Battery recommendations

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awardblvr
Posts: 13
Joined: Wed Nov 20, 2013 11:13 am

Battery recommendations

Post by awardblvr » Fri Oct 24, 2014 9:13 am

What are some solutions for powering a microView by battery?

LiPo? What config could get me to the acceptable voltage level?

Other ideas? Booster?

freddotu
Posts: 2
Joined: Sun Feb 06, 2011 4:29 pm

Re: Battery recommendations

Post by freddotu » Fri Oct 24, 2014 10:17 am

A simplistic option available would be one of the common portable charger packs that are advertised as a means to have additional talk time on a telephone. The output is typically low current, anywhere from 0.5a up to a couple amps, perfect for these gadgets. The output connector is usually USB mini or USB standard A type, unless you mistakenly buy an iPhone specific device.

A quick check on a discount web site finds this:
http://www.rakuten.com/prod/2600mah-uni ... 91179.html

There are many other options in that line of product, depending on your duration requirements and size restrictions. If you were to run with an ordinary battery option, you'd want one with a five volt regulator as part of the circuit. LiPo batteries are 3.7v per cell, running to 4.2v on a full charge. One is possibly too little voltage (I'm guessing here) while two is too much voltage, but perfect for a 7805 voltage regulator.

I'm not an engineer and I don't play one on television. My method of building things is to try something. If it burns, breaks or explode, I don't try that method again.

scotta
Posts: 43
Joined: Thu Jul 24, 2014 1:31 pm
Location: Toronto, Canada

Re: Battery recommendations

Post by scotta » Sat Oct 25, 2014 4:38 am

freddotu wrote:LiPo batteries are 3.7v per cell, running to 4.2v on a full charge. One is possibly too little voltage (I'm guessing here) while two is too much voltage, but perfect for a 7805 voltage regulator.
No need for a regulator. The MicroView has on board regulation. Just connect to the VIN pin 16.

skimask
Support Volunteer
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Joined: Sun Nov 09, 2008 2:11 am
Location: Minot, N.D.

Re: Battery recommendations

Post by skimask » Sat Oct 25, 2014 9:20 am

freddotu wrote:One is possibly too little voltage (I'm guessing here) while two is too much voltage, but perfect for a 7805 voltage regulator.
:roll:
Good luck getting a 5v output from a 7805 fed by a single cell LiPo...
Let us know how that works out for you...
:roll:
I ignore "one post wonders".

freddotu
Posts: 2
Joined: Sun Feb 06, 2011 4:29 pm

Re: Battery recommendations

Post by freddotu » Sat Oct 25, 2014 9:25 am

skimask wrote:
freddotu wrote:One is possibly too little voltage (I'm guessing here) while two is too much voltage, but perfect for a 7805 voltage regulator.
:roll:
Good luck getting a 5v output from a 7805 fed by a single cell LiPo...
Let us know how that works out for you...
:roll:
to summarize:
one is too little
two is too much voltage for straight five volt, but would feed a 7805 just fine. Low end voltage on a lipo is 3.2 (x2) = 6.4 but nominal for the two cells is up around 8+v

jremington
Support Volunteer
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Location: Eugene, Or

Re: Battery recommendations

Post by jremington » Sat Oct 25, 2014 11:02 am

A more energy-efficient approach to provide 5V from LiPo cells is to use 1 or 2 cells with a step-up/step-down regulator, like one of these from Pololu: http://www.pololu.com/category/133/step ... regulators

Help@GeekAmmo
Posts: 41
Joined: Fri Jul 18, 2014 11:45 am

Re: Battery recommendations

Post by Help@GeekAmmo » Sat Oct 25, 2014 1:50 pm

Guys,
Just to reiterate what scotta said, MicroView has a built-in 5V LDO. Just need to supply voltage above 5VDC + Vdrop (around 5.4V) to Vin and a regulated 5V will be fed into the ATmega328P inside the MicroView via the 5V LDO.

We have also tested a single Lipo directly to Vin of MicroView and worked till the Lipo voltage dropped to around 3-3.2V, take note that this is not a datasheet recommended working voltage. If you feed the Lipo to Pin 5 (5V), you basically avoided the Vdrop of the LDO and save about 340mV.

Cheers
JP

awardblvr
Posts: 13
Joined: Wed Nov 20, 2013 11:13 am

Re: Battery recommendations

Post by awardblvr » Mon Oct 27, 2014 8:53 am

Thanks for the discussion... but still, a great solution has not emerged... Because, I can't seem to find a simple, tiny, cheap, two-LiPo charging circuit/module. I would like to create my micro-view-based device with a micro-USB interface to charge it. And the inefficiency of having to use a buck-boost thing for a single LiPo is worrisome.

So... still looking for good solutions!

BTW.. Can anyone recommend a great TO-92 P-Channel MOSFET that I could use to high-side switch power to the MicroView?

jremington
Support Volunteer
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Location: Eugene, Or

Re: Battery recommendations

Post by jremington » Mon Oct 27, 2014 9:41 am

And the inefficiency of having to use a buck-boost thing for a single LiPo is worrisome.
A boost converter in the 3.3 -> 5V regime typically has 90% efficiency. See the graph here http://www.pololu.com/product/2562

If that worries you, you are out of luck.

scotta
Posts: 43
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Location: Toronto, Canada

Re: Battery recommendations

Post by scotta » Tue Oct 28, 2014 6:18 am

jremington wrote:
And the inefficiency of having to use a buck-boost thing for a single LiPo is worrisome.
A boost converter in the 3.3 -> 5V regime typically has 90% efficiency.
And keep in mind that using two LiPo in series, at nominal 3.7V per cell, gives you 7.4V. At 3.2V, when the cells are low, you will get 6.4V.

If you use this to feed the MicroView's on board 5V linear regulator, you will get only about 68% efficiency nominal and 78% at low battery voltages.

For better efficiency when using two cells in series, you would have to use a switching buck converter, which probably wouldn't be much more efficient than using the boost converter mentioned.

awardblvr
Posts: 13
Joined: Wed Nov 20, 2013 11:13 am

Re: Battery recommendations

Post by awardblvr » Mon Nov 24, 2014 3:16 pm

So... It looks like I've found a pretty good solution... Look on Ebay for "Lithium-battery-charging-charge-5V-step-up-protection-all-in-one-PCB-board"

Search for "121003094575". Or, click http://www.ebay.com/itm/Lithium-battery ... 1c2c58b22f

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