Are fuses or breakers permitted inside the battery box?

[Sunking]

I believe Sunking is alluding to the time he dropped a wrench and it welded itself to the battery + terminal and ground.

No sir the batteries I worked with vaporized the wrench and a big chunk of the frame.

[SunEagle]

Weld with a car battery

I believe Sunking is alluding to the time he dropped a wrench and it welded itself to the battery + terminal and ground.

[ChrisOlson]

You can weld with a car battery in a pinch.

I've tried that but you can only weld light steel like 1/8" and it's pretty hard to keep a steady arc because the voltage is too low. A 48V battery bank will hold the voltage at around 40 at the electrode at 250-300A with a 100 foot cable, which is more inline with what most DC arc welders run.

I've done a LOT of welding hooked direct to the bank over the years. I got an electrode holder all rigged up for it with a 100 foot 4 AWG welding cable with one of those big pin connectors on the end of it. And a 75 foot ground cable with a big pin connector. I got a socket in the utility room where I can plug the welding cables into and I can do either normal polarity or DC reverse polarity with 7018 by reversing the cables in the pin sockets.

Works really good with 5/32" or 3/16" rod. Although with 5/32" rod you have to limit the welding time to about 15-20 seconds at a time to let the rod cool or it turns the rod red and burns the flux off it.

[Sunking]

I guess I wouldn't trust that. If a bus bar or cable would melt and short out in the bus box you have pretty much unlimited current to the short without a fuse on the battery. Batteries are one of the more dangerous things when it comes to off-grid power. Generators will kill if the breaker don't trip, even utility transformers have fusible links that blow if a service feeder shorts out. Batteries can deliver in the thousands of amps for quite awhile if something shorts out.

Ever try DC welding with your 48V battery bank with a set of jumper cables and 7018 low hydrogen rod? It works really good - you can weld 1/2-3/4" steel with that setup.

You can weld with a car battery in a pinch.

[ChrisOlson]

Midnite's wiring diagrams don't show any OCPD between battery and ePanel.

I guess I wouldn't trust that. If a bus bar or cable would melt and short out in the bus box you have pretty much unlimited current to the short without a fuse on the battery. Batteries are one of the more dangerous things when it comes to off-grid power. Generators will kill if the breaker don't trip, even utility transformers have fusible links that blow if a service feeder shorts out. Batteries can deliver in the thousands of amps for quite awhile if something shorts out.

Ever try DC welding with your 48V battery bank with a set of jumper cables and 7018 low hydrogen rod? It works really good - you can weld 1/2-3/4" steel with that setup.

[mapmaker]

Yes it is permitted and best practice. In fact would defeat the purpose if not installed directly on the battery term plate/post.

So, I guess the Midnite ePanel is not best practice. My batteries (in a box) are connected (through conduit) directly to the bus bars in the ePanel, and all circuit breakers to controller, inverter, etc connect to that bus bar. Midnite's wiring diagrams don't show any OCPD between battery and ePanel.

Next system upgrade will be to put a fuse in the battery box and a disconnect between the box and the ePanel... I'm afraid to even open the ePanel without first disconnecting a battery cable.

--mapmaker

[Sunking]

Are fuses or breakers permitted inside the battery box?

If not, what is meant by NEC 240.21 (H)

Yes it is permitted and best practice. In fact would defeat the purpose if not installed directly on the battery term plate/post. In fact you use dual fuses, one protecting the wire to the controller, and the other going to load distribution.

For unrgrounded systems.



Devices to use:



For a grounded system you just eliminate the fuse on the non grounded circuit conductor.

[ChrisOlson]

Are fuses or breakers permitted inside the battery box?

If not, what is meant by NEC 240.21 (H) ?

As far as I know there is no law against that. We have a 200A fuse inside of a plastic container on the positive post of each string. We've had several installers look at it, and two inspectors (here to look at other things) in the past and nobody said anything about it.

[mapmaker]

Are fuses or breakers permitted inside the battery box?

If not, what is meant by NEC 240.21 (H) ?

Overcurrent protection shall be permitted to be installed as close as practicable to the storage battery terminals in an unclassified location. Installation of the overcurrent protection within a hazardous (classified) location shall also be permitted.

--mapmaker