Battery cable and alternator upgrade questions

[Faster Behr]

I'm replacing the existing 2/0 gauge (70mm²) battery cables on my Fairlady Z project. They are far too big and are improperly jointed. Our 280Z has 4 gauge factory wiring which equates to 21mm² - but the cables are arguably shorter due to the battery position (LHD) so there is little voltage drop. I was planning on using 25mm² which I happen to have kicking around. I'm keen to know what everyone else has used?

My battery has clearly been over charging in the past. Rather than mess around I'd like to update the externally regulated alternator to an internally regulated replacement. I'll be adding a fuel pump and some small additional electrical loads so the more power the better. I have read through a few articles but I'm struggling to understand A) what alternator I need and B) what I need to do to alter the wiring - there's mention of a plug conversion that some people have used? Any help on this would be very welcome.

 

[Rob Gaskin]

The alternator swop is straightforward as long as you can source a 280zx alternator and the special plug to enable internal regulation and prevent 'running on'. It's well covered on this forum.

 

[toopy]

This is the plug in adapter you need to bypass the external regulator, check the connection on your existing regulator is the same first though.
https://www.thezstore.com/page/TZS/PROD/classic10b04/12-4067

Most people have used a 280zx 60 Amp alternator which i believe is plug and play with the above adapter, there are also threads detailing the use of Mazda MX5 alternators or similar as well.

There never seems to be any mention of upgraded wiring to compliment the higher output, but I'm assuming peak voltage is rarely needed anyway unless your adding high power additional equipment, and therefore for the most part the existing cabling can more than cope.
It's obviously prudent though to check the condition of the existing wiring properly, especially underneath the fusible links and the links themselves, plus the spliced joints in the original engine bay loom if you can find them.

25mm2 cable is around 100 amps capacity i believe.

 

[Rob Gaskin]

I used this battery cable. Multi core for flexibility - it's about 9mm dia core.

Make sure your -ve is well 'grounded' from the bellhousing and with a smaller cable at the battery ( to body).

 

[Faster Behr]

That’s 50mm2 cable there Rob. You’d need a bank loan to buy that in this current economic climate

Thanks for your responses both. I’ll check all this out when I’m back with the car in the morning.

 

[Pondo]

I know BAE sell these.

 

[Rob Gaskin]

That’s 50mm2 cable there Rob. You’d need a bank loan to buy that in this current economic climate

Thanks for your responses both. I’ll check all this out when I’m back with the car in the morning.

I ran it from my battery through the bulkhead (well insulated) to a 'cut-off' switch on the centre console and then to the starter so a long run. It was a rally car.

I soldered the terminals (not crimp).

What length of cable do you need?

50mm2 345 A Amps Flexible PVC Battery Welding Cable Red 1 - 100M M Lengths AUTO | eBay

50mm2 PVC Battery / Welding Cables. - Single core battery & welding cables.Highly flexible whilst remaining seriously durable. PVC50 630/0.30 50 345 13.95 Black, Red. ALL CABLE IS CUT / WOUND TO YOUR CUSTOM LENGTH AS REQUESTED.

www.ebay.co.uk

 

[Faster Behr]

I only need to cross from the battery to the starter terminal so it’s just over a metre. The 25mm that I’ve got is good for 115 Amps so I’ll give it a whirl. It’s such a short run so the resistance and voltage drop will be tiny.

I’ll have a look at the wiring into the voltage regulator tomorrow to see if it looks to be compatible with the diode plug. I need a speedo drive seal kit so I’ll see if I can combine and get both from MSA too.

 

[Rob Gaskin]

I only need to cross from the battery to the starter terminal so it’s just over a metre. The 25mm that I’ve got is good for 115 Amps so I’ll give it a whirl. It’s such a short run so the resistance and voltage drop will be tiny.

I’ll have a look at the wiring into the voltage regulator tomorrow to see if it looks to be compatible with the diode plug. I need a speedo drive seal kit so I’ll see if I can combine and get both from MSA too.

What happens if you have to crank the engine for a while? I think you may get the same effect as cheap 'jumper cables'.

 

[Rob Gaskin]

Are you coming to Donington this weekend?

 

[Faster Behr]

Here’s a few pictures:

 

[Faster Behr]

Are you coming to Donington this weekend?

Me, sadly no. I’ve got 0/4 cars working!

 

[Rob Gaskin]

Me, sadly no. I’ve got 0/4 cars working!

You could come along anyway and meet us.

 

[Faster Behr]

You could come along anyway and meet us.

I'd rather have my head under the bonnet at the moment if I am honest, plus I have intermittent work commitments. But we will make some shows later this year for sure.

T3 emailed me last night to say they have finally got my front hubs machined for the RB "Golden Retriever" - ordered in November - so I'm hoping to have that on the road for the summer as well as the Fairlady.

 

[Rob Gaskin]

Looking at your pictures you appear to have an ammeter 'shunt' under the voltage regulator.

I've seen those on a 260Z.

 

[Faster Behr]

Looking at your pictures you appear to have an ammeter 'shunt' under the voltage regulator.

I've seen those on a 260Z.

Would the shunt not be present on all early cars with the ammeter rather than volt meter Rob?

 

[Rob Gaskin]

Would the shunt not be present on all early cars with the ammeter rather than volt meter Rob?

No, I've had three 240Zs without (edit: that shunt box). Only my 260Z had one of those.

 

[jonbills]

if you have an ammeter, you have a shunt.
on 240z, shunt was part of the ammeter apparently

what is a "shunt"

Ah so my car is missing it's shunt so .. 1) my ammeter doesn't work (I thought it was busted!) 2 I don't know what one looks like (cause it missing remember?) , any one have a picture of their shunt? 3)I have no idea where to get a replacement unit. 4) could one conceivably build one? Using the s...

www.classiczcars.com

 

[Rob Gaskin]

if you have an ammeter, you have a shunt.
on 240z, shunt was part of the ammeter apparently

what is a "shunt"

Ah so my car is missing it's shunt so .. 1) my ammeter doesn't work (I thought it was busted!) 2 I don't know what one looks like (cause it missing remember?) , any one have a picture of their shunt? 3)I have no idea where to get a replacement unit. 4) could one conceivably build one? Using the s...

www.classiczcars.com

Yeh, I have read that before Jon.

My point was that I was surprised to see a shunt box on this 240Z, perhaps that is special to the Fairlady?

So what is is different on the electrical side?

 

[Albrecht]

Yeh, I have read that before Jon.

My point was that I was surprised to see a shunt box on this 240Z, perhaps that is special to the Fairlady?

So what is is different on the electrical side?

It's an early 1974 production dated Fairlady Z-L, so it features many of the electrical systems updates seen on an early 1974 production dated UK market 260Z (plus many Japan-specific extras).