30A fuse in Shermans: is it a DC fuse rated for 100V+ ?

[supercurio]

Here's the fuse in the current Shermans, it's rated for 30A:

However, I'm reading now about the differences between AC and DC fuses aka how a DC fuses for higher voltages must have the ability to prevent arcing after breaking the circuit.

And this one doesn't look like it has the characteristics typically associated with these fuses:

• Fair gap between the two terminals.
• A filler material (like sand) which makes arcing more difficult than air.

So my question is: are these fuse actually gonna do anything in case one or two of the battery packs get shorted, or will they just arc, let the short continue and lead to an inevitable battery fire?

Notes:
I was originally looking a fuse for my battery DL/24P 180W capacity tester, to add in-line with a XT-60 plug just in case the tester MOSFET blows - leading to a short.
Since I have spare 30A Sherman fuses I thought they would do just fine, but now I'm concerned.

I already blew the DL/24P MOSFET earlier during a stress-test with a 84V charger, and it appears solid now after I upgraded it to a much stronger 400V MOSFET. But still, adding a fuse before testing a friend's Begode pack seem wise so I would welcome recommendations of fuse for this application.

Edited November 22, 2021 by supercurio

[supercurio]

Findings so far: it looks very much like the Sherman uses 2x of this fuse in its 30A variant
And here's the Datasheet

Bad news: unless I got the wrong one, it's just an automotive fuse, with maximum operating voltage of 32V.

Not suited whatsoever for 100.8V DC, expected to arc instead of breaking a circuit unless its actual capacity consistently more than 3* beyond spec.

Were you aware Leaperkim is using the wrong type of fuse @Jason McNeil, which will offer virtually no protection in case of short?

 

When my first Sherman board partially failed, the battery wires started to de-solder themselves from the board.
Needless to say, the battery packs could have been shorted a few seconds later.
I'm realising now as the fuses appears to be the wrong type, that the whole thing could have ended in a 3200Wh battery fire.

 

Edited November 22, 2021 by supercurio

[supercurio]

I'd like to request @RagingGrandpa and @Chriull's opinion on this DC fuse matter 

[RagingGrandpa]

On 11/22/2021 at 3:13 PM, supercurio said:

it's just an automotive fuse, with maximum operating voltage of 32V

Correct. It's the mini-ANL fuse size. Intended for 12V and 24V automotive systems.

On 11/22/2021 at 2:26 PM, supercurio said:

are these fuse actually gonna do anything in case one or two of the battery packs get shorted

Yes of course! They melt, and the circuit will open.

On 11/22/2021 at 3:13 PM, supercurio said:

offer virtually no protection in case of short?

Actually, they are quite effective...

But as you mentioned, there will be explosion of the fuse case, and a large, brief arc:

This is a hazard to other circuits, components, humans, etc in the immediate surroundings of the fuse. Thankfully, there's not much stuff inside an EUC to damage... the controller failed already (causing the fuse to melt), and the battery cells are big metal canisters that require prolonged heating to be damaged. And the human is shielded from the flash by a thick plastic wall

On 11/22/2021 at 3:13 PM, supercurio said:

the whole thing could have ended in a 3200Wh battery fire [if the fuse does not open the circuit]

Almost certainly not...

Having such a large battery pack, and relatively small wires to the controller, XT60 connectors, etc makes it far more likely that long before the cells runaway, other parts of the circuit will melt. It actually happens quite often: a controller fails with FETs stuck-on, and we get the "smoke and popcorn" experience of the PCB melting, but with no reported instances where this immediately caused a battery fire.

(I'm looking forward to demonstrating this, stay tuned.)

 

On 11/22/2021 at 2:26 PM, supercurio said:

I would welcome recommendations of fuse

If you use a 250VAC-rated fuse, it will melt without blowing apart its case or causing a fireball.
The tricky part is: such fuses are physically larger, which makes them more expensive, and more difficult to package inside an EUC. Certainly doable... but not trivial. And what happens if the fuse jiggles loose? Cutout crash. Care must be taken in the fuse holder design.

Recommendations here: https://www.mouser.com/c/circuit-protection/fuses/cartridge-fuses/?current rating=26 A~~40 A&voltage rating ac=220 VAC~~500V VAC&rp=circuit-protection%2Ffuses%2Fcartridge-fuses|~Current Rating|~Voltage Rating AC

 

 

Edited November 24, 2021 by RagingGrandpa

[thendless]

Little off topic, what is the configuration of the sherman packs? I understand they have 24S10P from reading somewhere... Does that mean 2 packs are 24S3P and the other 2 are 24S2P?

[Planemo]

No it means each pack is 12S 5P, then 2 packs connected in series to make 24S (100.8v). Add the other two packs on the other side to then get to the 10P.

[thendless]

Ahh that makes sense. So there is a total of 2 fuses for the battery packs, 30A on each side? Is there also a fuse downstream of the controller?

[Planemo]

3 minutes ago, thendless said:

Ahh that makes sense. So there is a total of 2 fuses for the battery packs, 30A on each side?

Yes

3 minutes ago, thendless said:

Is there also a fuse downstream of the controller?

No

[thendless]

I noticed in earlier batches it was 50A. What was the reason for downsizing?

[Planemo]

Just now, thendless said:

I noticed in earlier batches it was 50A. What was the reason for downsizing?

Not sure, someone somewhere decided that the board could fry before the fuses blew, but that can still happen with 30's in there so...

I'm not convinced that the fuses serve much of a purpose for most events tbh, the only one I can think of is a catastrophic overheat board failure where the battery inputs might detach themselves from the board and short out or the board traces end up shorting somewhere.

 

[Planemo]

On 11/24/2021 at 9:26 PM, RagingGrandpa said:

If you use a 250VAC-rated fuse, it will melt without blowing apart its case or causing a fireball.
The tricky part is: such fuses are physically larger, which makes them more expensive, and more difficult to package inside an EUC. Certainly doable... but not trivial. And what happens if the fuse jiggles loose? Cutout crash. Care must be taken in the fuse holder design.

Recommendations here: https://www.mouser.com/c/circuit-protection/fuses/cartridge-fuses/?current rating=26 A~~40 A&voltage rating ac=220 VAC~~500V VAC&rp=circuit-protection%2Ffuses%2Fcartridge-fuses|~Current Rating|~Voltage Rating AC

The recent S20 fast-track nuclear power plant exercise recently got me thinking about trying to fit some higher voltage fuses into the Sherman. I note that some in your link above do have some clip-in fitting which can be screwed/bolted down. Theres a fair bit of space in the area where the stock fuses are too, so I don't think real estate is an issue.

Regarding concerns about the fuse jiggling loose (which I totally agree with), the assembly minus the mounting area could be encapsulated within some adhesive-lined heatshrink which would ensure the fuses wouldn't have even the slightest chance of coming free from the clips.

So are we saying that using domestic 250v AC fuses is OK? They do list them in the 30A range.

[RagingGrandpa]

I own a Sherm with 30A fuses. 

The Leaperkim original fuses are name-brand (Littelfuse Clear MIDI series) and mounted very securely in a bolt-in box intended specifically for this size of fuse. 

... rated for 32V, so we expect the fuse's plastic body to blow apart when it melts.
But I think that's fine because: 
+ The positive wire leads are anchored securely by bolts, and won't be flopping around after the fuse blows. 
+ The negative lead doesn't come near the fuse. 
+ The fuse is shielded from the other parts of the EUC, by the plastic fuse box cover and other shell plastics.

For me, the bolt-in box is one of the nicest things about this design. I wouldn't want to change to a higher-voltage-rated fuse, unless we could find a fuse holder that is as rugged as this one.

 

  

42 minutes ago, Planemo said:

are we saying that using domestic 250v AC fuses is OK?

Yes, 250VAC fuses are great, and will almost surely melt without exploding, at 100VDC. 
Choose the rating carefully- different classes of fuse have different delay characteristics. 
And take care in mounting them, since a loose connection will result in an EUC crash.

 

Edited March 28, 2022 by RagingGrandpa

[supercurio]

And Kingsong S20 BMS 60A fuses rated for 60V DC:
https://www.uchidg.com/sale-11417521-477-series-brick-type-time-delay-surface-mount-fuse-1140-15-60a-72v-60v-dc-with-big-current.html

Maybe because they're tiny SMD fuse? With both leads very close apart.
They didn't seem to work in the recent fire, with a 95-126V pack.

Edited March 28, 2022 by supercurio

[RagingGrandpa]

2 minutes ago, supercurio said:

Kingsong S20 BMS fuses rated for 60V DC

Well, regarding the S20 fire, there are two separate paths of criticism: 

1. Did the fuse not melt?
   (suggesting: KS chose a fuse current rating that is too high) 
    
2. Or, did the fuse melt but then continue arcing or damaging other important things after melting?
   (suggesting: KS chose a fuse voltage rating that is too low)

Anyway, let's have the S20 design discussions in a Kingsong topic, not here in Leaperkim. 

[supercurio]

Good points!

It makes a good case for the type of fuse as used in Sherman or LiTech packs tho.
With the physical characteristics of their package and enclosure possibly helping them punch above their own DC rating.

Although I started this topic due to concerns, I kept the OG Sherman 30A fuses in place, and got this fuse holder for my battery tester use case:

Edited March 28, 2022 by supercurio

[Planemo]

56 minutes ago, RagingGrandpa said:

For me, the bolt-in box is one of the nicest things about this design. I wouldn't want to change to a higher-voltage-rated fuse, unless we could find a fuse holder that is as rugged as this one.

I agree, the stock Sherman fuseboxes are nice and rugged. I'm just nervous about the 32v rating, thats all. Theres a part of me that is concerned a fuse will blow during a simple high current requirement whilst at 100v...but I don't hear reports of Shermans blowing fuses, and many ride a lot harder than I do...so I guess I'm just being a bit paranoid

56 minutes ago, RagingGrandpa said:

And take care in mounting them, since a loose connection will result in an EUC crash.

For sure, I wouldn't use any fuse that wasn't bolted/screwed down.

BTW, the LiTech fuse is a common automotive type as well, max rated for 24v  so I guess I am even less worried about the Sherman 32v ones now...

BTW2...Kevin recently put out a vid of a Sherman where the bolts had come loose on the fuses...he suggested that everyone with a Sherman check them for tightness. I would have to agree with him. I'll be doing mine before my next ride.

 

[RagingGrandpa]

55 minutes ago, Planemo said:

vid of a Sherman where the bolts had come loose on the fuses

I think that's a risk only if the fuse has been removed during maintenance or repair... 

I don't recommend removing the fuse out of general concern.
By all means, pop open the fusebox cover and wiggle the posts and wires to be sure they're firmly secured and not moving. 
If it feels secure, leave it alone!
Every removal and reinstallation gives an opportunity for human error.
 

Edited March 28, 2022 by RagingGrandpa

[Planemo]

I agree. But I don't know if the Sherman in the vid had been worked on before. I don't think it had, hence the concern.

[.....]

Damn you @Planemo! now you have me wondering which fuse is in mine. I recall I got sent a newer fuse from Jason and I THINK I installed it. Of course, now I have no idea if it was larger or smaller. Oh well..

Fwiw, I think the fuse type should be okay. Its not intended for a/c use, but it will definitely open up and vaporize when it needs to. If it did manage to break and reconnect itself, I would imagine it would simply vaporize again and even more. I won't suggest that I know for sure that a bridged blown fuse wouldn't occur, but I've managed TONS of blown fuses over many years and they do just keep opening up until the current doesnt flow. I'm not sure being a/c or d/c, would make much diference in the mechanical aspect of it all. I would be much more suspect of an smd fuse or something that I havent dealt with for 30 yrs(just cause ingnorance<proven history). I do know that my home is a/c and I've had screw in type fuse boxes aplenty. They also open up witha  simple wire. I've yet to see one arc and keep arcing enough to cause fire. Typically its the connection point in the base, that likes to arc.

If people are securing their fuse holders in and not using loctite/rtv, perhaps they need "rethink" about the tech who's doing it. Lock washers AND loctite/rtv, should almost be a given on these connections. Remving a fuse isnt a maintenance thing. Go ahead and secure it. Just be mindful of loctite near plastic shells.

Edited March 28, 2022 by ShanesPlanet

[Planemo]

20 minutes ago, ShanesPlanet said:

Damn you @Planemo! now you have me wondering which fuse is in mine. I recall I got sent a newer fuse from Jason and I THINK I installed it. Of course, now I have no idea if it was larger or smaller. Oh well..

If you got new ones from Jason they would deffo be the 30A ones. whether you installed them or not is another matter. You probably just shoved them on your workbench with all the other crap you've been meaning to get around to whilst you rolled a fat one 

20 minutes ago, ShanesPlanet said:

Fwiw, I think the fuse type should be okay. Its not intended for a/c use, but it will definitely open up and vaporize when it needs to. If it did manage to break and reconnect itself, I would imagine it would simply vaporize again and even more.

Oh I've got no doubt that the stock 30A will vaporize, and the distance between the contacts is sufficient to not arc afterwards. I was more concerned over the 32v rating blowing BEFORE it was desirable, like when on a high current pull up a hill or something. I know Marty's didn't blow on OH hill but I think he had the 50A ones in at the time? I'm not sure. Either way, I guess I'm just nervous that a 32v 30a fuse is sufficient for all riding circumstances. But as I say, it's not like Shermans are blowing fuses all over the place so I guess they should be ok... 

In short, I'm not really fussed about having a fuse that protects the board. I just want one that will pop with a battery short, and even the 50A ones will do that. So in my head I'm just thinking 'why not just fit the 50's' and never have to worry about one failing whilst I'm riding the wheel, however hard I'm pushing it. Further, it's not like the 30A ones will prevent the board from meltdown anyway, given a long enough hill.

20 minutes ago, ShanesPlanet said:

I would be much more suspect of an smd fuse or something

100%. SMD stuff is just too cramped for me to be sure it wouldn't arc given the crazy voltages and currents we see in wheels now. Practically mini arc welders.

[Chriull]

15 minutes ago, Planemo said:

I was more concerned over the 32v rating blowing BEFORE it was desirable,

Voltage rating is just specified fir safe discnnecting wuthin specified timeframe.

There is no way the fuse will melt prematurely.

19 minutes ago, Planemo said:

100%. SMD stuff is just too cramped for me to be sure it wouldn't arc given the crazy voltages and currents we see in wheels now. Practically mini arc welders.

With higher voltages it will arc and this arc will eat some pcb track and stop.

Just a little bit later than specified, but nowhere enough stable material to withstand the arc and keep it up for any noteworthy time.

[supercurio]

43 minutes ago, Planemo said:

I know Marty's didn't blow on OH hill but I think he had the 50A ones in at the time?

For the record, @Marty Backe blew the first Sherman board on overheat hill before there was fuses.

43 minutes ago, Planemo said:

I'm not sure. Either way, I guess I'm just nervous that a 32v 30a fuse is sufficient for all riding circumstances. But as I say, it's not like Shermans are blowing fuses all over the place so I guess they should be ok... 

Still wondering if any Sherman which burned a board also burned a fuse, or if even at 30A they're still too slow acting.

43 minutes ago, Planemo said:

100%. SMD stuff is just too cramped for me to be sure it wouldn't arc given the crazy voltages and currents we see in wheels now. Practically mini arc welders.

Now you have a fuse
- oops sorry okay now you have a weld.

[RagingGrandpa]

17 hours ago, Planemo said:

I'm just thinking 'why not just fit the 50's'

 ... because a melt-type fuse with a 50A rating can pass >100A for >3 seconds.
It's unnecessary torture to the cells, especially considering that the maximum normal current is ~5kW = 25A per pack.

If we're lucky, you're right: 50A- and 30A-ratings might work equally well.
If the overload is very low resistance, we'll see a pulse >200A, and fuses will melt almost instantly. 
The trouble comes with a middle-value overload like 150A. High enough to risk internal cell damage; but low enough that the fuse doesn't open instantly.

My favorite soundbyte regarding the annoying details of melting fuse label ratings: 
"The rating tells you the amount of current the fuse can handle, forever, without melting." 
(But to know when it does melt requires study of the fuse specification's time-delay table.)
 

Edited March 29, 2022 by RagingGrandpa

[Planemo]

1 hour ago, RagingGrandpa said:

 ... because a melt-type fuse with a 50A rating can pass >100A for >3 seconds.

I thought Sanyo 18650GA in 10P could pass 100A anyway...

And I don't know how accurate the data is, but EUCW shows me peaks of around 7000w.

That said, I think I'll stick with the 30A, it sounds easier for my brain  As long as my board melts before the fuses blow, I'm happy with that.

 

[RagingGrandpa]

2 hours ago, Planemo said:

Sanyo 18650GA in 10P

(There's one fuse per pack, and each pack is only 5P...)