24v Wiring Questions

[marmel]

I have a 24v Safari that I am in the process of modding.

Part of this process has involved completely stripping the interior to sort out some rust issues in the roof. When the interior was stripped I found a few rust issues in the rear wheel wells as well so got them sorted at the same time.

Anyway this is a great time to get wiring in place for mods.

This is what I have planned:

- 36" LED lightbar on roofrack and 20" LED lightbar on bullbar. LED work lights on rear and passenger side, also mounted on roofrack. These are all 24v capable.

- 24v Warn winch

- 24v air compressor mounted in rear somewhere

- 24v to 240v transformer in rear to provide mains power if required

- GME TX3100 mounted in centre console

- Stereo moved to dash pod mounted on top of dash

- Drawer setup in rear

- Carling switches to run everything above mounted in space where stereo sat along with Auber EGT and Boost gauges

Anyway I have a good idea on how I want to wire everything up but have a few questions:

I was thinking of running a fused power distribution block from one of the batteries. I think if I then earth any of the equipment it would supply 24v anyway due to the dual battery setup. Would it be wise to run some accessories from one battery and then maybe the winch and compressor from the other?

I don't think the LED lights would need a relay as they tend to draw low amps, especially from 24v but I would assume a relay would be needed for the compressor, power transformer and winch?

I will run inline fuses in everything either via the power distribution block or normal inline fuses. Do these need to be as close to the battery as possible?

I guess if someone can tell me how the dual battery system in these work that would be a big help. I don't want to be putting a lot of drain on one battery only. The battery balancing kits I have seen online are designed for 12v vehicles using an extra battery for accessories, not native 24v vehicles.

I plan to start a thread in the mod section when I get started in the next week or so and will post plenty of pics to help out others that might be doing something similar.

[coxsy]

Unless it's a 24v radio a nice large 24 to 12 v inverter is what you need

[Mehrts]

All fuses go as close to the source as possible.

This means if there is a short in the wiring at any point in the circuit, then it is all protected.

Whereas, if you had a length of wire, and then the fuse, if there was a short circuit in this, then the wire would melt and fires and other bad things could happen due to there being no protection for it.

[CLUMZ1]

Batteries run in series.

Drivers side battery is "high" side, get your voltmeter on the (+) terminal to chassis ground it will measure 24v.
(Measure just the terminals on the high side battery and you'll get 12v.)

Passenger side battery is "low" side, get your voltmeter on the (+) terminal to chassis ground it will measure 12v.

Don't run any accessories to the low side battery unless you have a charge equalizer like the ones made by red-arc.
Discharging your low side battery with accessories will cause the high side battery to overcharge. (Hence using an equalizer)

[kbushnz]

One thing to watch with the 24V Nissans... is the wiring is smaller than the 12V version. As the 24v system carries lower amps...Hence lighter gauge wires.
So if you plan on running hungry accessories upgrade the wiring...

[T-mo]

Great idea pre-running the wiring, saves a lot of time.

Firstly, an this I cannot stress enough; NEVER TAKE 12V OFF THE HIGH SIDE OF THE LOW BATTERY OR THE LOW SIDE OF THE HIGH BATTERY. It's really bad for them and can cause more issues than just overheating, particularly when you get into the science behind the battery chemicals and electronics.
To answer your questions:

1. As CLUMZ1 stated, a 24V vehicle with two batteries runs a high and a low battery. This means you cannot run something off one battery and something else off the other one. They are wired as part of the same circuit. You can put a 24V distribution bar off the high battery and run all your 24V's off that. (Noting answer 3 below)

2. LED lights are fantastic for two reasons (one you correctly stated):
a. They have a significantly low current draw. In fact when you compare it to traditional bulbs and HIDs its almost like they don't draw anything.
b. They are multi-voltage, meaning if you every sold your truck but wanted to keep the lights you could fit them to a 12V truck (Surf/Terrano etc.)
However, just because they run at a low current doesn't mean you shouldn't relay them. Fuses most definitely, relays have there uses but its personal preference for LEDs. Believe it or not running relays can make the wiring simpler and easier, obviously its more expensive because you have to buy the relays. Anything of a high current draw like a winch or compressor needs a fuse, relay and a separate supply lead. Due to the current, heat and loses produced. Most wiring kits for these include the bits and bobs needed including drawings and installation instructions.

3. Run fuses for everything. As already stated as close to the source as possible. (In fact one circuit in my truck as four fuses between the batteries and the accessory, due to the way I wired it) They save a lot of time fault finding problems and can protect everything else electrical in you truck should you happen to upset the electron.

4. As stated above, high and low batteries. If you aren't tapping the centre of the batteries and running good batteries that are the same type, size, age, condition etc. and your alternator is running right, your batteries will stay level. The biggest downfall for a 24V truck in my eyes is jump starting one isn't normally possible due to the smaller number of 24V vehicles around. (NB: Though it is possible to jump a 12V car from a 24V, I wouldn't recommend it)


Also, as coxsy said run a 24-12V converter (A decent one) to use 12V accessories. There will be one fitted to your truck but it runs at basically maximum capacity from factory. It runs some of the instruments in the dash and their senders and the radio, however a decent aftermarket radio will cause it to fail and cut out. I'm running one of these in mine - http://www.jaycar.co.nz/productView.asp?ID=MP3066. You'll need one to run the GME radio anyway as they are 12V. I run a few other 12V bits off mine too as 12V gear tends to be cheaper than 24V gear, as most 24V applications are built for buses, trucks, ships, tractors etc. The cost of running one is cheaper than a Red-arc equaliser too.

If you need a hand with figuring things out PM me and I may be able to help. I work in the electrical engineering industry, so can show you how to calculate things out and give advise on circuit and wiring ideas.

[marmel]

Thanks for the replies.

What are your thoughts on running a battery charger and a separate battery to run the accessories?

If I want to run quite a few things including possibly a 12v fridge would it be better to take this approach?

Red arc make some suitable chargers, like this one:

http://www.offroaddownunder.com.au/inde ... Itemid=315

I have a couple of stereo amps I was going to install and using 24v-12v reducers with their small gauge wiring might not be suitable.

[keithal]

for that price i would be installing a completely seperate 12v system tbh

[T-mo]

I tend to agree with Keithal, if you want to run an accessory battery and charger, you might as well fit a whole second battery system. Especially if you want to be running fridges, big amplifiers and stereos off it.

It is possible to mount an extra belt driven alternator under the injector pump, I've seen extra bits tucked between the factory alternator and the air-conditioning pump too. Or underneath the air conditioning pump.

Its simpler and you don't need a $500 piece of electronics that can pack up on you, hearty gauged wires and a mechanical alternator will last a lot longer than a DC-DC charger. Getting a decent alternator should be cheaper than a charger plus it will produce more amperes and shouldn't add any noticeable extra load to the engine.

[marmel]

This morning I managed to score a brand new Redarc charge equiliser off trademe for $99. Retail is about $500 so i couldnt pass it up. They enable you to get a good 12v source whilst maintaining balance between the two batteries. They seem to have pretty good reviews online.

They are also used to charge a third battery which is what I will do. I will then have the option of changing to an additional alternator later if I want.

My aircon is lonv gone so I have room there to cbuck another alternator in if I need to.

What gauge cable should I look at running from the engine bay to third battery which will be behind the rear seats? Do I need to run an earth as well or could I earth to the body?

Thanks for the help so far.

[eins]

If you not using your aircon consider converting compressor to on-board air you won't regret it, it is easy to do and gives a much better air supply than any 12/24 compressor, especially with small tank and pressure on/off switch.

[keithal]

id be running 35mm2 welding cable at a bare minimum
but in all reality the bigger the cable the less voltage drop you will get

make sure what ever cable you use is a multistrand cable as it handles vibrations and movement much better than a cable with fewer large strands

another thing it would pay to do is put a circuit breaker or fuse at each end

[CLUMZ1]

another thing it would pay to do is put a circuit breaker or fuse at each end

Why the second fuse? Shouldn't it be one as close to the positive source as possible?

[T-mo]

another thing it would pay to do is put a circuit breaker or fuse at each end

Why the second fuse? Shouldn't it be one as close to the positive source as possible?

I agree, second fuse at the battery end is redundant. In saying that you need fuses on the outlets of the battery to your accessories.

Cable gauge does depends on the length of the run and how many amperes you will be drawing off it. The smaller the wire is the hotter it gets and the more losses you have. I'd be running 1 gauge. Depending on load a 4 gauge may do it but you'd probably get losses.

Earths need to be as short as possible. Preferably about 600mm or shorter, earth it to the chassis or body (chassis is better) with a big nut & bolt and ring terminal. The gauge of the earth wire should be the same as the positive wire.

Good score on the Redarc. The best place to run the positive cable is through the chassis rails, some times its hard to feed it through but it gives it a lot more protection (obviously). Consider using an Anderson Connector (http://www.jaycar.co.nz/productView.asp?ID=PT4424), close to the battery to aid in disconnection, at the battery end. If you wire it the correct way it means the +12VDC lead is covered when you take the battery out.

[keithal]

Why the second fuse? Shouldn't it be one as close to the positive source as possible?

I agree, second fuse at the battery end is redundant. In saying that you need fuses on the outlets of the battery to your accessories.

you have 2 positive sources
the battery is one and the charger is another
if you only had a fuse at the charger end there is still a live source (the battery) that can short out and potentially cause some major damage

[marmel]

The Redarc charge equaliser has wires coming out of it that are perhaps 3-4mm diamter to make the connections. The instructions at Redarc advise to place it as near to the 12v source battery as possible, the engine bay being the obvious choice.

Now im thinking if im going to be running 50mm welding cable to the third battery I will be charging then somewhere close to the Redarc unit im going to have to connect this huge cable to this much smaller one.

Isnt that going to prevent any benefit from running the large cable back to the third battey and isnt that short section of thinner cable going to get quite hot?

Just wondering what is the best way to do the connection.