Powerbank Battery Quest
November 18, 2014 3:51 PM   Subscribe

I need to power an electronic gizmo through USB. The requirements for the powerbank battery are: output - 5V, 1.5 - 2amp. I'd like the max practical mAh under $100.

The problem I've run into is fraud - so, f.ex. on ebay I'd find powerbank batteries from China or made in China with claims of 50,000mAh (5V, 1.5a & 2.1a) for, like $18 - which just does not compute on any level, and I suspect the 50,000mAh is a complete fabrication.

Basically I need reliable - not inflated - specs for the powerbank, for under $100, with the mAh as high as I can get - reliably - for the price (output 5V 1.5-2amp).
posted by VikingSword to Technology (9 answers total) 2 users marked this as a favorite
Anker has well-reviewed products. As far as I can tell, this is their most capacious backup battery: it's good for 20,000 mAh, and can deliver 4.5 A through 4 ports.
posted by adamrice at 4:01 PM on November 18, 2014

Which do you want more, reasonably compact size or battery capacity? If you don't care about size and weight, you might want to look into portable car jumper packs, many of which have 12v accessory plugs into which you could plug a USB auto adapter.
posted by Nerd of the North at 4:04 PM on November 18, 2014

I suspect the 50,000mAh is a complete fabrication.

it totally is. a guy i went on a trip with far away from any power this year had a 38k mAh one like that and it seemed to have less capacity than my trusty new trent 10.5k one... while being huge, and having a crappy case that felt like it would crack and fall apart with the slightest squish or drop.

Honestly, i'm not sure if i believe that anyone is selling anything much bigger than 20k mAh, especially under $100.

I honestly don't believe in most of the larger than 10-12k mAh ones being real, and when they are they're horrendously overpriced.

I'd like the max practical mAh under $100.

How portable does this need to be? I'm seconding the car jumper pack solution. Some of those contain the equivalent of several hundred thousand mAh, with the bonus that a decently efficient cigarette lighter car charger will extend that even further than it would converting 3.7v to 5v. 12v>5v is just inherently more efficient.

My $100 here would go to a $75-80 car jumper pack, and a $15 or so actually decent and efficient car charger(like an anker).

One of those jumper boxes will run a 50w boombox for over 24 hours, driven through an inverter. I forget what the capacity of that one was, which was over $100, but you can see where i'm going with this. From a bang/buck standpoint the car jumper box and car charger solution is going to take you way, way further. Especially since, as i mentioned, i don't really believe that 90% of the batteries over 12k mAh aren't just boxes of lies, and/or really really cheap cells that only really ever add up to like 15k mAh anyways.
posted by emptythought at 4:14 PM on November 18, 2014

The problem with those jumper packs is those car batteries are meant to pump out a large amount of juice for a short period of time. Using them for continuous output for long periods will kill them quickly. I used one for art shows for a while and after less than a dozen or so full days it was kaput.

What you want for this sort of thing is a deep discharge battery. You can buy one at any Walmart or some other big box stores. You'll need a charging solution but a slow trickle can be had for $20.
posted by phearlez at 4:29 PM on November 18, 2014

Response by poster: OK, actually size does matter. Basically this is to power a microphone mixer/recorder (Tascam DR-70D). The recorder is attached under the camera, so the powerbank (which would be connected to the recorder with a USB cable) would be attached as well. Basically a car battery is not the solution here. Also, as someone mentioned, this is about continuous powering for hours - I'd like a full charge to last me the 10 hours or so that it might be used during a shooting day.
posted by VikingSword at 4:54 PM on November 18, 2014

The "MiLi HB-P18 18000mAh Battery Power King" is the biggest reviewed unit I could find. I think it might actually supply 18000mAh because it seems to be a 19V unit that switched down or something. It uses special 19V charger which may be a pain. And it's like 8oz which is reasonably big for a battery. And it's $200.
posted by GuyZero at 5:00 PM on November 18, 2014

This one is another well-reviewed 19V unit on Amazon that is currently $99 rated at 26000mAh. I'm not sure what that's going to deliver at 5V after getting stepped down.
posted by GuyZero at 5:05 PM on November 18, 2014

I suspect the 50,000mAh is a complete fabrication.

In my experience it's been accurate, the trick is that it always refers to the mAh of the *batteries* in the powerbank, not the powerbank, so you need to know the cell chemistry before the number is meaningful (ie before you can figure out the watt-hours)

For example, a device containing four cheap AA NiMH cells at 2000mAh each means the device has a 10,000mAh battery, but it's a 1.2V 10,000mAh battery, ie 12 watts-hours. Once you step that up to 5V (or put cells in series, or whatever), that 12 watt-hours gives you just 2,000mAh output, even though the 10,000mAh claim is accurate.

I've used Aliexpress for powerbanks from China with success. If the cells are lithium, then assume any mAh numbers applies to 3.7V, not output voltage. I got a nice unit with lots of features packing about 75 watt-hours for $80.
There are plenty of listings, so you can always find one that has enough technical details and photos (which match each other) that you're comfortable. There is also escrow by default.
posted by anonymisc at 5:58 PM on November 18, 2014 [1 favorite]

car batteries are meant to pump out a large amount of juice for a short period of time. Using them for continuous output for long periods will kill them quickly.

Continuous output for long periods from any battery is actually more efficient and kinder to the battery than extracting the same total amount of energy from the same battery very quickly. This is still true even for car batteries deliberately engineered to be capable of providing hundreds of amps in brief bursts. Continuous output per se doesn't kill car batteries; repeated deep discharge does.

Car batteries die early if frequently discharged to below about half of their rated capacity. For example, if you had a car battery rated at 50 amp-hours, and you pulled 4 amps from it for 10 hours, it would only have 20% of rated capacity left at the end. Do that several days running and you'd certainly kill it. But it would happily supply 2 amps for 10 hours, day after day after day, as long as it was fully recharged overnight.

Even a deep cycle battery will suffer damage if run completely flat. This applies to lithium polymer batteries as well as lead acid types. So if you do end up with a battery that's otherwise satisfactory but doesn't run quite as long as you need, get two and swap them over pre-emptively. You can put the one you're not using on charge, which depending on charge and discharge rates could well give you very nearly continuous power availability at the device.
posted by flabdablet at 5:25 AM on November 19, 2014

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