Introduction: Minty Boost Extra

Picture of Minty Boost Extra

A v. 2.0 Minty Boost I just bought from AdaFruit (very similar to the one in Lady Ada's Instructable except that it apparently works better with iPhones now). I used a larger Altoids-type tin, not the gum tin - that gives me room for a spare set of batteries. I also made the hole in the side without just clipping a notch. Nothing special really, but I hadn't really seen that so I figured I post it.

Step 1: Making It

Picture of Making It

The Minty Boost is made per the kit instructions (available at Lady Ada's site). I wanted the USB port to be fairly flush, and I didn't want a big notch in the side. I had thought about using a Dremel to cut the hole, but after googling around a bit saw a mention of just using a hole punch. I put the minty-boost inside where I wanted it, then marked the outside with a pencil at the approximate location. It worked great - made 3 overlapping punches. Then I used a small file to enlarge the hole to the right size.

Step 2: Why Bother?

Picture of Why Bother?

I keep the Minty Boost in my bag as an emergency charger, Although the circuit is supposed to draw very little power at rest, eventually it will drain the batteries. This way I always have at least one fresh set. I've got some low drain NiMH on order so I don't have to keep buying AA's. I've tried it on an iPhone, iPod Touch, and old iPod mini - worked fine for all of them.


lorogan (author)2014-10-01

Nice USB charger... If you wanted to make a version of your own, then use a Voltage Divider! I used Matt Jenkins instructable, and Matt is a well respected member here, and the VD worked great. Just click on my name, and my charger will be there. Here's a link to it! Happy building and check out my flashlight for another 'ible. Happy Building!

lorogan (author)lorogan2014-10-01

Sorry! Link didn't work. Here it is. Building

lorogan (author)lorogan2014-10-01

Here's a direct link. It won't work using the link button...

ckgarside (author)2012-09-26

How much battery is drained if there isn't a switch? I thought if there is nothing drawing current from it, then it wont suck up power.

kwoeltje (author)ckgarside2012-09-27

There's no switch. It pulls very little power with nothing drawing current. According to another comment, the drain is not much worse than just the spontaneous drain of the batteries themselves. /K

ckgarside (author)kwoeltje2012-09-27

Ok thanks, I've had the mintyboost 3.0 for a while and i was just wondering if putting a switch on it would make any notable difference

ma3574 (author)2009-07-31

I'm a complete newbie but could you not make another cut on he tin and then add a switch between the MintyBoost and the batteries so that they aren't drained. Thoughts?

kwoeltje (author)ma35742009-07-31

You could, easily enough. I had thought about that as well. But Lady Ada's design seems to be pretty good - I've had batteries in for months and not seen much drain. I'm sure they'll wear down eventually, but at this point for me there isn't a lot of impetus to put in a switch. /K

scottinnh (author)kwoeltje2012-03-19

No switch was needed in the Minty v1 or v2, but in the Minty v3 circuit it seems a switch would help.

MAX756 quiescent current: 60uA
Linear 1302 quiescent current: 200uA

I use rechargables, but they are all Sanyo Eneloops (low self-discharge) and they remain nearly fully charged for months on the shelf. In a MintyBoost, they only last a few weeks even though the Minty has not been used any.

A Linear rep I spoke with claimed the Mintyv3 had "a direct path through the diode to the output when the part is in shutdown which will drain the battery" (I'm guessing this means the circuit lacks something necessary to automatically switch it into logic controlled shutdown mode, which the Linear spec sheet lists as 15uA... quite a lot less than 200uA!).

If any folks could confirm this or comment or suggest improvements (to take advantage of shutdown mode) that would be awesome. AdaFruit is really busy on new products and my sense (opinion really) is that new revisions to the Minty for problems like discharge are just not a priority.are not a high priority.

yazug (author)kwoeltje2010-04-11

around 2 years to drain the batteries if left plugged in.

kwoeltje (author)yazug2010-04-12

Too late for me on this one, but I'll do it differently next time. And great info for the next person to take it on. Thanks yazug!

ma3574 (author)kwoeltje2010-04-12

 2 years that's really good life. Thanks

the dashing hero (author)2012-02-14

ipod mini isn't that mini

the dashing hero (author)2012-02-01

ipod mini? you mean ipod nano?

bmondor (author)2012-01-02

I just bought minty boost and when I finished assembling it I put the batteries into the battery pack and the boost converter chip heats up and gets really hot. Also when I went to see what the voltage was for the USB output it wasn’t get the 5v like it is suppose to. If you know what the problem is will you please let me know. Thank you

kwoeltje (author)bmondor2012-01-02

My chip has gotten hot when I changed phones to one that draws a lot of current. Apparently sometimes soldering together the 2 and 3 USB leads can help ensure the phone sees it as a USB charger (see the very last set of instructions on It worked for me.

Not sure about the voltage. You could try Lady Ada's forums (

bmondor (author)kwoeltje2012-01-02

I tried soldering the 2 USB output together on one of my minty boost and the boost converter chip still heats up Are to older versions of Minty boost more reliable? If so do you know where I could buy an older version? Thanks

kwoeltje (author)2011-12-03

I'm sure you could. There are other Instructables showing how to use a solar cell to charge Minty Boost batteries. I think there is also a thread over on Lady Ada's forums.

yazug (author)2010-04-11

from LadyAda's comments and analysis the drain is the same order of magnitude as that at which batteries discharge by them selves.

kwoeltje (author)yazug2010-04-11

 Now you tell me :-)

yazug (author)kwoeltje2010-04-11

Found link

"That means that the self-discharge rate is ~2000mAh / 0.1mA = 20,000 hours, more than 2 years. Most batteries don't last that long! Therefore we don't need a switch, when nothing is plugged in, almost no power is being used."

D4NG3RNL (author)2009-06-01

You know what's the best about your little mod, the room you have left is great to store some additional battery's. in case the set that's in run dry!

aarone_14 (author)D4NG3RNL2009-08-09

or for some actual mints _
batteries is also good ;)

kwoeltje (author)aarone_142009-08-09

Mints? In an Altoids tin? Get real - who would ever put mints in those things? :-) /K

kimball100 (author)kwoeltje2010-02-25

you could get a larger batter try so it would charge faster

metalicaman8 (author)2009-05-07

if you want the batteries to live longer just put in two packs of two batteries with each pack wired in series and the packs wired together in parallel. The batteries in series adds the voltages while wiring the charge packs in parallel allows the current draw to be evenly split between the charge packs, thus doubling the battery life span. You could then cut another hole in the side to add a switch to cut power if you are really worried about battery drain.

jono456 (author)metalicaman82010-02-20

 If you are going to use 4 AA-cells the only way is to put all cells in series and completely eliminate and electronics to raise the voltage. That raising the voltage from 3 to 5 volts has a certain amount of waste (heat).

If you are afraid of the 6 volts you will get if using AA alkaline cells then simply put one or two in400x silicon diodes in series with the batteries to drop the voltage .7 to 1.4 volts. Very simple and the least amount of waste possible.

Don't over build, especially when it comes at a loss of efficiency. No switch will be needed. The cells will last their shelf life. If you are using NiMH cells (by far the cheapest solution) you don't even need the diodes. Just 4 AA cells in series and you have the perfect USB power solution with no undue waste.

jono456 (author)jono4562010-02-20

 Above that should read 1N400x series diode such as a 1N4001, 4002, 4004, 4006.

kwoeltje (author)metalicaman82009-05-09

You are absolutely right - a switch would work to eliminate the battery drain. I thought about wiring in 4 batteries like you described (and someone has one up like this on Lady Ada's site), but for me this is mostly for emergency charging. Even if it takes twice as long for the batteries to drain, they might still be dead when I needed a boost. And this way uses just the components in the kit.

Greeneyedggirl (author)2010-02-11

 Why not wire it up for four batteries and thus be able to have more power available in the extra space?  Just wire two in parallel that way the voltage stays the same, but the available power doubles?  This was you could use say for argument sake four 2300 mAh batteries to get an effective yield out of the little magic box of 4600 mAh?

That's what I think I'm going to do when I build mine.

kwoeltje (author)Greeneyedggirl2010-02-11

You could certainly do that. I didn't for the reason I mentioned - I use this primarily for emergency power, and this way I'm guaranteed to have at least 2 fresh batteries. The circuit will draw a little power even when nothing is plugged in.

greenie7888 (author)2009-10-25

Hi, Nice Instructable. I was wondering if you could use the mintyboost v 2.0 kit and instead of putting spare batteries into the extra space if you could put in another battery holder and wire them in parralel to the minty boost circuit?

Thanks, Sam

kwoeltje (author)greenie78882009-10-25

That should work. It's actually the v2 kit in mine. I thought about doing 4 batteries, but I wanted to keep a pair of unused batteries in the tin in case the first pair had run down. /K

harmless matt (author)2009-10-14

I bought three of the MintyBoost 2.0 PCB's, but I don't know what partsto get.

Is it the same parts as the Mintyboost 1?

I'd really appreciate it if someone could post a BOM.

kwoeltje (author)harmless matt2009-10-14


there are instructions, tips, etc at her Minty Boost site:


harmless matt (author)kwoeltje2009-10-14


syphek (author)2009-06-25

You might (not sure) be able to coil up an ipod connection cable an put it in the extra space?

kwoeltje (author)syphek2009-06-26

Good idea. I just tried it - an Apple ipod cable just barely fits. I've seen after-market cables in catalogs that have a shorter cable - that would fit better. /K

D4NG3RNL (author)2009-06-01

Haha, I forgot to check out the last picture when I posted that reaction xD I made a micro USB charger hub (2 ports & some cable) that would fit in there snugly! (its about the size of 2 AA battery's so) Altho I'm not sure if this thing provides enough energy to charge 2 USB devices simultaneously

kwoeltje (author)D4NG3RNL2009-06-04

D4NG3RNL, Yeah, I don't know if it would provide enough energy either. /K

sanguyen (author)2009-05-07

So can you tell me how many ohms R4 and R5 are? I don't know where to solder the resistors so yeah can you please let me know?!

kwoeltje (author)sanguyen2009-05-09

I used the 100K resistors for R4 and R5, since I'm using it with newer iPods. Limor has great instructions (including detailed photos of what goes where) on her MintyBoost site:

sanguyen (author)kwoeltje2009-05-10

Yeah I found the webpage that explicitly showed where to solder the resistors and what their values were after I had posted the comment. he he so yeah sorry about that and thanks for replying.

kwoeltje (author)sanguyen2009-05-10

No worries - there's a lot out there and things like that can be easy to miss. I've built a few of these now - the new version works fine for my iPhone (the old one didn't w/o a special adapter USB cable that I found somewhere). I think it's a good kit for beginning solderers- you get something genuinely useful at the end. Good luck. /K

sanguyen (author)kwoeltje2009-05-15

Yeah that's true. Okay, thanks!

squirt8500 (author)2009-04-13

Maybe you could use some of that extra space for a circuit for a solar panel on top of the tin, a never ending usb power source...

kwoeltje (author)squirt85002009-04-13

Great idea. I'll have to look into that. I wonder how long it would take solar cells the size of the lid to charge two AA batteries. /K

MrMatt (author)2009-04-13

Nice touch with the flush connector. I wish there were space in the gum tins to do that. I've also done the no notch connector hole in the gum tin but I used a utility knife with a fresh blade to make the hole. The key is to (very carefully) cut the hole the right size, but leave a flap of tin on the side and bottom or top to reclose and solder together around the USB connector.

kwoeltje (author)MrMatt2009-04-13

Didn't think of that - although I'm not sure I trust myself to cut the tin with a utility knife - afraid I might lose a digit. /K

About This Instructable




Bio: Favorites enjoy robotics, python, Raspberry Pi, Arduino, and making in general.
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