I just tried to start the mini, turned over for a second before I heard a small thud and then I had no power. Engine seemed fine so I opened the boot and there was a small amount of smoke coming from the rubber coating on the negative connector. The rubber was hot to touch and melting where it met the metal connector as I was removing it. The battery is 1 month old.

There is a lot of fraying where the wires meet the body, well it is almost separated entirely. This was a "must fix before getting rego" job, but I guess now it is a "must fix before burning down the garage" job. I will post a picture.

For the electronically minded out there, what happened?

Trying to pass too big a current down too few wires. Same principle as the old electric radiators where the conductors glow red hot.
Every time the earth cable is removed from the battery end and pushed back out of the way it's possible individual strands of wire are broken as they enter the boot floor connector. More likely as time passes and the wire becomes brittle. Looks like most of yours were broken so it was relying on just a few to carry the current.
Clean the connector and bolt really well, back to bare metal for a good connection, and install a new cable.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

Thanks, will do.

You can buy new ones at any auto parts shop around the battery section

Basically the cable's rooted haha

No worries, I'll get my wife to sit in the boot and hold it together.

Possibly not a good idea. ... Unless you have an unusually petite wife. Hahaha

I'd also check the earth wire under the bonnet body to clutch housing

Check what cable lugs are fitted when buying new battery earth or starter cables, I found Matson starter ones now have crappy sheet steel crimped lugs. They need to be real COPPER, they are carrying 200A+ when the starter is cranking. Thin steel lugs = more voltage drop = not what you want with the battery way back there in the boot.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thanks for the heads up dr

Or Go to your local Auto Electrician and ask him to SOLDER a new lug on the cable for you.

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DID I MENTION THAT I AM THE BEST SUPPLIER FOR MINI ELECTRICAL PARTS AND REPAIRS?
"Let us remove your "SHORTS"

I put a new cable on. When I go to connect it, it gives off a little spark (seems normal enough but more than before) and I have enough power to show a very dull ignition light but nothing else. I cleaned the connection, what could I be missing?

The little spark means that you have something turned on drawing a load. It could be as little as the interior light. As for the power issue - do you have a multimeter to help track down the voltage drop?

Replies to this seem to have stopped coming in. Did you fix this electrical problem. Did you by any chance get the battery properly load tested. Never judge a battery by it's age or looks. TEST IT.

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DID I MENTION THAT I AM THE BEST SUPPLIER FOR MINI ELECTRICAL PARTS AND REPAIRS?
"Let us remove your "SHORTS"

I picked up 2 second hand leads for a $1 each at a swap on sunday about 50 cm long I'm gonna use them to hook up 2 batterys in parallel for a boat winch I brought to pull me quad up on the trailer