[poll] What is the long term power consuption of your pandora?

[Binky]

Over an extended period of time (e.g. a week) what is the overall power consumption of your Pandora with the new, power saving kernel?


If you ran flat-out, 24/7 it might be about 1.6W


As its a 16Wh battery (roughly), if you ran it down to 50% battery every day thats:


0.5*16Wh/24h=0.33W


I ask because I am trying to work out whether solar chargers would make any sense - obviously they would have to output power in the same order of magnitude as my Pandora will use to be useful.


I know it will depend significantly on my useage patterns, but I would be interested to get a rough idea.

 

[TrashyMG]

Well I don't know for sure what my consumption is.. so I clicked the only applicable answer: I need to get a life.

 

[Darkknight512]

I run about half the battery each day. I keep the system on in my pocket all the time, no switch flicking just a closed lid. The power drain is about 35 mA. Under usage that is about 225 mA to 300 mA. So I would say my average power draw would be around 125 mA. So thats about 11 watt/hours per day. Or about 0.5 watts.

 

[spiralofhope]

Is there software available which tracks usage and power consumption?

 

[Binky]

I call it a battery meter and a calendar


Just multiply battery percentage used per day by 2/3


Shame I only got 1 meaningful vote though

 

[WizardStan]

I'm not sure that asking how much you use it in a day is a meaningful question. You don't get 24 hours of sunlight, calculating your average hourly usage won't really tell you how much sunlight you need.


My current use case has the wifi on and connected, the LCD on, CPU mostly idle, periodic input. This is about 8 hours non-stop and at the end leaves me with about 35% battery remaining. I used to close the lid to minimize LCD power consumption but with the new kernel that Notaz has awesomely provided I say nuts to that!


Anywho, under this usage, you'd need a 0.65*16/8 = 1.3W charger in order to keep up.


An idle CPU with the wifi and LCD off uses about 2% per hour, or about 50% per day. In order to keep up you'd need a 0.32W charger. In practice you get maybe 10 hours of good charging sunlight per day. You would need to recover 8WH in 10 hours, so at the absolute minimum you need a 0.8W charger. That's if you have a good day with 10 solid hours of light to charge your otherwise unused Pandora. I guess when the sun goes down and you aren't charging anymore you can drop it into suspend mode where it uses just 0.5% per hour, so I guess we can instead calculate 27% per 24 hours, so you'd still need a 0.43W charge at the absolute minimum.


To recap, if you do not use your Pandora at all during the day and you get 10 good hours of sunlight to charge, you would need a 0.43W charger minimum. Hmm... something is not working with my math, so we'll try a different approach.


The Pandora uses 1A/5V adapter to fully charge the battery while plugged into the outlet in 5 hours from 0. If we estimate only 50% use per day, you could get away with a 0.5A/5V = 2.5W charger in the same length of time. I cannot find such a charger for anything less than $100. You could probably build your own: here is a 1.5Watt cell for $19. Two of those will get you more than enough juice plus $10 for a some extra bibs and bobs and you could make a solar powered extra battery charger for $50. Find a 16Wh battery and it can store extra power when not in use: either buy a spare Pandora battery or use 6 AA li-ion batteries. I recommend the li-ion, they're cheaper and safer. Heck, use 8, have a (heavy) 24Wh battery pack.


Actually, this probably isn't a bad idea. Camping season coming up soon, I'll probably do this.

 

[Binky]

what about one of these:


http://www.voltaicsystems.com/switch.shtml


bag - 4W solar panels - 11Wh battery $130

 

[WizardStan]

That'd probably do it. *bookmarked*

 

[Link]

what about one of these:


http://www.voltaicsy...om/switch.shtml


bag - 4W solar panels - 11Wh battery $130

That battery will put about 36-38% charge on the Pandora. It needs SOLID sunlight to charge in a day, no shade or indirect, it needs direct sun to get a full charge to the battery on the charger.


http://www.voltaicsy...m/fuse10w.shtml


This is more like something to provide a full charge to the Pandora, but pricey and bulky.


But then again, check this out:


http://www.earthtech...ar-charger.html

 

[Binky]

That battery will put about 36-38% charge on the Pandora

3.7V*4.2Ah=15.5Wh


11Wh/15.5Wh=0.7


So that battery should charge 70% of a pandora's, surely?


I though Watt-Hours were important as batteries are often at different voltages


so their V39 (39Wh) battery seems more than enough (I asked, and they can ship and case with any battery)

But then again, check this out: http://www.earthtech...ar-charger.html

What are the specs on that? The page there isn't very informative

 

[WizardStan]

But then again, check this out: http://www.earthtech...ar-charger.html

What are the specs on that? The page there isn't very informative

500mA @ 20 Volt = 10 watts: Not anywhere close to even possibly beginning to even think about running a laptop. Either the spec is wrong or it doesn't work nearly as well as advertised. The 500mA USB would probably work, but you can get other USB chargers with the same spec for half the price or less.

 

[Neelix]

Erm... where does it specify 500mA? As Binky said the page isn't very informative.


- Neelix

 

[Binky]

That earthtech link doesn't work atm

 

[kuru]

Ecology rant, ignore if you drive an SUV


When considering solar cells, be aware that there has gone a lot of energy into producing those already. The cells would have to be in constant use for over half a century to make up for that. And it's a lot to lug around if you want decent current. Might as well go with a rechargable battery pack. At least there's hope that once those batteries are dead they will be properly recycled.


A kind of green alternative would be getting used cells out of broken garden lights and the like, or broken cell shards, and rewiring them to a panel of your own. But you'd need to get some sort of voltage regulator then. Dunno if the LM7805 would do the trick here.

 

[Binky]

Ecology rant, ignore if you drive an SUV


When considering solar cells, be aware that there has gone a lot of energy into producing those already. The cells would have to be in constant use for over half a century to make up for that. And it's a lot to lug around if you want decent current. Might as well go with a rechargable battery pack. At least there's hope that once those batteries are dead they will be properly recycled.


A kind of green alternative would be getting used cells out of broken garden lights and the like, or broken cell shards, and rewiring them to a panel of your own. But you'd need to get some sort of voltage regulator then. Dunno if the LM7805 would do the trick here.

So they're great for camping etc, but pointless when it comes to being green. Is there any chance of their efficiency or manufacturing process improving any time soon?


---


On the topic of SUVs, does anyone else get infuriated when they see an advert for some car/other which is supposed to be wonderfully fuel efficient, but encourages you to drive it 'like an athlete'?


Wouldn't you save more energy by keeping your old car, and driving at a steady 50-60 mi/h whenever possible?


---


Also, how long do li-Poly batteries last?

 

[WizardStan]

Erm... where does it specify 500mA? As Binky said the page isn't very informative.

On the specifications tab:


Output Capacity: 500 mAh @ 20V and 500 mAh at 5V


I can only assume when they say "500 mAh" they mean just "500 mA". Amp hours doesn't make a lot of sense.

 

[Binky]

Having a different battery capacity for different voltages would be a bit strange...

 

[kuru]

So they're great for camping etc, but pointless when it comes to being green. Is there any chance of their efficiency or manufacturing process improving any time soon?


---

I read that monocristalline cells are the best, delivering just under 20% efficiency. This can be improved a bit - efficiency vs. surface area - with small hemispheres, angling the light inside. I can't tell whether there's still room for improvement left in mass producing solar cells, don't think so.

On the topic of SUVs, does anyone else get infuriated when they see an advert for some car/other which is supposed to be wonderfully fuel efficient, but encourages you to drive it 'like an athlete'?


Wouldn't you save more energy by keeping your old car, and driving at a steady 50-60 mi/h whenever possible?


---

My old 190 Benz was able to go with 7,5 litres/100km, given a fore-sighted, non-agressive driving style. Something I rarely accomplished, driving fast is fun after all When hitting the pedal hard the 190 would use over 10 litres/100km.


Now I drive a VW Polo Diesel, minimum is somewhere around 4,5 litres/100km and I don't think I can use more than about 6,5l/100km. Of course those cars are totally different classes, buy the technological advance of 15 years also makes a huge difference.


Newer cars will always be better in terms of pollution thanks to eco laws improving, be it slowly. That's speaking for Europe. No big, fat oil millionaires in government, here. We have emission categories. So an old car for example gets put in category 3. Need to go to the city central? Forget it. Need class 5 to be allowed to. Also car holders get to save money on taxes as an incentive to get a car with lower emissions.

Also, how long do li-Poly batteries last?

In terms of cycles over 1000 according to wikipedia.

I have read a lot about capacitors recently. Seems that if you treat a modern cap properly, it is able to outlive you. Caps also can be rapidly charged and discharged. AFAIK you don't need a dedicated charge control circuit, just pump it up, as long as you stay under the maximum voltage rating. The downside is the physical size of high capacity ones. I would like to build a capacitor pack with USB out one day.

 

[Darkknight512]

Super capacitors have the potential of being great, but right now, they are expensive, heavy and they don't carry much energy. You would need a super capacitor many times (10 - 20) the size of a LiPo battery to provide the same amount of Watt*Hours.