Author Topic: Battery powered digispark: Best practices  (Read 20950 times)

psteinweber

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Battery powered digispark: Best practices
« on: February 01, 2013, 07:13:48 pm »
I've been researching for a while now, but I couldn't find any convincing ideas regarding small battery powered solutions for the Digispark. The 5v seem to be rather tricky.


I am looking for a solution which is primarily tiny. Ideally rechargable, or if not using conventional easy to buy batteries (eg coin cells). I was hoping for a LiPo + charger solution like the LilyPad has built in (110mAh LiPo is a nice size!), but with all the necesarry boosting it's getting expensive and bulky.
How about cell coin battery combinations? Are there parts existing which allow mounting 2-3 cell coins to achieve the 5v?

digistump

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Re: Battery powered digispark: Best practices
« Reply #1 on: February 01, 2013, 07:28:33 pm »
2 coin cells you could probably get away with feeding to the 5v line as you'd have 4-6volts - but no guarentees.


3 coin cells you could probably feed into the VIN pin.


We are working on a lipo+charger+booster solution, but it probably will cost a bit because it is pretty complex - the 5v is certainly a trade off - you get more compatibility and the ability to do USB without an external clock, but you loose easy battery power.

r4z0r7o3

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Re: Battery powered digispark: Best practices
« Reply #2 on: February 05, 2013, 11:53:07 am »
They make LiPo's in all shapes and sizes  :P

Here's a pretty small 7.4v 250 MaH pack not much bigger than the Digispark at 1.5" x 0.75" x 0.51".

The down-side is you need a balancing charger which is a bit more expensive.

BuudhaRich

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Re: Battery powered digispark: Best practices
« Reply #3 on: February 08, 2013, 07:53:45 am »
Hi There!


I'm obviously really new. New to arduino too.


I'm looking at replacing a headlamp that I wear on the top of my head with an arduino-controlled set of LED's. Hopefully the Digispark can take care of that. I was using a 12v with the headlamp that I was using before. It was a huge amount of weight.


This battery pack looks great as long as it could support the digispark and a series of up to 12 LED's maybe? I was hoping to find a project where the LED's were rotating. Imagine a trouble light. Or a TARDIS for those who understand the reference.

flyhigh42

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Re: Battery powered digispark: Best practices
« Reply #4 on: February 08, 2013, 01:10:38 pm »
Thanks everyone for the info and posting the chip specs. Based on that, I took the plunge and hooked up my digi to a battery supply. I had a 3.9v lipo that I use for RC and I hooked it up to the gnd and the 5V and it seems to be working fine.
Here's the lipo I'm using:

http://www.hawk-rc.com/index.php?route=product/product&keyword=hubsan+x4&category_id=0&product_id=1880

The lipo recharges on a USB plug also. The headers fit the batt. connection pretty well also. Have lipo, will travel :)

Bluebie

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Re: Battery powered digispark: Best practices
« Reply #5 on: February 08, 2013, 04:09:35 pm »
Do not charge any sort of lipo battery (especially an unprotected hobby aircraft variety!!) using anything except a lipo battery charger. inputting 5v in to it via a usb connection is a bad idea and will destroy the battery at best or at worst, cause an explosive lithium fire which will be difficult to extinguish. Lithium battery fires are very good at burning houses down, and the gas flames that shoot out of those battery packs can be a foot long or even longer. If you insist on charging the battery in the most dangerous way, make sure you do it outside via a long extension cable where everything of value and everything flamable are at least one meter away from the battery, and keep an eye on it, ready to unplug it if it catches fire.


Hobby aircraft batteries are exceptionally good at catching fire, often doing so if they're shorted out or overcharged. People who work with the sorts of little airplanes that use those batteries usually charge them in a ceramic pot on a concrete surface away from anything prescious, or inside a special bag designed specifically for charging dangerous lithium polymer batteries.


Seriously, don't burn your house down trying to save the $2 a USB lipo battery charger costs you on ebay.

MichaelMeissner

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Re: Battery powered digispark: Best practices
« Reply #6 on: February 11, 2013, 11:23:33 am »
Other than coin/lipo batteries, another option might be cell phone chargers that put out 5v.  However, I suspect that the size of the digispark would mean the usual battery is much larger than the microprocessor.  I have an EZOpower charger that provides two 5v 1amp power slots, and it is roughly the size of my Arduino, but the digispark is much smaller.  Most of these cell phone battery chargers can be charged by other USB slots or wall warts.  FWIW, after I got the EZOpower charger, which has a capacity of 5 amp/hours (5000 maH), I left my Arduino UNO R3 on it running blink, and it lasted for 3-4 days before the battery was drained.


I tend to think rechargeable coin cell batteries (potentially with the boost shield) would be the right form factor.
« Last Edit: February 11, 2013, 11:32:20 am by MichaelMeissner »

fr

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Re: Battery powered digispark: Best practices
« Reply #7 on: March 08, 2013, 01:34:38 am »
Je n'ai pas testé (les frais de port pour la France sont trop lourds) mais
https://www.sparkfun.com/products/10255
semble être la bonne formule.

d'ailleurs si quelqu'un a une solution pour des frais de port moins élevés...

I have not tested (the postage for France are too heavy) but
https://www.sparkfun.com/products/10255
seems to be the right formula
also if anyone has a solution for lower shipping ...

ronbo

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Re: Battery powered digispark: Best practices
« Reply #8 on: June 10, 2013, 09:52:14 pm »
Sorry to be so naive - i have a block of 4 1.25 V NiMH rechargeable batteries and I was thinking of just plugging that onto the USB connector on the digistump.  will this cause a disaster of some sort? 

Bluebie

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Re: Battery powered digispark: Best practices
« Reply #9 on: June 13, 2013, 06:23:31 pm »
That will be fine. As the batteries discharge the voltage the digispark is running at will be below 5v, until it reaches 2.8 volts where the digispark will turn itself off. Just be sure not to use higher voltage batteries with it in the future - if you power the digispark with over 5.5 volts via the 5v input it can cause it to break.

semicolo

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Re: Battery powered digispark: Best practices
« Reply #10 on: June 13, 2013, 06:40:43 pm »
I'd recommend monitoring the voltage with the digispark (or something else) and cut at 4V, discharging a NiMH cell below 1V isn't recommended.

mrmox

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Re: Battery powered digispark: Best practices
« Reply #11 on: February 03, 2014, 07:17:04 pm »
Since I found this post, I thought it would be useful to add to it.

"Powercell" looks like it can make your digispark a complete stand-alone rechargeable product
https://www.sparkfun.com/tutorials/379

"SquareWear v2.0 (Arduino Compatible)" has its own cell, but also has a bigger AVR and footprint and some other stuff
http://rayshobby.net/cart/sqrwear-20

Here is a recharger only for a coin cell
http://www.theledart.com/blog/archives/1917

I wonder what the Original Poster did....?