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Need advice from battery guru. Want to use 18650 in devices
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Author:  bigbisont [ Thu Apr 02, 2020 6:40 pm ]
Post subject:  Need advice from battery guru. Want to use 18650 in devices
Has anyone attempted/had success pulling the 18650 cells out of a laptop battery and creating a rechargeable alternative to D batteries? I have 18 of them thanks to 3 old laptop batteries. I would like to recycle them if I can. Swapping out cumbersome Ds in my props seems like a great way to do it.

I have seen these converter "Banks" online for dirt cheap. You can get them to convert most any number of 18650 cells (removed from an old laptop battery) into a rechargeable bank.
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I would imagine I could splice a USB charging cable into the device wiring and pop the USB end into one of these 'banks' (similar to below). Then I could run an extension cable from the charge port of the bank to the outside of the prop to act as a recharge point that would be accessible despite a sealed prop.

So 'D's are 1.5v each and the 18650s have a discharge of 3v each.

-Any chance it is as easy as as just using 1x 18650 (converted into 'bank') in place of 2x Ds?
-Would I be able to get a triple 18650 'bank', and replace the 6x Ds in the colony light?
-If it is more complicated than that, what are the stats I need to be respecting?

I would hate to burn my props to crisp, so don't want to just 'assume' anything.

**If you have info to contribute/correct me, PLEASE speak as if you are explaining this to a small child. :wink: !!**
**Also please stick to the usage of 18650s as that is what I have.
Author:  StephenDutton [ Thu Apr 02, 2020 11:00 pm ]
Post subject: 
A few tips but without examining the circuitry in person I can't offer any guarantees.

Be careful about having batteries, especially old ones inside a sealed unit. If the battery is faulty you may not notice anything wrong while it is charging until it catches fire. Of course having battery protection circuitry included could help against this but whenever I hear 'dirt cheap' used to describe anything to do with batteries I suspect that this was the first thing left out. Even if the battery is protected how would you replace a damaged one?

Having two series 1.5V batteries is the same as having a single 3V battery. The device shouldn't care where the power is coming from. I've used bench top dc power supplies at work to simulate batteries.
However, are you sure that the 18650 is 3V? Wikipedia suggests a voltage of 3.7V nominal (the same for most batteries of this chemistry) and li-ion batteries are regarded as fully charged at 4.2V. that's closer to having three alkaline D's in series than two. Don't trust just using a meter to read the voltage of the battery. This drops the more the battery is discharged.

Charging is dependent on battery chemistry (eg. lithium-ion, lead-acid, Nicad, etc) so the charger must be suitable for the type of battery you are using.

No matter what you do I strongly recommend testing your system on the bench before putting it into a precious prop.
Author:  bigbisont [ Thu Apr 02, 2020 11:27 pm ]
Post subject: 
I googled "18650 specs" to get the 3v. I see now that was the "minimum discharge voltage", not the "nominal". I got your point now.

I'll dig into the units. They are def chinese cheap crap, but seem to go from $1-$3.
Author:  Ttaskmaster [ Fri Apr 03, 2020 3:16 pm ]
Post subject: 
18650s come in two types - Those with protective circuits in the top caps and those without.
Laptops usually use those with no protection, such as the LG ones I have here. Whatever device you use them in must have all the protections integrated into it.
Also, different cells are rated for different maximum continuous discharge values, so while some are fine for use in low powered torches, you wouldn't want them in your 2,000 lumen tac torch, or to be vaping at 120w with them. I and most others I know will charge them externally (I use a Nitecore D4, myself), even the ones with built in micro USB charging, simply because it's safer.

It might just be easier to go up your local vaping shop (online, if needs be) or custom vaping mod store and order some proper 18650s with a matching battery sled. Probably cheaper and less hassle in the long run, too, as well as less likely to blow your hand off.
Author:  knoxvilles_joker [ Sun Apr 05, 2020 2:22 am ]
Post subject:  Re: Need advice from battery guru. Want to use 18650 in dev
I will only add do not buy the ultrafire batteries. Those only work in specific aplications as they are designed like a traditional battery and there are no real battery housings that they fit in.

Regular 18650s are smooth and the battery housings I have found to date only work with those.

https://www.aliexpress.com/item/32821269708.html

This is one I hae used with 18650 units. good for 7.2VDC output at max charge. You will need a separate charger for these though.

Most of the 18650 units are NIMH based.

Your other option is a dewalt or other device and adapter to output at 5v via USB and 12v via barrel connector:
https://www.amazon.com/LANMU-Battery-Ad ... B07DZZLH7Z

The dewalts are my current preferred option as the batteries are easily obtained locally and replaceable in a literal snap.

Note that those adapters are also made for other battery brands...
Author:  Noble [ Wed Apr 08, 2020 7:39 pm ]
Post subject:  Re: Need advice from battery guru. Want to use 18650 in dev
PM me if you have any questions.

I've designed a few 18650 flashlights.

And some headlamps that are pretty cool.
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