What batteries do you use with the Propeller?
Bergamot
Posts: 185
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?
What sorts of batteries are you using in your projects, and in what configuration?
Comments
-- Remy
For robotics - you want to use 1.2V, AA NiMH batteries.
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
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Stan Dobrowski
-Phil
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...
Happy Roboting!!..
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
"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...
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Paul Baker
Propeller Applications Engineer
Parallax, Inc.
Post Edited (Paul Baker (Parallax)) : 2/14/2007 10:11:42 PM GMT
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
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!"
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
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NerdMaster
For
Life
www.sparkfun.com/commerce/product_info.php?products_id=726
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Stan Dobrowski
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
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NerdMaster
For
Life
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
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
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