About fuses and choosing the appropriate fuse for your mod
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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
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Yes it is but the different is the fuses you need for DNA40. Check mamu quote on my edited post above.
So, all of the posts above seem a bit confusing?
In an earlier post Mamu stated 1x 7A LittleFuse (2920L700SLPR) on each batt of a dual/parallel 18650 DNA40 mod. But that only provides 14A ihold, which I believe is stated as nor sufficient in a later post due to the pre-heat of the DNA40?
So, should I double these up on each battery (4 total), or switch to another fuse, or have I completely confused myself?
In an earlier post Mamu stated 1x 7A LittleFuse (2920L700SLPR) on each batt of a dual/parallel 18650 DNA40 mod. But that only provides 14A ihold, which I believe is stated as nor sufficient in a later post due to the pre-heat of the DNA40?
So, should I double these up on each battery (4 total), or switch to another fuse, or have I completely confused myself?
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.
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.
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thanks mamu for all the work you put in this for us.
I have a question ...in two 18650 in series...I noticed on your t10 build you are putting the fuses on the pos side.
so the two batts are protected . but one of the batteries to the center point which I call the balance point is not .
using a balance external charger. also not worried about reversed batteries.becouse they are staying in the mod .
building a mod now and plane to two parallel fuses in the neg leg . but now the other battery is not fused either to the balance port!
where would you put the fuses so both batteries are protected in series and also to the balancing port ?
plane on using two sets of 3 amp fuses
I have a question ...in two 18650 in series...I noticed on your t10 build you are putting the fuses on the pos side.
so the two batts are protected . but one of the batteries to the center point which I call the balance point is not .
using a balance external charger. also not worried about reversed batteries.becouse they are staying in the mod .
building a mod now and plane to two parallel fuses in the neg leg . but now the other battery is not fused either to the balance port!
where would you put the fuses so both batteries are protected in series and also to the balancing port ?
plane on using two sets of 3 amp fuses
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.
Any further testing been done with fuses for a dual battery DNA40? I'm using samsung 25R batteries and am wondering if the 28 amp trip is a bit too high.
28A is not trip, it is hold if using 4x fuses (2x on each batt).
The goal is to protect the batts from reverse polarity damage from the huge current dump from shorting the batt if one is inserted backwards as well as not interfere with the current requirement of the DNA40. Littelfuse 2x 7A fuses per batt give the best protection/least interference for this. I've not found any other fuses that provide this protection, so the only alternative is to use a P-FET per batt.
I was mistaken on the max preheat of 16A. The DNA40 has a capable max input continuous current of 16A, a capable max output continuous current of 16A and a max output preheat burst of 23A.
The goal is to protect the batts from reverse polarity damage from the huge current dump from shorting the batt if one is inserted backwards as well as not interfere with the current requirement of the DNA40. Littelfuse 2x 7A fuses per batt give the best protection/least interference for this. I've not found any other fuses that provide this protection, so the only alternative is to use a P-FET per batt.
I was mistaken on the max preheat of 16A. The DNA40 has a capable max input continuous current of 16A, a capable max output continuous current of 16A and a max output preheat burst of 23A.
Just a quick question - do you wrap each set with electrical tape or use heat shrink tubing, or just use judicious placement?
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
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
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
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
Hmmm, strike that - I think one of my fuses may have lost it's special smoke? I hate tearing into things that are already "done"
mamu - any suggestion for a fuse on an unregulated dual/parallel 18650 for rev polarity & catastrophic failure?
Anything smaller than a square inch!!!!
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.
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.
Its very possible I over heated when soldering, had some difficulty with one of them. If overheated, can they fry "Open/tripped"?
An update on these fuses. I am assuming the original failure I had was due to overheating while soldering. I have now soldered about 8 in place without a failure. As you apply the solder you can actually hear the fuse "click" (It is faint, but audible if things are quiet) and I use that as an indication I cannot linger with the iron much longer and back off as quickly as possible. Still, I have kept applying the iron a few more seconds after the click without any more failures. After you are done soldering, the fuse will be "Open" due to the heat, but after 10 seconds or so (A little water bath helps too!) it will "Click" again and works just fine.
Also, I installed two on a dual battery sled and tested for reverse polarity protection. Inserted one battery upside down and then connected the negative tabs of the sled - almost immediately "Click" and resistance through the fuse jumped very high - remove the connection from the negative tabs and another "Click". Even had instances when both fuses would open. Also left the batteries in this state for a longer period (60+ seconds) and they returned to normal operation.
That's my experience with them anyway!
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