I wrote in
http://talk.maemo.org/showthread.php...40#post1059540
that I had problems with the external battery packs
Proporta USB TurboCharger 5000 World Pack
( https://www.amazon.de/Proporta-Turbo...1801695&sr=8-1 )
and
"Just Mobile Pro" ( https://www.amazon.de/Just-Mobile-Po...1801756&sr=1-1 ).

In my case it does not depend on voltage (both packs have 5V output).
I do not want to shorten the pins as shown in
http://talk.maemo.org/showthread.php...sb+charge+pins .
Even the speed of inserting the plug into the N900 does not
matter ( http://talk.maemo.org/showpost.php?p...6&postcount=18 ).
Some people were wondering, why it sometimes works and sometimes not ( http://talk.maemo.org/showpost.php?p...5&postcount=24 ).

I always tried the original data and charge cable Nokia CA-101 which works for all the USB connections of the desktop and laptop
machines that I have access to (work and home).
But this cable did not work for the above battery packs!

So I simply took the charge cable of the
Proporta USB TurboCharger 5000 World Pack
used the corresponding adapter for N900 and -voila- that works
with both extra battery packs, it does not matter if you switch the N900 on or off.
It seems to be necessary to take a pure charge cable.
Switch on the battery pack and connect to the N900.

The posting
http://talk.maemo.org/showpost.php?p...0&postcount=58
was the important one for me, thanks "nef919".
;-)

I must add that using CA-146C, you should be aware of the said product to melt. The older CA-146C had this notorious issue with melted adapter and the new one (still bearing the same model number and what not) I am unsure if it would melt but there hasn't been any new complaints of the it melting.

I personally didn't take the risk after seeing the pictures of melted adapters (and how much they cost for just a small little thing!) so I modded the adapter myself. Details are on my own blog.

I should really post pictures of my modded CA-146C however I haven't gone around doing so.

I was looking for some other USB/Micro USB B cable that should be a CA-101 without the data functionality.
Up to now I did not find a original Nokia cable for this.
The Nokia CA-100 would also need the CA-146C.

I recently tested how long I may get power with those 2 external battery packs and two fully charged BL-5J.
12040mAh if I calculated right.

It was approx. 14d without 230V.

Usage pattern: sometimes off in the afternoon (beach), approx 1hr WLAN or Internet per day. Low telephone usage.
BL-5J not fully discharged (no red battery indicator), so there may be 1 or 2 days more.
I will retest with a non-holiday usage pattern. ;-)

I can add that the same problem applies to the TeckNet iEP380-II 7000mAh external battery pack, and that the same solution of using a Proporta USB cable fixes it.

Well...

Some days after I bought the TeckNet battery pack, I received a "Product FAQ" e-mail from them which contained some incorrect information about the N900. I sent them a faintly narky e-mail with some corrections and a link to the USB batttery charging spec. I've just received their reply, which is constructive enough that I thought it worth posting here.

Dear Keith:

Thank you very much for your feedback, it is the most great feedback from our customers in 2011. We have updated the email template, so the customer will see the correct information. We are also trying to improve current two models (iep380 and iep380II) to adopt DCP specification, and 3 new model will be designed to use DCP specification as well.

Once again, thank you very much for your feedbacks.

With regards

Yanwei Shou
Director of TeckNet Online Ltd
www.tecknetonline.co.uk

If they make good on that (and I have no reason to think they won't), we'll hopefully see a range of microUSB battery packs that work out of the box with the N900. More power to 'em. So, credit where it's due. I bought the pack while they were actively soliciting customer feedback (by offering a £7 discount in exchange for a review), and it seems like they're actually interested in acting on the feedback they receive.

Now, if only Nokia would take a leaf out of their book...