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Old 09-11-2011, 05:36 AM   #1
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Default Lipo for tx?

If a transmitter calls for 8 AA which is 9.6 volts can you substitute a 11.1 volt 3S lipo, or will it burn something up? Over.
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Old 09-11-2011, 07:47 AM   #2
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Some Say do Some say don't. I Have before without a problem to the TX. BUt.. I Forget to turn off my Tx alot, so i ruined my lipo in no time. plus you have to watch out where you leave it. if its left in your car or sun, and gets too hot the battery can swell just like for your planes. I Went to walmart and picked up some 2300mah energizer Recharge, the Low Self Discharge NIMH's and an 8 cell holder From Radio Shack, and soldered the connector from the old battery to it. I dont have to worry about charging it at all. i usually fly many days in a row before i have to charge. I also don't have to worry about leaving it on. will post pics of the batt if you would like.

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Old 09-11-2011, 03:52 PM   #3
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A full 3S lipo is 12.6v. Technically this is over volt and a lot of TX manufacturers will state this voids the warranty. But, people do it all the time.

It's safer and actually easier to use low self discharge NiMh like Eneloops. They work great and are otherwise treated just like normal NiMh.

Do not be tempted by 2700mA+ [High Capacity] NiMh. Most of them are garbage. Unfortunately there is a LOT of NiMh garbage in the market now.

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Old 09-11-2011, 05:41 PM   #4
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A much better IMHO is to use Eneloops instead. They are very safe, proper voltage, very low self discharge and can be charged with just about any Nixx compatible charger. No worry about fires, long lasting, safe to charge in the transmitter and just as good as LiPo for holding a charge. The best of both worlds and very safe and can not be ruined by accidentally over discharging.
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Old 09-11-2011, 06:08 PM   #5
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http://www.headsuprc.com/servlet/the...SMITTER/Detail
I have been using these in 3 transmitters for about a year now with no problem. Fly every day and charge about every 3 months. Really like them.
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Old 09-12-2011, 03:39 PM   #6
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Originally Posted by flydiver View Post
A full 3S lipo is 12.6v. Technically this is over volt and a lot of TX manufacturers will state this voids the warranty. But, people do it all the time.

It's safer and actually easier to use low self discharge NiMh like Eneloops. They work great and are otherwise treated just like normal NiMh.

Do not be tempted by 2700mA+ [High Capacity] NiMh. Most of them are garbage. Unfortunately there is a LOT of NiMh garbage in the market now.
I have over counter supermarket 2300mAh NiMH and no problem ... charge is held for good time ... in fact IMHO means I don't look at Enerloops or such - as most NiMH nowadays are of low self discharge anyway.

I read so much about peeps wanting to fit LiPo's to Tx... and to this day still cannot see the point. a) the voltage is wrong, b) charging is a new ball-game and you cannot push such charge rates through the Tx socket ... max on those are typically 700mA ... you can push to 1000mA on some. Balance of LiPo cells is impossible and you would need to remove the pack to charge / balance ... my NiMH stay in Tx, battery cover rarely comes of, charger works through normal Tx charge socket ...

If you have the older 50mA charger - that can literally stay connected to Tx indefinitely as it's trickle charge for high capacity NiMH.

For quicker charging - I use a Prolux Peak Detect Charger ... which pumps out 1000mA ... yes it's on limit of my radios sockets - but they are OK with it. After a days flying ... its rarely charging more than 30mins unless its a real heavy flight day and then maybe an hour and it's all done.

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Old 09-12-2011, 03:43 PM   #7
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Originally Posted by Rodneh View Post
......................can not be ruined by accidentally over discharging.
Oh yes they can !! There are still chargers out there without peak detect or time cut-off.
You keep pumping into a NiMH and it will not like it. Only way you can is to use a very low rate charger ie trickle rate of 50mA or less.

With many chargers now knocking out 300 ... 500 .... 1000mA rates - you would soon knacker a typical NiMH pack if left too long.

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Old 09-12-2011, 08:38 PM   #8
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Solentlife, you need to read a little closer. No mention was made of overcharging, if you look more closely you will see I said "not ruined by deep discharge" which is 100% correct. As long as you do not reverse charge a Nixx cell, you will not damage it even if you take it down to zero volts as long as you do it at a rate that does not raise the internal temperature to the point of failure. I have no argument that overcharge can hurt any type of cell but that was not in the comment you quoted.
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Old 09-12-2011, 10:16 PM   #9
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Thanks everyone. Think I'll stick to nimh. I overlooked draining lipos too low. Over and out.
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Old 09-13-2011, 07:11 AM   #10
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Originally Posted by Rodneh View Post
Solentlife, you need to read a little closer. No mention was made of overcharging, if you look more closely you will see I said "not ruined by deep discharge" which is 100% correct. As long as you do not reverse charge a Nixx cell, you will not damage it even if you take it down to zero volts as long as you do it at a rate that does not raise the internal temperature to the point of failure. I have no argument that overcharge can hurt any type of cell but that was not in the comment you quoted.
Apology ... sorry should read more carefully.

Your point now about taking a rechargeable to ZERO volts is a very risky thing to do and usually is near impossible with a NiCD or NiMH cell. They have a residual voltage BUT if you approach that - you run risk of reverse voltage of the cell and then short life or ruined when 'zapped' to correct.
Taking a NiMH down to lowest level regardless of temperature or other is a NiMH doomed to fail sooner than later.
I have many NiMH in the box failed for that very reason.

Sorry to differ on this. My advise to anyone using ANY rechargeable is to keep them inside the working range charged at all times, unless it's LiPo of course and then you work on storage levels etc.

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Old 09-13-2011, 06:04 PM   #11
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Originally Posted by solentlife View Post
Your point now about taking a rechargeable to ZERO volts is a very risky thing to do and usually is near impossible with a NiCD or NiMH cell. They have a residual voltage BUT if you approach that - you run risk of reverse voltage of the cell and then short life or ruined when 'zapped' to correct.
Agreed:
Taking a Nicad or Nih battery to way below normal voltage levels is not good for them. But, you've got a fair to middling chance of recharging them, and keep using them for a long time.

That is not true of the LiPo batteries. Discharge them way below minimum voltages even once, and you've got damage.

As for the A123 cells, I've done that twice and got away with it. But one cell out of a club members two cell A123 battery quit when he left it discharge to zero.

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Old 09-13-2011, 08:30 PM   #12
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I have worked in the space industry for many years including when NiCad first became a reliable power source. Many tests were made on them. Results, NASA found that the best way to store NiCad's was to discharge each cell to zero volts, place a shorting bar across the cell and with the shorting bar in place store at a low temperature. They would last for years doing that. When ready for use, slow charge them and they were ready to go. You will not damage one by taking it all the way down to zero volts and you cannot reverse a single cell by discharging it, to do that you need two or more cells in series and then one of them has to be weaker (less storage capacity) than the others for that to happen. I do not know of any similar tests being made on NiMh but, since the chemistry is very similar to NiCad, I'd expect the same to be true for them.
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Old 09-13-2011, 09:25 PM   #13
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Originally Posted by Rodneh View Post
I have worked in the space industry for many years including when NiCad first became a reliable power source. Many tests were made on them. Results, NASA found that the best way to store NiCad's was to discharge each cell to zero volts, place a shorting bar across the cell and with the shorting bar in place store at a low temperature. They would last for years doing that. When ready for use, slow charge them and they were ready to go. You will not damage one by taking it all the way down to zero volts and you cannot reverse a single cell by discharging it, to do that you need two or more cells in series and then one of them has to be weaker (less storage capacity) than the others for that to happen. I do not know of any similar tests being made on NiMh but, since the chemistry is very similar to NiCad, I'd expect the same to be true for them.
Back in the early days, discharging the Nicads flat and leaving them in that position for a long length of time tended to result in shorted cells. What we suspected was happening was these cells sometimes have microscopic shorts between the plates. A fully charged cell would simply blow out the microscopic short, and all was well.

And as you note, discharging a multicell battery can result in reversed cells if the battery is discharged completely. That might add to the problems.

But in a dead cell, that microscopic short would grow into a permanent short. You could blow out that short by using a high powered charger, but often that cell would have its "shelf life" off of a charger reduced to a month or less before it was completely dead due to high internal leakage currents.

These were consumer grade Nicads, not the expensive batteries that might have been used by NASA.

Company I worked for went through some 100,000 24 Volt 1.5 Amp Hour batteries during the life of the control they were used in, over a period of some 30 years.

Working in the Service Department, I got to look at a LOT of the batteries that came back under warranty.

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Old 09-13-2011, 11:26 PM   #14
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I have thought about using lipo packs but i think better judgment took over and i put sanyo 2700 packs in my transmitters a year ago. So far no problems at all and my flying time has been great . I do not let any battery go down to nothing and always put a little more than half a charge in my lipos if they are going to sit a while. I have some lipo packs that are 5 years old and still work fine. joe
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