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.

Re: brainstorm: extending n900 battery life (mods)
 

You also need a chip to balance the two spare batteries if you connect them in series, and it's probably a bad idea to not use a protection circuit for preventing overdischarge/overcharge. If the N900 has "special charger" mode like N810, it will eat power down to 4.2V input, at which point your two series batteries will ideally be 2.1V each, which is too low for Li-Ion. Recharging them again after draining them that low could be dangerous or at the very least cause excessive wear&tear on the batteries. In worst case, if one of your spare batteries is older or has seen different use and thus aged differently, the two batteries will have different charge states, pushing one of them way below 2 or even 1V (when one of them gets empty before the other), which basically is "too dangerous to use again"-territory...

Protection Circuits can be found at batteryspace, for example: http://www.batteryspace.com/pcmwithe...02s20-265.aspx

Instead of having the batteries in series and dropping voltage with a linear regulator to 5V, I would have the batteries connected in parallell, and use a boost converter to bring up the voltage to 5V. This thing looks useable: http://www.dimensionengineering.com/lvboost.htm

This would do away with the balancing requirement, for connecting them in parallell you just need to make sure they're both at same level of charge before you connect them together. This would enable you to use a simpler and cheaper protection circuit, such as: http://www.batteryspace.com/pcbfor37...a-1alimit.aspx

Now you just need a charge regulator to make it perfect! The circuit above will cut off charge at 4.35V (or 4.275V if you believe the scan). Maybe a bit too high when considering wear&tear on the battery, but probably safe enough to avoid explosions and/or battery swelling :)

But a device like the one you've just designed already exists anyway, here's an example http://www.amazon.com/dp/B00152OCAQ/, both cheaper and more expensive models available..

Re: brainstorm: extending n900 battery life (mods)
 

Thats exactly what you do ( although not from a eee on standby obviously :) )

From the Specifications

I have charged my N800 twice without flattening it.

Rick

Re: brainstorm: extending n900 battery life (mods)
 

Thanks! I feel like I'm learning a foreign language by going straight to a new country and having to communicate there! I'm not completely dumb (well, not quite completely) but much of what is said here is going clean over my furry head. I can usually work out when something is said that might be useful to me, but often need to check I heard right!

Re: brainstorm: extending n900 battery life (mods)
 

Heat is the biggest enemy of a battery. Unlike notebooks, the N900 doesn't get hot, so this shouldn't matter.

I'd suggest to just use the device without worrying about the battery too much. There's already fancy electronics and software installed to keep care of the battery for you.

Just use the device and be happy. I usually charge my N900 every night and then can use it the whole day without worrying.

Re: brainstorm: extending n900 battery life (mods)
 

Can you give us an idea of your daily usage. Eg.
9am to 1am. How many bars left
- set to 3G
- surf web for X mins
- watch video for X mins, listen to X music
- how often does it connect to internet?
- minutes of voice calls
- ever connected to wifi

Re: brainstorm: extending n900 battery life (mods)
 

X2

AFAIK, A standard linear regulator usually needs a forward voltage 2-3V higher than its output to function correctly. Therefore as the batteries discharge, there is the potential a linear regulator might not be able to correctly control voltage.

Re: brainstorm: extending n900 battery life (mods)
 

I'd say, about 2h of playing music in the car using FM transmitter (you'd suppose this to drain the battery a lot, but it doesn't),
about in total 15 minutes web surfing on 3G spread over the day, about 15 to 30 minutes voice calls,
sometimes taking photos.
The device is always online. WiFi at home, 2G or 3G elsewhere. I set it to connect automatically.

The battery is then usually still half full in the evening. My G1 was half full in the evening too, but only if I did not do much more than carry it around with me during the day, reading a little email.

The N900 battery only begins to drain more quickly when disabling WiFi power management for connecting to the device via ssh.
I currently don't watch lots of video on it.

Re: brainstorm: extending n900 battery life (mods)
 

Thanks very much for the clarification. It does seem liveable for most light days

Re: brainstorm: extending n900 battery life (mods)
 

Yes, definitely. And not light days, well even the N810 didn't survive those with a single charge. :)

Re: brainstorm: extending n900 battery life (mods)
 

I have to add that I don't have the latest firmware currently. So in the end the battery life could be even better in the sales product.

Re: brainstorm: extending n900 battery life (mods)
 

one more question:
can i supply +5v straight to battery if i put this somewhere between:
http://www.batteryspace.com/pcbfor37...a-1alimit.aspx
?

i think i'll start making 3d-model of the casing today after work. now i'm glad our company buys all electronics from one place. better chances to negotiate more reasonable prices to these small private projects.

Re: brainstorm: extending n900 battery life (mods)
 

It was mentioned here before, but really: the Nokia DC-11 is the solution in terms of hardware. It is explicitly mentioned right on the first pages of the manual, in an advertisement (for this and the bluetooth speakers, to "share your experiences").

Re: brainstorm: extending n900 battery life (mods)
 

i know.

this is only a hobby for me. nice to have a project sometimes. specially now when i got moved to another department @ work. it means i can use companys soldering irons, cnc & manual machining tools and other equipment for free at my spare time(and when those aren't used for work) as long i don't do business with things i create.

and this is an idea that is easiest to pull through from all my crazy ideas. (EN1.4404 enforced camera module for any backpack, ESLUT -loudspeakers, and stuff like that aren't so easy to do compared to this)

Re: brainstorm: extending n900 battery life (mods)
 

According to this link: "Most cells are charged to 4.20 volts with a tolerance of +/-0.05V/cell. Charging only to 4.10V reduced the capacity by 10% but provides a longer service life. Newer cell are capable of delivering a good cycle count with a charge to 4.20 volts per cell"

The PCB you mention seems to have a cutoff of 4.35 volts. So it's a protection circuit rather than a charging regulator.

You should use a protection circuit like this one, but you also need a regulator. Again, according to the above link, a good way to charge lithium-ion batteries is:

• charge with a constant current (at the cell's rated charging current) until the cell is charged up to its voltage limit, then...
• maintain that voltage until the charging current drops to 3% of rated current, then...
• switch off the charger, i.e. don't keep trickle-charging

Regards,
Roger

Re: brainstorm: extending n900 battery life (mods)
 

Finally got things moving. I found out that the batteries already have safety circuits. plus I realized that the bundled charger adapter is a miracle maker.
http://www.dealextreme.com/details.dx/sku.29208
(NOT ORIGINAL!! AT YOUR OWN RISK!!!)

I can charge n900 only by plugging a battery to the adapter.

then I finally ordered a device I can charge external batteries with:
http://www.dealextreme.com/details.dx/sku.31488

now I only need to figure out how am I going to get three batteries charged with the charger. (plus casing after that)

Re: brainstorm: extending n900 battery life (mods)
 

finally I did it!

Just a spare CA-146C charger adapter, piece of wire plus plug from old nokia charger (big headed), 3x spare batteries and external charger from dealextreme.

http://www.dealextreme.com/details.dx/sku.31488

then I just soldered the wire into the charger and voila.

Now I can always charge external batteries with any nokia charger, and either use one external battery as spare power/minor loading or switch phone off and switch empty battery into full one.