The "WeekEnder"

[mikepetro]

This appears to be the MFG:
Shenzhen SmarTEC Technology Company
http://www.ayaatech.com/shop/?type=list&classid=66

Lots of very interesting boards on this site....

 

[Mike88]

hey bap, would you mind giving the dimensions of the nano naked? how hard was it to get out of the case?

sry should have read better

 

[bapgood]

hey bap, would you mind giving the dimensions of the nano naked? how hard was it to get out of the case?

sry should have read better

lol....it's all good....but just for reference they are written on it in the pic

 

[Mike88]

will the same charging board work for the lithium polymer battery?

 

[bapgood]

will the same charging board work for the lithium polymer battery?

Any "lithium" type charger for 3.7v nominal batteries will work. I have always used the Evolv charger it is cheap and small. It does take a while to charge something like the 6k nano. I only let it get all the way down a couple of times and it took ~12-14 hours to fully charge.

 

[rolf]

hi mike
looks like they are adjustable to !
I did not get any answers on my thread what to use... so I got some from battery junction ..want to use it on a lipo without the benefits of the dna20. on a simple mod. ....have funn

 

[mikepetro]

I wonder how these would be in a Mod?
https://www.fasttech.com/products/1/10003955/1563302-510-to-510-adapter-for-e-cigarette

They have a nice nut for attachment, just wonder if you can get them apart and reassemble to do the soldering.

 

[rolf]

wondering to !
nice find...just ordered 5 ...

 

[mikepetro]

This looks like it has potential to be a decent 510 connector for a Mod:
https://www.fasttech.com/products/1/10005381/1565103-replacement-stainless-steel-top-cap-for-chi-you

 

[mikepetro]

Ok, heres a couple of questions for you R/C enthusiast type folks.

This is a 6000mAh 25C bat that I took out its hard case.

I have noticed that a lot (if not most) Lipo batteries have Kapton tape on them. My experience with Kapton tape is that we use it on thermocouples to provide electrical insulation in high temp environments. Should I interpret this to mean that these lugs on the Lipos get hot? If so, is that just in the R/C realm where there are pushing the amperage to its limits, ie currents that I would not be exposing this bat to? I would never be pushing 150 amps out of a Mod, unless I was trying to self-destruct it!

I want to take these oversize lugs off of it and just solder a wire to it. It looks like the tabs are in those big blobs of solder. If I leave the little circuit board on there do I need to take any extraordinary precautions while doing the solder job?

 

[bapgood]

You should never be able the heat the tabs up vaping.

I take the circuit board and the lugs off, I recently compacted my 6k nano over another 1/8" folding down the top flanges.

If you have excess room, leaving the the pcb wont hurt and would be a little easier. The pcb doesn't have any electronics on it, its just there to solder the lugs to.

 

[mikepetro]

OK, next question, does anyone see anything wrong with this component.

Assumptions:
DNA20 min v cutoff is 3.1v
20w divided by 3.1v = 6.45 amps max current on a DNA20 (although their specs say 6a is the max)

I am considering using one of these fuses in my next build:
MF-LS340 Bourns | Mouser

They are rated at 6.8a trip and 3.4a hold.
Nice flat little suckers.

 

[bapgood]

I use two of these in parallel MINISMDC260F/16CT-ND

Using two in parallel halves the resistance imparted on the circuit. In reality the fuse(s) are only there to protect the battery from a dead short on the leads or etc. The DNA protects its self and "shouldn't" draw more current then it can handle.

IMHO you just want something that will break the circuit to the battery for those rare possible scenarios.

 

[mikepetro]

OK, so using two of mine in parallel would make the resistance about .008 - .013 ohms, or about a .03v drop (@ 11w/3a), and a trip current of 13.6a. This wouldn't protect the DNA but should protect the bat, or I could use one and live with a .06v drop and protect both with a 6.8 trip. Am I getting this right?

In light of a 6k mAh bat, I am not sure I am worried about a .0Xv drop, should I be?

 

[BJ43]

I still don't see how it protects the DNA. as Bap said the DNA will pull the amps it needs and no more, you do not need to limit it. The 6 amp max is on output and it controls that with or without a fuse. In the few times I have had a Lipo fire in RCs the fuse never prevented it so I quit using them...

 

[mikepetro]

I still don't see how it protects the DNA. as Bap said the DNA will pull the amps it needs and no more, you do not need to limit it. The 6 amp max is on output and it controls that with or without a fuse. In the few times I have had a Lipo fire in RCs the fuse never prevented it so I quit using them...

What caused those fires?

And what if I skipped the fuse? Would a fuse really protect against a dead short on the hot leg before causing thermal runaway?

 

[mikepetro]

What caused those fires?

And what if I skipped the fuse? Would a fuse really protect against a dead short on the hot leg before causing thermal runaway?

One failure mode I was envisioning is if the DNA malfunctioned and pulled too many amps then the fuse would protect the bat. The other failure mode would be the dead short of the hot leg that Bap mentioned.

 

[BJ43]

One failure mode I was envisioning is if the DNA malfunctioned and pulled too many amps then the fuse would protect the bat. The other failure mode would be the dead short of the hot leg that Bap mentioned.

The question is which is faster to blow with a dead short, the fuse or the internal chain reaction in the lipo. Most of mine that burned were from abuse, I fly a real helicopter much better than a model helicopter and I don't fly a real one upside down....

 

[mikepetro]

The question is which is faster to blow with a dead short, the fuse or the internal chain reaction in the lipo. Most of mine that burned were from abuse, I fly a real helicopter much better than a model helicopter and I don't fly a real one upside down....

Now theres a visual........

 

[BJ43]

Just for conversation, the DNA with a 1.5 ohm coil at 20 watts is putting out, 5.5v and 3.6a but how many amps is it pulling to step up the 3.1v minimum to the 5.5v?