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  1. #1

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    Lipo vs. Nicad?

    I am relatively new to this hobby. I was at a fly-in last month and was told by one of the pilots that if I converted over to lithium polymer batteries I could literally fly for 3 or 4 months, depending on the amount of flying I do each week of course, without recharging.

    Question # 1: Is this true?
    Question # 2: If it is true, why wouldn't everyone be using lipos instead of nicads??

    Please understand that I have very little knowledge of the battery side of this hobby. I simply charge my nicads for 10-15 hours the night before I go fly the next day. I just bought a 3D plane and the receiver battery for this thing will only last for about 4 good flights if I am lucky. This is what got me interested in finding out about lithium polymer batteries.

    Please help!

    Allen

  2. #2

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    RE: Lipo vs. Nicad?

    Definately NOT true.

  3. #3
    Hangtime's Avatar
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    RE: Lipo vs. Nicad?

    Hi Allen!

    Li-Poly does a great job as a power source for electric pilots in 'park flyer' type aircraft, and the limitis of serviceability are expanding all the time. In the near future that battery technology may dominate electric flite.

    As a Rx pack in a fuel powered plane it's still considered an 'unwize' choice due to the vibration sensitive nature of the cells and tabs.. however this may change too. Li-Ion, being a cylindrical cell rather than a flat prismatic 'poly wafer' buildup is more robust and has found some following in giant scale aerobatic applications, yet remains a questionable choice due to cost and safety considerations. There's times when using them make sense, but it's not the best choice for sport applications. There's more info on it here:

    Li-Ion vs Nicad & NiMH

    Hope this helps..
    Steve Anthony
    www.hangtimes.com
    NoBS Batteries

  4. #4

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    RE: Lipo vs. Nicad?

    Months without a recharge!?! VERY wrong. Li-ION and Li-POLY batteries have more charge than their Nicad eqivilents because of their chemical makeup. Their biggest advantage (in my opinion) is weight. A LI-Poly pack is much lighter than a comparable Nicad pack. They are not magic. An 1800Mah 11.1V Li-poly pack will last just as long as a 1800Mah 11.1v Nicad (even though it is not possible to get the same volts between a Nicad and a LiPoly becuase they have a different voltage per cell. For the sake of argument lets just say you can). The hypotheical Li-poly in our case would weigh a lot less than the Nicad. It will still power your device for the same amount of time. Of course, since the pack is lighter you can put in a much bigger Li-poly pack to get longer run times for the same total weight.

    Li-ION & Li-Polys are MUCH more delicate than NI-CADs. You CAN NOT charge them unattended as you do with your NiCads. There is a very real chance that they will overheat and vent flame. This is not an overexaggeration. Lithium is flamable when exposed to oxygen. If the pack is overheated and expands it may crack causing a fire. This is true in use as well. You need to make sure your power system does not draw more power than the batter can supply. Do not jump into Li-Poly's without getting all of the proper equipment. You need a Whattmeter, a Li-Poly Charger with Heat sensor, and batteries that contain an overcharge sensor. Test your setup before use.

    Li-Polys are great if you are careful with them. They will hurt you if you are not.
    The only way to make a small fortune in aviation is to start with a large fortune.

  5. #5

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    RE: Lipo vs. Nicad?

    Maybe what he was talking about is that with Lipo packs, once charged, you can let them sit for 3-4 months without a recharge. This is true. NiCads and NiMH will self discharge while LiPo's do it extremely slow.
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  6. #6

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    RE: Lipo vs. Nicad?

    Hey, thanks guys!

    That's why I came here for answers. I know that if something sounds too good to be true, it usually is, and that definitely sounded too good to be true! I really appreciate the info on these batteries. I will definitely stay with nicads.

    Thanks again,

    Allen

  7. #7

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    RE: Lipo vs. Nicad?

    OK, from someone who uses lithium ION batteries in all his jets let me give you the other side of the facts.

    Yes, LIPO and LI-Ion have to be taken care of or they can catch fire. Usually what happens is somebody is fast charging them or charging them with the incorrect charger and something goes wrong. I have been using duralites in my jets and my TX now for almost 18 months. I charge them in my trailer and have never had anything go wrong because I use the suggested charger for them and nothing else.

    Yes, depending on the application that you are using them for you can fly for almost 2 months without recharging. A club member that I fly with substituted a 4800 mah 4 cell lithium ion battery for his 1100 mah nicad on a trainer. The current draw on that airplane is almost nothing (4 standard servos) and he can fly 3 -4 flights a week without having to recharge for almost 2 months (5.1 volt regulator on the RX also).

    No, if you are going to put them in a very high current drain airplane it would be wise to charge them after every flying session.
    Yes the Li-Po are more sensitive to shock than others as they are a soft shelled battery where as Li-Ion's are packed in a metal can that can take a little more abuse. If you are going to use them, I would go with Li-Ion and protect them in the aircraft the same way you would protect nicads.

    There are alot of people out there using these batteries and if they were so dangerous you would hear about more problems with them than just the occassional, "My garage caught fire story." I would say 99.5% of the time you hear these kinds of stories it is user error and not the batteries fault. If that were the case you would see cell phones, pda's, laptops, handheld kids games, etc exploding and catching fire all over the place. The reason you don't is that the manufacturer gives you a charger to use and if you use the correct charger nothing goes wrong.

    This is just my .02 worth. Like I said I have been using them for 18 months now and I love them. If I thought they were unsafe I would not trust my $7K jets to them.


    Patrick.
    Perfect landing or total destruction crash, I still love this hobby!

  8. #8

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    RE: Lipo vs. Nicad?

    Thanks Patrick!

    I really needed to hear from someone who actually uses them. This is great information. I probably will consider going to lithium batteries sometime in the future, but for now I'm not prepared to incur the initial cost.

    However, I do have one other question. Is it possible to just use a lithium battery for my receiver and stay with nicad in my transmitter? The reason is obvious. My receiver battery ALWAYS drains much faster than my tx battery. If I could find a way to make my rx battery last at least as long as my tx battery then I would be fine.

    Any Suggestions??

    Thanks,

    Allen

  9. #9
    SwampFlier-RCU's Avatar
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    RE: Lipo vs. Nicad?

    Allan:
    TX and Rx signals are inmune as to where the current is coming from, which means there is no porblem in haveng LI-poly or other type hooken on to your receiver and NiCd in the transmitter.
    However, I would decide one way or the other for all just to be used to charging all my batteries the same way, and not worry that i used the nicd charger on my lipoly batteries and hencce fried them or the house [&:]
    NOw i must confess my ignorance but i don't think there arema ny LI-Poly's for transmitters are they? need toi regulate the voltage...
    (I use NIcd for my Rc applications)
    Regards,
    Patrick

    There is a very fine line between \"hobby\" and \"mental illness.\"

  10. #10

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    RE: Lipo vs. Nicad?

    batteries have been my downfall in this hobby but you cant make a simple comparison between li po and nicads..I switched over to nimh for rx and tx ..first no memory issue..second the extra time you get flying.unless you fly for hours on end a nimh is ideally suited for most sport flyers..li po is the best choice for electric based on weight and power.if your using a computer radio get the nickel hydrides..and nicads are great.someone like me can abuse the nicads and they are more forgiving than nickel..and I saw a fire from a li po at the neat fair last fall.trust me abuse them and you may have no house lol..


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