MYOG USB power bank

Vapcell’s in hand.  These things are sick, 50g @ 4000mAh, silicone sleeve 8g.  They fit/work in my Fenix winter torch.  So 8000mAh to use as any combo of battery pack or headlamp battery at 116g.   Not bad

The silicone sleeve weather seals out and protects the usb port and is easy to pull back to expose the port. It came with a 25g case that holds two, if you want more protection

can you verify they’re 4000 mAh?

Not directly, don’t have a USB meter.  But vapcell tests I’ve seen on line put the efficiency of their cells about the same as anker

I plan to see how many phone charges I get from it and compare it to my anker 10k

That would give a pretty good answer

Too good to be true, should have read the fine print, they’re just batteries.

Vapcell specs the battery and battery/bank identically except one line item, bastards.

To get o/p, need to up to the heavier 21700

https://www.vapcelltech.com/h-pd-126.html

I have some coming today from Amazon. Rated at 4100 MWh. Hopefully. Good reviews.

Isziii batteries @ Amazon

Nice, but not reversible as battery banks.

Edit: now for something completely different, https://www.aliexpress.com/item/1005006904804004.html

Cool little light. Twice the weight of a Zebra, but more features. Looks brighter. Cheaper.

I bought an 18650 battery from Amazon they said was 9,900 mah.

And it was $10 for 2 batteries.

I don’t know why I got that because that’s not possible

I tested it.  1,000 mah – 10% of spec

Don’t trust specs on amazon

Jerry – that’s wild.  The largest capacity I’ve seen to date in “legit” batteries is 5000maH in the 21700 format.  Just seeing the claim of 9900mah, especially in an 18650 format, immediately set off alarm bells in my head.

As a whole, I don’t trust Amazon sellers. They’re resellers of Chinese goods that they’ve never tested. The batteries I received are rated in watt hours which is a little more believable. I’m not counting on it though. I wanted something that I could charge off my power bank. I’m always buying new batteries before a trip and carry a spare, so using rechargeables will eliminate that practice.

That was obviously a typo, 9900 instead of 990.  See it all the time on Amazon goods, the description is wholly for a different item or partial cut and paste carry over from elsewhere.  It’s usually not a direct attempt at deception, just sloppiness.

“9900 mah” is printed on the outside of the batteries, doesn’t seem like a typo

An almost identical battery is sold by a bunch of different resellers.  Sometimes the name of the reseller is printed on the outside of the battery

They also claim to be low self discharge – 80% in 2 years.

Maybe AI created all of that content.  The AI noticed that many batteries advertise low self discharge so they added that…

It’s all sort of weird.

The voltage regulator efficiency is going to be your biggest issue with a MYOG. Unless you want to go the route of designing the circuit board yourself it will likely be pretty difficult to match the performance of some of the good commercial power banks. The circuit in the nitecore packs is very efficient, I want to say at or above 95%, but I can’t remember where I found that number before (probably a BPL article though). These cheaper boost power converters bleed off a lot energy as heat waste. It’s surprising how much this impacts the overall performance, but it really makes a huge difference for our use case.

Maybe 9900 mWh? I see them sold on Alibaba. Forty to sixty cents each when buying a minimum of 500. About $300. Great reviews on the seller. None on the product. Cost to sell on Amazon is $0.99/unit. Cost of credit is maybe $60. About $0.75 to mail. About $1,230 . Sold for $5 x 500 or $2,500. Double your money while only risking $500-560. Five sells a month @ @ 2/$10, you’re making a profit with no money out of your pocket. The hardest part is coming up with new brand names when your reviews go south. Most customers wouldn’t know the difference. Few would return them. If you ask for a refund, they might just tell you to keep them.

they asked me to return mine

which makes no sense

it’ll cost more to ship it back than the $10 it cost

how can I measure efficiency of my charger/power bank… hmmm…

I could use the usb power meter to measure the power charging it, then use the usb power meter to measure the power discharging.  Assume that half the inefficiency is charging and half discharging.  That would be close.

Since I returned my 18650 batteries, I now have none, but I have some that I accidentally left somewhere, and will be going back in a couple weeks, then I can test it

how can I measure efficiency of my charger/power bank… hmmm…

For your loose cell charger it’s pretty easy. Efficiency = (Output Power / Input Power) * 100

With a commercial sealed pack I am not sure how that would be done without tearing it apart.

Yeah

Normally I don’t care what the efficiency is charging the battery because it’s plugged into AC.

I only care about the efficiency is discharging

Actually, all I care about is the capacity of the usb power bank which includes the capacity of the battery and the inefficiency of the electronics that converts battery voltage to USB voltage.

Hey David D, that Wurkkos HD15 has been my staple for the last few years. Originally bought it for the power bank feature. Turns out it works well for small draw electronics but not great for modern smartphones. In fact modern phones don’t charge well from anything but a high output powerbank with at least 15w USB C output.

Great light though. Comes with a short tube for use with 18350 cells. Good modes with a spot and a seperate flood beam which can be combined. Moonlite mode is great. Just wish it had smooth ramping. Still my staple trusty steed.

i have no idea about what you folks are talking about. Too technical for me! good on ya though for your ohms and aahs and mahs…Hallelujah!… wait, maybe you mean something else…

(maybe…)

Meanwhile, I just bring new batteries in my Steripen and a full charge in my ancient Kindle with no backlight that I use for reading in the afternoons and at night before sleep. Of course, for a month’s long trip, one needs to bring in the ohms and the mahs and the voltage regulators. god forbid I should go out into the wilderness without a voltage regulator!

I kid.

That cheap usb power supply with one 18650 battery charged my phone okay.  Also it charged low current device like ear bud.

Thanks @DirtNap!

Somebody gave me some 3,000 mAh 18650 batteries.

I tried them in my power bank.

The battery only got 1,600 mAh.  Assuming the power bank is 100% efficient.  It’s probably 95%, so maybe the battery is actually 1,700 mAh.

I bet that’s common for random 18650 batteries.  On Amazon or wherever.

Maybe the Nitecore 18650 batteries are closer to spec.

Nitecore rates their NB10000 at 5400 mAh at 5v, so more like 55% efficient, depending on how you measure.

That is much closer to your measured result.