Make your own 3000mAH battery

[JustByZero]

So anything that takes a USB input would be good to use on it? I love the idea, is a little on the big side, but to be fair if i was going to take it anywhere, it'd be like going camping or something, I killed my car battery and had to get it jumped last time I left my phone charging in the car, I also guess you could take extra batteries and change them if you needed to charge your phone more than once, and miles from any kind of civilization.

I like it! =D

 

[Quatermass]

So anything that takes a USB input would be good to use on it? I love the idea, is a little on the big side, but to be fair if i was going to take it anywhere, it'd be like going camping or something, I killed my car battery and had to get it jumped last time I left my phone charging in the car, I also guess you could take extra batteries and change them if you needed to charge your phone more than once, and miles from any kind of civilization.

I like it! =D

I went to Asda (Walmart) and found a tiny version in a black plastic case for

 

[KiwiMark67]

Excuse my ignorance, Although the USB spec is 5.0v +/- 0.5 isnt that an operational voltage, My basic understanding is that to charge on cell the charging cell needs to be at a higher voltage, what does the Desires battery drop to voltage wise when empty, It wont be much below 5v but with 0 capacity?

Full charge voltage = 4.2V
Nominal voltage = 3.7V
Minimum voltage = ~3V (depending on where the designers decided/needed to set this)

Even if the phone circuitry can operate on a much lower voltage the battery would be damaged if its voltage were to go too low. Li-ion cells should be cared for to avoid a 'vent with flame' situation. I believe that the HTC phone does a good job of keeping the battery within the correct operational range of voltage with a smart CC/CV charging algorithm and a safe minimum voltage cut-off.

 

[KiwiMark67]

There are many ways of boosting the charge on your phone while away from power - the setup that Quatermass shows is a pretty decent way to do it. It would also be possible to take 4 x 10Ah D-cells (LSD type preferred) and build a similar 'power box' - but it would bigger and quite heavy. 4 x AA would be a really good option though - noticeably smaller & ligher with 2/3 as much capacity. Also many people have AA NiMH cells and chargers for them, but no suitable charger for C or D cells.


I have played with a few different emergency charging devices:

A Very cheap 1 x AA cellphone charger - not that great, there isn't all that much power stored in just 1 AA cell. I was able to run it from an Eneloop (2Ah LSD NiMH cell) and it worked fine but only put about 25% charge into the cell-phone battery, fairly slow too.

2 x AA Eneloop Stick Booster - much better quality device (made by Sanyo) and 2 x AA cells hold twice as much power as 1 x AA cell. No problem taking a flat battery to 50% from 2 NiMH cells. But the charge rate isn't fantastic - it took more than an hour to get that 50% charge.

Solar power charger with LiPoly battery - works OK, but didn't fully charge the cell-phone before its LiPo cell was drained. It takes quite a lot (several hours of full Summer daylight) of sun to recharge the LiPo battery again.

I have a new charger on the way that runs from 1 x 18650 Li-ion cell (replaceable) which should be the best one yet. This device has a 1 Amp output option which would give a very fast charge (equivalent to what the HTC wall charger delivers) twice as quick as a USB port on a computer. One single 18650 cell can have as much as 3,000mAh which should be enough to fully charge a flat cell-phone battery even with the normal inefficiencies of the step-up voltage circuitry (3.7V => ~5V). For me this is a good option because I have quite a few 18650 Li-ion cells lying around as well as several chargers to recharge them.
This charger is only costing me ~US$20 with shipping and comes with one 18650 cell (probably junk though, I have much better quality cells already).

For the size & weight the most energy dense NiMH batteries would be the AA sized ones - it is a popular size with lots of R&D work done to improve them.
For Li-ion cells the most energy dense would be the most popular size in that chemistry which is the 18650 size - primarily due to being the most popular sized cell for the production of laptop batteries. This makes a charger using this sized cell really good for its size & weight.

 

[MrSteve]

I admire the effort, and I have similar goals. I want to be able to take my desire HD away for the weekend and not be afraid of losing use of it. So I have come up with a plan:

1/. Bought one of these (Battery Bank 4 x AA USB A SKT with Switch Black - Jaycar Electronics). Runs fine on alkalines (not 1.2v rechargables). I keep this in my daily commute bag in case I run low. Gives about 80% charge.

2/. I bought up big on high capacity 7.4v lithum batteries for a camcorder for a world trip. Camera now dead. So I bought a car socket USB adaptor with input range of 10-18v ($9). Connect it to 2 of the batteries. Have yet to do (or need) but will clearly work. Will use for camping trips to charge GPS, phone, etc.

3/. If I get advanced notice of the apocalypse, I plan to buy (before the EFTPOS machines stop working) a DC-DC regulator from same shop. These take in 6-28v and put out 3-15 (adjustable). Should work with laptop, car and pretty much any batteries I find, but "Will need modest heatsink for large voltage differentials" is a bit of a worry. Maybe more suited to atomic winter scenario. Will let you know if I have a chance to use it.


Regards

Steve

 

[Quatermass]

I admire the effort, and I have similar goals. I want to be able to take my desire HD away for the weekend and not be afraid of losing use of it. So I have come up with a plan:

1/. Bought one of these (Battery Bank 4 x AA USB A SKT with Switch Black - Jaycar Electronics). Runs fine on alkalines (not 1.2v rechargables). I keep this in my daily commute bag in case I run low. Gives about 80% charge.

It'll have a small diode in series to take away 0.6V to give ~5.4V. I have something similar that takes AAA batteries.