Battleborn ‘add a battery’ diagram.

Robermcm

I wrote to Battleborn, curious about what gauge wire they recommend as I added a second of their 100ah batteries to my trailer. Took longer than I’d hoped to get an answer, but they shared a picture that I thought was useful.  Only question I had was about the 200a fuse. I think my tab version of that is the glaso 40a?

Grumpy_G

The diagram is a bit of a CYA answer. Two batteries that can deliver 100A each (typically, Battleborn doesn't list the max current) so just multiply by 2 which requires a 200A fuse and 1/0 AWG wiring. If you just want to increase the time between charging you don't need to change the 40A breaker or the existing wiring because the current demand stays the same.

Robermcm

Solid, helpful answer. Thanks @Grumpy_G. 

If I may ask another question of you, how does nu_camp compute that 4ga wire and a 150a breaker is the right combo for the aims 1200/2400w inverter, tied to a single 100ah lithium battery?

My simple understanding is that the 1200 continuous watts inverter would produce 120v up to a max of 10a of a/c.  That’s 120 watts at 12v coming from the battery (85% efficient). 

     - The 150a fuse must be for shorts only
     - the 4ga wire is at the edge of its ability. And running hot as heck. 

Is that about right? Maybe add that the inverter self protects at some amperage or duration below the 1200w?

Grumpy_G

Your math is basically right. The 150A breaker can accommodate the current surge when the inverter tries to start up a heavy load. The wire gauge is somewhat questionable, but something you see commonly. There is a difference between solid core and various stranded wires, 4 awg solid core is rated for 120A but stranded variants go from 70A all the way down to 35A.

DaveC

I contacted NuCamp support about adding a second 100 ah Battleborn battery to my 2023 400. Will the 4 gauge wiring and 150 amp fuse handle this additional battery?

Here is their response:

"Yep, that will be fine as you are just adding a second battery for capacity - the voltage will not change. 

So you will want to make sure to wire the new battery in parallel - this will keep the same voltage (12V), but double the amp hour capacity. 

​You are essentially just adding more battery amp hour capacity, and not changing the flow / voltage that comes from the battery/ies."

Robermcm

That makes sense, agrees with grump_g’s overview. 

I went with 1/0 cables from windynation. Recommened by others here.  They were amazingly flexible. Not sure whether that means their amp rating is more suspect for that gauge, but made it easy to replace the 4ga cables and add the new battery. Now I can add a 3rd battery, a larger inverter, more loads off the bussbar, etc. without re-replacing my battery cables. Price for thicker wire not all that different. 

I left the inverter 4ga cables alone.  May go back and replace them with 1/0 as well, if I use it much. They’re the largest draw of anything in the trailer besides a short!

klenger

Small diversion here: I've always thought that inverters in the 1000-1200 watt range to be somewhat useless for their size.  1000 watts is way more power than you need to run the TV or other entertainment equipment, but not enough to run a microwave, hair dryer, some coffee makers, etc.  It will run a cock-pot and a few other devices in the 600 watt range.  My thoughts are to install either a good true sine wave 400-500 watt inverter or move up to a 2000 watt true sine wave inverter. Now back to the regularly scheduled program.

rh5555

Grumpy_G said:

There is a difference between solid core and various stranded wires, 4 awg solid core is rated for 120A but stranded variants go from 70A all the way down to 35A.

This is not correct.  A single conductor of 4 AWG wire is rated 120A regardless of stranding.  What does impact the current-carrying ability is if you have multiple 4 AWG wires in a single cable (or conduit) and they all have high currents passing through them.  This is because the whole cable heats up and the insulation between the wires could fail.  As long as your 4AWG wire is able to dissipate heat, you are good for 120A.  The cable will feel warm to the touch.

elbolillo

Not all wire is created equal. Here is an image of the specs for the wire I used for my installation. Comparing solid vs stranded wire really isn't that helpful. Most are going to use a stranded wire for the flexibility that it offers in installation.

KK1L

Fuse and breaker sizing is independent of the capacity of the power source. Fusing is typically intended to protect equipment especially when located at the device consuming power. It is typically sized for the load. Breakers are (should be) sized to the wiring and protect from longer term overcurrent having the wiring get too hot. Breakers are not designed to trip immediately at the rated current like a fast-blow fuse is.

The loads are not changing when more batteries are added. What does change is the max current that the battery system can demand when charging. The internal resistance of the batteries is in parallel and is halved when a 2nd battery is added. From experience I can say the 40A GLOSO breaker will trip after a few minutes when passing 52A. I did not have an issue charging from say 30% state with a single battery, but when I had discharged pair of Lithiums to a similar state I hit the 52A mark. This was the max that the 8955AD (WFCO) would put out. A 10ga wire can handle 55A when the insulation (wire coating) is rated to 90C, but 40A if limited to 60C which is typically what is quoted in tables. I changed the GLOSO to 50A version. This current is flowing from the 8955AD charger to the battery and that is the path of interest. UPDATE: After typing the above I rechecked the wiring from the WFCO through the disconnect, GLOSO breaker, and to the battery. It is 8ga with 105C rated insulation in my 2023 T@B400 and the wire is not bundled (close bundling lowers the rating). There is zero concern to up-spec the breaker to 50A (or a little higher) as there is lots of headroom in this wiring path to the batteries. The wiring to the solar panels is thinner and fused appropriately.

If you change the load on the batteries by beefing up the inverter (for example), then you will want to scale the fuse and the wiring to something appropriate. If you don't change any loads, then you won't have to do anything. 

KK1L

DaveC said:

I contacted NuCamp support about adding a second 100 ah Battleborn battery to my 2023 400. Will the 4 gauge wiring and 150 amp fuse handle this additional battery?

Here is their response:

"Yep, that will be fine as you are just adding a second battery for capacity - the voltage will not change. 

So you will want to make sure to wire the new battery in parallel - this will keep the same voltage (12V), but double the amp hour capacity. 

​You are essentially just adding more battery amp hour capacity, and not changing the flow / voltage that comes from the battery/ies."

The wire gauge you use will depend on how you wire the batteries.

1/0 for the combined current path is a bit of overkill; 2ga would be fine (Heck though the likelyhood you would be sourcing enough sustained current to have a problematic voltage drop or enough heat in even 4ga wires is hard to imagine). You would not have to change the fuse or the wiring to the inverter. The fuse is sized to protect the inverter and is independent of the capacity of the power source. The GLOSO breaker is sized to protect the wiring (and is quite conservative).  I am open to commentary.