VW Electrics battery to dash

Penned by Covkid

Upgrading power to dash and headlights

There could be several reasons why you might want to upgrade the power cable to dash, but for anyone fitting headlight relays or needing a really good connection at the dash without voltage losses, this is the ultimate heavy-duty way to do it. I don't for a minute suggest that this is the only way, but this method does make a neat job of it and solves a few problems along the way.

Your battery may be under the seat or in the engine bay, but assuming you've also upgraded main power cables (see: http://wiki.club8090.co.uk/index.php/VW_Electrics_main_cables if not, do that first) then you will probably want to do the same at the front.

The existing cable to the ignition switch and fusebox in the T25 (Vanagon) was quite adequate at the time the vehicle was in production, but a 6mm cable is somewhat modest and not suitable for all the upgrades we tend to fit in order to match modern driving. Its akin to sucking treacle through a straw. It is not unusual for an ageing blower motor to put enormous strain on the existing fusebox, causing wires to heat up or even melt if fuse sizes are incvreased. Certainly if you want to fit headlamp relays, you'll need to at least double the existing 6mm cable. Rather than do that, its simpler to fit a new supplementary cable back to the battery that can meet the demands of all the power-hungry stuff and take the load off the fusebox.

Firstly, if you reorganise things properly, you'll lose the mutitude of extra cables that can end up fastened to the battery positive terminal. Most campers seem to end up like this with several cables crammed together at the battery which can create the potential for sparks/shorts between other things - particularly the underside of the driving seat. Whilst you can lay carpet across etc, it is not ideal and it all starts to get messy and unreliable. Its therefore better to relocate these cables in a secure junction box and only have the one single cable to battery positive. From the junction, you can run a new thicker cable to another junction box under the dash.

I chose to use 16mm 110amp cable for maximimum surface area but a 10mm cable would be perfectly adequate. As stated, VW used 6mm for the original shared feed to ignition and to supply interior lights with ignition off. Everything up front effectively runs off that 6mm cable and if you start adding items that require current, it can struggle. For this project, you leave the 6mm feed exactly as it is, but run the heavy stuff like headlights, off the new mega-cable. The relay circuit for headlights is covered elsewhere - you just tap into the new junction box for a good supply.

Materials

The new cable I used is similar to the upgraded power cables used on high-powered stereos, described in some places as simply 'battery cable'. In any event, its multi-strand and very flexible. I bought a complete reel of it (just under £40).

This is the stuff I used - 16mm 110amp (20p coin for reference):

For the terminal block, you need to look at marine/auto terminal blocks in the 300amp range. You'll never draw that much ofcourse but there are many more terminal blocks out there that are only rated for low-draw stuff and they often rely on little more than philips screws to hold cables firm. You do NOT want those - too lightweight for this job. The junction box must also have some kind of lid/cover to protect against accidental shorts.

The type I used (above) consists of two 8mm nuts and bolts house in a black insulalted case with a snap-down lid. It doesn't take up too much space and can be screwed/bolted to a convenient position - say inside wall of seat mounting base or the inside of engine bay. Its robust enough and more suited to heavy battery cables. You'll need two of these - one for battery end, and one for under the dash. I paid under £12 for both of them including postage.

See photo below of terminal block with cables in place and lid off:

If you look, the thin red cable on right is the original 6mm cable to dash (hard to believe I know). On the left is the uprated one which now runs to the terminal block under dash. Beneath these cables (extreme right) is the now single cable to battery positive and the other thick green/yellow wire (ignore the colour) goes to starter - four cables in all. If you have a split charge relay there will be at least five cables. There is plenty of room for more should you need them - such as a quick battery plug connector to make jump charging/starting easy or a mains charger.

Fitting a box like this means all those annoying wires that originally terminated at positive terminal can now be fastened inside the terminal block out of harms way, with just one to starter battery. It makes removing the battery a lot simpler too. I use quick-release clamps on mine.

For reliability, you'll need to source good quality connectors for this - soldered 'Copper Tube Terminals' (as below) - not conventional crimp ring connectors, and use proper shrink tubing:

Toolstation do the solder-on lugs cheap (branches everywhere and in some places they're based in Wickes): http://www.toolstation.com/shop/Electri ... ugs/p32996

I bought 8mm ones (correct size for terminal block I used) in 6mm, 10mm and 16mm sizes (10 of each in pack) - £6.35 for all of them (30). Its well worth buying all three bags as they're so cheap at Toolstation and you'll always want one in future. Theres also enough thread in terminal block to stack washers between connectors if you want to space them better.

Part numbers for Toolstation lugs: 55534, 87832, 11930

You'll need 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.

I discovered 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 - no probs. Well worth buying one next time they come in if you don't have a gas soldering iron. Very useful. Forget how much it was - prob under £15.

Above: All cables mounted in junction box screwed to side of seat base. One cableb to battery positive from this box.

The best way to route the cable would be underneath the vehicle, suitably tied up out the way (always use grommets on any holes you make) and bring it up behind dash and ideally as short a run as possible. You could run it inside but its awkward to hide and not ideal under carpets! From there (with fuses) you can supply headlights or run all the heavy stuff like rad fan & blower etc and leave the existing fusebox running on the 6mm stuff for low-draw items or even install an extra mini fusebox - up to you.

Conclusions

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 at all, and even on standard bulbs you'll see the difference but throw in some Osram nightbreakers, relays and modern 7" headlight units and you won't want for much. Providing a good source of power can really transform the lighting out front as well as reduce the ever-increasing load on an old fusebox. Re-route the radiator fan and blower unit (with fuses) to the new cable and your existing fusebox can go into sleep mode on the original 6mm feed. Well worth doing.

Covkid