Question about Charging Li-Ion batteries while still using them

DiablodeMorte

Here's the situation:
I have a RC blimp which I'm trying to convert into an autonomous blimp. The blimp is made by Megatech(http://www.megatech.com/product_detail_aircraft.php?ID=8302) and it utilizes a CR123A Li-Ion battery(Sold rechargable at: http://www.batterystation.com/cr123a.htm). I googled "Li-Ion Charger" and found the following instructable(http://www.instructables.com/id/USB-Li-ion-battery-charger/) but I'm still unsure of a few things:

A) Can I use the charger found on Instructables(http://www.instructables.com/id/USB-Li-ion-battery-charger/) to charge a rechargable CR123A?
If (A) can I use the charger to charge the battery from a long distance away(Cord length of about 1 to 2 ft)
C) If (A) can I charge the battery while also using it to power the propller?
D) can anybody tell my why batterystation is selling the CR123A(non rechargable for about $2 where as everywhere else it's at least $7?)
E) If not (A) can someone suggest a charger and a way to charge the battery while it is still in use in the blimp?

Thanks in advance for any help!
-Regards

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Current Projects:
Robot Control Via Skype API - Dev Stage(50% Complete) - Total(25%)
Robot Localization Via Xbee's - Research Stage
IR Tracking with Propeller - Research Stage

sam_sam_sam

DiablodeMorte


Take a look at this

Be very care when using these batterys·THEY ARE NOT·like Nicad

http://forums.parallax.com/showthread.php?p=709460

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··Thanks for any··that you may have and all of your time finding them

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Sam

Post Edited (sam_sam_sam) : 5/1/2008 5:02:27 AM GMT

erco

Your·MegaTech blimp is designed for a 3-volt disposable lithium battery, like the $1.50-$2.00 batteries on your website. Those·are not designed for recharging, as warned at http://www.batteryjunction.com/1pcsofcrteli.html

So I assume you are talking about charging the $9.00 rechargeable RCR-123A
Lithium-Ion battery. That is rated at 3.6 volts @ 900 mAH, but peaks at 4.2 volts at full charge. That's significantly higher than your blimp's stock 3-volt battery, make sure the electronics can handle it.

Wiki has good info at http://en.wikipedia.org/wiki/Lithium_ion_battery· and Powerstream suggests charge currents up to 0.7C at http://www.powerstream.com/li.htm·but long term trickle·charging will hurt them. These cells·don't suffer from memory effect, so you can recharge them before they're fully depleted, but if you draw power off them during charging, a "simple" charger won't·be able to properly monitor charging current and deliver a full charge.

In·the blimp scenario·you describe, that begs the question: why·will you need to run the prop if you're connected (tethered) to the charger? You're not free-floating, and the weight of your contacts and charging cable will bring your properly-ballasted blimp down to contact Mother Earth.

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·"If you build it, they will come."

DiablodeMorte

@Sam_sam_sam: thanks for that information, I'm using it to build my schematic
@Erco: Thanks, I'll factor in the higher voltage.

Using the information provided by the two above, and some time in ExpressSCH I've come up with a schematic detailing what I want to put in the blimp. There are multiple stages detailing which components I intend to put in first, second, third, last. If anyone has some time could they look at the schematic and give me any comments on it. I really just need to know If i've set up the propller correctly.

#The schematic is attached

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Current Projects:
Robot Control Via Skype API - Dev Stage(50% Complete) - Total(25%)
Robot Localization Via Xbee's - Research Stage
IR Tracking with Propeller - Research Stage

erco

Now I get it. You want to power the Propeller CHIP while you're charging, not power the (motor-driven) propeller. Honest mistake.

Cool project, post some pics when you can. I'm a huge blimp & LTA fan. I've built several flying·R/C airships, including one for the Zeppelin company in Germany of their fairly new NT airship. Pics from Friedrichshafen attached.

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·"If you build it, they will come."

Post Edited (erco) : 5/5/2008 3:05:53 AM GMT