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Preferred solutions for smaller 48V loads?

Mithril

New Member
Joined
Feb 15, 2022
Messages
155
Hey all,
I'm trying to figure out the sane way to add a bunch of small consumption loads to a 48V system. I have a t-class equivalent for the main system feed. I'll have a fuse (with proper AIC) from my main distribution that could feed a smaller bus bar, distro, what have you , but there's about 4 things I've like to connect that should ideally be fused 5-10A for 2, and 2 at 25-30A (just for context). something that allows for 6-8 devices might not be the worst idea, for future expansion.

There's a TON of fuseblocks for 12V systems but without looking at them handson I'd worry about clearances, and if the AIC of the fuses are enough. Something like a Lynx power in (with the fuse mod) feels way overkill here when I'd be looking at 10-20A of nominal draw and under 70A "worst case peak draw", for this part of the system

Per discussion elsewhere fuses downstream don't need the same AIC as your main, but still should have a decent level. It feels rather silly to have a 5A or 10A load on my main busbar. Plus it can be a challenge to find smaller fuses for certain styles.

So, does anyone run several smaller loads (or even small SCC I guess :) ) and if so do you just run them to your main bus bar, or have another solution?

PS: if you ever ask yourself "did I leave enough room for the system?" the answer is no, because you'll figure out you want something added/more later... :ROFLMAO:

Edit: there's TONS of stuff on ebay and amazon, so I super appreciate any "first hand" accounts like @SamG340 offered :)
 
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How about this ? 1 cable from your main bus into the big mega fuse , 4 smaller loads from the midi fuses
 


How about this ? 1 cable from your main bus into the big mega fuse , 4 smaller loads from the midi fuses
Oh thats a clean look, only rated for 24V, but with an upstream properly rated fuse (for AIC) and a separate ground (so no clearance issues) might be alright?

Is that a product you've used? Sometimes things look nice but the build quality is terrible ?
 
Oh thats a clean look, only rated for 24V, but with an upstream properly rated fuse (for AIC) and a separate ground (so no clearance issues) might be alright?

Is that a product you've used? Sometimes things look nice but the build quality is terrible ?

Yes I have one here , it's ok , not bad . Really it's just a plastic box with a few nuts and bolts & a bus bar - but it does the job


I am using it for 48v
 
I'm not sure if the mega & midi fuses are actually any good . Seems you know more than I do about fuses lol
 
For a load center, I'd think about the Midnite MNPV6 or MNPV12 boxes. They come with a busbar you can use for your loads. Just feed it with a sane breaker/fuse off your main busbar, and the breakers to go in the box are available in pretty much any size you'd like and aren't horribly priced.
 
For a load center, I'd think about the Midnite MNPV6 or MNPV12 boxes. They come with a busbar you can use for your loads. Just feed it with a sane breaker/fuse off your main busbar, and the breakers to go in the box are available in pretty much any size you'd like and aren't horribly priced.
Looks like a fairly beefy option for 48V! It's certainly an option!
 
Yeah, a bit beefy for 48V, but AFAIK, none of the major solar companies bother with 80V breakers, and 48V rated is shy for a 48V nominal system. Maybe you can get some cheaper breakers from the Carling QY series elsewhere, but I've already looked and not found it easy to find them at all. Slightly wider breakers (four per 6 slots used by the QY breakers) are available, but I haven't noted a meaningfully better price. For … reasons … I know rather more about these breakers and availability than I really wanted to.
 
Yeah, a bit beefy for 48V, but AFAIK, none of the major solar companies bother with 80V breakers, and 48V rated is shy for a 48V nominal system. Maybe you can get some cheaper breakers from the Carling QY series elsewhere, but I've already looked and not found it easy to find them at all. Slightly wider breakers (four per 6 slots used by the QY breakers) are available, but I haven't noted a meaningfully better price. For … reasons … I know rather more about these breakers and availability than I really wanted to.
Sure, I also don't really need breakers for this application, or at most a single breaker for all of these "sub circuits".

Still adding it to my "think list". Need to price the breakers I'd use and that might really change my mind lol

At these kind of prices the temptation is to get the 4 position bus bars from Current Connected, do inline ceramic fuses or something. I wouldn't feel too bad about doubling up on the stud for 5A loads if its a M8 stud.
 
Fair enough. You'd mentioned a couple different fuse sizes in your OP, so that, along with my way overthinking these exact boxes and breakers right now, got me suggesting it. These guys have a pretty decent price on most things.
 
Fair enough. You'd mentioned a couple different fuse sizes in your OP, so that, along with my way overthinking these exact boxes and breakers right now, got me suggesting it. These guys have a pretty decent price on most things.
So I'm looking at say another 60 bucks for breakers. The value add is easier isolation of loads (assuming my alternative is bolted/screwed fuses)
There other added benefit is theres lots of expansion room.

I would need to measure clearances (including for cable egress) since it has defined locations for the cables to go and is a decently sized box.

Hmm, concern with using MNPV6 is it's "backwards" from what I'm doing, are the compatible breakers directional?
 
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Yes, the breakers I can find to put in it are directional. Supposedly those breakers were discontinued Q3 2021(!) and replaced with non-polarized, but I can't find evidence of the latter actually existing anywhere.

The busbar is a chunk of copper with teeth at the breaker pitch, so it could be put in either way, albeit at the cost of slightly more complex cable routing inside the enclosure. If you don't mind the reversed operation, AFAICT from the datasheet the breakers are fine with being mounted "upside down" if it improves the wire path.

Midnite has a couple other DIN rail breaker boxes, but I'm not so familiar with the details.
 
A couple of relevant threads. In short, yes, this is a confusing space. The midnite breakers were what I settled on. I wish I'd just gone for the MNPV6 or 12 option in the first place. Perhaps more palatable if you consider that you can also put AC distribution in there as well.





polarized breakers, midnite's kind of confusing poster about polarized vs non-polarized

Would love any updates in this space, including blade fuses and fuse holders that are rated for a 48v nominal/60v actual system.
 
A couple of relevant threads. In short, yes, this is a confusing space. The midnite breakers were what I settled on. I wish I'd just gone for the MNPV6 or 12 option in the first place. Perhaps more palatable if you consider that you can also put AC distribution in there as well.

...

Would love any updates in this space, including blade fuses and fuse holders that are rated for a 48v nominal/60v actual system.
Thanks for the links, more reading! :)
 
For a load center, I'd think about the Midnite MNPV6 or MNPV12 boxes. They come with a busbar you can use for your loads. Just feed it with a sane breaker/fuse off your main busbar, and the breakers to go in the box are available in pretty much any size you'd like and aren't horribly priced.
I recently got an MNPV12 and I think they'd be great for this application. In particular you could do your AC load center and breakers on one side and your 48v breakers on the other side (that's a supported option in their documentation). You can probably also fit a shunt in there, as well as a grounding bar. Definitely that would have seemed overkill to me initially but I wish I'd gone that direction in our RV (which has 120v AC, 48v nominal DC, and 12v nominal DC through a blue seas blade fuse).
 
Hmmm, I think a DIN rail with the modular glass or ceramic fuse holders looks like a sensible option. Picked it up from this thread: https://diysolarforum.com/threads/low-ampere-48v-fuses.40164/

McMaster-Carr has ceramic fuses at 250v DC (equivalent to Littelfuse 314). These fit into "Modular DIN-Rail Mount Terminal Blocks" which can be expanded with insulated bus-bars that I think fit in the top (sort of like comb bus-bars for circuit breakers), called "Bar Jumpers". Looks like the run from sub-1amp up to 30amps. So that seems a solid option for 48v distribution. https://www.mcmaster.com/7641K861/

Note that the thread above linked to the "Fuse Blocks for Glass-Tube and Ceramic-Tube Fuses" but those don't seem to have a DC rating (only 300V AC). Almost all the other holders have 250v DC ratings.

Would love someone to post experience with these, I can't find a video of them being put together.
 
Wanted to comment that I also found the Optifuse APR58-UL (standard blade fuse ATO/ATC form factor) at Digikey and used them as the individual fusing for paralleling the packs in my DIY powerwall. I was also trying to find a good solution for low-current distribution/collection for my 48V system. I wish automotive-style fuse blocks were available for mini fuses that frequently are rated to 58V volts!

Current collection system:
IMG_9262.jpeg

Writeup on whole parallel-pack powerwall FYI:

Cheers,
Mike
 
Wanted to comment that I also found the Optifuse APR58-UL (standard blade fuse ATO/ATC form factor) at Digikey and used them as the individual fusing for paralleling the packs in my DIY powerwall. I was also trying to find a good solution for low-current distribution/collection for my 48V system. I wish automotive-style fuse blocks were available for mini fuses that frequently are rated to 58V volts!

Current collection system:
View attachment 207213

Writeup on whole parallel-pack powerwall FYI:

Cheers,
Mike
Woah, that's a pretty cool idea.
I legit would've used that if it knew it existed.


I just read through your whole blog post, good job. 👍

I don't have any individual fusing at all on my 36v eBike battery bank, but I have them all paralleled and run through a Class-T fuse and a circuit breaker before going to my inverter.

Btw I also am dealing with the same situation you are in, where I am really left in the dark as to whether any individual pack has failed or not, it's hard to tell without occasionally individually checking each.

I have all of the batteries running through a shunt, so I occasionally unplug every pack but one and read the voltage that way, doing it for each of my 10 packs.
 
Woah, that's a pretty cool idea.
I legit would've used that if it knew it existed.


I just read through your whole blog post, good job. 👍

I don't have any individual fusing at all on my 36v eBike battery bank, but I have them all paralleled and run through a Class-T fuse and a circuit breaker before going to my inverter.

Btw I also am dealing with the same situation you are in, where I am really left in the dark as to whether any individual pack has failed or not, it's hard to tell without occasionally individually checking each.

I have all of the batteries running through a shunt, so I occasionally unplug every pack but one and read the voltage that way, doing it for each of my 10 packs.
Thanks!

I was really interested in individual fusing of the packs as a last resort. In the event there is an internal cell short on a pack that does not trip the cell CID, AND the BMS malfunctions and does not catch it, there is a 10A fuse to prevent giant inrush of current into the pack. For external issues, the main breaker for the whole system has a current rating greater than the theoretical short circuit current of the whole shebang, so I figured that will take care of it. An extra Class T would also be good backup!

A lot of arcing/smoldering damage can happen before any one of these protections goes off, though. But really what I want to protect against is catastrophic thermal runaway. On another DIY portable power station I've burned up XT60 connectors via an oopsie-daisy even though there was a BMS, electronic overload protection of the charge controller load output, and two thermal fuses in line with the current path.

And for individual pack monitoring -- right, I use an amp-clamp to check each pack while charging occasionally to make sure current is flowing. Could add a hall-effect current probe to each line but that seems bulky and wasteful.
 

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