18650 for single cell USB Power Banks.

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jerm03
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18650 for single cell USB Power Banks.

I like to give a single cell USB charger to folks who sometimes need a charge for their phones away from home. I buy the case and install a battery. I have been using unprotected Panasonic NCR 18650B 3350 mAh batteries from IMR. I am about to buy some more, and wonder what is among the best to use and at minimum cost.

Advice please.
Thanks, Jerry

Agro
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Samsung 35e. The cheapest of quality “3500 mAh” cells. And with marginally higher capacity than the others.

jerm03
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Thanks, Agro, I ordered some.
aI noticed that the description of the box is “USB Power Bank Case Kit 18650 Battery Charger DIY Box. It states a capacity of 2650mAh. Does that preclude batteries with more capacity, ie 3500 mAh?
Jerry

agent80
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What is a good DIY box for 1×18650?

Wildcat
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agent80 wrote:
What is a good DIY box for 1×18650?

Miller ML-102. The best Smile
jerm03
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Here is what i use to make a gift. I am not sure why these indicate 2650 mAh since it has no battery.
https://www.ebay.com/itm/Portable-2600mAh-USB-DIY-Power-Bank-18650-Batte...

SIGShooter
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2600mAh batteries were one of the most common before so I’m guessing that’s why they use that.

Are you going to test what they charge the battery to before giving them away?

jerm03
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No.I think those I gift them to are not very interested in such things, will just use them to charge phones and plug them in to the wall.
Jerry

SIGShooter
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jerm03 wrote:
No.I think those I gift them to are not very interested in such things, will just use them to charge phones and plug them in to the wall.
Jerry
I was mostly concerned that they would overcharge the batteries but I haven’t seen any instances of that happening with power banks, so it’s probably a moot point.
jerm03
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If I use one for myself I take the battery out of the “box” and charge it in my Nitecore charger. It is faster.
Jerry

Danglerb
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We used to think why would anyone get one, then got one, now have half a dozen of different types. Its easier to own several and leave some on the charger so you always have a full power bank to grab and use.

Still a bit dim

Barkuti
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Make sure to optimize the cell connections as much as possible. If you can't spot weld or low temp solder the cell(s), at the very least I would suggest using neodymium magnet stuck (if nothing better) copper discs (to maximize contact surface) fixed with some sort of glue as cell contacts. This should be enough for the low drain requirements of a power bank board.

I've built some power banks in the past with certain inexpensive but good DIY circuit boards, may someone suggest something a bit beyond the basics? I mean, an efficient board with extra features beyond the usual 5+V 2A output. I prefer boards which output well above 5V or with configurable voltage output, Quick Charge and the like is nice also. Oh! Any board with selectable maximum battery voltage? 

 

Cheers Party

flydiver
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jerm03 wrote:
Here is what i use to make a gift. I am not sure why these indicate 2650 mAh since it has no battery. https://www.ebay.com/itm/Portable-2600mAh-USB-DIY-Power-Bank-18650-Batte...

I tried a number of those sort of chargers/PB. All worked…at first > all died or had problems. IMO, don’t bother.

chanamasala
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I bought a DIY 18650 charger on eBay.

If I throw an unprotected cell in there, do these things have some sort of low voltage over-discharge protection usually?

Danglerb
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chanamasala wrote:
I bought a DIY 18650 charger on eBay.

If I throw an unprotected cell in there, do these things have some sort of low voltage over-discharge protection usually?

Don’t count on it having anything. For cheap and quick I bought an Xtar single cell charger, for better I bought an Engineer 500, Letokala something like that.

Two my cheap chargers had cold solder joints that failed where the shiny long contact wire connected to the circuit board. Easy to fix except case did not survive opening.

My latest bank is a Toumo M2, still in transit.

Still a bit dim

d_t_a
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I bought this DIY 1x18650 powerbank/charger from Gearbest to test it out:
https://www.gearbest.com/chargers/pp_187285.html?wid=1433363

first I drained a Sony VTC4 and charged it with the powerbank, which resulted in this charging curve:

- max charging current is 0.8A, which may be a bit slow for 18650s
-> surprise: it charged to exactly 4.20v (measured with my DMM)

 

then I used EBD-USB+ load tester to drain the VTC4 inside the powerbank at 1A discharge rate:

- the powerbank is not really able to sustain 1A discharge rate, notice the voltage already dropped to below 4.50v in about half an hour..

*forgot to check the VTC4 battery voltage after it had been fully discharged in said powerbank

Danglerb
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Good cells aren’t in the same level of cheap as cheap DIY powerbanks. I dipped my toe in the cheapos, but after buying a few high quality cells I’m done and sticking to premium banks. The cheap ones are false economy.

Still a bit dim

Barkuti
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To Danglerb and everyone who believes you can't have it cheap: you can. It just is what you believe in your mind, which ends up creating the reality you experience. Let me show you an example:

 

Dual USB 5V 1A 2.1A Mobile Power Bank 18650 Battery Charger PCB Module Board @ Banggood

Volume discount links found: 3pcs  5pcs

The above board has been purchased by me many times, and may be found a few cents cheaper in AliExpress. Outputs up to 2A or thereabouts and charges its internal battery at 2A, tested. Used the board in custom cased powerbanks, with cells low temp soldered. Reliable. It can be found with case:

 

DIY Kit Dual USB 5V 1A 2A Power Bank 18650 Battery Charger Box @ Banggood

See user pictures and you'll have proof it's the same black colour board.

 

Cheers Smile

Danglerb
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When I dropped the cheap $2 DIY banks I skipped the middle ground and went straight to name brand $10 non DIY (no soldering, just add cells), thanks for the suggestion though it looks pretty good.

Still a bit dim