Anyone know the diameter of the battery earth lead?

I have to admit I am going to Halfords to get a new earth lead for my battery. Presumably bigger is better? Or is it all about resistance?

Existing lead is corroding st the clamp end, and I need it to be a bit longer too - the new bargain battery (800 as opposed to the 590 that was fitted), has the terminals on the wrong ends, so I had to turn it round.

The live is a bit near the battery clamp too, so some insulation going on there today.

I'd go out and measure it, but its 0645, and I have to unbolt the range seats to get at it!

I'd estimate 8mm , but that's just just a guess. Bigger cross section is better that smaller. I'll go and measure it if you haven't gone to shops yet

I used welding cable for mine with the clamp and ring terminal soldered on.

Bigger (dia) electrical cables is better and will have less resistance than smaller, for your application it wont make a difference. It will take a really long cable run for you to have any difference in resistance with the stock size cable. If you have a winch, a 1000 watt sound system etc., bigger diameter cable will help.

Having an 800CCA battery as opposed to 590 does not make a difference in current draw/flow if all electrical units and components remains the same, so a bigger cable will do nothing regarding this..all the 800CCA would do is deliver more current (if load was increased) and last longer ( same load) when the engine is off because it has more capacity.

As for corrosion, you can get electrical intended lithium grease, placing a thin coat on the terminal and lugs before and after connecting.

got the same diameter from Halfords, and a new clamp for a tenner, which is nice! Thanks for the advice

16mm2 110 amp or 25mm2 170 amp cable.

Barbados said:

Bigger (dia) electrical cables is better and will have less resistance than smaller, for your application it wont make a difference. It will take a really long cable run for you to have any difference in resistance with the stock size cable. If you have a winch, a 1000 watt sound system etc., bigger diameter cable will help.

Having an 800CCA battery as opposed to 590 does not make a difference in current draw/flow if all electrical units and components remains the same, so a bigger cable will do nothing regarding this..all the 800CCA would do is deliver more current (if load was increased) and last longer ( same load) when the engine is off because it has more capacity.

As for corrosion, you can get electrical intended lithium grease, placing a thin coat on the terminal and lugs before and after connecting.

Click to expand...

Coming from a marine background, battery capacity (and electrics in general) are a topic of perpetual discussion and much misunderstanding. In fact, the CCA figure - Cold Cranking Amps - is not a measure of a battery's capacity, but rather of its ability to deliver very high currents for very short periods; as the name implies, this is mainly when starting the engine. The measure of battery's capacity is the AH or Amp/Hours figure. In theory, this tells you how much current a battery can deliver, at more normal rates than during engine start, for how long. In fact, letting the sort of battery that we mostly use in our vehicles drop below 50% of its capacity more than very rarely or not recharging as soon as possible is the main cause of battery death.

Widgeon3 said:

Coming from a marine background, battery capacity (and electrics in general) are a topic of perpetual discussion and much misunderstanding. In fact, the CCA figure - Cold Cranking Amps - is not a measure of a battery's capacity, but rather of its ability to deliver very high currents for very short periods; as the name implies, this is mainly when starting the engine. The measure of battery's capacity is the AH or Amp/Hours figure. In theory, this tells you how much current a battery can deliver, at more normal rates than during engine start, for how long. In fact, letting the sort of battery that we mostly use in our vehicles drop below 50% of its capacity more than very rarely or not recharging as soon as possible is the main cause of battery death.

Click to expand...

Widgeon...indeed more CCA is intended for short bursts of higher current, which also means that the battery has higher current capacity so its Ah rating will also increase. More CCA is more amps overall...all up to how you use it, regardless if you need more crank up power (which more CCA is intended for) or listening to AM all day and night.
Car batteries are not rated in A/H they are rated in CCA for a reason. You cannot increase CCA and not have an increase in A/H if you were to calculate A/H based on your electrical load.

I don't like to list or note my experience, but since you did, I will... LOL

(1) I am a certified electronic tech since the vacuum tube days
(2) Been in the automotive tech business for over 30 years
(3) A licensed HAM radio operator on all bands up to 1,500 watts TX power.
(4) I build and fly giant scale aerobatic gasoline and electric powered airplanes
(5) I have built and installed tons of high power car audio systems
(6) I build and have built many radio and TV transmitting stations since 1992
(7) Built many, many power inverters from scratch..unsing self wound transformers and Motorolla 2n3055 or NTE 181 transistors
(7) and the list goes on LOL

I am joking about listing my expertise...however its all true.

Barbados said:

Widgeon...indeed more CCA is intended for short bursts of higher current, which also means that the battery has higher current capacity so its Ah rating will also increase. More CCA is more amps overall...all up to how you use it, regardless if you need more crank up power (which more CCA is intended for) or listening to AM all day and night.
Car batteries are not rated in A/H they are rated in CCA for a reason. You cannot increase CCA and not have an increase in A/H if you were to calculate A/H based on your electrical load.

I don't like to list or note my experience, but since you did, I will... LOL

(1) I am a certified electronic tech since the vacuum tube days
(2) Been in the automotive tech business for over 30 years
(3) A licensed HAM radio operator on all bands up to 1,500 watts TX power.
(4) I build and fly giant scale aerobatic gasoline and electric powered airplanes
(5) I have built and installed tons of high power car audio systems
(6) I build and have built many radio and TV transmitting stations since 1992
(7) Built many, many power inverters from scratch..unsing self wound transformers and Motorolla 2n3055 or NTE 181 transistors
(7) and the list goes on LOL

I am joking about listing my expertise...however its all true.

Click to expand...

Are you sure?

wonderdust said:

Are you sure?

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Some do...having lived most of my life in Canada in one of the coldest cities..I focus more on CCA than Ah rating. Having to crank a motor overnight at -40 degC makes us seek more CCA than Ah ratings.

steveo said:

I have to admit I am going to Halfords to get a new earth lead for my battery. Presumably bigger is better? Or is it all about resistance?

Existing lead is corroding st the clamp end, and I need it to be a bit longer too - the new bargain battery (800 as opposed to the 590 that was fitted), has the terminals on the wrong ends, so I had to turn it round.

The live is a bit near the battery clamp too, so some insulation going on there today.

I'd go out and measure it, but its 0645, and I have to unbolt the range seats to get at it!

Click to expand...

The std earth system is pretty poor, best to do some add ons whilst you are there, best way is battery neg to chassis then continue on to engine near starter and an additional lead from body to chassis, basically you cannot have to many earths.

Well, that was a fail. The terminals on the new lead didn't fit the isolator switch, so it all had to go back as it was. At least I tidied up the positive terminal, removing the dodgy additional lives to the seat recliner motors, and generally covered up exposed wire !
I will have to have a look around for bigger cable with a bigger end and clamp

steveo said:

Well, that was a fail. The terminals on the new lead didn't fit the isolator switch, so it all had to go back as it was. At least I tidied up the positive terminal, removing the dodgy additional lives to the seat recliner motors, and generally covered up exposed wire !
I will have to have a look around for bigger cable with a bigger end and clamp

Click to expand...

If they were ring terminals, maybe you could have reamed them to fit.

You could get them in different sizes..this one reams from 5-18 mm dia.