After quite a bit of YouTube and wider research into electrical starting/charging upgrades, there seems to be a lot of chatter about upgrading the so-called BIG 3:
1. Battery -ve terminal to chassis ground/earth cable
2. Engine block to chassis ground/earth cable
3. Battery +ve terminal to alternator cable

The main benefit is that through optimising the car’s electrical system, it can alleviate and prevent so many other common issues and also allows the engine’s drivetrain and car’s electronics to perform at their best. Sounds good, right?

Weirdly, all the stuff on YouTube on the BIG 3 seems to be from the USA, and I’ve found barely anything on the same topic from UK channels. Anyway, if you watch one of the explainer videos it makes perfect sense to me as to why you would do this, especially on a car as complex as the FFRR. A great example of a how-to video is here: How to install the big 3 upgrade

I’ve had a few starting issues since I got my 4.4TDV8 and having replaced the battery, starter and now the alternator, I can’t see any reason why I wouldn’t finish it off by upgrading my cabling to the best possible solution. I don’t just want to get the vehicle to be ultra reliable, but I want to bring it up to a superior spec befitting of the car and one that will help maintain its longevity. The question is (as an electrical systems beginner): what am I missing? I’d be really keen to hear your thoughts. Especially, why are there not more posts on this kind of upgrade on the forum as I can’t find any, but I can find lots of posts on electrical starting/charging/running problems?!

So, a few things to note if I am going to do this properly (do thoroughly, upgrades last longer than car etc):
- I would use the best possible wiring and connectors I can get for the job, probably 35mm2 (345A) welding cable with pure copper connectors for maximum conductivity/efficiency.
- All wiring-connector interfaces shrink-wrapped for max protection.
- All engine and chassis mating surfaces wire brushed for best possible contact, then Clearcoat so sealed/protected thereafter.

So, the big question is: why wouldn’t I do this?

The main barrier I can see is the +ve cable, due to battery crash blow-off thingy and access to the rear of the alternator when in situ. The latter alone may make that upgrade one for when I next have cause to get that far into the engine with a fan cowl out job like pulleys, belts or water pump. However, the other two -ve cable upgrades seem like a no-brainer, especially given how the existing earth/ground cables are and the problems this can cause if they’re not 100% up to the job.

I’d really appreciate thoughts, especially from those who have more car electrical knowledge than I. If it is such an effective upgrade then why aren’t more people doing it or talking about it?

Taking this one step further, I’m even thinking about the potential improvements that a specific earth cable attached to the alternator case might bring; a cable terminal under one of the mounting bolts would be easy to do and link that either to the chassis or even directly back to battery -ve. I would go as far as to say if doing it for the alternator then why not the starter motor case too, as both components are earthed through direct contact with the engine block. The logic being the better the earth to key parts of the electrical starting and charging system, the more optimised the performance of those components will be.

I can only conclude that either:
1. This is completely unnecessary as LR did such a good job designing the 4.4TDV8 in the first place
2. This is a terrible idea as it’s unsafe/dangerous or will more likely cause problems than improve the design
3. I might actually be onto something here and, stand-fast the obvious barriers already highlighted on the +ve cable side, the -ve cable upgrades would be simple and, quite possibly, very effective!

I am all ears and really happy to try and bottom this out with some science-based arguments or professional knowledge. If there’s any auto-electricians on here then I definitely want to hear from you. If this is something that would be useful to all, then maybe this could even become a wiki and I would happily do a specific upgrade post to summarise the knowledge gained and include a how-to if I proceed

Never had to change 1 or 3 but as a matter of course l always fit a supplementary 2 to any vehicle l buy. Manufacturers always seem to fit engine / body / chassis earths in the most unfavourable positions which inevitably cause problems down the line due to corrosion.

Thanks for the input! I agree that engine block to chassis is the easiest and likely biggest ‘upgrade’ from the factory parts. I will be doing this as a minimum without any doubt! Andy

2010 4.4TDV8 Vogue SE in Santorini Black with Ivory interior
2017 Audi SQ5 3.0 V6T Quattro in Volcano Red
2001 Audi Allroad 2.5 TDI manual with low-range in Highland Green. Currently SORN whilst undergoing some serious restoration!

If it's not broken then why fix it? By all means check and clean any connectors but the wiring itself will be designed to carry more ( much more) than the maximum load as a designed in safety margin. 2012 TDV8 Vogue (L322)

As above, if anything I’d probably check and clean the connections, but unless I physically saw anything wrong with the wires I doubt I’d bother changing it all 2009 (2010 MY) 5.0 Supercharged Autobiography
2007 TDV8 Vogue SE
2005 BMW E63 645ci
2024 Porsche Macan

JayGee wrote:

]but the wiring itself will be designed to carry more ( much more) than the maximum load as a designed in safety margin[/b].

I don't think that's true.

Short runs of even the smallest gauge cable are capable of taking hundreds of amps. The most you're going to get anywhere on these vehicles is 900 amps, as that's what they crank at. 6mm core diameter is all they need to be and they're much more than that.

The best thing you can do with these cars is fit an AGM battery.

And copper rot isn't so much an issue on cars - copper wire can be dead on a boat in a salt water environment in 10 years but, cars don't (or shouldn't at least) live in salt water. 2015 Range Rover Autobiography 4.4 SDV8

You might be right, I'm no electrician but my 1st 3.6 needed a new underbonnet harness fitted at 8 years old because of corrosion issues

I replaced the loom on mine a couple of years ago as there was some internal corrosion on the cabling bit of a pig but all doable.
I had the same issue with my p38 battery to starter cable had internal corrosion must be something I do