Question about battery fusing in Midnite wiring diagrams

[Hedges]

Midnight's site lists as Non-Polarized but the CB manufacturer has this diagram.

True, that shows "Line" and "Load"

For a switch, this sometimes distinguishes which terminals go to recessed conductors mostly out of the way of fingers.
For fused disconnect, cuts power to fuse holder in particular.

But for this breaker, no apparent difference between the poles.

It would be interesting to see AIC test limits to failure with each polarity.
And for fuses, AIC limits vs. voltage. We expect higher current handling at lower voltage (e.g. class T at 60V max), but most types only have one voltage reported.

 

[Tecnodave]

The casting of the housing of breakers and switches used on the entire line are the same, The ratings are not.

I have never had any breaker or switch from Carlingtech fault and I have been using them for many a year. There is a huge difference between a “Tier 1” manufacturer and some others.

There have been some fires due to some breakers that could not extinguish a fault from the direction that it would be assumed that it would come from.

I think that there is a huge difference between a hydraulic/magnetic circuit breaker than a thermal breaker.

I find that most “cheap” breakers are thermal (long time delay) and most high quality DC breakers are hydraulic/magnetic.(very rapid trip)

 

[Hedges]

I think that there is a huge difference between a hydraulic/magnetic circuit breaker than a thermal breaker.

I find that most “cheap” breakers are thermal (long time delay) and most high quality DC breakers are hydraulic/magnetic.(very rapid trip)

There probably are some thermal-only breakers. I haven't been paying attention, but maybe those cheap surface mount ones are.

Most AC circuits in the US, at least for residential and light industrial, use thermal-magnetic breakers.
Thermal allows surge for motors and delayed trip. Magnetic provides fast trip for overloads, 5x rating for typical small breakers.

The thermal component varies with ambient temperature and is affected by heat from the wire.

There have been problems with counterfeit ones that lacked any overload protection.

 

[Tecnodave]

@Hedges,

Yes, the UL listed AC breakers are thermal magnetic breakers. In order to meet U.L. the breakers do need that 5X overload rapid trip overload capability but the offshore ones that are not U.L. listed are the ones that I find are thermal only.

That specifically includes ones that are copies of the buss surface panel mount ones such as the tocas units that sell on flea bay and scamazon.

I do bench test /inspect failed breakers with a welders hammer and anvil to open them up to find the fail mode. Pretty ugly in there in fail mode....None survive the hammer/anvil test....lol

Amazon itself is a way better bet than the sellers that buy space to sell on Amazon. Amazon does qualify products far better than those companies who buy selling space on Amazon.

Amazon does work like a flea market in some of it’s operations, they only sell the selling space, they are not obligated to regulate the quality in those spaces.

 

[Zil]

Breakers under discussion are dc current.

Note that the only thing connected to that bus bar is the charge controller. It's not a primary bus bar in the way that you're thinking. From that bus bar it goes to another breaker for the charge controller.

All circuit protection in these dc systems should protect the wires from battery discharge to short circuit. For practical purposes the LiPo battery is a massive unlimited source. The solar and other chareing devices are self limiting sources. Those wires should be sized to carry that amperage.

 

[Tecnodave]

The one thing that is missed is that the SCC needs to “see” the battery voltage, not the voltage some distance from the battery including the voltage drop caused by some device loading down the wire from the battery.

If I were to design a SCC it definitely would have voltage sense wires connected directly to the batteries that are totally seperate from the voltage output wires of the SCC itself.

Even very high end SCC’s do not have voltage sense wires, this is exactly why my system all SCC output wires go directly to the battery itself and not to any busbar. Any they are very oversized to minimize the voltage drop in the wire that distorts the true battery voltage. In my case I am sizing the overload device to protect the device, not the wire that is already protected as it is oversized to the load on that wire.

Very high quality Lab grade power supplies do have separate voltage sense wires........There is protection against failure in the voltage sense wire failure supplied by secondary voltage sense on the output circuits of the lab bench supplies. Look at the circuit wiring in Hewlett-Packard bench supplies, they do have remote voltage sensing as well as local voltage sensing as a “fail safe”.

Yes, that does incur additional expense...

 

[Hedges]

Yes, my HP supplies have remote sense. I've looked but haven't found economy supplies with remote sense, which would be better for parallel balancing cells. Wouldn't cost much to have sense terminals, internally connected to power terminals by resistors. But handling and addressing large delta voltage between power and sense terminals would be extra circuitry.

The HP (or other?) instructions say to use a diode when charging batteries, due to their crowbar function. Also, that remote sense can't be used in that case (although I think I could sense past the diode with suitable circuitry.)

Where you do get SCC sensing directly at cell terminals is when a BMS does the sensing and communicates requirements to inverter/charger.
Sunny Island with various batteries, and REC BMS for DIY, should do that. Colorist has said a number of brands standardized on the same de-facto communication standard.

Branching SCC and inverter separately from batter would be about the best you could do with stand-alone units. Maybe some LC filtering (needs an inductor that won't saturate at SCC max current). One guy had SCC branched off inverter cable, and surge or overshoot was knocking it off line.
Considering the high ripple current an inverter draws from battery, voltage across any cable resistance is going to vary.

 

[Tecnodave]

I have looked closely at the Chargery setup where the Chargery power supply is directly controlled by the Chargery BMS. I did not buy the Chargery setup due to the cost of their system as compared to the JBD for my very strange “pouch cell” lithium batteries that I am using. They are still very much “experimental” here as I do require a very stable power source. I still have not seen anybody else who is using the “pouch cells” that I am using. They are probably from an automotive source.

 

[Lien]

James,
Don't worry so much about battery protection from within the e panel as 7 hit it on the head. The batteries need fused or breakered at the batteries as close to the + terminal as possible. Some battery arrangements or chemistries need even more elaborate protections at the batteries. Any breaker or fusing from the batteries inside the e panel just has to be rated at the current you intend for your system, but is quite redundant otherwise. The real protection is needed at the batteries.

 

[jameshowison]

"The real protection is needed at the batteries."

The real protection is needed at the batteries.

Sure, but that was the initial confusion ... in the diagram there is no protection at the batteries, because the DC loads are wired directly to the input of the big DC breaker (so the breaker isn't doing anything to protect the wires going to the DC loads).

If they mean have additional protection at the battery, prior to entering the ePanel meaning that the big DC breaker is not involved (only protecting the wire going to the inverter), that's fine, but the figure doesn't show it.

 

[Lien]

Midnite is wrong in not showing protection at the batteries and a breaker in the e panel on the battery input is useless. No confusion that batteries need fused or breakered as close to the battery B+ as possible usually in or at the battery box(es) to protect as much of the wiring from shorts as is possible. Wires aren't meant to carry the current of full shorts.