I previously made a MYOG USB powerbank https://backpackinglight.com/forums/topic/myog-usb-power-bank/
That was an interesting exercise but probably not useful generally
I did make a powerbank with an 18650 battery. 2.5 ounces. 12.3 Wh. 4.9 Wh/oz. I think that’s the lightest possible weight to make a powerbank with 18650 batteries. Mainly, it’s that it doesn’t have a heavy case.
But it seemed like a NB1000 powerbank would actually be a better solution. I couldn’t help myself so I bought one.
I charged it, then discharged with a 1A load and measured the output as 33.5 Wh with USB power meter. It weighed 5.44 ounces. So that would be 6.2 Wh/oz.
The specs for NB10000 are 38.5 Wh and 5.29 ounces. So it weighs 3% more than spec. I guess I can’t complain but it annoys me that manufacturers usually exaggerate their specs.
I don’t think they even measure the actual Wh output. They just multiply the mAh rating of the battery (10000 mAh) by the nominal voltage (3.85 V). My measurement is 87% of that. It’s possible that’s the inefficiency of the electronics. I can’t access the NB10000 battery so there’s no way I can determine it’s output efficiency, but with my MYOG powerbank, I could, and it was 93% efficient. That is, the Wh coming out of the powerbank was 93% the Wh coming out of the battery.
Anyway, the NB10000 was 6.2 Wh/oz. My MYOG was 4.9 Wh/oz. If I had two 18650 batteries I would double the capacity and get 5.9 Wh/oz. Three – 6.3 Wh/oz. So, I could save a little weight with my MYOG version, and especially, I could take just as many batteries as I needed for a particular trip. But that’s too complicated, easier to just use the NB10000.
It took 3.75 hours to charge the NB10000. This would be good for a long trip where you want to recharge it mid trip. I think thru-hikers like this.
My (obsolete) Anker 13000 is 4.7 Wh/oz. And takes maybe 12 hours to charge. 9 ounces. 42 Wh. Actually, that works fine for me and I am being wasteful buying another powerbank : )
The NB10000 has a low power mode. When my Anker 13000 charges my ear buds, it’s too low current so it shuts off. I have to restart it maybe 100 times before the earbud is charged. With the NB10000, you push the power button for about 3 seconds and this white LED comes on, and then it won’t shut off a low power device like the ear buds.
The NB10000 has two USB outlets. One is a USB A (the rectangular outlet, old technology) that is an output to charge a device with. The other is a USB C (newer technology rounded outlet). This is both an input and an output. You can plug in the USB cable from a charger and it charges, or you can plug in a USB cable to a device, like a phone, to charge it. I noticed that the output voltage was 9 volts, so it will do fast charging of a phone, but that doesn’t seem very important to me, you don’t need to fast charge because when I’m done using the phone for the day, I charge it and it doesn’t matter how long it takes. Fast charging of the NB10000 could be useful if I had to wait for it to charge at a 110 V outlet.
Most powerbanks use 18650 batteries internally (I think). You can see that the outer dimensions are a little bigger than an 18650 battery. And they use Li-ion chemistry.
The NB10000 is a little different – Li-poly chemistry. It comes in a foil package, as opposed to the metal package of a 18650. Li-poly has a little higher voltage than Li-ion. I think that maybe Li-poly doesn’t have as long a lifetime. I guess I’ll make sure and only use my NB10000 when I’m backpacking. I’ll use my Anker(s) when I’m at my car.
I noticed another spec – rated energy – 6400 mAh at 5V. That would be 32 Wh. That’s a little less than my measured 33.5 Wh. Ahhh…. that is what I would expect for a spec – a little less than the typical or actual. Maybe I have to take back my criticism of them being under spec for capacity. I just need to ignore “capacity”, because it doesn’t mean anything. Look at the “rated energy” instead.
If I look at the 4 powerbanks I have:
Anker – 13000 mAh – 42 Wh actual
Anker – 10000 mAh – 26 Wh actual (this is pretty old so possibly degraded from new)
Anker – 20000 mAh – 60 Wh actual
NB10000 – 10000 mAh – 33.5 Wh actual
Then the mAh rating of the powerbank is actually pretty good for comparing two powerbanks. For example if a 10,000 mAh lasts half as many days as you need, then you can get a 20,000 mAh one.
