One of those 5.4 unloaded, 3.6 under load chargers might be a little too low, actually.

There are specifications available:
http://www.forum.nokia.com/main/reso...nterfaces.html

The charger should provide 5.7-9.3V into an open circuit, but the specification covers a lot more, so I recommend the whole thing to anyone considering any charger modification or fabrication.

hey

I use the tekkeon mp1550 mobile charger. takes 4 AA batteries and includes charge tips for quite a few models. It even doubles as a battery charger.
I use it with sanyo eneloop 2100 rechargables, which gives me close to two full charges for my n800.

To offer my solution as well:

Payed 40 EUR for this device, which is at $60 right now according to that link.

First of all it's very light and small - small enough for me.
In addition I bought it from an amazon market place lowest price seller and it was not working (i.e.: All devices reported charging errors).
I contacted APC directly, even though they didn't sell it to me and
- They were very fast to respond
- They provided me with a replacement device as soon as they got a 'proof' that it's new: They accepted the copy & pasted content of my amazon confirmation mail
- They didn't require me to send the defect unit back. Basically this means that they trusted me, were _very_ helpful and I could've totally screwed them, owning now two chargers.

Don't know about you, but for me customer support like this is a really nice surprise.

Obligatory image (for size comparison, the quality sucks though..):


The capacity in 10 Wh is quite - strange. In layman's terms (i.e. for me): They claim that you can charge an iPod Nano completely about 10-15 times with one charge of the USB battery. The probably more NIT-alike PSP should be able to recharge 2-3 times completely. Source is the presentation from APC, google it ;) Mine is still mostly full, I used it twice so far with a NIT at 50% power.

The cable to connect both is this one, which was suggested on #maemo sometimes. Small, works.

Hey thanks! I was looking for a document like that as I've been trying to resolve the strange behavior with the after market mobile charger I've been trying to use.

So anyway, to others, please ignore most of what I said in the previous post until I review this document to see what the official specification is.

So then, trying to figure out the NIT's hardware, I wonder is there is another inverter sitting in front of the power system that was part of the OMAP2 family chipset that then generates the 3.6 volts that it wants, or do they use a different circuit to charge the battery?

I've been doing some reading on the forums and in other places about chargers, and I'd like to state here what I THINK I have learned, and perhaps someone with more electronics knowledge can confirm or correct it. There was a thread about the powermonkey not working exactly as hoped because it only delivers 700 mAh and the n810 expects 890 mAh. On the other hand, the Solio Hybrid 1000 works completely as expected, since it delivers 1200 mAh max. On the other hand, the Solio Hybrid 1000 only gives 3V output (as opposed to the 5V of the n810 charger), but this doesn't seem to be a big deal. Thus, if I'm looking for a charger, I must be sure that it supports at least 890 mAh, but it doesn't necessarily have to output 5V. Does this sound about right?

Sounds about right; considering that the battery in the NITs is only a 3.3v cell anyways I would bet that Nokia shipped 'em with a 5V charging setup more for general compatibility and ease of manufacturing than for actual electrical requirements. I haven't read through the full spec that Benson posted but I know that from a charging/electrical point of view it's the higher current that you'll need rather than a higher voltage; the numbers are around somewhere, but basically the NIT won't go into charging mode unless it can draw at least a certain level of current; once you provide that base amount, any higher current capacity simply means that the NIT will charge faster (to a reasonable maximum of course! Don't expect to charge it to full in 5 minutes with a 2A charger!).

For the record the Solio products are definately some of the best I've seen in terms of charging capacity and charging times, but you pay for it in the cost and size of the devices (the hybrid 1000 is slightly larger than my N800, and the Solio classic is about the size of the N800 screen but three times as thick overall. Excellent for mounting on a backpack/bike/whatever, but definately not for carrying around in your pocket.

-Rob

"""Anyone know where you can get those tiny Nokia 2mm power connectors?"""

from dealextreme.com
http://www.dealextreme.com/details.dx/sku.3867 That price includes free shipping, can't be beat. Just cut the end off.

I use a slightly different adaptor I got from them that charges the n810 from a USB port, costs about the same. It's probably still available through them.
===============
By the way, this is what i made that works with both my Zausus, and n810 (with a small adaptor to convert the tip to 2mm). It takes a standard 9v battery, and delivers exactly 5v to the tip via the use of a small rectifier(??) that I bought for a $1. The rectifier is inside that protective shrink-wrap sheath, and is bolted to a strip of brass as a heatsink(not that it produces any noticeable heat though).
though it would probably supply enough power to drive a n810 for a couple of hours, I basically only use it with the Zaurus between battery changes so I don't have to reboot, but it'll work as a recharger for the onboard battery as well as running the pc independently.

That'd be a regulator, not a rectifier...

But from a 9V, a ~9 Ohm resistor gives a decent, and reasonably high-current, fit in the I-V envelopes given; when I get to it, that's what I'm figuring on doing. Very similar to yours in layout and construction, just with an even dumber/cheaper passive component for bringing the voltage down. And I plan to make at least 3 while I'm making...

Hey noboysbusiness, thats a cool gadget!

My sister carries her N800 everywhere and I got her a PowerMonkey for her birthday (without the solar panel, reviews said charge time was dreadfully slow). It comes with an array of connectors so she can use it to charge her cell phone or N800 in a pinch... which apparently she has. Score one for a useful gift. (Which makes me feel better 'cause she always gets me awesome stuff.)