so im double checking, if i use a single 18650 with a dna 40, i dont need a fuse. if im using dual 18650 i would need fuses?
so im double checking, if i use a single 18650 with a dna 40, i dont need a fuse. if im using dual 18650 i would need fuses?
I have seen lots of people report getting "Weak Battery" messages.
Here is something that came across the beta Forum:
.Board reads weak battery with fully charged batteries
its the preheat I think, it constantly puts the fuses in high hold but not quite trip at first. Over time the fuses weaken and hit trip faster and that is when you see a fresh battery read week after a couple of pulls.it doesn't seem to manifest right away and only for the higher wattage users,
Many folks still have a bunch of the 7A fuses left over from DNA30 projects, and essentially we are under-rating our fuses if we only use 2 of them in the DNA40. The DNA40 can pull a max of 16A. If you use two 7A fuses, as we did with the DNA30, then you are right on the verge of the trip point during preheat. Over time, the fuses get a little weaker and start partially tripping (ie high resistance without fully tripping), and the "Weak Battery" messages start happening.
From Mamu:
The Littelfuse 4.5A smd fuse 2x on each batt works - 9A on each batt for a total of 18A with dual parallel batt configuration.
From Bap:
Need to double up the fuses. I'm now running 2 on each battery, 4 total.
(He is talking about the 7A ones.)
The moral of all of this is to be sure you fuse to least a total of 16A........
On this page mamu mention about single and parallel 18650 fuse, check post #43 and #50
http://www.e-cigarette-forum.com/fo...ses-choosing-appropriate-fuse-your-mod-5.html
Edit: Update from mikepetro post about fuses
thats for the dna 30, would it be the same for a dna 40?
lol yes it is getting a bit confusing.
I've been adding 1x 7A fuse on each batt with dual parallel batts (14A total Ihold, 28A total Itrip). I personally have had no issues, but I'm running the DNA40 at 400F at 25W.
For those running higher watts, higher temps, and max preheat amps (16A), each time the preheat amps exceeds the total Ihold (14A) of the fuses, the fuses are put in a pre-trip state which results in the fuses heating up with subsequent increased resistance. With repeated exceeding of the Ihold current, the fuses' resistance never returns back to normal and remains high. The increased resistance interferes with the DNA40 reading the input voltage which then displays Weak Battery and won't fire the atty - even with fully charged or nearly fully charged batts.
To prevent this, use 2x 7A fuses on each batt with dual parallel batts. Which is what I'm doing with my current DNA40 build. I would HATE to have to redo my mod if I start getting this issue, so best to take care of it now and not have to deal with it later lol.
Ideally, we would use fuses with 16A total Ihold for the DNA40. I have other smd fuses on order to test, but for now I'm using the 7A fuses as they are the only ones I currently have that provide reverse polarity protection for shorting of the batts if one should be inserted backwards. I re-checked the 4.5A smd fuses and they are no go for reverse polarity protection with using 2x 4.5A fuses per batt for dual parallel batts, only with using 2x 4.5A fuses for a single 18650 batt.
The primary purpose for using these fuses is for catastrophic batt failure and reverse polarity protection for shorting of the batts if one should be inserted backwards. Although total Ihold and total Itrip is on the high side, 2x 7A fuses per batt with dual parallel batts meets this purpose as well as not interfere with circuit resistance and the DNA40 working correctly.
And many thanks to bap for giving us the heads up for the weak battery message and isolating the most common cause - fuses with too low of an Ihold current when running high preheat amps.
parallel for each batt - stack one on top of the other with ends matching and solder together - do the same for the other set of fuses, then solder one set to each batt.
Yes, I've used those fuses - not with the DNA yet though, only with my unregulated MOSFET coil build/test mods. Easy to work with, easy to solder. I need to test to see if it will also provide reverse polarity protection for shorting of the batts with the DNA with dual parallel batts, haven't gotten around to it yet.
I would say yes to the reverse polarity! I used these in my Box Mod and in my haste to see it work the first time I put one battery in upside down Flipped it over and it fired just fine
well that sucks, NaCl. No, haven't delved into fuses more than just these for unreg. mods.
You have to be careful when you apply solder to this fuse though. I've read that too much heat during soldering and it fries the fuse and you may not know that until you need it to kick in and it doesn't.
Hi Mamu,
Have you seen the new fuse design...........http://www.mouser.com/ds/2/418/NG_DS_DS28403_A-109895.pdf
I'd like to see your thought's on this.................Thanks