Nimh vs Lithium RX Pack?

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Dane McGee
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Nimh vs Lithium RX Pack?

Post by Dane McGee »

How many prefer lithium Rx packs and where are you buying them?

What is the weight,cost etc?

Lee posted some info about a 6v rx pack using a couple of 900 mah A123 cells and I was thinking of going that route. Looking for advice.
Rabbit Leader
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Post by Rabbit Leader »

Dane, I've been running a Li-Ion pack in my Multiplex for a couple of years now, and I love it. Now, The Multiplex is an odd beast in that it uses a 7.2 volt 6 cell pack from the factory, the stock pack is only 60mah and the "upgrade" was 1000 mah, I think the pack I'm using is 2 cells and 1500 mah. I know this much, I can fly it all day and then fly it a couple of weekends later without recharging, and I have yet to have it go anywhere near the low-voltage cut off.

Thinking about converting my HiTec Optic 6 also..
Cash
Rabbit Leader
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Post by Rabbit Leader »

DUDE..just noticed that yer talking about RX packs...sorry, been a little discombobulated past week or so..
Cash
Vapor
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Post by Vapor »

I'm not flying combat at present but I run all 2 cell A-123 packs in all my planes now. If your interested I have a link to a site that has 600ma A-123 cells @ 17 grams each, so a pack would be 34 gr + wire & shrink= 36 gr. ? So about 1 1/4 ounces. NOT BAD!
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Dane McGee
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Post by Dane McGee »

Rick, very interested in the link. Thanks in advance!
Vapor
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Post by Vapor »

Here you go, I have batteries from them, only problem is their shipping. They charge a rather high flat fee + so much per battery so it is more cost effective if you order a lot at once---------rick
http://store.peakbattery.com/index.html
crash_out
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Post by crash_out »

I've used Li-poly for rx packs-they work great, other than having to use a regulator..You want to plug the pack directly to the switch, then use the regulator on the rx side of the switch. Otherwise, the regulator will continue to bleed off until the pack is d-e-a-d. Ask me how I know.

The Li-Fe or 3.0 volt Li-Ion cells are better suited, I think. They require a charger capable of charging them, but no regulators are needed. Plus, they are tougher overall cells than the Li-poly. But the Li-poly are probably going to be lighter, if weight is that much of an issue...I know Li-Fe(A123) cells also have a rather quick drop off on the discharge side. The common practice is to simply set them to recharge after a couple of flights to stay out of low voltage range. This isn't much of a problem since they can be recharged in only a few minutes.

2 cell(6 volt) Li-Ion 680mah pack: 1.5 oz, cost around 6 bucks if you solder it yourself
2 cell lipo(7.4v) 850 mah, regulator: 1.5oz+regulator weight, $10-15, plus another 10-15 for regulator
2 cell LiFe(6.4volt) 1200mah: 3.6 oz, about 17 bucks

I think the li-ion is the way to go, but it looks like you'd have to solder the packs yourself, or get someone to do it. It's also determinate on the type of charger you have available...
Lee Liddle
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Post by Lee Liddle »

Dane, I`m using the Li-ion cells when I`m not using the BEC from an ESC. It`s a 2 cell 6v pack that I solder myself. Very easy to solder. They cost about $5 per cell, shipped. They are 900mah and are good for up to 8 heats without recharging. I`ll be gald to find a link if you`d like one.
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Dane McGee
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Post by Dane McGee »

Is this the one Lee?

http://www.all-battery.com/rcr123a30v90 ... ttery.aspx

Do you like 6v better than 4.8 and can you tell any appreciable difference good or bad?
Lee Liddle
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Post by Lee Liddle »

Yep, that`s it. I`ve been flying 6v for 4 or 5 years now. I like the extra servo speed that I get out of my $10 GWS Mini Satndard servos. Also the extra torque is good for Open B and "was" good for 2610.

On my SSCs, I`ve been trying out a new ESC with a switching bec. The switching bec allows it to be used even when you go above 4s for the power system. It only has a 5v bec, but the weight saved is worth it.
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Dane McGee
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Post by Dane McGee »

Sounds good Lee, I'll give them a try. Thanks for the help.
davidturner
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Post by davidturner »

Lee,

How do you solder Li-ion? I know too much heat can ruin the packs? I tried to get some of that metal I see on my other packs at Radio shack without success.

I did solder a few with wire and they seem ok. They charged in about 15 min. On my Futaba loaded volt meter I can only get them to read 4.1 volts though??? I guess the solder took or I would only see 3 or less volts I would think??

Any help is appreciated!!
Lee Liddle
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Post by Lee Liddle »

David, I just use a good quality rosin core solder. I get my solder from a computer/electronics supply store. There is so much junk solder being sold. That is the only place I`ve found with good solder. I use a Weller 140w soldering gun. Heat it up quick and pre-solder the ends, then come back and solder on the connector. I just use "easy solder" tin sheet from the hobby shop to connect the batteries.

Over heating the ends is not really a problem because the ends are isolated from the actual cell. One the "button" end, the button is elevated off of the cell. And on the flat end, what you solder to is not the end of the cell. There is a mini circuit board in there (really) and you are soldering to a kind of cap that covers the circuit board.

Your charger must not be charging the cells properly. The very minimum reading you should get is about 2.8v per cell, or 5.6v. Any lower than that and the circuit board cuts off the connection so that the battery cannot be over discharged. Fully charged, mine read about 7.0v to 7.2v no load. I charge mine with a Hobbico MkII field charger. I use the NiMH setting. I`ve tried the LIon setting and it doesn`t charge the batteries right.

I also use the lowest amp setting for charging , that`s .2 amps.
davidturner
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Post by davidturner »

Thank you Lee,

I was charging on the li ion setting with the same charger you mentioned. I will try the NIMH setting and then check it with a volt meter.
David
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