Melted -ve Battery Cables - Please Help

[spages]

Hi All
Yes I am a newbie and this is my first Post
But hopefully you can help me out.

I have a KE55 Corolla (round head lights) and just rebuilt my 5K engine (after 5 years)
It started first time and ran for about 5mins
I drove to the servo to fill it up but it suddenly lost all power after 2 corners
I open up the bonnet and my earth cables were melted and smoking.
Both cables, from battery to chassis and engine to chassis were stuffed,
I checked the main engine fuse (15A) in the cabin and it was fine.

It also killed the battery (3months old Century Battery 330CCA)
but when I put a multi meter onto the battery it shows 12v still.
But when I put the battery back into my other car it was dead.

The things that I think it might be are:
I am using an Alternator out of another KE55 Auto (square head lights)
which was running fine 1 year ago and the alternator was reconditioned about 3months before that.

The other thing might be my Thermo fan, It was working fine before but I might have got
the wiring a bit mixed up, I dont think this is the problem but it is a possibility

Having the car sit for 5years and the cables may have deteriorated.

Can any one help me?
Thanks

[SLO-030]

Cables shouldnt deteriorate to that stage. But then again they might have,

Also Keep in mind that cars need a minimum of 13.8volts to crank,

[RobST162]

mate i'd replace those cables with nice fresh new ones and make sure they're bolted down to the chassis and engine good

must have been a lot of resistance in those wires

[Gavatron]

Also Keep in mind that cars need a minimum of 13.8volts to crank,

No they don't. Where'd you pull that BS from?

[Hiro]

Cables shouldnt deteriorate to that stage. But then again they might have,

Also Keep in mind that cars need a minimum of 13.8volts to crank,

Expanding on this - car batteries usually show 12V-ish when disconnected, often regardless of the internal condition. When cranking they'll often drop down to about 10V, and when hooked to a running alternator they'll be about 14.4V.

If you see 12V when disconnected but the voltage tanks during cranking, then most likely the battery has dropped a cell and is useless. If the voltage stays healthy but the car still won't crank, then it'll be either the starter motor or the wiring running to it, both of which are prime candidates to be in poor condition based on the age of the car and the time spent off the road.

[JustCallMeOrlando]

Sounds like something was drawing a buttload of current. First thing I'd suggest is as above, fresh cables all around. Hit Jaycar or the like, they have nice cabling.

Secondly, double-check your thermo wiring. They do draw a lot of current, and they sound like an addition since the last time you had it running, so they're a likely culprit if wired incorrectly. If you didn't upgrade the earth wiring to begin with, there is a chance they were just undersized when the thermos were taken into account.

Lastly, a car doesn't need 13.8V to crank. They only make that when they're charging while running. During cranking on many occasions, I've seen the voltage drop down to 6V and the think still turned over. An extreme case, but what's possible.

[Gavatron]

A good battery should have between 12.5v and 12.6v. Any more is just surface charge. It should not drop below about 9-10v when cranking.

[JustCallMeOrlando]

It should not drop below about 9-10v when cranking.

It shouldn't, but most batteries get a thrashing when doing a conversion

[Gavatron]

If you really give a crap about battery condition, you can use a load tester.

Me, I just keep the electrolyte topped up and as long as it starts the car, it is good

[spages]

Excellent advice guys
I will upgrade all the earth cables and hopefully a new battery underwarranty, disconnect the thermo and see what the voltages do when cranking/running. But this wont be until next weekend
I dont want to swap out the alternator unless I have to, but I am thinking the regulator might be stuffed. I think it has a regulator on the back of it. (Can anyone confirm?)
Does anyone know what type of Voltage/Amps would fry a 10mm earth cable?
And why would it melt the cables without blowing any fuses? and why the -ve?
A friend of mine advised to put in a 30Amp fuse from a Amp in line
which I think would be cheaper than replacing a battery

[WHITCHY]

30A fuse will be useless, the starter motor will draw more than 30A when cranking and blow the fuse!

[spages]

This is awesome
I thought I would have to wait weeks for someone to answer my post
but you guys are right onto it
Thanks for your help

Ok 30A Fuse BAD
Just saved me $50

[LeeRoy]

A 6 cell lead acid battery is 12.6 volts (as each cell is 2.105 Volts). Batteries measuring less than this can be the result of a plate which has dropped to the bottom of the battery. Over time the plates slide down with gravity and eventually touch each other - meaning you now have 1 less cell in your battery.

Voltage is electrical pressure so when you crank your car, and drop electrical pressure, the battery voltage also drops.

Spages,

Google AWG or wire gauge v. current rating and you will find a reference to wire size and it's current rating. I doubt your ground wire is likely to be underrated for the job you want it to do but if it is loose, worn, slightly broken etc then these will all contribute to its failure.

[Sciflyer]

If you are melting battery cable then assuming it is the correct gauge cable (ie, substantial) you have a short somewhere, i would not be leaving any battery connected unless you are fault-finding as the potential is there to either fuck another battery or start a fire/melt more wiring

Putting fuses in is not the answer

[RA35GT]

Normally the only unprotected cable on the battery is the starter motor, everything else would of either blown the fusible link or a fuse. (Assuming wiring is factory).

I'd check the wiring to the starter motor for shorts. If wiring OK, I would suspect the starter motor itself.

Rudi