Homemade Battery For Impulse AQ Ltd

[bklein]

12 hours ago, Steve Herschbach said:

Battery Quote From Carl:

“Originally 4x18650. The Impulse consumes 8 watts and 4x18650 is roughly 48W-hrs, or 6 hours run time. The new system will still be 4x18650 but will use drop-in cells instead of a pre-made pack so you can easily buy spares.”

I was rather shocked when I visited the local vape shops to buy 18650’s last Black Friday. Seems they have some kind of approval for that use now (and everyone was out of the high capacity cells). Looking online proved different too. Must be difficult/expensive to ship.  Then came the tv ads inferring that using these cells will end in a flash fire.  Lipo packs for RC use are still available for sale from hobby shops online, but many of the local hobby shops vanished - even before the virus.  Anyone know more about 18650’s for vaping and what the “certification” for them infers? I’m thinking it may be for high run current but what would that be? They custom label many of them. Recommendations?

[PimentoUK]

Individual cells come in two 'flavours' , raw cells, and one with protection circuitry integrated. Protected cells are slightly longer, due to the pcb etc, so won't fit every e-cig, flashlight/torch etc, and they may limit the discharge current too much, which makes them unsuitable for high power uses, like RC flight packs, ridiculous vape rigs. RC packs/cells tend to state the max discharge rate, in terms of 'C', so a '10C' pack can be drained at 10x its capacity, eg. 22A for a 2200mAh pack ... probably similar for vape branded ones.
Then there are Lithium-Iron cells, which are specifically aimed at the very high drain applications, but have noticeably lower capacity, 60% of most other Li cells. They need charging differently, too, a max cell voltage of 3.8V, not the more common 4.2V. They are not really suitable for our needs.
And there are now some 'graphite' chemistry variants, that are charged to 4.35V, the RC sellers brand them Li-HV. Probably good for model power, but not beneficial for our low drain uses.

As for recommendations ...
Watch out for fraudulent cells, like unbranded types claiming high capacities, anything with xxxxFire in the name -- all guaranteed junk.
Sanyo-Panasonic are considered the best brand, their best 18650's manage 3400 mAh.

[Steve Herschbach]

Why all the emphasis on 18650 batteries? I just got a Tarsacci, and it comes with a couple EBL 26650 batteries. These things are sweet! 5000mAh 3.7V each, four (14.8V) with some kind of drop in battery design for the Impulse would get a full day of detecting I think. Four would be a nice counterweight to the coil, maybe add a little more weight overall than the 18650, but I think balance would work out well. And only $20 for a four pack!

https://www.newegg.com/ebl-2-pack-lithium-batteries/p/14R-01BT-000W8

https://www.walmart.com/ip/EBL-4-Pack-26650-Battery-3-7V-5000mAh-Li-ion-Rechargeable-Batteries-for-Flashlight-Vapor/822287699

https://www.ebay.com/p/1753415266

High Performance: The advanced batteries provide maximum reliable power for the need of your devices. The high-quality pre-charged battery can be conveniently used immediately out of the package. The batteries can be recharged up to 1200 times when fully or partially drained, which is extremely economical and powerful. The advanced batteries provide an expected lifespan similar to that of the device in which it is used. Besides, the highly improved low self discharge makes it still maintain 75% of capacity after 3 years of non-use.
Universally Used for Devices: EBL 26650 lithium rechargeable batteries can be universally used for household devices, such as digital cameras, toys, remote controls, hand held games, 2-way radios, PDAs, flashlights, alarm-clocks, LCD-TVs, electronic toothbrushes, shavers and portable audio players, you name it.
Trustworthy Quality: Certified by CE and ROHS, EBL brand batteries, such as AA/AAA/9V/C/D/18650/26650 rechargeable batteries, have trustworthy quality and good reputation.

The Tarsacci runs on only one of these, so one is a spare. Nice dual battery charger also.

 

[cdv]

Steve , my thoughts too on those batteries. Wish I was able to figure out how to assemble a pack for them. My two for the Tarsacci are still going strong after a bit over a year.

Cliff

[PimentoUK]

One of the reasons 18650 size is favoured is because that size has had a lot of development put into it, firstly in laptop computers, then electric vehicles. Other sizes, both larger and smaller, seem to have lower capacity than what you would expect, based on 18650 specifications.
The internals of these cells are basically rolled up sheets of aluminium & plastic, so any technical improvements should immediately be applicable to smaller/larger cells. It just doesn't seem to have happened.
I have just tried a 'math comparison' with 26650 size , and I would expect a capacity of over 7000 mAh should be attainable. But so far, 5500mAh is the best claim I recall seeing for one. [this is the 'ShockLi' brand, which sound awful and dodgy, but seemingly are not, and are also sold under other names, particularly when re-packaged as 'protected' types. At low-drain 0.2C rate ( ie. about 5 hours discharge time ), they test at near 5800 mAh]

In practice, energy per unit volume is not always the important characteristic, energy per gram weight may be more relevant. If the cells are lighter as a result of being under-capacity, they will meet this requirement.
Does a detector battery need to be small? Or is there an optimum weight range, for example?

[Steve Herschbach]

41 minutes ago, PimentoUK said:

Does a detector battery need to be small? Or is there an optimum weight range, for example?

As far as I am concerned the optimum weight in an under elbow configuration is that which properly balances the detector. I get that the 18650 is “more proven” but the 26650 certainly does not seem “unproven” either.

Well, I’m no battery expert, but I like the form factor, nice for fumble fingered types.

 

[PimentoUK]

It would certainly be worth experimenting with added weights, to see how much the battery pack could weigh. Then use that data to influence the design of a homebrew battery pack.
Going by its appearance, and my familiarity with the F75, I expect it could be quite a substantial battery. 12 x 18650, 8 x 26650 may be practical. Or 11/12 x A-size NiMH.

[Skull diver]

I'd love to try this 26650 beasts to modify with only 4 of them my battery pack for the Tdi.

Assuming a 535mAh / hour consumption this will last sooo long in it!

At least 8 hours at full gain.

[Elbert]

Good to hear that you now have a AQ and the Tarsacci. It will be interesting to see how they compare in the extremely black sand conditions in Tahoe. Maybe on your next trip.

El.

[Steve Herschbach]

2 hours ago, Elbert said:

Good to hear that you now have a AQ and the Tarsacci. It will be interesting to see how they compare in the extremely black sand conditions in Tahoe. Maybe on your next trip.

El.

It’s not a pressing concern for me. I got the Tarsacci to try as a nugget detecting machine, and hopefully will be doing that in the next couple weeks. I plan to get up to Tahoe again tomorrow to hunt with the AQ but my plan is to go detecting, not testing. I did enough of that to satisfy myself on the last trip. When I next get to a nugget location I will be using both the Impulse and Tarsacci looking for gold nuggets, and will be comparing the Tarsacci to my other VLFs, so I may gain some insight at that time.