Anyone familiar with the myriad of "Portable USB Chargers" which contain a battery of some kind with 5v output? It seems you plug them into a laptop USB port or a USB charger to recharge the internal battery. Anyway, with 2200-mah and higher capacity ratings I'm wondering if they might make a decent portable 5v SBC power supply? Can anyone tell me if these devices use an SMPS (switch mode power supply) to boost battery voltage for the 5 volt output and how clean the output is? Can anyone recommend one that they've tested and used?

TIA. Cheerful regards, Mike

I've never opened one up, but I would assume most of them use a single Li-Ion cell. Since a single cell only produces around 4V, and the voltage depends on the charge level, they would need a boost converter to produce 5V. The 5V could well be noisy, especially if the product is cheaply made. Whether that's going to be a problem is impossible to predict.

I wouldn't go with 2200-mAH and what you don't know is that some of the cheap batteries are from recyled laptops (....think used batteries....think... that you're buying someone's E-Waste). You want a powerbank with 10,000 mAH for about $20 to be reliable. What I've learned from Lithium batteries is that they work until they give out so unless they are rated by the manufacturer, you don't want them in your smoke detector. Duracell is the only battery that goes in my smoke detector because the others won't last six months. I have some of those smaller rated 2200 mAH power banks and they aren't worth it to me because they don't last or maybe it is because some of them don't work right.

I don't feel like posting a lot of the information here and I'm not naming names because I don't want to be sued but here is the post on another website and "no", I am not trying to steal users but here is the information because I don't feel like posting it again and again but 6502 users can feel free to copy the information from this link:

http://zappbots.altervista.org/forum/vi ... ?f=2&t=145

I recommend this power bank. It is cheaper than the competition that you will find in most places trying to make money off of you and I spent a lot of time shopping around. It is also in an aluminum case.

Poweradd Pilot 2GS 10,000mAh Portable Phone Charger External Battery Pack with Fast Charging for iPhone, iPod Touch, Samsung Galaxy, LG, HTC and more - Silver

http://www.amazon.com/gp/product/B00ITI ... ge_o03_s00

You can't beat that quality for that price. We have one and it powers an iPod 5th generation for about two or three days and my ISP says that we are power users for FIOS even though I'm not on it. I have my own in case the power goes out and we need it for storm related emergencies.

Thank you for the info', Gentlemen. I really appreciate it...

I've had a few of these things and used them for powering electronics. The main issue is that they can be very noisy. Most USB devices are okay with noisy power supplies, because most USB ports on computers are awfully noisy.

As Arlet speculates, most use a single cell Li-ion or similar configuration that produces ~3.7V, which is then boosted to 5V. Some might use series cells to produce 7.4V and drop it, but in either case there will be switching noise. The better ones will be switching at 1+MHz, the cheaper ones maybe as low as 50KHz. The good ones will have some stuff on the output to clean it up a bit.

Then there is charger noise. When connected to a charger there will be even more noise in the system, as another switching regulator is used to regulate charge current into the battery.

Again, the cheap ones tend to have poor output regulation and critically little in the way of current limiting. The better ones will limit to 500mA as the spec says they should, but be aware that you could pull a few amps from those things if you are not careful.

My solution is usually to use a linear regulator to clean the output and limit current, but if you need 5V... You can get ones that put out 12V or more, for laptops.

Andy Brown wrote a post on filtering the USB line. It is for ARM but maybe some of you that can read electronic flowcharts can pick up on how to do it:

http://andybrown.me.uk/2015/07/24/usb-filtering/