Wiring question…

[reverse01134]

Hello I am building 100ah power bank for camping uses. (diesel heater, phone charging, etc)

No need for inverter so it will be just the battery and 2 usb ports and 2 cigarette lighter sockets. For use of higher amp devices, I found heavy duty cigarette lighter sockets that support 12v 20a. I will add a switch to usb and cigarette lighter sockets to cut any idle wattage.

I have a few dumb questions…
1) Is 20a switch enough to handle 2 usb ports (12v 3a) and 2 cigarette lighter sockets (12v 20a)?
2) 20a cigarette lighter socket uses 14awg. Should I use 14awg for all connections? (Battery - switch - usb/cigarette lighter socket)
3) If I need to add fuses, where should it be located and what size fuse?

Thanks in advance for your help!

 

[Darren67-72]

I'll start by giving you my opinion, and soon there will be others chime in to tell me that I'm wrong. Then, you can decide what you want to do.
Ok, that's out of the way....
20a at 12v dc is a fair amount of power. If you start your wiring project with a 20a fuse, your fairly safe. I would use 14g wire where it is not too difficult to work with. As for the u.s.b. just use what wire is convenient and fuse that "run" accordingly.
Fuses are cheap, locate them, as close to the source of power. As possible.
If it helps to remember.... fuses protect the the wire and components (to a point) so anything before the fuse could get hot and/or burn.
Hope that helps a little.

 

[Rednecktek]

1) Is 20a switch enough to handle 2 usb ports (12v 3a) and 2 cigarette lighter sockets (12v 20a)?

No. You need to have your switches and breakers total load. If you're going to have a single point of feed, add up the total load and add 20% so 20+20+3+3×1.2= 55.2a, so 50, 55 or 60a whichever is available.

2) 20a cigarette lighter socket uses 14awg. Should I use 14awg for all connections? (Battery - switch - usb/cigarette lighter socket)

That's suprising, I would expect 12awg for 20a. Can that be upgraded? The factory 14awg is overkill but that's not a bad thing.

3) If I need to add fuses, where should it be located and what size fuse?

So my recommendation, if you want to have a central point would be:

12v --> 55a breaker -> fuse block ->
Fuse block -> 25a fuse -> cig socket
Fuse block -> 25a fuse -> cig socket
Fuse block -> 5a fuse -> USB
Fuse block -> 5a fuse -> USB

 

[Darren67-72]

I told you, and... your welcome!!!

 

[Darren67-72]

Btw, add up all your loads in your house and you will need a 4000 amp main.... NOPE! GOOD BYE my job here is DONE.

 

[Rednecktek]

Btw, add up all your loads in your house and you will need a 4000 amp main.... NOPE! GOOD BYE my job here is DONE.

Granted household AC loads are calculated by the average estimated run time and a 4000a drop and panel would be a LOT more expensive than a small DC fuse block...

But it would be AWESOME!!

 

[Darren67-72]

I appreciate your sence of humor. I would agree, 12g wire would be better.
Always, up wire gauge when possable. And everything is so cheap and chinchy these days.
As well, 12v dc can create a lot of heat in wires. People try to push their 12v too hard.

 

[reverse01134]

Thanks for the comments from both of you and sorry I didn’t respond sooner as it’s been crazy busy at work… This is a diagram I created based on some of your suggestions:


I did not add circuit breaker since I don’t think I will ever pull 55amp simultaneously which would discharge the battery less than 2 hours…lol. But feel free to tell me I am wrong if you think circuit breaker is still needed. Anything else I am missing or wrong here?

 

[Rednecktek]

The circuit breaker is there for 2 reasons. Firstly it protects the wires and such down the line, secondly it gives you a convienent disconnect to take the 12v bus offline for service/repair/troubleshooting.

Your current diagram has a lot of things connected to the battery terminals, going to a fuse block keeps things a bit neater.

 

[reverse01134]

The circuit breaker is there for 2 reasons. Firstly it protects the wires and such down the line, secondly it gives you a convienent disconnect to take the 12v bus offline for service/repair/troubleshooting.

Your current diagram has a lot of things connected to the battery terminals, going to a fuse block keeps things a bit neater.

Thanks, I will look into the fuse block. If I add the circuit breaker, where should it be placed? Between the battery and the switch? (And I guess at that point the SAE connectors should come from the circuit breaker)

 

[Rednecktek]

I'll have to whip out a krappy MSPaint sketch later but basically:

Battery Pos+ -> Breaker -> Fuse block 6awg
Battery Neg- -> shunt -> fuse block 6awg
Fuse block -> 15a fuse -> Diesel heater 10awg
Fuse block -> 25a fuse -> Cig outlet 10awg
Fuse block -> 25a fuse -> Cig outlet 10awg
Fuse block -> 10a fuse -> USB 14awg
Fuse block -> 10a fuse -> USB 14awg
Fuse block -> 30a fuse -> Charging plug 10awg

I tried to keep the wire sizes as common as possible for cost, but there's no reason you can't go larger. I just went for minimum recommended off-the-shelf wire. I know from experience that diesel heaters can be affected by voltage drop when firing up which is why I upsized that wire.

I've been happy with my T Tocas breakers, they have that balance of affordable and reliable. I also like the fuse block I used on my cart, lots of spots for fuses and indicates if you have a blown fuse. Having a few extra slots is always handy if you want to expand later.

 

[reverse01134]

I'll have to whip out a krappy MSPaint sketch later but basically:

Battery Pos+ -> Breaker -> Fuse block 6awg
Battery Neg- -> shunt -> fuse block 6awg
Fuse block -> 15a fuse -> Diesel heater 10awg
Fuse block -> 25a fuse -> Cig outlet 10awg
Fuse block -> 25a fuse -> Cig outlet 10awg
Fuse block -> 10a fuse -> USB 14awg
Fuse block -> 10a fuse -> USB 14awg
Fuse block -> 30a fuse -> Charging plug 10awg

I tried to keep the wire sizes as common as possible for cost, but there's no reason you can't go larger. I just went for minimum recommended off-the-shelf wire. I know from experience that diesel heaters can be affected by voltage drop when firing up which is why I upsized that wire.

I've been happy with my T Tocas breakers, they have that balance of affordable and reliable. I also like the fuse block I used on my cart, lots of spots for fuses and indicates if you have a blown fuse. Having a few extra slots is always handy if you want to expand later.

I will follow exactly what you suggested! Thank you so much for putting this together. Ordered parts from ebay and amazon. Hopefully they get delivered by weekend!