Retro Rechargeable USB Booster

Portable iPod and phone chargers are by no means anything new.  However, there are two main aspects of portable chargers that I think could be improved without sacrificing any of their functionality.  These are:

1. Aesthetics.  There is nothing wrong with an Altoids  tin, but there is also a lot of room for improvement as far as looks are concerned.
2. Batteries:  The vast majority of DIY portable USB chargers use alkaline batteries, which means that they must be replaced when they run out.  Also, their capacity is not especially impressive.

My goal was to fix both of these problems, while using only parts I had lying around.  Every single component of this charger I either already had, or I pulled out of some broken electronic device.  Because I only used what was available, the charging circuit uses a 7805 voltage regulator, meaning it is not especially efficient.  On average, it will still be more efficient than a 9V charger, because the peak voltage of the Li-Ion battery pack is around 7.5-7.8V.  Had I built a Mintyboost type circuit, it would no doubt have been more efficient.  However, as the battery pack I used is significantly larger than AA batteries or a 9V (it is 1/3 of a 15" Macbook Pro battery, in fact), this device should be able to power any iPod, phone, or other USB powered device for hours at a time before it must be recharged.

Step 1 Tools and Materials

Electronics:

• 7805 Voltage regulator
• Resistors: 2x 49.7K, 1x 43K, 1x 74.9K (values do not need to be exact, and are taken from this instructable)
• 2X Lithium Ion Cells (I got mine from a "dead" Macbook Pro battery)
• DPDTslide switch
• Barrel jack
• Thin gauge wire
• Female USB connector
• Heatsink (for the 7805)
• iPod cable
• 13cm ribbon

Case and Structure:

• Hot Glue - All the internal bits are glued together and insulated with this stuff
• Aluminum flashing (approximately 12cm x 16cm)
• 1/4" plywood, preferably good looking (I used marine mahogany)
• 2x small wood screws
• Epoxy
• 3mm Stainless Steel rod
• Black paint
• 2x small neodymium magnets
• Tung Oil
• Satin spray-on acrylic

Tools

• Soldering iron and solder
• Dremel/rotary tool with sanding wheel
• Needle files - square and circular
• Scissors
• Philips head screwdriver
• Multimeter
• Drill and small drill bit

Comments

[Rainh2o]

Hard drives are insulated against magnetic damage for the most part...you can get some mighty strong neo magnets out of a nice old hard drive

[icsnerdics]

what a nice pipebomb.

http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

[Technochicken]

There is no danger of overcharging the batteries (assuming that overcharging would cause the batteries to explode, as you say), as the charger I am using was designed for charging Li-Ion batteries. Once the batteries reach the correct voltage, the charger shuts off.

[icsnerdics]

despite you didn't mention about the li-ion charger in the instr, i was quite sure you used one of those to charge those batteries.
the point of what i didn't say (at least what link say), handling batteries is not rocket science and also over-discharge is something to take in consideration.

nuff said.

[Technochicken]

I actually did mention it - Step 4 is entirely devoted to the charger. Over-discharging should not be an issue, because once the battery cells drop below about 6.5-6V, (3-3.25 volts per cell) the output voltage will be below 5V, and the charger will not charge any devices. 3 volts is above the typical bottom threshold of about 2.7 volts, so the cells should not be damaged.

[icsnerdics]

i missed step 4, my bad.
from what i can remember about the 7805 datasheet, as you mention, you're working below the ideal input voltage to work in the linear regulation range and despite what many people think the 78XX family is not predictable in that range, so whatever is the differential voltage the regulator may feed current to the load (or maybe not), so be careful, that's it.

[confu]

Hi there,

great work and nicely documented!
I particularly like how you dealt with the charging and discharging problem :)

But I have two minor concerns:

First, how hot does the heatsink get in operation? Maybe there are better options than hotglue to hold it in place?
The other is, minature, but strong neodymium magnets close to a magnetic harddrive like in an Ipod, "possibly" could cause problems (?!).

And now an additional idea, what are the measurements of the components? Maybe one could fit all of it into a external harddisk case instead of custom-building one.

Regards,

Confu

[Technochicken]

The heatsink gets very warm, but not nearly hot enough to melt the glue. I was a bit worried about how hot it would get as well, but it has been fine so far.

As far as the magnets, I would personally not use a hard drive based iPod with the charger, because as you say, it may very well cause problems. However, I do not own a hard drive based iPod, and the trend is moving away from magnetic storage.

As I built it, the components are 6.5cm by 11.5cm by 2cm (at the very thickest point, which could be reduced), so all the parts could easily fit inside a 2.5" portable hard drive enclosure.