RunRyder RC Helicopter Topic - Li Ion Packs?

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Radio - Servo - Gyro - Gov - Batt > Li Ion Packs?

PC12DRVR
Senior Heliman
Location: Manchester NH

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Anyone here built their own Li Ion Rx packs? I want to try it for a couple of different things, but not sure if you have to have internal protection cicuitry or if that is accomplished with the appropriate charger?

I use the Fromeco 7.4V 2600mah and they are all fairly new, I dont want to have to cut one apart.

11-06-2009 06:42 AM

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jsenicka
Elite Veteran
Location: Hampton VA

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You do not need or want the internal protection circuit. You can by 18650 cells on eBay and make your own packs.

Jim Senicka
3x T700N/OS91 - 3x Vibe 50/OS55HZ - Trex 450 Pro

11-06-2009 11:45 AM

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PC12DRVR
Senior Heliman
Location: Manchester NH

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So you can just solder the cells together as you choose add your connector and charge with an appropriate charger, no worries about the cells becoming unbalanced? It seems alot of the non RC related packs have the PCB built in. I am assuming this is becuase in most uses the batteries are not being charged by a smart charger?

11-06-2009 03:28 PM

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jlchapman
Heliman
Location: Mapleton, Utah

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Have you checked out HobbyKing for batteries? I cant imagine not finding what you need.

JC

11-07-2009 12:40 AM

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PC12DRVR
Senior Heliman
Location: Manchester NH

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Thanks, I have no problem finding batteries, its just that I can build a 2C pack for $20.00, most 2C packs are $40-$60 at a retailer. I need to replace the batteries in five machines, amongst a few other projects just trying to save $ where I can.

11-07-2009 02:50 AM

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jsenicka
Elite Veteran
Location: Hampton VA

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if it were me (and it is,since I am updating some stuff)
I would buy a set of LiPoFE 2100 packs like this http://www.allerc.com/product_info....82d20268bd73322 and ditch the regulators all together

Or just buy these if you want to stick with Li-Ion http://www.batteryjunction.com/tene...0-tab-2600.html

Jim Senicka
3x T700N/OS91 - 3x Vibe 50/OS55HZ - Trex 450 Pro

11-07-2009 03:46 AM

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PC12DRVR
Senior Heliman
Location: Manchester NH

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Thanks jsenicka,

Yes those tenergy cells are the ones I was looking at, you can buy a set of 16 on Amazon for $99.

My question still remains. I know from charging my existing Li Ion packs that I do not balance them and the charger knows the min-max voltage so there is protection for over charge/discharge.

But without cutting the wrapper off one of my packs, does anyone know if there is an internal cicuit installed that balances the cells?

11-07-2009 04:05 AM

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Hellsiege
Senior Heliman
Location: Colorado Springs, CO

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Quote
We only recommend using Lithium Ion rechargeable batteries with a control circuit (protection PCB) to assure safe charge, discharge, etc, use of lithium ion batteries with a protection circuit is potentially hazardous

I was looking at doing this but wasn't sure why this warning was there... So are we ok since we have "smart" chargers? I also think that last sentence should be "without a protection circuit"?

11-07-2009 04:13 AM

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Rick_H
Key Veteran
Location: Boulder City, Nevada

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I build my own Li-Ion packs and I use a the protection circuit for the charging circuit with a dedicated charging lead, I go direct from the battery to the receiver bypassing this circuit to keep the protection circuit from shutting the power off from the receiver from over discharge. You can put a diode on this receiver lead to prevent charging from it for safety.

I also use 7 amp PolySwitch on the pack to prevent an overload from destroying the pack (ie fire). If your receiver is pulling over 7amps you have a problem and your heli is coming down in flames anyway. Once the current draw is lowered the PolySwitch resets itself.

Rick

11-07-2009 04:54 AM

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Dr.Ben
rrProfessor
Location: Richmond, VA, USA

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For those who don't want to assemble their own packs, Central Hobbies sells 2S 2600 LiONs for a sensible price complete with balancing lead attached. They work well.

http://www.centralhobbies.com/Elect...nmp/nmpbats.htm

Ben Minor

Representing
MRC Hirobo Helicopters and Team Futaba for Radios
Morgan Fuels
OS Engines

11-07-2009 07:39 AM

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PC12DRVR
Senior Heliman
Location: Manchester NH

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Quote
I was looking at doing this but wasn't sure why this warning was there... So are we ok since we have "smart" chargers? I also think that last sentence should be "without a protection circuit"?

The way I understand it, correct me if I am wrong, is,, the PCB is not necessary becuase it is a protection for overdischarge/charge. Being that most of us use chargers that auto detect or are "smart" this circuit is not necessary. Hellisiege I think you are right, that must be a misprint. I also seem to be discovering that it is not necessary to balance Li Ion cells, but if you do it will lead to longer cell life?

Dr. Ben thanks for the info, that is a good price. Do you know if that pack has heavy gauge wire connected the picture looks like a servo lead unless thats just for balancing?

11-07-2009 01:39 PM

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Radio - Servo - Gyro - Gov - Batt > Li Ion Packs?

Dr.Ben
rrProfessor
Location: Richmond, VA, USA

My Posts This: Topic Forum

The main lead is a high quality servo lead with silicone wire. It's not rigged for really high current set up, but then LiIONS aren't rated for over 4-6 amps continuous, either. BTW, you can't see the balance lead in their pic; the pic is old.

Ben

Representing
MRC Hirobo Helicopters and Team Futaba for Radios
Morgan Fuels
OS Engines

11-07-2009 02:37 PM

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Revolution Models	.	CarbonXtreme	.	Midland Helicopters
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Radio - Servo - Gyro - Gov - Batt > Li Ion Packs?

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