Power Pack Charge Current Requirement

[Martin109]

I have acquired a Tigra Power Plus Battery Pack, to go with the Tigra mount for the Galaxy S3 I'm using as a GPS.  So far I've been charging the battery pack via USB satisfactorily,

On the road, I'll be keeping it charged from a Son Delux and an e-werk, so I wanted to know from CycleWiz what the charging requirements for the battery pack are, but they don't know!  They said they'd get back to me.

If they don't, or if they still don't know (which I'd find strange), I'll need to come up with something. 

Am I right that the standard for USB charging of anything is 5V at 1A, ie that's what any USB connection produces?  If so, it sounds like it'd be safe to set the e-werk to those values.

[Biggsy]

Am I right that the standard for USB charging of anything is 5V at 1A, ie that's what any USB connection produces?

No.  Standard USB 2 max current is 0.5A, although it can be higher with some specially designed/configured USB 2 ports, eg. some Asus ones.  It's also higher with standard USB 3: 0.9A

[Martin109]

So I should be safe feeding the battery pack with 5V at 0.5A all day?

[Biggsy]

Yes, it's labelled "Input 5V 500mA" and should have over-charge protection built in.

[Martin109]

Thanks, Biggsy.

Clever of you to have spotted the spec on the label in the photo - which I missed!

[andrew_s]

You can get USB current meters that go between the lead and the power socket (cheap & basic version)
It may be interesting to see what current your battery pack takes when charging from mains or PC, and set the eWerk to a similar value.

[Kim]

Surely the E-Werk just sets a voltage and the current is determined by the load?  Or does it have current limiting as well?

[Martin109]

Surely the E-Werk just sets a voltage and the current is determined by the load?  Or does it have current limiting as well?

Kim, the e-werk provides output voltage between 2.8V and 13.3V in steps of 0.7V, and output current between 0.1A and 1.5A in steps of 0.1A, according to the instruction manual.

[Martin109]

Here's a pic:

[Kim]

Interesting.  Presumably it works like a bench supply, regulating within both limits.  I suppose that's important for charging devices which only limit battery charge current by the capacity of their wall-wart.

*peers at manual*

Ah, they explicitly talk about charging batteries directly.  That's another good reason for current limiting.


Anyway, a USB device is unlikely to care.  USB ports supply 500mA (or sometimes more) and tend to just shut down when overloaded, rather than dropping voltage, so you can't really treat them as a current source.  5V and a current of 500mA or higher should be fine for a USB device.

[Biggsy]

Sorry, I was thinking of INPUT (charging the e-werk) when I answered the original question, which I now realise was about output.

It'll be safe to power typical USB devices with the e-werk at its maximum current setting as the device will take only what it needs.  I'm not sure I'd trust that with every cheapo Chinese product, though.  People are plugging all sorts of bizarre things into USB these days.