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Old Jan 21, 2003, 07:14 AM
Size Matters!
RocketRob's Avatar
San Francisco Bay Area
Joined Dec 2002
2,654 Posts
Li-Poly & Ipaq

Quote:
Ipaq(PDA) charger charges my PDA battery at 2000ma. I know the Ipaq battery is around 850-950ma(LiPoly), which makes the charging at 2c and above
Funny I read the back of my Ipaq yesterday...something about gluing a Kokam 1020 on the back side of it. My Ipaq, the 3600 with memory and flashrom upgrades says a 5v li-ion battery. This may be the reason for the 2c charge - uness they changed the battery chemistry with the newer 3800 or 3950 models?

I use the Ipaq in the Harmon Rocket airplain (avatar) with the add on GPS and control vision moving map display, and have wanted a stronger more reliable battery in case the ship's power went down.
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Old Jan 21, 2003, 03:16 PM
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Stuka: You may charge the Kokams at up to 2C. or general operation, it is best to use 1C for best longevity.
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Old Jan 21, 2003, 06:58 PM
MULTI ENGINE FANACTIC
CESARNOGUEIRA's Avatar
SAO PAULO,S.P.,BRAZIL
Joined Dec 2000
543 Posts
Re: Kokam Lithium Polymer Batteries!

I have a Dash-7 from Robbe, with 2 Speed 400+2Speed 480, with 8x2400 Nicads.

Have also a Grumman Albatross with 2 Speed 480 and 8x2400 Nicads.

-Do you thing it would be possible use a pack of 3670 lypoli?
-how many cells?
-How to charge?
-What ESC?
-Price?

PLEASE, HELP: Altough flying electrics for the last 4 years, I confess: I'm completely lost and fascinated as well with the possibilities opened with the lipoly batteries!!!

HELLP!!! :confused
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Old Jan 21, 2003, 07:15 PM
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KOREA
Joined Dec 2002
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Re: Li-Poly & Ipaq

Quote:
Originally posted by RocketRob
Funny I read the back of my Ipaq yesterday...something about gluing a Kokam 1020 on the back side of it. My Ipaq, the 3600 with memory and flashrom upgrades says a 5v li-ion battery. This may be the reason for the 2c charge - uness they changed the battery chemistry with the newer 3800 or 3950 models?

I use the Ipaq in the Harmon Rocket airplain (avatar) with the add on GPS and control vision moving map display, and have wanted a stronger more reliable battery in case the ship's power went down.
-------------------------------------------------
Hi,

kokam released 2 serial connected 3300mah "external" battery pack 5VOLT(reduction voltage from 7.2 volt) in korean market for PDA application which needs absolute more power.kokam needs times to launch in usa market to get the UL approval.

THANKS
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Last edited by JJ HONG; Jan 22, 2003 at 12:49 PM.
Old Jan 23, 2003, 05:48 PM
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2 c charging vs 1c charging

most of PDA uses 5volt operation with one or two lithium cells.
at the beginning of Ipaq the battery was a trouble issue but o.k now.however most of PDA companies feels that they need more power.

There is some tricks for indoor flyers that they could have quick and simple charging power source.that means they buy or build 5volt 3300mah external battery pack for PDA and charging battery of 145 or 500 cell.that pack is very handy.you can put it in the pocket! i hope it may help for your indoor simple flying
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Old Jan 23, 2003, 05:52 PM
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2 c charging vs 1c charging

most of PDA uses 5volt operation with one or two lithium cells.
at the beginning of Ipaq the battery was a trouble issue but o.k now.however most of PDA companies feels that they need more power.2c or 1c charging takes same time actually to complete 100% charging.if you are not hurry,1c is more efficient.There is no big chemistry changes.

There is some tricks for indoor flyers that they could have quick and simple charging power source.that means they buy or build 5volt 3300mah external battery pack for PDA and charging battery of 145 or 500 cell.that pack is very handy.you can put it in the pocket! i hope it may help for your indoor simple flying
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Old Jan 24, 2003, 09:06 PM
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coming back to the first page

Thanks to ASPERKINS and FRED this thread continues up to now and changed some concept of lipo vs nicd/nimh.
coming back to the first page ASPERKINS expected 35-40 amp draw cell.kokam new cell is capable to draw 8C 84%/10C ,54% so that new kokam3300 will be capable to draw 33amp.That means kokam high rate was improved twice as before. 145,300,600,740,830,1000,1200,3300,----------30000mah will be launched gradually.

Thank you ASPERKINS!

COUNT DOWN 100,000 FROM NOW!!!
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Old Jan 24, 2003, 10:11 PM
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Arlington, TX, USA
Joined Jun 2001
455 Posts
Thank you Mr. Hong for your participation in these forums and more so for your efforts to bring a new and very exciting battery technology to the electric r/c marketplace.

I think I speak for us all when I say Thank You!
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Old Jan 24, 2003, 11:18 PM
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Thumbs up JJ!
These cells are the whip!
Bring on 8c!
Thank You
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Old Jan 27, 2003, 06:44 AM
MULTI ENGINE FANACTIC
CESARNOGUEIRA's Avatar
SAO PAULO,S.P.,BRAZIL
Joined Dec 2000
543 Posts
Re: coming back to the first page

Quote:
Originally posted by JJ HONG
Thanks to ASPERKINS and FRED this thread continues up to now and changed some concept of lipo vs nicd/nimh.
coming back to the first page ASPERKINS expected 35-40 amp draw cell.kokam new cell is capable to draw 8C 84%/10C ,54% so that new kokam3300 will be capable to draw 33amp.That means kokam high rate was improved twice as before. 145,300,600,740,830,1000,1200,3300,----------30000mah will be launched gradually.

Thank you ASPERKINS!

COUNT DOWN 100,000 FROM NOW!!!
Dear Mr. JJ,

Please, consider more than 40 amps:
The most important use of cells in electric flight for sure is for multiengines airplanes ,example:
4 engines, 2 engines.
These airplanes are not the future, are the present!
30 2400 or 3000 nicads cells are very usual presently.
Please, and thanks!

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Old Jan 27, 2003, 09:08 AM
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EpowerFan's Avatar
Sacramento, CA
Joined Apr 2002
308 Posts
8-10C??

JJ I'd like to add my thanks for your participation here and the great batteries.

The new kokams that deliver 8C are even better-- what do you mean by 84% and 54%/10C? And of course I want to know when I can buy these cells from Fred and other distributors?

I think the most demand for an 8C cell is the largest capacity (1020-1575?) you will put in a width of 43mm or so, because the 95mm width of the 2070-3270s makes them more awkward to put in some fuselages. Of course if you made the 2070 & 3270 cells 43mm wide, and 8C that would be better.

Mark
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Old Jan 27, 2003, 10:04 AM
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Mid-Michigan
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I think he meant percent of nominal capacity at the given current drain, i.e. 84% of capacity at 8C, 54% of capcity at 10C. The drop in delivered capacity at high C is already being used as a knock on Lithiums, but even given this issue, they're still far ahead of anything else.
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Old Jan 27, 2003, 11:47 AM
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what's the meaning of 8C,84% kokam

we checked most of famous lithium ion or lipo batteries in the world. They are all commercialized for mobil phone /computer application. even 1-2 years ago nobody tries to make cells which can be applied for more than 3c.Rc people can say easily 4c,5c discharge rate battery and complained about less retention capacity. oh~~~no.if you check all of other batteries at 8c discharge rate,they will stay only 0%(80%) 3%(10%),5%(8%) or max25%(2%).

8c means, if you have 1000mah cell,you can draw 8000ma current continuously for 7.5 minute.This is 8c ,100%

narrow width (less than 43 mm)and more than 3000mah,8c-10c capable battery will be considered soon.we have small orders for
3300mah.I think people need less size,low cost.i do my best!

Thanks
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Old Jan 27, 2003, 09:10 PM
Electric baptism 1975
DavidN's Avatar
Vernon, BC, Canada
Joined Dec 2000
2,891 Posts
Lipo(suction) ramblings

I am particularly interested in 20 cell (nicad) conversions of 40-60 glow planes. Full throttle 40-45 amps. average amps per flight 20-25. I would guess 7 cells of 5000 - 7500mah would work. The other consideration are weight. Saving 35% of nicad weight would be heaven. Easy recharging at the field. Do we have any lipo chargers that canhandle 7 cells at these new fast charge rates? Width. Cost on par with nicad/Nimh cells.eg. one Lipo 6000 = 6 Nimh 3000.
I would love to have a GP Giles 202 that could fly for 15 minutes. and go round twice if needed for landing. Maybe I would even waste electrons and TAXI OUT

I think with cost I would try something in the Accord 47 size first.
DavidN
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Old Jan 28, 2003, 07:29 AM
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Mid-Michigan
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David - If you're running 20 cells now, 6 Li-Polys in series will be enough. Question is, what current do you pull? You may want to parallel 3270 Kokams to keep the current per cell in line. While they will deliver 5C, they will give you a greater percentage of nominal capacity if you discharge them at lower rates.

Somebody recently noticed that a 12v lead-acid battery has the same full-charge voltage as a 3-cell-series Kokam pack. Thus, if you build the packs as 3-cell-in-series subsets, you can charge them from a car battery, IF you use a suitable resistor in series to hold down the initial current to 1C. I've been using a car headlight as the resistor. ( See earlier posts. ) Chargers that are Lithium-safe and deliver high currents are just coming to market. ( See many earlier posts. ) One more time: never charge Lithiums from a NiCad charger. Lithiums must never, ever see more than 4.2 volts per cell. A NiCad charger neither has nor needs voltage regulation, so it will most definitely ruin the Kokam cells.
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