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I was constantly getting "weak battery" with the Keystone sled.  With this sled I finally got one when the battery was down to 3.48 volts, HD2.  It is surprising what a decent contact between the battery and the holder can do.  Somebody should start making a decent battery sled that is capable of handling the current that batteries can produce.  Not to mention the loads a lot of gear, besides mods, can put on them.  Somehow 24 gauge doesn't seem quite appropriate to me.

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Bad "Battery Holder Case":
1.  https://www.fasttech.com/products/0/10002233/3895100-1-18650-battery-holder-case
Good "Battery Holder Case":
1.  https://www.fasttech.com/products/1009/10002233/1290005-1-18650-battery-case-with-connect-pins
2.  https://www.fasttech.com/products/0/10002233/3827701-1-18650-battery-holder-case-w-smd-mount
3.  https://www.fasttech.com/products/3023/10018241/3827703

If holder have springs is no good idea, and don't helps metal plate. 
Springs for the purpose of springs. Curved metal - firmly in bending.
sorry my bad english

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It depends a lot on the spring diameter, length and material, I get better performance with a cut down ProVari spring (mod in the show me your 75 thread pg 1) than from the flat spring holders like those and the Keystone, but I only have the spring at one end.  You can bend the flat springs to increase the contact area (hard to get right) and solder the wire as close to the battery to improve them, but personally I wouldn't use them for higher power mods.  My mod of the Keystone and Awsum's mod of the spring type holder will get much better results than any flat spring holder, but the ProVari spring one is very close and hard to tell the difference in everyday use. 

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I dunno.  The spring only provides tension to hold the battery tightly against the positive contact.  Both contacts are flat, providing maximum contact area with the battery terminals versus the small contact area of a piece of bent springy steel, which also has significantly lower conductivity than brass even if nickel plated.  The spring does not conduct because the negative contact plate is connected by a piece of braided, tinned, copper shield.  Overall a much lower resistance, higher conductance, solution than two small, springy, steel connections.

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jurdanas said:

"...and hard to tell the difference in everyday use". o.O


I get almost the same run time from both before Weal battery with 75 W preheat.

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i gotta say i'm pretty impressed with smy's battery sled in the sdna 75. the posi spring is tight and both that and the neg contact have good surface area contact with an 18650. i don't get the flashing battery bar (new weak battery message with the new FW) until 25%-20% batt when running 75w preheat, 2 sec, 11 punch. granted i'm running only lg hd2c batts. i'm sure dwcraig1 can confirm this with his mod. as in no premature weak battery message.

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jurdanas said:
maybe something like this jurdanas.............

http://www.ebay.com/bhp/battery-contact

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I just asked what the compression force rating is and what the current rating is on those springs.  Lets see what the reply is.

By the way, we're not trying to build suspension for a car here, just hold a battery firmly enough to insure good connections (said with a smile and tongue in cheek).  It is interesting to note that "modern" automotive suspension is either coil spring or torsion based.

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ChunkyButt200 said:

maybe something like this jurdanas.............

http://www.ebay.com/bhp/battery-contact




NO.
I bad speak English. Time will convince.
Sorry

Untitled.png

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He got back to me about current capacity.  He apologized for not knowing, saying they are just "spring guys", got a print and made the springs.  He did say they were originally made for use in "vaporizer pens" though.  I suspect that it would be fairly high, on the order of 20 amps or higher but I am always circumspect with beryllium, it's a know carcinogenic.  Granted, we're not going to vape the spring, but machining it can lead to spoils/particles/dust which isn't a good thing.  I may buy some just for hahas though.

In the mean time I'm working on another sled for another Proto/ERM/DNA75.  This time the positive button will be a disk of 1/8" brass rather than 1/16".  The extra space allows more clearance for the wire connecting at the bottom corner of the mounting plate and will also add just a little more pressure from the spring.  I'll post some photos after the JB Weld hardens, probably Wednesday.

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(Oscar Pistorius) leg prosthesis design, curved band - optimal, strong support with good support area.
We need such a principle of construction.

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Wave spring? Proven to have greater spring rate than coil springs.

If Oscar Pistorius was a high jumper he'd use wave sprung prosthesis ;)

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Again, I want to stress that my goal is firm, broad, low resistance, contact, not the strongest possible spring/contact.  Too much spring strength makes it too hard to install and remove the battery.  A wave spring would be nice but coils are more readily available.

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Here's the latest iteration with an 1/8" brass positive contact and a 1/16" brass negative contact.  The negative has a braided connection to the 14 gauge connection lead.  I have one more improvement to make which is changing the spring from the stock one to a copper/beryllium, silver plated, spring.  It still won't be a current path but after careful, scientific, testing (pressing down on the springs while on a small scale) I found the copper/beryllium/silver plated one needs three, plus, pounds versus just over two and a half for the stock spring.





One of the good features is that there are no exposed solder points or wires.  I've been using 14 gauge silicon wire to also minimize losses even though the lead lengths are under two inches.  All connections are inside the sled, nothing exposed anywhere.  The sled also fits snugly enough that it doesn't need to be wedged, or glued, into an ERM enclosure (at least the Proto/ERM enclosures).

Looking at it in eScribe, the sag has been significantly reduced under preheat using this sled style which would seem to validate the improved conductivity of the contacts.

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I am convinced that a good 18650 is more than suitable for the DNA75 IF the battery sled is good enough to support it.  After a few batteries worth with the new sled, the batteries are consistently going on the charger at 3.2 volts or lower.  Before this sled they were normally in the 3.5-3.6 volt range going on the charger.  I'm getting a full tank, plus, using an Aromamizer compared to less than a half tank with the Keystone sled.

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So to get in on the act I took my HE4 in my SMY SDNA75 down to 3.3, that's when I got to see the battery bar flashing for the first time. Using @ 40 watts/50 preheat.

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Based on that, SMY seems to have a decent battery sled.  I haven't used an HE2 in mine, yet.  The HEs I have are pretty old with lots of cycles on them so I got some HD2s and HG2s.  HDs for the current rating, HGs for the mah rating.  I get over a tank, Aromamizer V1, out of an HG and about a tank out of the HDs.  I'm running 40 watts but 75 watt preheat.

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i'm quite happy with smy's batt sled in the 75. i only get the weak battery message at around 20% batt. this is with 75 watt preheat, 11 punch for 2.3 seconds at a set wattage of 65w. this is with my LG HD2C batts. really great batteries, i definitely recommend them for high wattage vaping on the 75. they're a cheaper alternative to the vtc4, while having the same if not a little better CDR. it's also a lot of fun to open and let the battery door snap closed with your fingers while holding the mod.

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