The Official Unofficial Super Pacific X1 Camper Thread

Quick question for all the electrically inclined folks out there.
I'm mapping out my house/secondary battery setup and I was wondering if the following two examples are in essence "the same'. I'd like to use the bottom diagram if possible because it seems less involved/complicated.
The diagrams below are a bit simplified... All "connections" will include both positive and negative cables of appropriate AWG and fuses (where appropriate) and a Positive and Negative busbar.
It seems to me that they are the same since in the top version, the ring terminals for the busbar, charger and inverter are all touching on the house battery terminals anyway, so why not have them all touch/connect on the busbar(s) instead.

 

FWIW I'm wiring my setup as your #2 diagram. Easier and cleaner.

 

Should function the same - there are pros/cons to each depending on how you build it out. The bottom config will use up space on your busbar, so you'd want to buy one bigger than if you go with the top function. You'll also want to be sure that your busbar on the bottom is able to handle the loads (specifically the charger and inverter as those tend to be larger amperage than simple 12v accessories).

You'll have to step up your gauge on the second config coming from busbar to battery as well if you're going to use that for charging.

 

Oh, and follow-up question. Here is the wiring diagram from RedArc (I'm using a Redarc BCDC as my "charger").
Can all of the grounds shown in the diagram be connected to a common busbar that routes back to the starter battery's ground busbar (which is grounded to the chassis)?

 

Sure. Although with grounds, the more connections the harder to troubleshoot and the more likely you have a wonky connection (which can be a PITA to trace back). You can skip grounding to the battery if you don't want to run that cable and go directly to a body mount or chassis bolt. I have all of my stuff grounded in the back seat to avoid running a fatty ground wire back to my main battery.

 

Yeah, it is a 250 amp BB that I intend to use. Max draw from the inverter is listed at 150a 12v, so that would give me an extra 100 amps to "play around with.
Fuses from the starter to the BCDC and from the BCDC to the busbar (which leads to the battery) are 60amp, as recommended by RedArc in the illustration I copied from their owners manual. I was also going to put a 250 amp fuse between the Busbar and the Inverter. Inverter is listed as 150amp, but I thought there might be momentary peak-loads that would be above the normal working current. Inverter instructions do not list the need for a fuse (probably bc they have a circuit breaker built in), but I thought I'd add one anyway for redundancy.

Does the above sound good to you?

 

Ok... I can certainly choose a separate ground from the main battery that is closer to the "house" one, but I'd like to avoid running anything into the main cabin. Will try to find something under the truck instead.

 

What would be the absolute max amount of current running through the BB? What's your charger rated at?

Also - sometimes the busbars are fused per terminal- you'll want to make sure it can take the 150amp from the inverter from one slot.

 

Charger is 50 amp (in)... The most continuous power draw would probably be the 150 to the inverter, 5 amps to a fridge (connected to Busbar directly) and other accessories would be through a switch panel (also connected to Busbar) that is listed as:
Working voltage: DC 12-24V
Max current: 60A
Rated voltage: 12V 20A / 24V 10A
Operating at 12 Volts: max power rating of 720W

What confuses me about the draw of the switch panel is if it is 20 amp (rated voltage), or 60Amp (max current).

Either way, the max would be 150+5+60 = 215 Amps.
Hmm... Maybe that 250amp fuse I was planning on putting between the Busbar and the inverter would be better placed between the house BATTERY and the Busbar. Thoughts?

 

So, in theory, if you were running your charger, inverter to max, and maxing out your switches you could be over your 250 amp rating of current passing through the busbar (i believe its a total flow factor not in/out for the rating but I'm not 100% certain). I'd size up to get you a 20% factor on the busbar and fuse ratings - OR - just run your charger directly to the battery and that clears up a ton of headroom and keeps your in/out currents isolated.

 

Yeah, that is what was perplexing me. If I ran the charger directly to the battery (pos and neg), the wires "from" the charger and the wires "to" the busbar would be touching each other on the battery terminals anyway. It isn't like electricity has a directional flow... It just floods the system and follows "pressure". Draw is negative pressure and input is positive pressure so to speak. So when the loads from the busbar draw from the house battery, if the input from the charger is connected to those same battery terminals, then they are already physically touching each other. It isn't like the input from the charger goes in one side of the battery and out the other. The battery, charger and busbar are literally already physically in contact with each other, so is there really a difference between touching each other on the battery terminals vs the busbar?

 

I am using 4awg copper wiring for all my main power connections. I am also using a buss bar for grounds to not just have everything on one post.
But I am also not running much. Basically powering a fridge, and some led lights. 100AH battery off the Renogy 30A DC/DC MPPT controller. Which is actually only 15A MPPT and 15A DC/DC simultaneously.

From watching a bunch of Will Prowse and other people. Basically take max and add 20% and build off that. So, 215 max amps +20% is 258 so you can stay at 250 or get a 300+ you want.

 

I believe busbars are rated for through current, not net current. A busbar doesn't care if it's coming or going, so your draw and charge would compound a flow through the bar - you'd want to add those numbers to determine the rating you need for the BB including safety factor.

 

Sorry if it seems like I'm splitting hairs here, but wouldn't Through Current be the same as the net? Unless there is a load (either draw from the accessories, or draw from the battery charging), there is no through current.

To expand upon this "theory", it seems to me that total current in = total current out. If a battery could theoretically put out 300 Amps, it isn't going to do that unless there is a draw of 300 amps. If the draw is only 100 amps, then the battery only puts out that much. I'll do some research to see if that is correct.

Ok, so here is an example that I THINK proves my point. The electrical panel in your house is basically a busbar. The electricity coming from the street could be 10,000 amps (or some other ridiculously high number). That does not dictate the amount of current the fuse panel is rated for... All you need to determine is the max LOAD (amount of power you actually use at any given moment). If you only had a single circuit on the fuse panel and a single load applied to it (like a spotlight or pump), then you only need a small panel. The current through the panel is not dictated by the supply side. It is dictated by the LOAD side.

Again, this is just my theory... Feel free to poke holes in it as you see fit.

 

I see what you are saying - do you have a link to the busbar you're looking at?

 

On your load question, you are correct. The current passing through the busbar is going to be determined by the loads. Sources (such as batteries) will attempt to provide as much current as the load is requiring. Your busbar should be rated for the summed current of all your loads. Lights, fridge, inverters, etc.

 

Yea, the more I think about this the more I think it could be the net not the sum. If you've got your charger also wired into the bus bar it's possible that while running that would "help" to power whatever is drawing off of the bar. So if you've got a draw for 150amp and your charger is pumping 50amp, then your battery will cover the extra 100amp needed (net draw leftover) - you wouldn't have 200amps (sum) running through the bar.

Again, though - the individual terminal ratings are important too. Sometimes busbars are rated for like 250amp but that's only 5 terminals at 50amp each (which you might want to increase to allow for spike voltage unless your charger is a hard stop max at 50amp, for example).

For the fuse, yea generally your largest fuse will be between your battery and bus at the total max draw your system is built for plus your safety factor

 

$20 Heart Horse Power Distribution Block Bus Bar 5/16'' Terminal Stud 4 Post with Cover 250 Amp Rating for Marine Automotive and Solar Wiring RV Boat (250A, 5/16'', Red+Black)

https://www.amazon.com/gp/product/B09YCTBCVG?ie=UTF8&smid=AG8DEZ0E1CHZH

 

That’s the one I have as it was listed as the “recommended” on Will Prowse RV 12v setup

 

FYI I used the grounding screw on the frame inside the driver side rear wheel well.

I've had no issues using that for my battery system.