diy solar

diy solar

Question about cable size from 48V battery to busbar, and busbar to inverters.

BillSF

New Member
Joined
Aug 2, 2021
Messages
33
Hi, I am building a system with 4x 6548 in 2x2 split phase config connected to a bank of 4x Trophy 48V batteries.

I want to be able to charge an EV at up to 10 kW without maxing out the system if the electric water heater or A/C is on (hence the somewhat excessive 4x 6548's instead of 2, and can't go with only 3x because I need split phase).

What is the recommended wire size in this situation for battery to busbar for short distances (less than 5 feet)? 2/0 or 4/0?

Busbar to inverter? 2/0? Is a 200a fuse to each inverter (between the busbar) still sufficient (theoretically 135A draw per inverter split between 4x for max draw)?

Also, for now I'm going with a 4 stud 300A busbar to get started (affordable options for larger busbars were out of stock). Currently, I only have a Nissan Leaf which charges at 6.2 kW. However I assume I should upgrade this when I actually get to the point where I potentially need the extra 4kW of draw for a newer EV without minding other system loads?

If the batteries are rated at 100A, I assume a 600A busbar is large enough to prevent excessive heating of the busbar? Also if I were to get an 8 stud 600A bar, I should theoretically be able to add 2x more 48V batteries before exceeding the capacity of the busbar? Actually, is it ok to double 48V batteries on one stud or should I be sticking to 1 stud per battery?
 
Hi, I am building a system with 4x 6548 in 2x2 split phase config connected to a bank of 4x Trophy 48V batteries.

I want to be able to charge an EV at up to 10 kW without maxing out the system if the electric water heater or A/C is on (hence the somewhat excessive 4x 6548's instead of 2, and can't go with only 3x because I need split phase).

What is the recommended wire size in this situation for battery to busbar for short distances (less than 5 feet)? 2/0 or 4/0?

Busbar to inverter? 2/0? Is a 200a fuse to each inverter (between the busbar) still sufficient (theoretically 135A draw per inverter split between 4x for max draw)?

Also, for now I'm going with a 4 stud 300A busbar to get started (affordable options for larger busbars were out of stock). Currently, I only have a Nissan Leaf which charges at 6.2 kW. However I assume I should upgrade this when I actually get to the point where I potentially need the extra 4kW of draw for a newer EV without minding other system loads?

If the batteries are rated at 100A, I assume a 600A busbar is large enough to prevent excessive heating of the busbar? Also if I were to get an 8 stud 600A bar, I should theoretically be able to add 2x more 48V batteries before exceeding the capacity of the busbar? Actually, is it ok to double 48V batteries on one stud or should I be sticking to 1 stud per battery?
You have 4 AIOs and 4 batteries.

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

Which trophy battery?
Can each battery deliver 159.31372549 amps?
 
You have 4 AIOs and 4 batteries.

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

Which trophy battery?
Can each battery deliver 159.31372549 amps?
The TrophyBattery model is 48V100E-1 (100AH face value, 105 AH cells). These support 100A continuous output and it looks like built-in overcurrent protection in the batteries will kick in at 110A. Which would presumably cause a cascading trip of all 4 batteries.

Based on your formula above, to keep battery draw from tripping from 4x batteries, my max delivered power will be limited to around 16.3 kW (100A per battery x 4) to 17.0 kW (105A per battery x 4)....at least when the batteries are approaching low voltage. This is probably fine until I get a newer EV that can draw more than 6.2 kW. Even then, I can current limit my EVSE to the same 27.5A that the Nissan Leaf draws (or adjust the EVSE limit upwards as high as 40A)

To be able to service the fully rated inverter capacity of 26 kW for 4x 6500 down to a 48V cutoff voltage, it looks like I would need about 6 of these batteries in parallel.

What does the current from the batteries to the inverters look like if I have 6 kW of solar power actively flowing into the inverters at the same time I'm drawing 12 kW of load? What
about with 10 kW of solar and 12 kW of load? And I guess to contrast with positive in inflow, 10kW of solar and 6kW of load?

The most likely use case is that I will primarily charge my car during daylight, possibly a short charge if I'm getting home at night.

This will be a weekend/vacation house until my daughter finishes High school. I'm hoping by then they'll be a cheap, bulk battery system I can upgrade too that has sufficient current specs (iron-air battery?) for fast L2 charging an EV.

I currently keep my water heater off when I'm not there (costs $1.50 or so in electricity per day if I don't), but with solar, I will probably leave it on since the stored heat amounts to another 9 to 10 kWh of storage.
 
What does the current from the batteries to the inverters look like if I have 6 kW of solar power actively flowing into the inverters at the same time I'm drawing 12 kW of load?
The inverter will draw all of the solar and the deficit will come from the battery.
What about with 10 kW of solar and 12 kW of load?
see ^
And I guess to contrast with positive in inflow, 10kW of solar and 6kW of load?
The balance goes to the battery.
 
The inverter will draw all of the solar and the deficit will come from the battery.

see ^

The balance goes to the battery.
Ok, so I found a wire gauge and current rating chart and it says 1 gauge wire can handle 130A, 0 gauge 150A.

Since my batteries only allow up to 110A draw before tripping anyway, is it fine to go with 1 or 0 gauge instead of 2/0 or 4/0 that Will recommends in his 48V off-grid system?
 
Ok, so I found a wire gauge and current rating chart and it says 1 gauge wire can handle 130A, 0 gauge 150A.

Since my batteries only allow up to 110A draw before tripping anyway, is it fine to go with 1 or 0 gauge instead of 2/0 or 4/0 that Will recommends in his 48V off-grid system?
1 AWG copper wire is fine for 110A. But you are looking at roughly 220A - 230A (for 10kW) You have to use the wire that can cope with the draw current and fuse accordingly.
 
Back
Top