Is this adequate protection for my batteries? House burn down thread inspired

[JaVid]

The house burn down thread got me thinking about my battery protection. I thought I had a safe set up, but at this point I am not sure and I could use some guidance from smart people on this forum whether this is a safe set up for my batteries.

I have (6) 280ah 24v diy batteries in parallel. Each battery has 100a JBD BMS. From each positive, I have 4' of 2/0 cable going to a MNEDC175 breaker. After the breaker, I have 2' of 2/0 going to 100a MEGA fuse in Victron Lynx Distributor busbar.

Here is the spec for the MNEDC175 breaker:

• NON POLARIZED
• Environmental Rating - Type 1 (Indoor)
• Width 1.5 Inches (39mm)
• 125VDC Panel Mount Breaker - 3/8" Studs
• AIC 50,000 At 125VDC

I have attached the trip graph and chart for the breaker. The MNEDC175 is the (14) delay in the chart and MEDIUM graph.

 

[cs1234]

I have a nearly identical setup with those breakers. My house hasn't burned down yet. Not to say my crappy FET using, death trap open loop batteries might not get stuck closed upon FET failure and burn things up anyway.

At some point you either need to put the batteries in a bunker or just cross your fingers and pray.

 

[740GLE]

In before people cry foul of the Mega Fuse will burn your house down!! I say this as I also run Mega on my 24v system and feel safe with it.

I have to say 6 MNEDC175 breakers is very impressive.

You have any pictures to share?

 

[JaVid]

I will get some pictures. My breaker boxes are made of plywood.

I just can't really figure out if there was a high amp event whether the wire insulation would disappear before the breaker tripped...

 

[cs1234]

I will get some pictures. My breaker boxes are made of plywood.

I just can't really figure out if there was a high amp event whether the wire insulation would disappear before the breaker tripped...

Are you talking about a short circuit from a single battery being stopped by the 175amp midnite breaker? What's the insulation temperature / amperage specs on your 2/0 cable? I would think the Midnite breakers are giving you some very good protection for your 2/0 on each battery assuming it's open air and not sealed tightly in some conduit.

You could always test it out to some degree by shorting one of the batteries all by itself on the Midnite breaker and see what it does. It's not a full test, as the BMS might cut it off before the breaker trips, but it would be fun to watch. Film it and post it here.

 

[JaVid]

Are you talking about a short circuit from a single battery being stopped by the 175amp midnite breaker? What's the insulation temperature / amperage specs on your 2/0 cable? I would think the Midnite breakers are giving you some very good protection for your 2/0 on each battery assuming it's open air and not sealed tightly in some conduit.

You could always test it out to some degree by shorting one of the batteries all by itself on the Midnite breaker and see what it does. It's not a full test, as the BMS might cut it off before the breaker trips, but it would be fun to watch. Film it and post it here.

Thanks for reply. My 2/0 is 105C. My wiring is all open air. I guess I was worried about something happening to one of the batteries like everyone theorizes happened to the house burn down thread: One cell shorts out and all the other batteries pump amps into that battery immediately to make up voltage difference.

I would think if CC or Inverter has fault that my protection would be adequate....

 

[cs1234]

Thanks for reply. My 2/0 is 105C. My wiring is all open air. I guess I was worried about something happening to one of the batteries like everyone theorizes happened to the house burn down thread: One cell shorts out and all the other batteries pump amps into that battery immediately to make up voltage difference.

It's not impossible. You've got just about the best protection you're going to get for each battery in the parallel group though. Those Midnite breakers are very high quality, the rough equivalent to a tclass fuse AIC wise. Not sure about speed of disconnect wise.

I would probably put the equipment on something other than plywood. The wood might have a lower burning point if it gets exposed to repeated lower but hot temperatures. It gets kind of "seasoned" and ready to burn at a lower temperature through repeated hot temperature exposures.

I'm just an idiot with no real world experience however, hopefully one of the much smarter people on here will chime in some more.