Battery negative hot !!!

[glenn77]

Just went out to start the van and put my hand on the short earth wire that goes from the negative terminal to the chassis - it was quite hot to touch . Now i know this isnt right - but what may be causing it ??? Could be the reason for my poor starting problem - any ideas - thanks

[jamesc76]

Corrosion, so whip it off and cleaned the ends and where it attaches, then look under the van and do the same process to the earth braid on the front of the gear box then see if it gets hot!

[Red Westie]

Heat is an indication of high resistance...either on the terminal ends (braided wire to chassis or wire to the battery itself) OR the braid has gone thin and only a proportion of the wires are intact. If this is the case then replace it with something that is at least as heavy as the original.
As james points out...check the other braided cable on the gearbox, the main positive feed to the solenoid terminal and the much smaller spade connector that switches the solenoid...the last being particularly surceptable to corrosion and poor contact.
Martin

[glenn77]

many thanks for the help guys - just got to love this club for all the excellent help and advice - will get under the van tomorrow to give it the once over - hope it works - thanks again

[Mr Bean]

many thanks for the help guys - just got to love this club for all the excellent help and advice - will get under the van tomorrow to give it the once over - hope it works - thanks again

Totally agree on the resistance issue but At easily 100A plus for a winter start a five Ohm resistance will generate (Current squared times resistance) = 5 x 5 x12 = 300 watts. Point is that five ohms wouldn't strike you as being high!
Cheers
Wolfie

[tonytech]

Totally agree on the resistance issue but At easily 100A plus for a winter start a five Ohm resistance will generate (Current squared times resistance) = 5 x 5 x12 = 300 watts. Point is that five ohms wouldn't strike you as being high!
Cheers
Wolfie

Yes. Power is equal to Current squared times resistance. but the figures are wrong!!
If you had a 5 Ohm resistance in the circuit the max current that could flow is 12v / 5= 2.4 Amps Not enough to light a headlight let alone turm the starter.

If the starter Current is 100A. then the circuit resistance must be less than 12v / 100A = 0.12 Ohms.
If the strap and connections contribute the 0.02 Ohms the power lost as heat in the connections would be

100 x 100 x 0.02 = 200W.
So even a very small resistance will dissipate lots of heat.

T

[AngeloEvs]

Bolt that secures the lead from battery neg to chassis - bolt thread and captive insert corrodes resulting in poor continuity at this conx. If corroded will probably shear when attempting to release it.