Melted Earth Lead

[ChrisG]

Had a mishap yesterday with the Royal Star. After a coffee stop I started the engine, first kick as usual. The it suddenly stopped. I tried again and after a pop and bang under the seat and a cloud of smoke it stopped again. I removed the LH sidepanel and found the red + earth lead from the battery to the earthing point had fried. The fuse in the negative lead was intact but the battery was somewhat drained.

As I couldn't remove the seat to investigate further I had to call Peter James recovery. The AA was there within 10 minutes and he removed the seat. There was no damage to any other components so just the lead was the problem. However, the Battery, a Motobatt super duper jobby, is struggling to take a charge 24 hrs later (started at around 7V, up to 11.8 V now) although that may be because  the charger is being gentle with it and has a lot of juice to replace.

I am told that a loose connection will cause excessive heat so I suspect the connection to either the battery or the frame was maybe loose. However, why should that cause the battery to drain as surely the current would have flowed through the negative lead and been in excess of 17 Amps fuse capacity?
Any electrics officianados got any ideas?

Chris 

[idie]

I would guess that has taken the path of least resistance. You may now find that the battery plates are damaged.

[chaz]

are you using a Motobat charger?  some discharge and desulfer themselves before re charging.

Im working on a 1995 Aprilia RS125 at the moment, the neg cable got hot and the outer cover melting when trying to start, only has electric starter, I found previous fiddler had left the lead to the starter motor loose. its ok now.  no effect on the fuse either.

another possibility could be a broken wire or strands in a wire.  may have warped plates.

I had a Honda Firestorm 1000, rode home one day , fine, next day went to go on the first ride for hero's event and wouldnt start. battery lead had come loose.. I did a few miles the day before, why it loosened itself overnight???

[Spaceman]

It sounds as though the earth lead must have become damaged, for example, resulting in broken strands and a higher resistance at that point causing it to overheat at a much lower current than the fuse rating in the -ve lead and eventually burning through. If this was the case then the higher resistance in the earth wire would have produced a voltage drop that would have reduced the voltage generated across the battery by the RR or Zener diode (depending on what is fitted) probably limiting the amount of charging of the battery.

I can't see why the battery should have been damaged but the symptoms don't look too good. I assume an intelligent charger is not being used to recover it?

[ChrisG]

Thanks everyone! I am using an intelligent charger and it's been trickle charging for two days now and the Voltage is stuck at 11.8 ish volts.
Should I try another charger to see if that does the trick?

Chris

[idie]

You would need an old fashion type charger. One like I use with  just a transformer and rectifier. If the battery is reclaimable  that will do it.

[Spaceman]

Thanks everyone! I am using an intelligent charger and it's been trickle charging for two days now and the Voltage is stuck at 11.8 ish volts.
Should I try another charger to see if that does the trick?

Chris

I use both Optimate 4 and Oximiser 900 intelligent chargers. Neither will enter the bulk charging phase (constant current) until the voltage has risen to ~12V and will therefore enter a recovery charging mode which involves pulsing a relatively high voltage across the battery (19 V). Having carried out extensive testing on duff batteries, I found that the Oximiser struggles to recover batteries but the Optimate usually succeeds unless the battery is completely duff (eg with open or shorted cells). When tested in this way, the Optimate normally succeeds after a few hours.

[Mike Farmer]

 

Sounds a bit to me like you had a dead short circuit somewhere. Thats the only thing I can think of that will produce your symptoms. What or where/--- not even going to try to guess.

I too use the old fashioned charger, I'm happy with that cos if you drained the battery, then started the engine, the alternator would belt the wiggely amps back in and fully charge it in about 15mins.

I am aware of the arguments pro and con this idea, but it works for me.

Mike

[Spaceman]

I dug out an old fashioned battery charger earlier to see how it performed on one of my more problematic old batteries - normally, the Optimate 4 will charge this particular battery but only after subjecting it to its pulsed voltage recovery mode for a few hours. Surprisingly, although applying a voltage of about 14.8 V across the battery, the charging current generated by the old fashioned battery charger was very very small. At this current, it would have taken forever to charge the battery! When used with my other old batteries, this charger generated a charging current of about 1 A.

Had the battery been in good condition but was simply discharged, I think either type of battery charger would have succeeded in charging it up fully. What the old fashioned charger couldn't cope with was a sulfated battery which must generate a large internal resistance that restricts the amount of charging current that can be generated. What the Optimate 4 is able to do is to break down the sulfation via its recovery mode and eventually allow it to charge the battery normally.

Unfortunately, if a battery is proving to be difficult to charge by whatever type of battery charger is being used, it is probably time for a new battery!

[ChrisG]

After much thought, it looks like the following occurred.

First of all the earth lead between the Battery Terminal and the Frame has a M/F spade connector in the middle(for quick removal) and was actually quite short which resulted in very little slack.

Second when looking at the battery secured in the battery carrier with the engine running, the whole shooting match vibrates significantly, like a blurr at high revs.

So, it highly likely that the lead was being pummelled by the vibration and this resulted in the middle connection becoming slack and heat was generated there.

So, with hindsight, I should have (and now will) put longer, slack leads on both terminals and make sure the connections are TIGHT!
Chris