Building my own portable battery pack...

[box]

For a while I've been looking at means by which I can power my phone while out on my bike. I use my phone (HTC Desire) for GPS tracking and telemetry logging when I do long bike rides. In this role, it does well ... I can get around 6-8 hours out of it with the GPS on and 'Airplane Mode' enabled, which gets me 100km+ on the road. However, I'd like to try and go a step further and actually use the phone as a cycle computer in tandem with the above functionality, displaying either speed and altitude information or mapping. But this creates a problem ... power.

I've sampled the market a little for ways to up the power capacity of the phone, but have so far been unimpressed with what is on offer. I've looked at both a bigger internal battery (in both capacity and size) as well as external options. Both of which have so far proved to be unsatisfactory in terms to quality, reliability and actual capacity.

So I've moved on to another line of thinking - can I build my own? There are numerous posts on the net where others have done so, but this is mainly to power lighting, which isn't quite so delicate electronically! I'm worried I wouldn't get the power regulation right, and end up frying the thing. But then there's an alternative ...

Why don't I leave the power/voltage regulation to a stock travel charger, and simply worry about providing it with the correct voltage?

In other words, one of these, connected to one of these, padded and placed into one of these, then connected to this.

Any reason why it wouldn't work?

A before anyone asks, I've posted in GD because this question is of a general nature! Not necessarily phone or bike specific

 

[Danthus]

Go on shorter bike rides.

 

[Ahleckz]

I don't know if it would provide enough power, but why not looking at putting a dynamo onto your bike and power your phone through that.

 

[box]

I don't know if it would provide enough power, but why not looking at putting a dynamo onto your bike and power your phone through that.

Well the plan would be to rig it with 10 1.2V Duracell rechargeable batteries. The current generation AA ones are rated at 2450mAh each, so 24500mAh for the whole lot (on paper at least). To put this into perspective, the phone has a 1400mAh battery as standard.

I would go with a more extravagant battery option, but with standard sizes you know you're dealing with something that works, is maintainable, and can be charged by almost anything.

A dynamo would add a whole new level of complexity to the situation, as the power output wouldn't be constant, not to mention fitting the thing. I was really just trying to judge whether I could do what I wanted to do while keeping things simple and stupid. If not, I'll move onto other things.

EDIT: Capacity calculations obv wrong

 

[Monkeynut]

Your batteries will drop in volts as they discharge so it's worth checking whether the charger will accept say 11V or 10V etc. Otherwise it looks good, good luck!

 

[Monkeynut]

Well the plan would be to rig it with 10 1.2V Duracell rechargeable batteries. The current generation AA ones are rated at 2450mAh each, so 24500mAh for the whole lot (on paper at least). To put this into perspective, the phone has a 1400mAh battery as standard.

I would go with a more extravagant battery option, but with standard sizes you know you're dealing with something that works, is maintainable, and can be charged by almost anything.

A dynamo would add a whole new level of complexity to the situation, as the power output wouldn't be constant, not to mention fitting the thing. I was really just trying to judge whether I could do what I wanted to do while keeping things simple and stupid. If not, I'll move onto other things.

If the batteries are in series then they will only have 2450mAh of capacity overall.

 

[Ahleckz]

I don't think a dynamo would be that complex to implement onto your bike, there isn't much to them. You may be wise in wanting to get the basics down first before trying something more extravagant. I'm also doubtful if it would provide enough power.

 

[FreeStream]

Well the plan would be to rig it with 10 1.2V Duracell rechargeable batteries. The current generation AA ones are rated at 2450mAh each, so 24500mAh for the whole lot (on paper at least). To put this into perspective, the phone has a 1400mAh battery as standard.

I would go with a more extravagant battery option, but with standard sizes you know you're dealing with something that works, is maintainable, and can be charged by almost anything.

A dynamo would add a whole new level of complexity to the situation, as the power output wouldn't be constant, not to mention fitting the thing. I was really just trying to judge whether I could do what I wanted to do while keeping things simple and stupid. If not, I'll move onto other things.

10 1.2V cells gives you 12V @ 2450mAh.

2x10 1.2V cells gives you 12V @ 4900mAh.

My iPhone uses a 5V source and I would assume that your phone also uses USB 5V to charge too?

So 3x4 1.2V cells gives 4.8V @ 7370mAh.

Assuming 30g/cell = 360g for the cells alone.

So basically you need four cells in series for the required voltage then keep adding sets of four in series for capacity.

Personally i'd buy a battery pack (5000mAh @ 3.3V for £25, 10000mAh @ 3.3V for £40.. etc)

 

[box]

If the batteries are in series then they will only have 2450mAh of capacity overall.

Good point. I couldn't work out why the numbers were so big

In that case I would probably try two packs of 10 in parallel, although to be honest, 2450mAh would probably give me hours of trickle charging as it is.

 

[FreeStream]

Good point. I couldn't work out why the numbers were so big

In that case I would probably try two packs of 10 in parallel, although to be honest, 2450mAh would probably give me hours of trickle charging as it is.

Just get this:

http://www.amazon.co.uk/New-Trent-i...?ie=UTF8&qid=1311968312&sr=8-1&tag=acleint-20

My mate has the 5000mAh version, and it's worked fine for him.

Edit: I know you've tried external solutions but the batteries are expensive on their own as it is!

 

[d_brennen]

Phones charge (albeit slowly) off of 5v USB do they not? OP isn't really needing to charge the phones battery, merely maintain it for longer. I know very little about electronics, just throwing it out there

The USB 1.x and 2.0 specifications provide a 5 V supply on a single wire from which connected USB devices may draw power. The specification provides for no more than 5.25 V and no less than 4.75 V (5 V±5%) between the positive and negative bus power lines. For USB 2.0, the voltage supplied by low-powered hub ports is 4.4–5.25 V.[34]

Article

 

[Glaucus]

Look at li-po battery cells. They also come in thin rectangles.

These sort of shape. Although you would need to source the correct voltage/ah

 

[AHarvey]

Doesn't Mytracks do all of that?

 

[box]

Just get this:

http://www.amazon.co.uk/New-Trent-i...?ie=UTF8&qid=1311968312&sr=8-1&tag=acleint-20

My mate has the 5000mAh version, and it's worked fine for him.

I've used the 5000mAh version. It's satisfactory at best. Gives me two full charges normally, but dies in a couple of hours if I try to trickle charge, then messes up my phone's battery stats making it think it's got 25% left when it's actually dead. Cue the unexpected shutdowns Cheap chinese trash tbh. Not to mention the majority of their reviews on that site are paid for

 

[FreeStream]

I've used the 5000mAh version. It's satisfactory at best. Gives me two full charges normally, but dies in a couple of hours if I try to trickle charge, then messes up my phone's battery stats making it think it's got 25% left when it's actually dead. Cue the unexpected shutdowns Cheap chinese trash tbh. Not to mention the majority of their reviews on that site are paid for

Used my mates twice now, charged my iP4 from 10-80% twice, as expected. (1450 mAh iP4 battery with 3300mAh capacity at 5V + losses)

Charges his 3GS twice fully (12xx mAh battery IIRC)

*shrug*

I think what your trying to achieve is a little more complicated than adding a load of batteries together...

And you can't really blame it for your phone having a **** battery status indicator can you?

 

[box]

10 1.2V cells gives you 12V @ 2450mAh.

2x10 1.2V cells gives you 12V @ 4900mAh.

My iPhone uses a 5V source and I would assume that your phone also uses USB 5V to charge too?

So 3x4 1.2V cells gives 4.8V @ 7370mAh.

Assuming 30g/cell = 360g for the cells alone.

So basically you need four cells in series for the required voltage then keep adding sets of four in series for capacity.

Well the idea was to run it through a standard car phone charger, so I don't have to worry about getting the voltage spot on, and 12V is easily attainable.

Doesn't Mytracks do all of that?

Read the OP again.

Look at li-po battery cells. They also come in thin rectangles.

These sort of shape. Although you would need to source the correct voltage/ah

Will have a look, thanks. Although I'm a little worried these will be more expensive in terms of replacing/recharging.

 

[Josh107]

Why has nobody said the obvious? Buy a cycle computer?

 

[King Damager]

I still think the best thing would be to add a dynamo, you seem against it, but it seems like the best idea

kd

 

[box]

Why has nobody said the obvious? Buy a cycle computer?

I was really just trying to judge whether I could do what I wanted to do while keeping things simple and stupid. If not, I'll move onto other things.

--

I still think the best thing would be to add a dynamo, you seem against it, but it seems like the best idea

kd

Dynamo output voltage would depend on cadence though right? Hence the increased complexity.

EDIT: Not to mention it would throw out AC...

 

[Amp34]

ALthough the idea in the OP may work I'd suggest looking at a single decent rechargable 12v battery (or regulated 5v battery and do away with the transformer). I can't see the battery being that expensive, normally the cost ramps up when you start getting circuitry with them.

Also I'd look into creating a fake "battery" for the phone itself so I could run the phone directly from the home made battery. Constant trickle charging may damage your phones battery (and would also reduce the voltage needed for the battery). If you got a reasonable regulated battery/system then it should be fine and it could last for days!

Also may be worth looking at the candlepower forums, yes they are mainly torch fanatics but the regulation and general circuitry will be the same.

Just depends how interested/much of a whiz you are in electronics and how much you want to spend.

(I love doing this sort of thing myself)