Fusing

[mikepetro]

Considering there is an onboard fuse on the DNA200, is it still recommended to fuse the LIPO?

And if so, what does Evolv recommend?

[SSV]

Not sure what Evolv recommends, but in ANY device I design or work on (trained EE here) we always include an inline PTC/thermistor immediately after BMS (unless BMS includes one, on board)

[John]

The fuse is directly inline with the battery, and is a tertiary protection as is. It should only come into play in the event of catastrophic board failure or unprotected reversed battery. That said, if you have space I will never argue against an extra fuse.

[Theravenmn]

Ohh john why would anyone want to be safe!??? Pfff! Now I'm going to go put this fork into the socket

[Willy]

[SSV]

John can you provide a datasheet or P/N for the thermistor used?  i am curious about it's min/max thresholds....thanks in advance...

[mamu]

Mike - the onboard fuse works great for protection and pops uber fast.  I tested it last week and no damage to the board or batteries.  If the fuse pops though, will need replaced.  Replacing that teeny tiny fuse is a pita lol.

You can visually see if the fuse is blown as the top covering melts off - intact = green; blown = white - which is good for troubleshooting.

I don't see a reason to add another one since the onboard fuse is already essentially at the battery level, unless you want to add another one so you'll never have to replace the onboard one as I said it's a pita to replace.

[macz]

mamu said:

Mike - the onboard fuse works great for protection and pops uber fast.  I tested it last week and no damage to the board or batteries.  If the fuse pops though, will need replaced.  Replacing that teeny tiny fuse is a pita lol.

You can visually see if the fuse is blown as the top covering melts off - intact = green; blown = white - which is good for troubleshooting.

I don't see a reason to add another one since the onboard fuse is already essentially at the battery level, unless you want to add another one so you'll never have to replace the onboard one as I said it's a pita to replace.

I think that's what Mike had in mind, add another fuse without going through that. I assume Evolv can replace the onboard fuse for us if we unable to replace it ourself?

[mamu]

If I were to add an external fuse so I would never have to replace the onboard fuse, I would use 2x in parallel these 15A TE fuses soldered directly to the positive lead of the lipo pack:

http://www.digikey.com/product-detail/en/RF3038-000/RF3038-000-ND/3748599

Tiny so they don't take up much space and pop uber fast.

[macz]

mamu said:

If I were to add an external fuse so I would never have to replace the onboard fuse, I would use 2x in parallel these 15A TE fuses soldered directly to the positive lead of the lipo pack:

http://www.digikey.com/product-detail/en/RF3038-000/RF3038-000-ND/3748599

Tiny so they don't take up much space and pop uber fast.

Thanks Mamu, I have this one http://www.digikey.com/product-search/en?vendor=0&keywords=MHP-TA15-9-77 instead of the link above. I used those for my previous DNA40 lipo build

Specs shows the same, just parts number are different. Will this work?

[mamu]

oh wait... the fuses I linked are good for 9v max, so no can do for the DNA200.  Will have to find an alternative.

[mamu]

macz said:

[QUOTE=mamu]If I were to add an external fuse so I would never have to replace the onboard fuse, I would use 2x in parallel these 15A TE fuses soldered directly to the positive lead of the lipo pack:

http://www.digikey.com/product-detail/en/RF3038-000/RF3038-000-ND/3748599

Tiny so they don't take up much space and pop uber fast.

Thanks Mamu, I have this one http://www.digikey.com/product-search/en?vendor=0&keywords=MHP-TA15-9-77 instead of the link above. I used those for my previous DNA40 lipo build

Specs shows the same, just parts number are different. Will this work?[/QUOTE]

Yes, those are the same, but pop at a lower temp.  Also, they fry fairly easily if applying too much heat when soldering, whereas the 90 don't.

But, these are no go for the DNA200 as the max volt they can handle is 9v.  I use them for the DNA40 which max volt is 4.2v.

[macz]

Ah okay, tbh I got no issue with one I linked for my DNA40 build. Anyways let's get back DNA200 fuse, ignore that DNA40 

[mikepetro]

Thanks Mamu. Yes, replacing that onboard fuse would be a major PITA. Basicly a user would have to send the Mod back to me as most wont have the capability. Would love to find a PTC or similar that was rated 2 amps lower than the onboard fuse. Not much play there though, onboard fuse is rated for 25A and input requirement as high as 23A. Maybe a 20A rating, as I doubt a 12v 23A fuse will be found.

[Havensal]

Would something like this work?

http://www.mouser.com/ProductDetail/TE-Connectivity-Raychem/RHE1300/?qs=sGAEpiMZZMsxR%252bBXi4wRUNGWMrBHmeaA13jYVkBMbiY%3d

Manufacturer: TE Connectivity

Product Category: Resettable Fuses - PPTC

RoHS: No  RoHS Version Available

Brand: TE Connectivity / Raychem

Hold Current: 13 A

Trip Current: 24 A

Current Rating - Max: 100 A

Maximum Voltage: 16 VDC

Resistance: 10 mOhms

Mounting Style: Through Hole

Termination Style: Radial

Series: RHE

Operating Temperature Range: - 40 C to + 85 C

Dimensions: 23.5 mm L x 28.7 mm H

Packaging: Bulk

Factory Pack Quantity: 250

Type: PolySwitch Resettable Fuses

Part # Aliases: 194113-000

[mikepetro]

The value you care about is the "HOLD" current. Theoretically 2 of those in parallel would still be higher than the 25A onboard fuse. Just one would trip prematurely.

Plus, they are large, and obsolete.

[mamu]

mikepetro said:

Thanks Mamu. Yes, replacing that onboard fuse would be a major PITA. Basicly a user would have to send the Mod back to me as most wont have the capability. Would love to find a PTC or similar that was rated 2 amps lower than the onboard fuse. Not much play there though, onboard fuse is rated for 25A and input requirement as high as 23A. Maybe a 20A rating, as I doubt a 12v 23A fuse will be found.

The problem with having a fuse with an Ihold rated lower than the max input current of the DNA (<23A) is that if the user runs the DNA200 at or close to max input there may be inadvertent tripping, or a pre-trip phase where the internal resistance of the fuse rises and it gets very warm.  This increased circuit resistance would interfere with the DNA200 correctly working with a subsequent weak battery message even with fully charged batteries.  The DNA200 would see it as the batteries not capable of the current needed.

[mamu]

You can look at this way, Mike.  If the onboard fuse blows you're gonna be getting that mod back from the user anyway to troubleshoot it for why the fuse popped and more than likely replace the lipo pack.

I used a hot air gun to remove the blown fuse and just a regular soldering iron tip to solder a new one on.  It was a pita, but not a major biggie to get it done.  My experience with removing and soldering the cable end on the DNA regular screen def comes in handy here.

[mandro]

Hi mamu I'm glad you added your knowledge on this subject and it's good to know that changing the fuse is do able. I had been thinking wether to add an external fuse but was concerned about the weak battery issue when using a fuse that's rated below the required amps. Also, if I was to use a fuse with around 23amp hold, would it trip in time to protect the on board fuse. ATM I've decided to leave out the external fuse.

[mikepetro]

mamu said:

You can look at this way, Mike.  If the onboard fuse blows you're gonna be getting that mod back from the user anyway.....

Good point! Plus, the delta between the input requirement and the onboard fuse rating is just too tight to really make a PTC work. The range between IHold and ITrip on those things just isn't precise enough to accurately spec for this application.

I wonder if some small 24A 12v automotive fuse is available. It certainly would be easier to replace, of course you would still have to figure out why it blew.