voltage drop to fuse box.

[123-jn]

Hi everyone, just wondered if anyone had any thoughts on the following. I have just replaced the cable from my alternator to the starter terminal with some nice thick 10mm cable. The cable already fitted I would guess was around 4-5mm at best. Considering the alternator has a max output of 70 Amps surely the original cable is not man enough!! Anyway the voltage at the alternator is 14.2 V and at the battery we now have an increase from 13.8 to 14.1v. Now I tested the voltage at the fuse box with the engine running and we have only 13.9V. So I have lost 0.2 V on the way. I decided to look at the cable from the battery to the fuse box and was suprised to see a cable that looks no bigger than 5 or 6mm sq at most which has a current capacity of around 42 amps. If I add up the current used by my twin lights on main beam and add the heater motor and other lights, wipers etc The current draw is around 40 amps. This cable even is new condition is very close to the maximum it will need to carry. I propose to beef this up with new cable of 16mm sq which should allow a max current of 80A over a short run This should hopefully get rid of my voltage drop and be safer?
Anyone done this?

[keytouch]

You could do the headlight relay mod with new wires run specifically, to give those a boost at the same time as freeing up some capacity in the existing wiring.

[California Dreamin]

This is something John (Ghost123) has been banging on about....and the second poster has a point, the full relay mod takes separate feeds straight from the starter battery which removes 20 amps load from fuse box main feed.

Martin

[CovKid]

I've already done this. The existing cable to the fusebox was quite adequate at the time the vehicle was in production but only just copes with all the upgrades we do now. My cable to the dash is a slightly smaller version of the guage I use in the WIKI 'main cable upgrade' I penned a while back. Its a multi-stand 16mm 110amp cable for maximimum surface area. Its similar to the upgraded power cables used on high-powered stereos, described in some places as simply 'battery cable'. I bought a reel of it (just under £40). It terminates at an insulated ring-post under the dash and from there to the fusebox. Headlights now run independently of the stock fusebox (which now only handles low loads) from this same post.

In fact the only change needed now is to fit another insulated post under the drivers seat to reduce the amount of cables to the battery clamps (bit cramped in there right now). Its a lot of upheaval and expense to do all this, but once done, reduces voltage drop to the absolute minimum, or at least in a way that is affordable. It also matches that seen in more modern big cars.

I should point out, this is probably not neccessary for most owners, but its certainly an option if you want to ensure your headlights get all thats possible. You could get away with less than 110amp cable to be honest - 80 amp would be absolutely fine and easier to work with. Cheapest way to do it might be to cut up a long jump cable and solder/crimp ring terminals on. Wilco do jump cables at very reasonable cost. From alternator to starter and battery I used thick 200amp stuff.

This stuff - 16mm 110amp (20p coin for reference):



For posts, look for 'marine busbar' or similar on ebay. These would do:

http://www.ebay.co.uk/itm/Automotive-Ma ... 4ad874d6a4" onclick="window.open(this.href);return false;

[ghost123uk]

This is something John (Ghost123) has been banging on about....and the second poster has a point, the full relay mod takes a separate [+ve] feed straight from the starter battery, which removes 20 amps load from fuse box main feed.

Yep, that is what I did

[CovKid]

Or just run a beefier cable altogether and supply both.

[123-jn]

Thanks for the replies, I think I may join in and add a new cable to the fuse box probably 16mm sq . I guess my starter to batter cable seems ok as the voltage drop is so low and the starter turns nice and quick.

[CovKid]

16mm is thick stuff though. Hunt for some 10m (80amp)- Plemty of overhead and a lot easier to install and work with.

[123-jn]

I took the battery out today and can see some mild melting of the insulation on the first 3 inches of the feed wire to the fuse box. For now I shall cut it off and solder a new ring terminal to it, then I think I will run a new 10mm feed direct to a post under the dash to feed the headlights. This should take some load off the fuse box. I will use the old circuit as a trigger for two relays. One for main and one for dipped. I will use a 40 amp fuse at the battery end and then protect each relay with 20 amp for dipped and 30 amp for main. (I wasnt going to go down this route but I think it is the best to avoid further overheating.)

[CovKid]

This may be better for under the dash

http://www.ebay.co.uk/itm/Automotive-Ma ... 338470217b" onclick="window.open(this.href);return false;

[123-jn]

I like that insulated twin post thing covkid, I will order one of those for the headlight upgrade. For now I have rewired the fuse box with new 10mm sq to the battery and now have no voltage drop whatsoever. With the engine running and side lights on I have 14.4v at the battery and at the fuse box now. With headlights on it drops to 14v which I reckon is pretty good. If I put main beams on as well I'm down to 13.8 not sure how this compares to others but it's enough to charge the battery still!! The headlights seem a bit brighter now so I'm not sure I need the relay upgrade yet but we will see how it goes.

[CovKid]

I would also recommend another terminal block under drivers seat (if your battery is there) as you can then sort the multitude of cables that may terminate at positive battery clamp. This is often a bone of contention for many owners. If you terminate everything properly like this, you'll only have one cable to battery positive. It also makes removing/replacing battery far easier and significantly reduces the chance of shorts. You could even fit quick-release battery clamps as I did.

Fit the second terminal block under the dash via a beefy cable and you'll have a raw source of power for heavier items like lights, blower, fan etc (each fused obviously) and virtually no voltage drop at all, other than the little you might lose in a thick copper cable (insignificant).

That would then free up much of your fusebox for low-draw stuff. Admittedly its a more 'heavy-duty military' approach but much tidier and infinately more reliable. In combination with things like headlight relays, its a real winner.

Since I replaced all the main cables, much of this has become obvious and when you look at modern vehicles, its pretty much the norm now. I'd still fit headlight relays but consider upgrading wires to headlights too if budget allows.

Finally, if you really want to light up the road for relatively little outlay, follow this: http://forum.club8090.co.uk/viewtopic.p ... 8&start=45" onclick="window.open(this.href);return false;

[Oldiebut goodie]

You can get batteries with 4 terminals for those that want numerous connections. I have an old one in the workshop, I'll dig it out and measure it up and see what make it is. It is handier for diesels where you would have difficulty adding a terminal post/connector somewhere sensible.

[CovKid]

I suppose you could mount the terminal block somewhere on the engine bay wall but I agree, its not exactly flush for room that end. At the front, it just goes under your seat.

The other thing that occurs to me is that because a heavy duty battery connection is then available under the dash, technically (providing the cable is thick enough (I went overkill on this), you could jump start via there or even jump start someone else or even put power to a winch, all sorts. In any event, a cable like that beats the pants off that fitted by Volkswagen and you no longer have to think about running extra cables to battery from then on. job is done.

The ebay link to the terminal block (below) was also best I could find on price if buying two as postage is combined then (£11.98 the pair inclusive). There are other types but they tend to be too small, or rely on a screw to hold cabes ends in place, or are exposed and have the cheek to charge extra for a cover.



Obviously youi'll need to source good quality connectors - 'Copper Tube Terminals' (as below) - not conventional crimp ring connectors, and use proper shrink tubing:



Toolstation do them (branches everywhere and in some places they're based in Wickes): http://www.toolstation.com/shop/Electri ... ugs/p32996" onclick="window.open(this.href);return false;

I bought 8mm ones (correct size for terminal block) in 6mm, 10mm and 16mm (10 of each in pack) - £6.35 for all of them (30). Theres enough thread in terminal block to stack washers between connectors if you want to space them better.

Part numbers for lugs: 55534, 87832, 11930 - some places charge a WHOPPING £3 for ONE lug terminal so bear that in mind!

Needs a mini blowtorch or gas soldering iron, flux and solder to fit them but not too tricky and best connection you'll get. REMEMBER to slide shrink tubing on BEFORE you solder on lugs, then slide it back over join and shrink. Incidentally, I discovered today that although I have a small blowtorch, the ALDI workzone gas soldering iron (with soldering bit removed) will also do the job. Did five lugs on the trot with that - not probs. Well worth buying one next time they come in if you don't have access to a gas soldering iron. Forget how much it was - prob under £15.

Below - terminal block under seat about to be fastened down.



I guarantee if you go to all this trouble (perhaps a couple of hours max), voltage drops to fusebox or anywhere under the dash won't be a problem, but the headlight harness may need upgrading to really get the best out of it.

Some might consider this too much work but I can't see the point in messing about with small stuff and scimping, if you want a really good supply at dash end and more reliable and tidy connections at battery positive. This supplies all you could need and probably more.

Now WIKI'd: http://wiki.club8090.co.uk/index.php/VW ... ry_to_dash" onclick="window.open(this.href);return false;

[Oldiebut goodie]

You can get batteries with 4 terminals for those that want numerous connections. I have an old one in the workshop, I'll dig it out and measure it up and see what make it is. It is handier for diesels where you would have difficulty adding a terminal post/connector somewhere sensible.

It was an Ultra Plus battery from Alpha, 190 high, 170 wide and 280 long, I will have to scrutinize it closely to find any numbers but had a quick look on the Alpha site and couldn't see it there.