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View Full Version : What batteries do you use with the Propeller?



Bergamot
02-14-2007, 09:27 PM
I'm building a mobile robot, and I'd like for it to operate for a while between battery changes. All the sensors are 3.3V, so I shouldn't need to run a separate 5V rail.

What sorts of batteries are you using in your projects, and in what configuration?

Forrest
02-15-2007, 12:18 AM
For size, weight and power - (6) 1.2V AA Lithium Ion batteries work very well in robots/electronics that have a high current draw. You'll find these widely available at Radio Shack, hobby stores, Walmart, Target, etc

Remy Blank
02-15-2007, 01:03 AM
Forrest said...
For size, weight and power - (6) 1.2V AA Lithium Ion batteries work very well in robots/electronics that have a high current draw.

I thought Li-ion was 4.2V or 4.3V per cell? I think you must be referring to NiMH (no memory effect but lower current) or possibly NiCd (higher current, but memory effect), both have 1.2V per cell.

-- Remy

Forrest
02-15-2007, 01:10 AM
Sorry about that - I just recently replaced my iPod Lithium Ion battery.

For robotics - you want to use 1.2V, AA NiMH batteries.

Stan671
02-15-2007, 01:47 AM
Energizer makes a Lithium-based AA-sized 1.5 volt primary (non-rechargeable) battery.· These are great batteries·because they fit all AA applications,·have much more capacity than Alkalines, weight less, last almost forever on the shelf and work better in cold weather than Alkalines.

They are not "Lithium-Ion" and are not rechargeable.· Unfortunately, they cost more per power unit than Alkaline unless you find them on sale.· But even at a somewhat premium cost, they are·worth it.

http://www.energizer.com/products/lithium/default.aspx (http://www.energizer.com/products/lithium/default.aspx)

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Stan Dobrowski

Phil Pilgrim (PhiPi)
02-15-2007, 01:47 AM
If your system will run at 3V instead of 3.3V, the 3V (3.28V, no load, when fresh) lithium CR123 packs a wallop in a small space and can be had for about a buck apiece in bulk here (http://www.all-battery.com/index.asp?PageAction=VIEWCATS&Category=379). If you're willing to settle for less energy density, you can also get a rechargeable version (http://www.all-battery.com/index.asp?PageAction=VIEWCATS&Category=198) (Li-Ion) of the same. (I'm a little leery of Li-Ion batteries, though, due to the number of fires they've started.) Battery holders for the '123s can be obtained from DigiKey.

-Phil

Joe "Bot" Red
02-15-2007, 02:12 AM
I am using Lithium-Ion Batteries that I recycled from laptop battery packs.. and they pack a lot of energy for its size, they run at 4.2 Volts fully charged, there are commonly 4.1 and 4.2 Volts versions, so take that into account when choosing a battery charger, in my case, since I don't have the money to buy a fancy and expensive Lithium-Ion battery charger, I built my own using the LM3622AM-8.2 IC from National Semiconductor, I did extensive research on Lithium-Ion charger ICs and so far this is the simplest to use, with less external components, and it allows you to recharge two batteries in series which you can then connect in parallel to obtain 4.1 or 4.2 volts.. the concern raised by Phil about the fire started by Lithium-Ion battery packs is a very important one, although I am only aware of laptop battery packs catching fire, not an individual battery, one thing is that the laptop battery packs have a recharger circuitry densily packed inside, including a temperature sensor and several ICs, I wonder if the fire issue is related to faulty internal recharging ciruitry or a batch of faulty battery cells... :-(

Lithium-Ion are very particular in their charging profile, initially it will have to be charged at a constant current of about 1 amp for one hour (the exact current and timing depends on the battery specs), and then it changes to a constant voltage with an slowly decreasing current for about two more hours, so, you get the point now, you need either a especialized Lithium-Ion charger or you can build your own, trying to charge the Lithium-Ion on a NiCAD charger will make it catch fire or even explode!!

Anyway, I think Lithium-Ion is commonly used in robotics now, the main issue was the price, but they are way cheaper now... http://forums.parallax.com/images/smilies/smile.gif

Happy Roboting!!..

Phil Pilgrim (PhiPi)
02-15-2007, 02:39 AM
Joe,

I have friends who are RC glider enthusiasts and who no longer use Li-Ion/Li-Polymer rechargeables. They've told me of at least two car fires they've either witnessed or heard about that were caused by these batteries during recharging via a commercial charger run from the cigarette lighter outlet. I've got one of the CR123 rechargeable systems, but I won't run the charger indoors unless I can monitor it constantly.

I've heard that new rechargeable litium chemistries that address the safety issue are on the way. It can't come soon enough!

-Phil

Joe "Bot" Red
02-15-2007, 04:25 AM
Hey Phil... do you have any more information available about what happened to them??... I wonder if the issue of Lithium-Ion catching fire is exclusive of recharging, or if you heard of any situation where the battery pack catches fire during operation of the RC/Robot?? scary stuff!!.. http://forums.parallax.com/images/smilies/smile.gif

"I won't run the charger indoors unless I can monitor it constantly." yes, it is amazing how we tend to forget the dangers of chemistry/electricity and leave a high wattage lamp running for days, or charge batteries without supervision.

Lithium-Ion batteries seem to be definitely a riskier approach. they can shortcircuit if you let them drop hard, and if the battery is deeply discharged and you try to charge it with a recharger that it not smart enough, you can reduce the battery life or damage it.

But, they can provide good power for its size.. just before they explode... http://forums.parallax.com/images/smilies/smile.gif

Paul Baker
02-15-2007, 05:05 AM
While the most common cause is faulty charging it is not the only means for it to explode,·here's a video (http://www.pcpitstop.com/pcsafety/video.asp) where they intentionally compromised the battery to demonstrate the destructive capababilities. I believe they created an over-discharge condition for the video (by disabling the battery's over-current monitor and creating a short).

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Paul Baker (mailto:pbaker@parallax.com)
Propeller Applications Engineer
[/url][url=http://www.parallax.com] (http://www.parallax.com)
Parallax, Inc. (http://www.parallax.com)

Post Edited (Paul Baker (Parallax)) : 2/14/2007 10:11:42 PM GMT

Dennis Ferron
02-15-2007, 05:58 AM
I had a small robot based on a 7.4 volt lithium battery. The robot fell just 2 feet onto a floor and the square battery hit corner-first. That was all it took to cause the battery to swell up to the size and shape of an orange. Even since then I have only used NiMH batteries in projects, though I use Lead-Acid in my larger robots. I know that lead-acid batteries have their own saftety concerns, but I have a better understanding of how to take care of a lead acid battery than I do Li-Ion.

QuattroRS4
02-15-2007, 07:45 AM
Oh dear - Just plugged out my laptop charger after watching that !!

Lawson
02-15-2007, 11:41 AM
heh these guys http://www.valence.com/saphion.asp make one of those "non-incindiary" Lithiom Ion chemistrys. They do seem to be selling batterys but I've yet to see the A size cells anywhere.

they DO have a rather cool saftey video on the site. http://www.valence.com/SafetyVideo.asp (lots of smoke and FIRE!)

I've also seen a really simple and cheap charging bunker while wandering the web. Put a cinder block on it's side on either a piece of concrete board or on a concrete slab. Place the battery in one of the holes in the cinderblock while charging. Cover the hole in the block using a larg zip-lock bag filled with several pounds of sand. Now If the battery starts burning, the bag melts smothering the fire in sand. This is unlikely to put the fire out, but it will contain the fire and keep ambient oxygen form making the fire any worse than it has to be.

laterz,
Marty

RinksCustoms
02-15-2007, 02:00 PM
http://forums.parallax.com/images/smilies/rolleyes.gif·you must take into consideration that the use of a LI-Poly/Li-Ion pack are subject to the following conditions:

http://forums.parallax.com/images/smilies/skull.gif·Li packs of either strain should be isolated from shock loads greater than 20-40 G/msec and should not be subjected to puncture or torque loads as these conditions warrant an internal short, see result 1.
http://forums.parallax.com/images/smilies/jumpin.gif·Li packs that are hot from charge/use should be allowed to cool to room temperature before more activity, as overheating the pack isn't good, see result 1

http://forums.parallax.com/images/smilies/idea.gif·Trying to be a cheap CENSORED by not buying a second pack and trying to rush a charge by doubling the charge rate will lead to shorter pack life and disatisfaction, see result 1

http://forums.parallax.com/images/smilies/shakehead.gif·Result 1: Some side effects may include swelling, hot flashes, or failure, serious side effects include fire, property damage,· explosion, or http://forums.parallax.com/images/smilies/skull.gif ! Consult a qualified represenative if you have any questions on how to use these packs correctly.

I have an Extra 300 Flat out. (a model plane made from 1/8" sheet foam and carbon fiber, see google about Tower Hobbies), and have had a few of these crash with the same LiPoly pack (11.5V/800mA/15C) isolated from shock loads using 1/2" rubber foam for recievers as a cushion. I do push the charge on the battery up to 50% when it isn't warm, you get a quick (but not full) charge and a warm pack (not good for instantaineous heavy current loads, see result 1) but good enough for another ten minute flight.

I think the Li technology is very good, high energy density/mass ratio, not to mention discharge rates up to 30 times the capacity of the pack. GM, Toyota, Honda, and Mercedes think it's a good tech too! What do you think is in those Hybrids?

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Definetly a E3 (Electronics Engineer Extrodinare!)
"I laugh in the face of imposible,... not because i know it all, ... but because I don't know well enough!"

QuattroRS4
02-15-2007, 05:26 PM
With all the current airport security checks - here in Europe any fluid over 100ml is not allowed as carry on luggage,lighters and such have to be packed in seperate mini bags etc - After watching that video - how long will it be before Laptops are banned on a flight ? Clear and present danger ? - Bypass the the safety on the LI-ION packs and what do you have ?

Lawson
02-15-2007, 11:17 PM
RinksCustoms said...


I think the Li technology is very good, high energy density/mass ratio, not to mention discharge rates up to 30 times the capacity of the pack. GM, Toyota, Honda, and Mercedes think it's a good tech too! What do you think is in those Hybrids?


um... I'm pretty sure Current Hybrid cars use NiMH cells. Heck they probably just use one or two strings of "C" or "sub-C" cells. Hybrids need high discharge rates AND high charge rates. I've yet to see a Lithium battery that can charge at 4-5C. Only time I've seen Lithiums in a hybrid is the plug-in hybrid that UC Berkly (i think that's right) made. And thay used Saphion cells. (aka if the 300lb battery pack could self immolate u're using the wrong chemistry)

Don't think they'll ever ban laptop batterys. They still allow any number of lighters on board airlines. and all that's needed to bypass the safety on a Li-ION pack is a strong metal pen. (think ice-pick that gets past airport security)

later,
Marty

crgwbr
02-16-2007, 12:29 AM
Lawson said...
·...I've yet to see a Lithium battery that can charge at 4-5C...
What do you mean by C.

crgwbr

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NerdMaster
For
Life

Bergamot
02-16-2007, 01:27 AM
RinksCustoms said...
http://forums.parallax.com/images/smilies/rolleyes.gif you must take into consideration that the use of a LI-Poly/Li-Ion pack are subject to the following conditions:


http://forums.parallax.com/images/smilies/skull.gif Li packs of either strain should be isolated from shock loads greater than 20-40 G/msec and should not be subjected to puncture or torque loads as these conditions warrant an internal short, see result 1.

http://forums.parallax.com/images/smilies/jumpin.gif Li packs that are hot from charge/use should be allowed to cool to room temperature before more activity, as overheating the pack isn't good, see result 1



http://forums.parallax.com/images/smilies/idea.gif Trying to be a cheap CENSORED by not buying a second pack and trying to rush a charge by doubling the charge rate will lead to shorter pack life and disatisfaction, see result 1



http://forums.parallax.com/images/smilies/shakehead.gif Result 1: Some side effects may include swelling, hot flashes, or failure, serious side effects include fire, property damage, explosion, or http://forums.parallax.com/images/smilies/skull.gif ! Consult a qualified represenative if you have any questions on how to use these packs correctly.
Would any of these problems be solved by using something like this?

www.sparkfun.com/commerce/product_info.php?products_id=726 (http://www.sparkfun.com/commerce/product_info.php?products_id=726)

Stan671
02-16-2007, 08:08 AM
Lawson said...
heh these guys http://www.valence.com/saphion.asp make one of those "non-incindiary" Lithiom Ion chemistrys. They do seem to be selling batterys but I've yet to see the A size cells anywhere.

they DO have a rather cool saftey video on the site. http://www.valence.com/SafetyVideo.asp (lots of smoke and FIRE!)

Yes, these are the batteries used in the Segway Personal Transporter.· The Segway has two battery packs, each one weighting about 10 pounds and putting out 200 Wh.· That's a lot of juice, but they are the safest Lithium-based battery technology there is right now.· Because of the specific chemistry of the Saphion batteries, they do not have that thermal runaway reaction no matter what you do to them.

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Stan Dobrowski

Lawson
02-16-2007, 09:45 AM
crgwbr said...

Lawson said...

...I've yet to see a Lithium battery that can charge at 4-5C...
What do you mean by C.


crgwbr


In this case "C" refers the capacity of the battery pack in Amp/Hours. A 4-5C charge rate translates to about a 12-15 minute charge time. At charge rates like these NiCd and NiMH cells can buildup heat, but there is nothing in the chemisty of the cell to prevent charge rates this high or even higher. (the little "zip zaps" toys use a NiCd cell that charges in like 20 seconds. this works because it's a tiny cell that can shed heat quickly) The fastest charge rates I've seen for Lithium chemistries are 1C to start and taper off once a peek voltage has been reached. (so a full charge takes ~2hours instead of the 1hour that charging at 1C implies)

Ah cool Stan671, do you know what voltage the Segway batteries are? I'm mildly curious to know if the Segway uses the A-cells, one of the large-format batteries, or a custom cell in those battery packs.

Marty

crgwbr
02-16-2007, 07:39 PM
Thanks Lawson. I've seen the term C used in many other places, just never quite knew what it ment.

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NerdMaster
For
Life

Stan671
02-17-2007, 03:58 AM
The original Segway battery pack used NiMH cells.· Each 72 volt pack contained 60 C-sized 1.2 volt NiMH cells electrically arranged as two blocks of 36 volts each.· And there are two of these packs on the Segway.

Segway's new Valance Technologies Saphion Lithium-Ion packs use the totally safe Lithium chemistry and provide almost twice the capacity of the orginal NiMH packs with only a slightly larger case.· Inside each of these packs are 23 larger than D-sized cells of about 3.3 volts each providing about 76 volts per pack.· And there are two packs per Segway.

Even though this particular Lithium chemistry is intrinsically safe, just the amount of Lithium contained in each 10 pound battery pack makes it too much to be allowed to travel on commercial passenger aircraft, even in luggage.· The hazardous materials regulations need to catch up to the advances in technology.

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Stan Dobrowski

big_mark
02-18-2007, 05:31 PM
Another option for powering your prop. would be one of these : www.farnell.com/datasheets/68012.pdf (http://www.farnell.com/datasheets/68012.pdf). Scroll down to page 10 and have a look at figure 26. With just a few components you can create a 5.1volt 2.5 amp supply. Add a 3.3volt regulator and you have a good power supply you can run on just about any battery power source.

I've built two for a project I'm currently doing. It is designed to run on a 48vdc power supply, though for testing I have been using a 12vdc power supply. Makes no difference to the output voltage. It would probably run on anything as low as 6 volts, though I haven't tested this. Anyway, heres a pic of my circuit boards : i157.photobucket.com/albums/t41/gyro_gearloose/Circuits.jpg (http://i157.photobucket.com/albums/t41/gyro_gearloose/Circuits.jpg)

Starting from the left we have both power supplies, then the Propellor board in the middle, and finally a dual stepper motor driver board. Of the two power supplies, the one at the top is a 5.1 volt supply for the motors, and the other is the 5.1/3.3 volt supply for the logic circuits (I need a 5 volt logic suppply as that is what the motor driver chips need)

Post Edited (big_mark) : 2/21/2007 1:27:32 PM GMT