DC breaker as disconnect between inverter/charger and battery bank

[wayne530]

I bought some DC breakers to use as a disconnect, however I plan to install them on the negative cable because I have fuses on the positive side and no room beneath the fuses to install another inline device. I mainly want to use it as a disconnect vs. an OCPD. The terminals are marked line and load and I intend to connect them such that current flows from line to load, which on the negative side of things would have the inverter connected to line and the battery bank connected to load. The inverter/charger is capped at delivering 30A of DC charge current so I was less concerned about flow in the other direction. Anyone have any advice on this? Are my assumptions about current flow correct? Should I be using a DC breaker when flow is bidirectional? It's not absolutely essential, but it would be nice to be able to completely disconnect each inverter from the battery bank to do maintenance or troubleshooting.

 

[sunshine_eggo]

I bought some DC breakers to use as a disconnect, however I plan to install them on the negative cable because I have fuses on the positive side and no room beneath the fuses to install another inline device. I mainly want to use it as a disconnect vs. an OCPD. The terminals are marked line and load and I intend to connect them such that current flows from line to load, which on the negative side of things would have the inverter connected to line and the battery bank connected to load. The inverter/charger is capped at delivering 30A of DC charge current so I was less concerned about flow in the other direction. Anyone have any advice on this? Are my assumptions about current flow correct? Should I be using a DC breaker when flow is bidirectional? It's not absolutely essential, but it would be nice to be able to completely disconnect each inverter from the battery bank to do maintenance or troubleshooting.

You're proposing putting a DC breaker on the (-) conductor that's appropriately rated for the current but to be used as a manual cut-off switch?

If so, that will work fine.

 

[mopat]

The inverter/charger is capped at delivering 30A of DC charge current so I was less concerned about flow in the other direction.

What's the maximum current the inverter can draw from the batteries?

Bussman Type III circuit breakers are nice for this application:

 

[wayne530]

What's the maximum current the inverter can draw from the batteries?

Bussman Type III circuit breakers are nice for this application:

View attachment 95580

It's 6500W / 48V low DC cutoff = ~136A. I bought 200A breaker to allow some headroom for temporary surges. The breaker I bought looks very similar to the one you're showing: https://www.amazon.com/Tocas-Circuit-Switchable-Waterproof-Flush-Mount/dp/B06Y4172LP

 

[sunshine_eggo]

Too cheap. Rating is optimistic.

Recommend a Bluesea for about $90.

 

[wayne530]

Too cheap. Rating is optimistic.

Recommend a Bluesea for about $90.

Have you/others used these breakers and had issues with them? Just curious. If I were using them for OCPD absolutely I’d spring for the Blue Sea but I figured since I just need it for disconnect it’s be alright. You’d still recommend against it?

 

[sunshine_eggo]

Have you/others used these breakers and had issues with them? Just curious. If I were using them for OCPD absolutely I’d spring for the Blue Sea but I figured since I just need it for disconnect it’s be alright. You’d still recommend against it?

Not me personally, but there have been reports on this site. The problem is the cheaper ones pop well before their rating, i.e., a 200A breaker is tripping at 100A.

A blue sea battery disconnect is cheaper, but if you're space constrained, it might not be an option.

 

[wayne530]

Not me personally, but there have been reports on this site. The problem is the cheaper ones pop well before their rating, i.e., a 200A breaker is tripping at 100A.

A blue sea battery disconnect is cheaper, but if you're space constrained, it might not be an option.

Good to know! I will return these and take a look at some other options. Appreciate the help!

 

[Israel24]

Too cheap. Rating is optimistic.

Recommend a Bluesea for about $90.

I agree. They are expensive but worth the protection. I bought a Blue Sea T-class Fuse and the block it sits on. From what i read, they are the best possible for fusing your battery cables. I would place it as close as possible to the battery on the positive cable.

 

[cs1234]

Too cheap. Rating is optimistic.

Recommend a Bluesea for about $90.

What about one of these if you only wanted 100amps? The Midnite Solar-MNEDC100 ?