diy solar

diy solar

Cabling Question

MDANIELE

New Member
Joined
Aug 10, 2022
Messages
4
First, I'm a newcomer to this forum and solar in general, and appreciate suggestions and constructive comments from this community..
I've bought al the components to build out an off-grid system lie the one Will Prowse shows in his Complete 48V Offgrid Solar Power System
youtube video
but with only 4 batteries. The only thing I haven't bought is the wiring, and with the price of wire cable being ridiculoulsly high these days, I'm curious if anyone has sucessfully used automotive battery charging cables for the 2,4, and 6 gauge wire connections. Would it be safe to use them as you can get them much less expensive than wire from a big box store.?
 
Did you already buy...
3x eg4 batteries
the rack complete with busbars
over-current protection devices
secondary busbars
any thing else?
 
Hello and thanks, I've bought all that is in the video,
2 - 6500EX-48 EG4 6.5kW Off-Grid Inverters,6500W Output,
8000W PV Input, 500V VOC Input, UL 1741 Certified
4 - EG4-LifePower4 Lithium Battery | 48V 100AH
1 - EG4 Enclosed Battery Rack | 6 Slot
2 - IMO DC Disconnect Rooftop Isolator Switches
2 - Nader DC Circuit Breaker | 60V 200Amp (not sure I needed these because I bought the disconnects)
2 - 300A Bus Bar Heavy Duty Module Design Power Distribution Block 12V 24V 48V DC Busbar Box
 
Please provide a product link to the busbars.
Also to the breakers.
 
Busbar
Breakers
Those busbars are made of brass and only rated for 300 amps.
I doubt they can actually take 300 amps without melting.
If possible I suggest not to use them.

6500 ac watts / .85 conversion factor / 48 volts low cutoff = 159.31372549 service amps
159.31372549 service amps / .8 fuse headroom = 199.142156863 fault amps
199.142156863 fault amps * 2 inverters = 398.284313725 total amps

If possible I suggest you attach both inverters to the battery rack busbars using 1/0 awg pure copper wire with 105c rated insulation.
1/0 awg wire is the largest wire that will fit in the load side mechanical lug.
It would be ideal if you could take the mechanical lugs off the line sides of the breakers and connect the copper combiners directly to the busbar.

The positive wires and negative wires are connected diagonally.
Positive to the top of the busbar and negative to the bottom of the busbar or vice versa.
This makes the path resistance more equitable between each battery.

You can probably use the newly removed mechanical lugs to connect the negative wires to the rack negative busbar.

Hope that is clear.
If not just holler.
 
Short answer, don't try to save money on the wire, you can loose a lot of system efficiency there. use heavy gage pure copper
 
Check at your local welding supply store for DC cable.
If you shop the internet I would only by windy nation. Lots of copper clad aluminum out there.
 
So, is the overall opinion that I shouldn't use the 300A busbars at all, and just connect the inverters to the battery rack using heavier gauge ( 1g) cable?
 
The only thing I haven't bought is the wiring, and with the price of wire cable being ridiculoulsly high these days, I'm curious if anyone has sucessfully used automotive battery charging cables for the 2,4, and 6 gauge wire connections. Would it be safe to use them as you can get them much less expensive than wire from a big box store.?
You are not going to find cable cheaper at the big box stores versus online. Plus I have no big box store where you can get 50' of 2ga.
Be cautious though, good majority of the cable you see in brick and mortar stores are AL.
 
So, is the overall opinion that I shouldn't use the 300A busbars at all, and just connect the inverters to the battery rack using heavier gauge ( 1g) cable?

No, the recommendation is to buy better bus bars. Look at Blue Sea Systems.

The cable you buy at the big box store is going to be coarse strands as opposed to finely stranded welding cable. If you have tight corners to run cable through or limited space, you'll want welding cable. It's much easier to work with. The extra expense is worth it.
 
As others have stated, don't cheap out on your cables, you'll only handicap your system by doing so. Assuming you don't want to make the cables yourself, others have used windy nation cables like these: https://www.amazon.com/Gauge-Copper-Battery-Inverter-Cables/dp/B01F4P1JNM. Verify the lug hole sizes you need and length of course.

For future reference since you should not need this since you have the rack with bus bars already, here is one example of high quality bus bar: https://www.solar-electric.com/victron-busbar-600a-4-terminals.html
 
Last edited:
@DavidPoz youtuber just did a comparison of daisy chaining 4 x Jakiper (5kwh) batteries in a rack vs using a bus-bar with a 200a load. He shows that in daisy chain, the amps (and heat in the batteries) build up - 50a, 100a, 150a, 200a - as you follow the chain of wire. But with a busbar config, each battery + / - to the busbar stays at 50a and it's the main take-off wires from the busbars to the load that carry the 200a.
In the next earlier youtube, he discusses (and has links to) cheaper/more-expensive busbar examples you might consider.

You'll notice that in the OP @Will is using busbars in the youtube thumbnail....
 
Last edited:
No, the recommendation is to buy better bus bars. Look at Blue Sea Systems.

The cable you buy at the big box store is going to be coarse strands as opposed to finely stranded welding cable. If you have tight corners to run cable through or limited space, you'll want welding cable. It's much easier to work with. The extra expense is worth it.
We disagree again.
Adding a second set of busbars just unnecessarily increases the circuit resistance.
The battery rack already has a set of busbars.
Adding a 4/0 wire just to add a second set of busbars is an avoidable choke point.
This all assumes that the breakers can be decently mounted to the rack and its busbars.
 
Last edited:
We disagree again.
Adding a second set of busbars just unnecessarily increases the circuit resistance.
The battery rack already has a set of busbars.
Adding a 4/0 wire just to add a second set of busbars is an avoidable choke point.
This all assumes that the breakers can be decently mounted to the rack and its busbars.
I agree
 
I have the same rack, why the additional bus bars?

If you watch the video that was posted, he shows that running parallel cables to a set of bus bars results in significantly lower cable temperatures than daisy chaining from one battery to the next.
 
If you watch the video that was posted, he shows that running parallel cables to a set of bus bars results in significantly lower cable temperatures than daisy chaining from one battery to the next.
His rack doesn't have built on busbars.
That is why he added a set.
 
Back
Top