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7.4v 3000mAh Li-Po battery for arduino/xbee
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7.4v 3000mAh Li-Po battery for arduino/xbee

by rizla420 on Fri Jan 21, 2011 10:57 am

Hey,

Has anyone been using li-po batteries for their arduino/xbee projects? I needed a good battery source for a project so that it can run at least two hours without any issues. I found some LiPos on ebay and bought them hastily without doing much research on whether or not i can even really use them with the arduino.

From the little research i've done on Li-Pos (they're new to me). These batteries have two cells at 3.7v each which require a special load balancer and charge to charge them correctly, which I also picked up.

I plan on connecting the power Leads from the battery to a male DC barrel jack with screw connectors: http://www.sparkfun.com/products/10287

Then i'll just plug in the barrel jack into my boarduino. Will this setup work as I imagine it to? Are there any gotchas I should be aware of? I didnt go with the 11.1V batteries because I figured it be overkill since the arduino steps it down to 5V, 7.4 seemed ideal. Thoughts?

I have code thats pretty intensive max sleep between the void function is probably about 500ms, and then it blasts data out to through the xbee only when something changes. You think i'll get good usage time with 3000mAh?

I wont know how well this works until i get the batteries, but just wanted to think outloud and see if someone has gone down this road. If not, i'll post a followup with my results.

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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by adafruit_support_bill on Fri Jan 21, 2011 11:56 am

7.4v is a good voltage for the Arduino. And you should be able to get 2 hours from 300mAh easily.

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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by rizla420 on Fri Jan 21, 2011 12:04 pm

arduwino wrote:7.4v is a good voltage for the Arduino. And you should be able to get 2 hours from 300mAh easily.

you said 300mAh, the battery is 3000mAh (is that technically 3Ah?) so will it be more like 20 hours? or was it just a typo on your part? This battery is for RC helicopters

Basically i have 40 LED's that use about 20mA each, the arduino, and the xbee which transmits every 3 mins or so a string.

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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by adafruit_support_bill on Fri Jan 21, 2011 12:30 pm

Sorry, that was a typo. I meant 3000mAh.
I believe the XBees are about 50 mA. The Arduino is less than that. Depending on how much of the time your LEDs are lit, they may be the dominant factor in your run time.

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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by richms on Sat Jan 22, 2011 4:28 am

Watch the cheap ebay RC lipos carefully. I have just found the 2 that I bought to make the mega tv b gone have all puffed up, so they are now sitting outside on a rock under a ceramic flowerpot since I dont trust them.

The cheap mystery charger off ebay was used to charge them and then they have just been sitting there for a while, so not really subject to abuse.

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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by rizla420 on Tue Jan 25, 2011 12:46 pm

richms wrote:Watch the cheap ebay RC lipos carefully. I have just found the 2 that I bought to make the mega tv b gone have all puffed up, so they are now sitting outside on a rock under a ceramic flowerpot since I dont trust them.

The cheap mystery charger off ebay was used to charge them and then they have just been sitting there for a while, so not really subject to abuse.


Well, i did the get the cheap LiPo off eaby.. Reviews were good, so i figured they were trust worthy. Do you know which "brand" they were? King Max?

The whole Chinese "wholesaler" thing on ebay is a crap shoot. I've had really good success getting bulk LED's from them, but not such good luck with some reed switches. Bought some other components here and there that were good too. The plusses have outweighed the minuses.

The whole allure to me is cost, obviously, but the thinking i have going into it is that practically everything you buy is being made in china. So if chose a US reseller, they're just marking up the same stuff i could have bought for cost. Alas, they assume the risk if something is defective, whereas if something doesn't work, the time/effort/cost to return it to china is not even worth it.

I always assume the worst and am happy when things work out, so far i've had some pretty good experience with Chinese quasi wholesalers.

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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by Ramjet1 on Tue Jan 25, 2011 2:17 pm

I'd be pretty careful about some of the junk lip's on eBay. Aside from not working, they have a nasty habit of blowing up or catching fire. They even have 'safety' bags in the consumer sector to contain these nasty problems. Either spring for m spec (I'm spoiled) or order the ones from adafruit. Make sure you use a suitable charger - don't try using nicad chargers. You have been warned.
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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by rizla420 on Tue Jan 25, 2011 2:35 pm

Ramjet1 wrote:I'd be pretty careful about some of the junk lip's on eBay. Aside from not working, they have a nasty habit of blowing up or catching fire. They even have 'safety' bags in the consumer sector to contain these nasty problems. Either spring for m spec (I'm spoiled) or order the ones from adafruit. Make sure you use a suitable charger - don't try using nicad chargers. You have been warned.


the adafruit lipo's dont have the mAh i need. I made sure to buy a balance charger that supports 2S since thats what the 7.4v have. I've read/seen some blow up bags in some RC forums.. It seems like its going to be trial and error. If i find a "suitable" battery I'd be happy. I'm not sure what the 'm' spec is. I've just started dabbling in lipo's after doing a little research. Im looking for 7.4v min 2500mAh 25C or greater.

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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by adafruit on Tue Jan 25, 2011 3:29 pm

use a brand name camcorder battery

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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by rizla420 on Tue Jan 25, 2011 3:50 pm

adafruit wrote:use a brand name camcorder battery


For a one off, that would work, but I need to be able to order a steady supply of them that can all be charge with a compatible charger. If they discontinue making a particular camcorder battery + charger i'd be f'd.

Since you guys have had success finding a battery wholesaler, what are some tips? How do you know you have a good person that will sell you a reliable product? I dont want these blowing up on potential customers. Just think of the children! :D

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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by adafruit on Tue Jan 25, 2011 4:46 pm

it is more likely your project will die way before fuji/sony camcorder batteries and chargers change.

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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by zener on Tue Jan 25, 2011 4:48 pm

Xbee uses more power when receiving. If you just sleep and then blast out you could go possibly weeks or months with that battery.

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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by rizla420 on Tue Jan 25, 2011 5:19 pm

adafruit wrote:it is more likely your project will die way before fuji/sony camcorder batteries and chargers change.


Thats not nice :( {cries in hands..}

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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by rizla420 on Tue Jan 25, 2011 5:20 pm

Zener wrote:Xbee uses more power when receiving. If you just sleep and then blast out you could go possibly weeks or months with that battery.


Good to know because they are primarily transmit, the only receiving node will be fed by a computer on USB powah

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Re: 7.4v 3000mAh Li-Po battery for arduino/xbee

by Ramjet1 on Wed Jan 26, 2011 10:00 am

M spec should have read mil-spec. iPad typo.
You could always wire 2 battieries together to get the capacity you need.
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