Anyone surprised?
I was when it was explained to me as I rewired a car for the umpteenth time following some idiots desire to hang a string of spotlights on his car that pulled exactly 35 amps though a 2.0 mm² 25 amp rated wire fitted with a 20 amp fuse.

Now go out and look at your BOV (bug out vehicle).
At that array of spotlights you’ve fitted.
Hands up all those cringing a bit.
Those now thinking about your wiring.

And finally
To complicate things, if you move away from automotive fuses, you can get fuses that are designed to cope with life’s little current surges.

FF (very fast and totally unforgiving)
F (fast can take a little abuse)

SB (Slow Blow)
TL (Time Lag)

The last two (SB and TL) are designed to cope with “transient surges”.

Put a FF or F fuse where a slow blow or time lag fuse should be fitted and “POP GOES THE FUSE”

What to do if a fuse blows.(Caution, dangerous advice)
It’s blown for a reason guys (and girls).
Look and sniff aka use your nose. DON’T TOUCH!
If something is discolored or smelling hot, that’s probably why your fuse blew.

It’s really for the learned person or experienced engineer.

I will take no responsibility for damage, injury or subsequent loss
if amateurs or even experts do this.
I do it because I’ve got YEARS of experience of fault finding.

If there is NO APPARENT REASON why a fuse blew, you might consider putting in a half sized fuse and switching on.

The reason is most clever designers rate their fuses at round 70-80% continuous rating.
Putting in a half rated fuse should allow the circuit to at least start.
If it blows immediately and “explosively” when on switch on, you could have one serious problem.

Sometimes fuses age, just like me!
The older I get the less I can tolerate surges in activity.
Fuses are the same so it could just be the fuse got tired and gave in.

The maths for you.
A circuit is designed to “pull” 10 amps.
A good designer de-rates his fuses by around 20% to cope with this so he puts in an 8 amp fuse.
Some experts say that automotive fuses blow fast at twice their rating so in this case that’s 16 amps.

If nothing is readily apparent (i.e. excessive heat, smelly, signs of distress),  I will now slip in a 4 amp fuse.

Typically it will blow at 8 amps but will struggle to keep going if the load isn’t too excessive.

Remember all I’m trying to prove is whether the fault is catastrophic.
If it blows BANG on switch on, it’s catastrophic aka you’re knackered.
If it keeps going, it could just be a tired fuse.

I will take no responsibility for damage, injury or subsequent loss
if amateurs or even experts do this.
I do it because I’ve got YEARS of experience of fault finding.

Bunny Heaven

There comes a time when commonsense and meat on the table clash with tree huggers and corporate interests.

I’m sat near a river bank SWARMING with happy little bunnies yet I’m not allowed to snare, trap, shoot, or otherwise dispatch meat that would keep me going for ever and reduce the profits of our local supermarket by a couple of hundred pounds a year.


After all rabbit is a pest as listed by Natural England and “All occupiers have statutory obligations regarding wild rabbits that are harboring on their land”.

An Order under Section One of the Pests Act 1954  declares England and Wales a Rabbit Clearance Area. In this area, every occupier of land is responsible for controlling wild rabbits on his/her land or for taking steps to prevent them causing damage. This is a continuing obligation.

Hell most people have to pay for rabbit control, I’ll do it for free!

Yet here I am prevented from eating well by corporate B.S. , probably political correctness, and definitely the wants and desires of  a minority group of tree hugging drongo’s who would probably drop dead in horror if they were served rabbit stew.


Aghhhh. It’s driving me nuts.
All that wonderful free meat and I can’t touch any of it (officially).

So what to do?
Well autumn is here and winters coming so I feel a few late nights coming on.
I’ve identified a few key burrows so will set a few long snares at first.
As for persec in the night? We’ll see.
There’s one CCTV camera to blind and a sodium lamp to extinguish first.
After all it’s not outside the realm of possibility that they may fail naturally, simultaneously like (snigger).

G’day, cobber.

I’m intrigued.
Someone from Oz regularly looks at my scribbles.
I’d love to know who and why i.e. what’s got your interest?

108 countries have visited the blog yet I only know about a dozen names.
Pity that because I’m all for a bit of global networking, hows about you?

After all for all you know I may be that mad UK based freebander on 555 with the extremely bad technique and two tone morse key you sometimes try to QSL.

Crimp, Terminal Block, Or Solder

An Interesting question from an emailer.

What do I prefer to do when joining wires?

  • I suppose it depends on what the size of the wire is,
  • How many wobbly amps (current aka  work) is being asked of it,
  • What the working voltage is,
  • What the frequency is (that for my radio ham followers)
  • What the environment is.

OK, not quite the YES/NO question and answer I guess they were looking for but it’s all important factors.

Crimp is how I generally join low current, low voltage power or signal / control cables which are going to be forgotten about.
Then I either slide a tube of heatshrink tape over the joint and shrink it tight or use self amalgamating (self fusing) tape.

Terminal strips I like for when I know I’m going to be “fiddling round” with the setup.
Solder for when I want to make a permanent join (current permitting), one which I’m going to seal with “pre-gunked” waterproof heatshrink tubing.

Yet that’s not quite the end of it.
If I’m using stranded wire, I NEVER fuse the cable end with solder (aka tinning the wires to stop fraying) before crimping.
A crimp CRUSHES against the wires thus forcing a good strong mechanical and electrical joint.
Soldering a multistrand wire and then crimping it, the stiffness of the wire (now a solid mass) can prevent a good overall crushing crimp.

Single strand wires can be crimped YET unless you are using a REALLY GOOD QUALITY crimper, you may not get the same electrical bond as when using stranded wire.

So why use stranded or solid? Good question.
Stranded wire is usually better at handling vibration and mechanical stress.
So if the wire is open to the weather or abuse? Personally I go stranded.
Solid wire can stiffen and turn brittle with age.
That doesn’t mean stranded won’t, it does, BUT not to the same extent.
As for crushing a wire? Stranded or not, that’s never a good idea.
(Memo to CB / COAX users, don’t crush the coax in the car door frame, it hurts the wire, upsets the tuning, and you lose power!)

Hows about joining wires permanently?
Crimp as above in preference BUT I also use solder on some joints (current permitting) AFTER twisting them together before soldering as mechanical strength is as important as a good electrical joint. After all laying two wires alongside each other and hoping your soldering is good? I think not.
Then I heatshrink or self amalgamating tape the joint.

Bullet connectors. Used a lot in cars. Just remember, if you can push something together, it can vibrate it’s way apart.
That and you put the FEMALE on the supply line and the MALE BULLET on the load end. That way when the joint falls apart you have some protection i.e. not a bullet sparking against the chassis.

Do I ever  tape wires. (Shall I lie? NO)
Occasionally YES I use a self amalgamating tape which “fuses” itself into a solid mass.
Do I tape joints using insulation tape? NOPE, NEVER, and neither should you.
That doesn’t mean to say when working I won’t cover a live wire with insulation tape or use tape for identification BUT as a permanent joint?
You’ve got to be really silly to do that.

Hows about covering terminal blocks with tape to keep out the damp?
Hows about you not being so tight-fisted and buying a proper connector in an environmentally sealed box?
Yes it will add to the cost but what price safety?

As a sort of rule of thumb, I won’t solder anything carrying 10 amps or more (12 volts or not).
On HEAVY current loading I prefer to use a screw terminal block “fed” by crimped on terminals.
The only time I won’t crimp is if the termination block has got a crushing fixing for the wires.

Hope that’s it. Feel free to ask more.

12v Systems

Found this when browsing.
As always, I’ve quoting from the internet so it’s up to you to check what I’m writing is correct.

Stranded Battery Wires
16 mm² 110 amp
25 mm² 170 amp
35 mm² 240 amp
50 mm² 345 amp

Stranded Wiring Amps
0.5 mm² 11 amp
1.0 mm² 16.5 amp
2.0 mm² 25 amp
3.0 mm² 33 amp
4.0 mm² 39 amp
6.0 mm² 50 amp
8.5 mm² 63 amp

Blade fuse Colors
1 amp Black
2 amp Grey
3 amp Violet
4 amp Pink
5 amp Tan
7.5 amp Brown
10 amp Red
15 amp Blue
20 amp Yellow
25 amp Natural
30 amp Green
40 amp Orange

And not forgetting I found this information on a British (UK) site so wherever you live may not be as uncivilized as we are.

Or to put it another way, check it out, take nothing on trust!

Moon Watching

moonhowlEvery now and again I go and howl at the moon. Curiously on a full moon.
Dunno why, feels good I suppose yet the moon has got mystical powers for some.

It also is a pain in the butt when hunting as it sometimes gives the edge to the prey let alone improving those night vision thingies that all good preppers should carry round (together with the other half tonne of essential equipment the experts deem you should have).

Yet when the calendar goes for a bucket of chalk (TEOTWAWKI) the moons phases would be a good way to keep time.

I could never work out why someone thought the world needed 30.44 days a month.
Yet the moon repeats itself every 29.53 days.

Stupid timing isn’t it?
You would have thought nature would have got that right i.e. moon cycle EXACTLY 30 days! As for man, nuff said, he was stupid from day one. We are born with ten fingers and our counting system is built round ten, so why use 24 hours in a day? Stupid.

Ho hum.
The moon has compelling forces on the tides too.
New / full moon you get an extra high and low tidal range tides (spring tides) and on the half moons and a limp sort of tide (neap tides).


There again I also just like watching the moon as it waxes and wanes.


Yet again another stupid man type phrase, “Waxing and waning”.
Which dimwit though that one up?


Basic batteries. 12 volt “car type”.
If they slosh around i.e. have liquid in them, that liquid contains sulphuric acid. ACID BURNS skin and destroys metal.
A typical mix is 35% sulfuric acid and 65% water.
It’s posh name is electrolyte.
The more charged the battery is, the stronger the acid.
The stronger the acid the thicker it gets and to measure the thickness aka battery charge you use a device called a hydrometer.

Simple eh? Well not quite, the warmer the battery, the thinner the soup so it will appear less charged than it actually is. Read the little scrap of paper that came with the hydrometer for how to work that bit out or, as I live in a temperate climate:-

Green good,
White Needs attention,
Red means I’m flat H E L P!

When a battery is being charged in a car, a boat, or from a wind turbine, it generates hydrogen gas. Kaboom type gas.
So a golden rule, no smoking, naked lights, oil lamps, or sparks where the batteries are being charged.

Remember the Hindenburg?
Same gas, small spark, end result:-


Finally a battery stores a LOT of electrical energy.
Don’t just think that 12 volts can’t kill. It can.
Don’t think that touching two wires together looking for a spark is safe.
You can get one heck of a burnt hand doing that stunt.
Dropping a spanner onto the two battery terminals and standing close while your battery goes into melt down is one of life’s little DON’T DO THAT!
Batteries are heavy, drop one and the snapping sound will be your toes, the crunching sound will be the battery hitting the ground, and the splashing sound could be your feet being covered with acid.

Batteries come in two main groups.

Wet cell (common automotive) or maintenance free (leisure / marine) and
Gel-cell and AGM aka absorbed Glass mat which are specialty batteries.
Which is best?
Gel and AGM don’t spill liquid BUT they are a heck more expensive.
Gel Batteries are good for DEEP cycle applications.

There is another less spoken of type, traction batteries.
Think fork lift trucks.
Built like brick outhouses, if you want long life batteries these are the puppies you need EXCEPT they aren’t really for cranking.

Hellishly expensive (unless you rip off a fork life truck) they are by far the best for frugal living / survival.

Cranking and Deep cycle.

Think engine starting.
They need the ability to deliver LOADS of current even in the cold.
Not a lot of good if you are deep cycling them. i.e a type of electric battery that can be totally discharged and recharged several times.

Deep cycle?
Think less instant energy but more long term.
Deep cycle batteries have thicker plates and can survive a number of full discharge cycles.

So whats CCA.
Cold cranking amps at 0 deg F for 30 seconds.

Know when the winter arrives and your engine turns over like it’s in molasses? The fault is probably your battery as the colder it gets the worse instant current it can produce.

Why do manufacturers list this?
Duh, it gets cold in winter.

-32C / -20F your battery will be working at around 25% efficiency.
-22c / Zero F you’ll be lucky to achieve 40%
0 C / 32F 60-65% is typical
27C / 60F 100% of pure punch is available.



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