A Little Electrical Help (1 Viewer)

[fjfar80]

Guys -

I am currently planning on buying all the extra parts for my dual battery and electrical system. I have already purchased the Painless "sealed" system as a starting point. I know there are some experts on here when it comes to 12 volts...and I know I am not one of them. I did buy the book "Managing 12 Volts" and have read it twice...so, I think I am better off than just taking a stab in the dark.

Anyway, this is my design as currently planned.

I think I have the breakers and fuses correct, what I am having a hard time with is the wiring. If I could get some comments on the wiring size that would be great. I am looking for:

1. size to run from Painless solenoid to each battery;
2. size to run from each battery to battery switch;
3. size to run from battery switch to winch;
4. size to run from battery to power distribution block;
5. size to run from power distribution block to fuse panels; and
6. anything else I missed along the way.

Thanks guys in advance for your assistance. Any comments and/or changes you could suggest to the system would also be greatly appreciated.

Cheers.

- Mark

 

[NLXTACY]

Here is what I used to determine wire size. If in doubt round up:
http://www.btc-bci.com/~billben/maxwire.pdf

1/0, by the looks of your power demand, is probably going to be what you are going to use.

Just remember that power requirements are measured in BOTH directions. So if its a 10ft run, look at the AWG requirement for 20ft.

Also plan your ground paths too, not just your power.

 

[NLXTACY]

Jump System? Gee whats that?

 

[NLXTACY]

Here's what I did which isn't too far off actually.

 

[alia176]

I have some questions on your fuse sizing:

What's the purpose of the Heavy Duty battery 4 pos battery switch if the Painless system can do the same thing with a minor exception?

250 amp x 2 = are these two mega fuses feeding the winch? I don't usually fuse winch feed line so this is different. A loaded winch will draw over 400 amps. Also, when your engine is running, Painless will bring both batteries together (green position of switch). So, effectively, you have two batteries plus the alternator feeding the winch. Does this sound accurate? This relates to my question above on needing the 4 pos batt switch.

150 amp x 2 = Does painless require the use of these two breakers? Again, I haven't seen this before. Mine doesn't have them. Our alternator only puts out 85 amps so there's no need for a 150 amp breakers IMHO.

150 amp fuse that feeds the power dist block - I question the size of this fuse. What's your total draw of the lights + air comp + electronics? I doubt this equals 80 amps.

This brings me to question your second 80 amp fuse feeding the rear fuse panel. Again, what's your total draw? A pump is usually 5 amps, Engel is 3 amps (set to freezing), Outlet is maybe 20 amps.

Once the proper fuse size is achieved, then the 150 amp fuse may end up being smaller.

Again, no offense is meant, just some constructive criticism! Let's hone in on your total power requirements for each circuit before selecting a fuse and wire size.

Cheers.

 

[fjfar80]

Alia -

I'll try and answer your questions...and trust me no offense is taken...I need all the advice I can get. I want to do this once and do it right.

1. I wanted to be able to take the Painless solenoid out of the equation if I wanted to. Thus, the 4-position battery switch.
2. I was thinking that if I used both batteries to power the winch that I should protect the system for any "draw" greater than 500 amps. I was going to operate under the impression that if the winch was under a "vehicle" load than I should put the switch in the "both" position. I really wanted to be able to either run the system through the painless solenoid and/or take it out of line as well.
3. I sent an email to Painless asking them if I were to use breakers between the solenoid and the batteries...they indicated that a 150 amp breaker would be best. I don't think it is required but, again I am trying to protect the solenoid from any excess.
4. I eventually am planning to add a inverter (haven't decided) which one yet so, I figured it would be best to future proof by putting in a 150 amp fuse...just in case I ended up going with something crazy in the future.
5. Again, since I was planning on adding an inverter (front or rear) I figured if I used an 80 amp breaker then I would be safe for whatever I added to the fuse box.

My real objective of this system was to create an excellent base that was well protected and easily expandable. I may have over built it. I am working on the lights, refrigerator, inverter, etc. selection now...so, once I have those I can probably more accurately figure my actual amps flowing through the system. Anyway, let me know your thoughts on the additional information and where I may have made some bad assumptions.

I should also add that I am upgrading my alternator to a 150 amp unit.

NLXTACY -

I certainly looked at your work when I designed mine. Although you are probably going to be using a bit more power than I will, I did like your design. I found a "jumper" system on line that I liked...I think it was from where you got some of your components but, they had a whole kit that looked pretty appealing to me.

Thanks.

- Mark

 

[NLXTACY]

Well I would say is work backwards. What I did was go pie in the sky in what I was ultimately going to have installed in the truck. Then I found what the amperage draw was going to be for those items and I just started adding all of those and then just built back to the fuse panels. From there I figured 80A would be plenty to cover what I was doing. Then from there took a look at my overall load going to my distribution points and rated my cable from there. Basically just working backwards to get to what you see on my truck today. I've never had an issue, never killed a battery and I've used tons of electronics to test it but I still haven't come close to its true potential. Once I get Photoman's alt mod done I will be much happier. I've had that thing for almost a year and I STILL haven't gotten around to put it in....for the third time

 

[sandcruiser]

keep in mind, the breaker(s) and fuse(s) aren't there to protect the device(s), they are they to protect the wiring.

If you are using 1/0 wire, you need to determine the max ampacity, then add a fuse that is below that ampacity. if you are going with smaller wire, smaller fuse.

The fuse keeps the wires from melting/catching fire. That's about it. It would also pop if you have a bad short, which would alert you to the short, but that's a pretty minor concern with this setup, I would think.

RE: wiring to the winch-- search on mud, there are many winch installs.

Wiring from the alt to the painless to the battery---it is all about what your alt can put out.
according to this chart: solar electric wiring guide for solar power systems
You can move up to 200amps for up to 3.6 ft (one way) in 2ga wire. I imagine that your alt can't get anywhere near 200 amps. 150amps can go almost 5 ft. That should be more than plenty to get from the alt to the painless to the switch to the batteries.

FWIW: I'm running 6ga from the battery back to my fuse box in the cargo area. Plan to run a compressor (max 20amp), a fridge (dunno max draw, 10amps?) and an outlet or two that won't draw more than 10amps. At some point, I may have to upgrade the wiring if I add more stuff back there (like an amp, extra lights, etc) But only maybe- as I don't really think that I'll be running lights, compressor, fridge, amp, etc all at once. If I do, and stuff dims or slows, I'll turn something off!

Just my thinking.

 

[fjfar80]

Thanks for the opinions guys...now I just need to order some wiring products and get busy...

- Mark

 

[fjfar80]

After looking at the wiring guide, it looks like I will do the following:

1. 2 gauge between the Painless and the batteries;
2. 1 gauge between the batteries and the battery switch;
3. 1 gauge between the switch and the winch;
4. 2 gauge back to the power distribution block;
5. 6 gauge to the fuse panels.

I hope this works out well...I rather be over built than under built. If anyone sees anything wrong with the above, please let me know. The last thing I want to do is catch my Land Cruise on fire.

Cheers.

- Mark

 

[TrickyT]

Another thing to remember is that fuses don't blow precisely at their rated value. They will often continue to pass current for relatively long periods at far above the number of amps stamped on the fuse. You can find some charts on the Littelfuse web site illustrating this, although the best I could up with in a couple of minutes of searching is this hard to read graph on the MAXI fuse: http://www.littelfuse.com/data/en/Technical_Articles/TB98-001.pdf. Still, you can see from this log-log plot that even at 10x the rated current the fuse continues to conduct for a short period of time. So you are better off choosing values for your fuses conservatively. In order words, don't pick a value based strictly on wire size in the circuit, but undersize them. In this way, the wiring will be better protected because the fuse will blow more quickly when current reaches your maximum design value.

Another chart that you should dig up is voltage drop versus run length for a given size of wire. Here's a good web site with a chart and calculator: American Wire Gauge table and AWG Electrical Current Load Limits. Some equipment (e.g. ham radios) is very sensitive to voltage, and hence you want to minimize the voltage drop between the battery and the load by choosing the correct wire size or even upgrading the size for selected equipment.