Batboard

Hi, all...

Does this sound righteous, reasonable, and Batlabs-worthy?

To power:

25A --- 2 high-power MCS2000's (VHF & UHF), one keyed
20A --- Cencom controlling two 8-module TIR3 Dominators & an SP314
20A --- 1 Mini-ITX form-factor PC with 10" monitor
15A --- Various accessories (cell amps, scanner, GPS, power points, etc.)

Totals 80A. 80A * 1.25 = 100A capacity required for main power bus.

Main power bus should be 1/0 gauge from battery to the block in the trunk, where RF decks, Cencom, computer, and most accessories live. The bus will be protected near the battery with a high-amp fuse (like those found at Waytek, 100A).

From trunk block, 10 ga. secondary power bus forward to cab block to power scanner, power points and other low-current accessories.

I'd hate to have to go to a stereo shop for a piece of 1/0 ga., but I can't seem to find anywhere that'll sell it to me in short lengths (15-25 feet). Places like Waytek have some neat stuff available, but I really have no use for (and don't want to waste the money on) 100 feet of 1/0 in red and another 100 in black. Perhaps the stereo shops'd have the tools to crimp terminals on the ends of 1/0 ga. as well... dunno... stereo shops tend to attract kids, and we all know how kids' installs usually turn out. I might take the vehicle to the local PS equipper's install shop, but I'm already familiar with their work.

Anyhow... just want to make sure that I'm not over/underdoing this or missing something. Many thanks in advance for any input or opinions. (And apologies in advance to the Admins/Mods if I dropped this into the wrong forum.)

Well, the first question I'd ask is, does your vehicle use the chassis/frame as the ground reference? If so, that makes your life a bit easier.

When calculating wiring sizes and lengths, not only do you need to take into account the maximum current, but also the voltage drop of the wiring.

The reason I asked about chassis/frame ground is that if you can do it that way, it essentially turns your negative/ground side return from your main power distribution bus into a huge fat pipe. The way it was explained to me is that electrons "like" to travel along the outer surface of your wire (I know it's cheesy but it's early, bear with me), therefor the more surface area of your conductive material you have, the less voltage drop there will be. Your vehicle's chassis/frame exposes a huge amount of surface area, and you really don't have to worry about length of wire due to routing.

So, with that out of the way, let's do a few rough calculations. We'll presume that you can use chassis/frame as a ground reference, and therefore the bulk of the high current cable you need to run is the V+ lead between your battery at the front of the vehicle and your main bus in the trunk, and conservatively estimate that it'll take about 20 feet of cable to do it.

Remember, because we're using chassis/frame as ground, this not totally but effectively eliminates non-trivial voltage drop from our calculations.

Here's the approximate resistance and voltage drop for a selection of wiring sizes:

0 AWG -> 0.0020 Ohms, 0.2v
1 AWG -> 0.0025 Ohms, 0.25v
2 AWG -> 0.0032 Ohms, 0.32v

I don't have the calculations for 1/0 AWG handy, but these should do.

So, under maximum theoretical load of 80A w/ 125% overhead, I'd say you could probably get away with 1 AWG. Presuming the vehicle is running, a 0.25v drop from 13.8v gives you about 13.55v, which should still easily be acceptable for your 12v applications.

Now, if you plan on running a lot of this equipment with the vehicle parked and not running, I would definitely encourage the addition of a second battery in the rear compartment, along with a battery isolation system. This is due more to the current draw than the voltage drop issue, although if you do do a secondary battery, you may be able to reduce the size of your wiring, since the equipment will draw off the aux battery and the V+ run from the primary battery/alternator would keep the back battery charged.

Regardless of which way you go about doing it, you'll want to make sure that your alternator is appropriately sized, not only to provide power to your equipment when the vehicle is running, but to be able to recharge one or both batteries after a period of sitting parked.

Your fuse ideas sound ok. I think I would increase the main bus fuse to at least 150A, and I would add a second one on the negative side of the bus, in the wiring from the negative bus to chassis/frame ground, and close to the bus itself.

Hopefully all this info will provide to be usefull. The calculations I used and also a very good article you may find usefull were obtained from this page:

http://www.stealth316.com/2-wire-resistance.htm

Also knowing what kind of vehicle this is may bring some input from those that have worked on them before, and some other suggestions.

Good luck with your project!

As far as the wire, I have two sources:
http://www.solar-electric.com/ Good-quality stuff (it's actually entertainment-grade cable with the inner white jacket, very flexible)
http://www.tsunamionline.com/ Good stuff, and I happen to be a dealer.

You'll want to find a hookup for getting the stuff you need to distribute the 1/0. You're going to get raped if you buy it off the shelf at your local thump-thump shop.

Personally, I usually run 150A down 30' of 1/0ga without any real issues. I'd give your power budget a little more headroom, in case you want to add more stuff later (little things like convertacoms, flashlight chargers, etc. add up).

As far as the connectors for 1/0ga., the car audio stuff is all compression (check out Tsunami's Lok-Nut products - very nice). As far as the connection to the battery, the right way is crimp + silver solder.[/url]

akardam wrote:Well, the first question I'd ask is, does your vehicle use the chassis/frame as the ground reference?

Yup. Planning a heavy-duty ground from the block to a trunk-hinge support.

akardam wrote:... and conservatively estimate that it'll take about 20 feet of cable to do it.

That seems fair... it's all going into a Taurus.

akardam wrote:So, under maximum theoretical load of 80A w/ 125% overhead, I'd say you could probably get away with 1 AWG.

Which means that 1/0 would provide a step worth of overhead...

akardam wrote:Now, if you plan on running a lot of this equipment with the vehicle parked and not running...

I don't plan to (right now, heh). When my vehicle's in-service, it remains running 100% of the time.

akardam wrote:... you'll want to make sure that your alternator is appropriately sized...

130A Bosch alternator, two years old.

akardam wrote:I think I would increase the main bus fuse to at least 150A...

Why so large on this fuse?

akardam wrote:... I would add a second one on the negative side of the bus...

I know there's been some debate on the board here about fusing the ground lead. What's the trade-off between fusing and not-fusing in terms of safety and reliability?

akardam wrote:Hopefully all this info will provide to be usefull...

Absolutely... I've done countless of what I consider "small" (up to 20A) and "medium" (up to 40A) installs. I've not done one yet that I might consider to be "large", like this one is, and I want to make sure that I don't burn down my car, hurt anyone, and that my equipment works.

tvsjr wrote:As far as the wire, I have two sources:

I'll have to check those out.

tvsjr wrote:You're going to get raped if you buy it off the shelf at your local thump-thump shop.

I was kinda worried about that. I don't mind paying a reasonable amount for what I need, but I don't want to get stuck overpaying for things I don't need (like an extra 75-80 feet of cable) or because a merchant's regular market segment likes it pretty and is easily separated from their cash (as seems to be the case with stereo shops).

tvsjr wrote:I'd give your power budget a little more headroom, in case you want to add more stuff later...

The 1/0 should provide this headroom for some time (at least until I replace this vehicle). I've already figured for the major power suckers (radios, lights, computer, and almost a dozen low-current accessories). I don't expect to add anything else... but then again, we are all prone to "installationitis" at times, and things get added here and there... heh.

tvsjr wrote:As far as the connection to the battery, the right way is crimp + silver solder.

I've been considering prefab 2/0 battery connectors with ring lugs from battery to a wafer fuse holder and between the fuse and junction block under the hood (then the 1/0 back to the trunk via the rocker channel), as well as for the trunk ground. Those that I see on solar-electric.com seem like they're well-constructed---any idea if they are properly constructed for automotive use?

Another issue that I'll have is getting the 1/0 through the firewall properly. Anyone with previous Gen3 Taurus (it's a 1998) experience on this, please feel free to expound...

Many thanks again...

I'll chime in to add info for the CenCom. The large red 8 gauge inputs can be fused at whatever you are powering (just the two 8 lamp Dominators I see). The 10 or 12 gauge red power wire is for the amplifier and for the switching relays, which should be fused at 20A and ignition switched through a relay (well, thats how we hook it up) so that the whole unit is on/off with the key.

2112:

Look at this thread, and ask him what input (if any) he has...

http://batboard.batlabs.com/viewtopic.php?t=53800