Parallel Wiring with Anderson Connectors

[mattleonard]

This schematic above is exactly how I have my portable/modular rig setup. I have several of the Lion ut-1300 batteries wired/boxed in pairs at 24v series, each pair with a bolt-on fuse and then an Anderson SB175 1/0 cable. Each battery box is a reasonable weight for transport.

On the inverter side - I have a bus bar that has several short SB175's coming off it. This allows me to quickly plug in a single pair (24v, 105ah) of batteries, or multiple pairs depending on my needs at the time. I have rubber dust caps on all cables to ensure no shorts for cables that aren't plugged in. I just wish SB175's had a better panel-mount option rather than pigtails.

I do have to make sure batteries are charged equally, and that my SCC/battery monitors are configured for whatever Ah I'm using at the time. But that takes just a few seconds. On the solar side - I also use Anderson SB50's off the change controller (which does have a panel-mount option I found on Ebay), and an SB50 cable that breaks out to (4) PowerPole 45's. All my panels are rewired for the PP45's - which lets me quickly shift from parallel or series wiring depending on my needs (I have other 12v SCC rigs)

 

[ohhimark]

Connected my Big Battery PowerBlocks in Parallel. Using my small power station in the winter for power outages. In the Spring it will go in my Ford Connect Van and add some solar panels for going on camping trips.

What are the busbars rated at? I have 3 batteries, might expand to 4, trying to understand what's an appropriate size bus bar similar to your setup

 

[Living hakuna]

What are the busbars rated at? I have 3 batteries, might expand to 4, trying to understand what's an appropriate size bus bar similar to your setup

The bus bars are 250A

 

[ohhimark]

The bus bars are 250A

Thank you. I haven't been able to find a clear cut answer, if you don't mind, how do you predict the max amps flowing out of the batteries, say if I had 4 of these batteries?

 

[ohhimark]

To add to the above,
I know the cont discharge is 175a on the battery and max discharge is 350a, but I'm not sure how that relates when 4 batteries are hooked up in parallel (I assume it increases the cont discharge?) and I'm not sure how realistic that is, as it sounds like it'd drain the battery rather fast

Therefore it's hard to understand why 250a would be okay, in the above 2 batteries, I'm clearly missing something. Any thoughts?

 

[HRTKD]

Thank you. I haven't been able to find a clear cut answer, if you don't mind, how do you predict the max amps flowing out of the batteries, say if I had 4 of these batteries?

The estimate of the amps coming out of the battery bank depends on your loads. You need to calculate the maximum amp draw from your loads that could occur at any one time. Don't add up all the devices and assume that is your number. Nobody runs the air conditioning when the furnace is running. I'm throwing that out as an extreme example, not that you would actually do that.

I calculated my load at 4,000 watts per day. But the maximum watts at any one time was no more than 1100 (coffee maker) and that was for maybe 10 minutes.

 

[schmism]

Nobody runs the air conditioning when the furnace is running. I'm throwing that out as an extreme example, not that you would actually do that.

As the A (or Z) coil sits ontop of my furnace, yes the blower in the HVAC runs when the AC compressor is on. The amount of power required to run the gas burner is negligible.

so yes, my "furnace" is running when the AC is on.

 

[HRTKD]

As the A (or Z) coil sits ontop of my furnace, yes the blower in the HVAC runs when the AC compressor is on. The amount of power required to run the gas burner is negligible.

so yes, my "furnace" is running when the AC is on.

The assumption I made here is that this is a mobile environment, not a house. I don't know why anyone would use Anderson connectors in a house configuration.

 

[HaldorEE]

What size is the fuse or circuit breaker protecting the cable? You need to use wires large enough to handle the max fault current that can flow without the overcurrent device interrupting the current. Its not just the load you plan on powering. Its what could happen if something malfunctions.

6 AWG is rated for a max of 55A at 40 degree C ambient (max 75 degree C wire temp).
Going to 4 AWG bumps only increases that to 70A.

Ampacity Calculator

The purpose of this calculator is to determine the ampacity of conductors in conduit, cable, or directly buried. All calculations are based on the National Electrical Code®.

www.cerrowire.com

I use 1/0 cable and 150A fuses with Anderson SB175 connectors. 1/0 is rated for 150A in above conditions. This is the limiting factor in my wiring (not the SB175). I am powering a 2000W inverter (25.6V at 85A max continuous, 170A max for surge). Fuses and circuit breakers take more than their rated current to trip and wire can handle higher surge current for short periods of time (at least long enough to start a motor) without a problem.

If you parallel multiple conductors they need to be identical (conductor size, type, length and insulation). I would also derate their max ampacity if they are going to be bundled closely together since they can heat each other up.

I try to size everything to the same spec which is roughly double what I actually plan on using. That way things just keep working, even if I messed up a bit. I am a fan of that.

 

[HaldorEE]

I'm getting 4 24V @170 batteries, connect then in series (48V) and parallel (340Ah). They use an Andreson 175 connector so to get 3cables in 1 connector is impossible when using (1/0 gauge) cables so I will be connecting them like this Using bus bars View attachment 29181

Why not use three bus bars? That would conceptually simplify your wiring.

• +48 Bus
  • Two 1/0 wires to + of right pair of SB175 connectors
  • One 2/0 wire to + inverter
• +24 Bus
  • Two 1/0 wires to - of right pair of SB175 connectors
  • Two 1/0 wires to + of left pair of SB175 connectors
• Ground Bus
  • Two 1/0 wires to - of left pair of SB175 connectors
  • One 2/0 wire to - inverter

I hope you have fuses in each of the individual battery pack harnesses (the other side of the SB175 connectors you didn't show). If not, then you need to add them. The fuses or circuit breaker ratings determine what size wire you use. Is your inverter an inverter/charger? If so you should have a fuse/circuit breaker on the + Inverter.

Think about what would happen if something got shorted. With fuses or circuit breakers, you just fix the short and replace the fuse or reset the breaker. Without something to deal with overcurrent, a fire is a possibility.

Fuses and circuit breakers should be located as close as possible to the source of current. A fuse will not protect you from a short in the wiring between the current source and the fuse. Considering how many, high current rated large circuits you need to protect, I would use ANL fuses, they are smaller, cheaper and easier to mount than circuit breakers.

ANL fuses

 

[HaldorEE]

ANL fuses are rated for 32VDC which is fine for your individual battery pack. But I would use a T rated fuse for the inverter

Blue Sea Systems 5119 Fuse A3T (Class T) 300 Amp

I am confused about your systems max current draw. Did I just read 350A max? Are you the same guy that was talking about using 4 AWG wires? Or was that a different poster? Please tell me that was a different poster.

I wouldn't be using connectors of any type if I planned on drawing 350A through a pair of them. And I certainly wouldn't be using 250A bus bars either.

These are appropriate bus bars for a 350A rated system

Blue Sea Systems 2104 PowerBar Heavy Duty Bus Bar

-Edit-

And double the wire size recommendations in my previous post. 2/0 for the individual battery packs and 4/0 for the inverter wiring (heck I would probably use 500 wire size for the inverter). Ampacity of a wire does not scale linearly with diameter. Double the wire size is not able to carry double the current.

I hope your 350 A comment is not accurate.