Re: brainstorm: extending n900 battery life (mods)
 

A- Is obvious I will pass it
B- Is same as A
C- Only if you are using Nickel (NiMH) batteries. You actually do it to try to get ride of time-effect on these Nickel based battries.
The good thing about Lithium battires is that they don't suffer of this and when its charged then you are ready to go.

Re: brainstorm: extending n900 battery life (mods)
 

With it you can connect your old Nokia charger to the N900's new microusb port.

The separate product Nokia DC-8 is a portable charger device that takes a single AA and puts out voltage suitable for charging through Nokia 2mm charging plug. The power available depends on what batteries you use. From best to worst: Energizer Lithium AA, LSD type NiMH batteries (Sanyo Eneloop, GP Recyko, etc), regular nimh, alkalines, heavy duty.
Alkalines and heavy duty batteries are so weak they probably wont do anything useful at all.

Then there's the Nokia DC-11, which is essentially an external Lithium-Ion battery for your phone. It contains a 1500mAh LiPoly battery.


There's no need. You can use it right away. You can charge it whenever you want, you don't have to wait until you get battery low warning. You don't have to charge it full when you start charging, you can interrupt the charge whenever you want. Li-Ion batteries actually like it if you charge often. You can use the device while charging.

Re: brainstorm: extending n900 battery life (mods)
 

this is good point. i am thinking about putting 2 spare batteries into case (if device doesn't stay on when switching, no need to have 4 batteries, one is enough i think)

casing + solar panels in cover + usb out. so it will basically be improved version of the nokia's charging block. as long as the rechargeable charger isn't needed, it could be charged in sun. if i end up doing this for real, i could publish drawings for the case (so one could ask from machining shop how much is it to make one case from PO for example). because i need drawings for myself if i make it. and it means i have to make 3d-models to minimize design flaws and to be sure that all fits in.

Re: brainstorm: extending n900 battery life (mods)
 

started allready sketching. and then one big question came to my mind.

battery loading with solar cells. there would be 5.5v 33mA modules with good size and voltage. and sensible prize tag. what would one need between the modules and battery to be 100% safe against li-ion overloading?
http://www.youtube.com/watch?v=jjAtBiTSsKY though that shouldn't be problem with low current solar cells, i'd rather be 110% certain there are no risks. 5.5v would be great so one could charge the unit via usb too from same wires. (electronics would be easier?!?)

Re: brainstorm: extending n900 battery life (mods)
 

Li-Ion does not tolerate trickle-charging, so even small solar panels connected directly to a Li-Ion battery sounds like a bad idea. It might not explode or catch fire if you're lucky, but if it trickle charges after the battery is full, it will most certainly damage the battery, reducing its capacity.

Re: brainstorm: extending n900 battery life (mods)
 

I've been using this 3400mAh Lithium-Ion usb battery pack ( ~£20 + ~£1 for tip ) its the best I've seen yet.

http://www.portablepowersupplies.co....atterypack.htm

Both in and out are usb and tips are cheap.

Allnameswerout
I dont know about other laptops/netbooks but I can certainly charge from usb ( eee ubuntu ) while in 'suspend' mode.

Rick

Re: brainstorm: extending n900 battery life (mods)
 

Errr You what?

Short words please! (I'm a bear of very little brain!) You charge it up from your computer via the usb, in about 5 hours. Then you plug it into your device and charge that from it - fast enough not to trickle the Li-ion battery. And being a li-ion battery itself, you can top it up after you've used it, rather than wait till it's drained. Yes?? (Or did I misread?)

And this works for a nokia tablet? Sweet!

Re: brainstorm: extending n900 battery life (mods)
 

Let's rephrase that and say "Li-ion does not tolerate trickle-charging when it is fully-charged". I know that's what you meant, but it might not be clear to others that you can happily use a trickle-charger to charge a discharged Li-ion battery, provided you disconnect the charger when the battery is fully-charged.

Also, if you connect an external charger to the micro-USB port on the N900, it's not being connected directly to the battery but is going through the N900's charging circuitry, which should take care of isolating the battery at the proper time.

The N810's charger had full specs published, which you could use to homebrew a compatible charging device. I guess a similar document will exist for the N900's charger.

It does seem that the best way to use solar power is to use the solar panel to charge an external battery (like the Freeloader does), then when that external battery is charged up to use it to recharge the N900's battery "all in one go".

More details here: "Charging lithium-ion batteries"

Regards,
Roger

Re: brainstorm: extending n900 battery life (mods)
 

I agree this is probably the sanest and safest method. Bypassing the N900's charge circuit would just confuse it. Trying to keep the N900's charge circuit fed by power straight from solar panel is probably quite hard to do. A small battery in between, so that you can store up some sun before you feed it to N900 in one even and steady portion at a time.

Re: brainstorm: extending n900 battery life (mods)
 

this is what i ment.

i have 3 spare batteries for n900. i thought that i put 2 together into casing serial and make them output to usb port +5v DC with regulator. then with almost same amount of work, one could integrate a couple of solar panels within the package. making the battery box open like a wallet (then it protects panels when not used and so on..). so now i need to figure out how to handle loading those two batteries via 1) usb and 2) solar power. so i think i must put some electronics between power input and batteries.

so the casing would have
a) usb port for loading the battery pack
b) solar panels for loading the battery pack
c) usb port for loading external devices with battery pack

c) is taken care of, a) and b) is problem atleast for now.

solar panels have 5,5v 33mA nominal values so 4pcs would be smallest reasonable amount of those... glad those are only 2-3mm thick!. but at the same those can be put parallel to gain 5,5v 132mA nominal values.

that means that i must load one battery at time. then when it's full switch to another and when both are full, switch power output to a resistor. is this ok?

and the concept once more:
-put the casing to the sun and forget it (unless it starts to rain!)
-surf the internet until device's battery is about to die.
-connect those 2 things above
-surf more.