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Old Oct 10, 2012, 04:45 AM
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Futaba LiPo Replacement

Hi Guys,

I have a Futaba 9C radio and I am purchased this LiPo battery to replace the NiCd.

http://www.hobbyking.com/hobbyking/s...dProduct=16529

I have a couple of questions regarding this battery:

1) What rate should I charge at in order to achieve a 1C charge rating? Would I charge at 2.65A ?

2) My Futaba NiCd battery usually sends off a low voltage alarm at roughtly 8.7 volts. This LiPo battery is 3 cells and so if it drops to 8 or 9 volts... it would obviously be damaged. So how do I know when my battery is too low to fly?

3) I'm not sure how to charge this battery with the given connector. The connector (as shown in the image) is basically a servo cable connector which has a red and black wire. In order to charge it... would I have to then get a female servo connector and solder it on to some banana plugs which would in turn be plugged into my charger?

4) Is there anything else I should know about using this battery in my Futaba radio?


Thanks guys!
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Old Oct 10, 2012, 10:53 AM
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United States, CA, Bear Valley Springs
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Originally Posted by williamjames View Post
4) Is there anything else I should know about using this battery in my Futaba radio?
Yeah. Don't.
Get a pack of Eneloop AA Low Self Discharge cells and don't worry about #1-3. they have all the capacity and low self-discharge of the lipo without any of the hassle. Seriously.

I own two 9Cs myself, btw.

mw
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Old Oct 10, 2012, 12:40 PM
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OK, I'll add my two cents also
For many, the Eneloops are a great option in older transmitters that are not designed for using a lipo.
In this case, if WJ has a good balance charger, maybe flies lipo powered models exclusively, then a low C rated TX lipo is an option. For the 9C, I would just put two rectifier diodes (at least 1 amp rating or higher) in series with the battery. This way, fresh off charge with a lipo your radio will read right about 11.3V, just like with the stock battery, and the low voltage warning at 8.7V (what Tx sees) will be at about 10V at the battery. It's all about how comfortable you are with dealing with Lipos.
I have Futaba 8FG, I had very good performance with the stock 1700mAh Nimh, but now keep it as a backup. A 2S 2500 Lipo made to fit the radio is 1/3rd the price of a new 6 cell Nimh, and of course there's no issue running a fully charged (8.4V) lipo in a Tx designed for a fully charged 6 cell Nimh, also 8.4V. TRhe radio also has user settable low voltage warnings, so I set it to 7.4V (nominal for the 2S lipo) and get a good 9 hours of run time before I see that voltage. Works for me, no hassles
Pete
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Old Oct 10, 2012, 01:33 PM
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I would just put two rectifier diodes (at least 1 amp rating or higher) in series with the battery.
Where can I get more info on adding rectifier diodes? I don't know what they are and have no clue how to use them.
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Old Oct 10, 2012, 02:27 PM
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A waste of time, effort and money, imo.

mw
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Old Oct 10, 2012, 03:47 PM
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A waste of time, effort and money, imo.

mw
Mark, can you please elaborate. I'd like to know why you think it's a waste.
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Old Oct 10, 2012, 08:30 PM
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Mark, can you please elaborate. I'd like to know why you think it's a waste.
I'd be glad to although this information has been repeated ad nauseum.

In a transmitter that requires an eight-cell AA pack, the fully-charged voltage is around 11.4 volts. You already have a perfectly good charger in the supplied wall unit. In order to use a 3s lipo, you will need to reduce the fully charged voltage to under 12 volts or risk stressing the components that are not designed for that high voltage. With a lipo, you have to remove the battery to properly charge it and you still only get around 2000mah...the same as a AA Eneloop pack that uses the supplied charger and is designed for our 9Cs. Why bother with a bunch of kludges that you don't even understand yet rather than a simple drop in for the same runtime and safer operation? In short, K.I.S.S.

How's that?

mw
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Old Oct 10, 2012, 10:06 PM
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I risk the wrath of the moderators and raise the BS flag on the last post. I ran a 3S LiPo in a very old 8UAP (pre super) for three flying seasons.. The radio worked as well the first day the LiPo was installed as it did last weekend in the hands of its new owner.
I just ran the LiPo box stock fully charged and reset the radio total on time counter after each full charge. I ran the battery for a couple of flying sessions and settled on charging after 6 hours run time.
The supplied wall wart charger that comes with radios is crap. It does not peak detect so will just keep on pushing long after your batteries are full and now cooking.
A quality charger is an almost required tool now and not that costly compared to the variety of battery chemistry's they handle properly.
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Old Oct 11, 2012, 12:05 AM
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Joined Sep 2012
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Originally Posted by williamjames View Post
Hi Guys,

I have a Futaba 9C radio and I am purchased this LiPo battery to replace the NiCd.

http://www.hobbyking.com/hobbyking/s...dProduct=16529

I have a couple of questions regarding this battery:

1) What rate should I charge at in order to achieve a 1C charge rating? Would I charge at 2.65A ?

2) My Futaba NiCd battery usually sends off a low voltage alarm at roughtly 8.7 volts. This LiPo battery is 3 cells and so if it drops to 8 or 9 volts... it would obviously be damaged. So how do I know when my battery is too low to fly?

3) I'm not sure how to charge this battery with the given connector. The connector (as shown in the image) is basically a servo cable connector which has a red and black wire. In order to charge it... would I have to then get a female servo connector and solder it on to some banana plugs which would in turn be plugged into my charger?

4) Is there anything else I should know about using this battery in my Futaba radio?


Thanks guys!

I have a board specifically designed to allow use of 3-cell Lipos in 9.6V Transmitters! It keeps the voltage to your Tx less than 12V on a fully charged pack, and when the pack reaches 9V it cuts the battery off so it does not ruin itself if you leave the Tx switch on accidentally all weekend! By the way, it won't shut off your Tx during use, because your Low Voltage alarm will come on, and your LCD display will go blank long before the 3-cell pack gets down to 9V. I've sold hundreds of them! Don't worry about the 9V cuttoff being "too low," either. Lipos discharging at less than 1/10th of their 1C rating down to 3V per cell survive just fine! The "dime-sized" board plugs in between the battery and your Tx. Search Li-Po Power Board on e-bay. Just tell me what Tx you have, and I will get you the right connector. I'll be selling those boards and more at the 2012 Tucson Aerobatic Shoot Out next weekend!
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Old Oct 11, 2012, 12:13 AM
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Flashburn, of all the posts I've read on R/C Groups, yours make you sound like the kind of guy I'd enjoy flying with!!
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Old Oct 11, 2012, 01:32 AM
DrV
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Originally Posted by Mark Wood View Post
I'd be glad to although this information has been repeated ad nauseum.

In a transmitter that requires an eight-cell AA pack, the fully-charged voltage is around 11.4 volts. You already have a perfectly good charger in the supplied wall unit. In order to use a 3s lipo, you will need to reduce the fully charged voltage to under 12 volts or risk stressing the components that are not designed for that high voltage. With a lipo, you have to remove the battery to properly charge it and you still only get around 2000mah...the same as a AA Eneloop pack that uses the supplied charger and is designed for our 9Cs. Why bother with a bunch of kludges that you don't even understand yet rather than a simple drop in for the same runtime and safer operation? In short, K.I.S.S.

How's that?

mw

Agree with mark 100%. I still have my 9c and use it as a backup to my 12z. I also had a 3s lipo (now eneloops) in the radio. The truth is a fully charged 3s lipo does stress the final transistors of the transmitter for which it was not designed for. It's a gamble, it may work for a long time or it may suddenly stop transmitting. The electronics (mainly the finals) are overvoltaged thus working outside their designed parameters and eventually will burn out. If you want stability and long term use, stay within designed voltage parameters.

It's your radio and you get to choose what to power it with safely.

More opinions here

http://www.rcgroups.com/forums/showthread.php?t=1748944
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Old Oct 11, 2012, 10:48 AM
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This was very true on 72Mhz, but a 2.4Ghz module in the 9C is fully regulated.
I personally would not run a radio such as the 9C on 3S lipo directly, if I still had my 9C and wanted to use a Lipo, I'd just use two diodes in series, in this case better than a regulator, since it allows you to see where you are on battery life through the voltage display.
Pete
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Old Oct 11, 2012, 11:45 AM
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But the main point is that with the diodes you still wind up with equal to OR LESS available voltage from the lipo than if you simply went with modern 2000+ AA cells in the first place.

The OP stated in post #4, and I quote:
Quote:
Where can I get more info on adding rectifier diodes? I don't know what they are and have no clue how to use them.
So, why bother when the OP admits to not knowing a thing about lipo modification and runs the risk for a questionable kludge?

Do what you want though. It's still a free country.

mw
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Old Oct 11, 2012, 12:43 PM
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okay, so after much reading and several posts here it looks like the rc community is split down the middle.... that includes Futaba 9C owners. I think I'll take the extra precaution and just stick to the eneloops. Thanks to everyone for their feedback... it is much appreciated
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Old Oct 13, 2012, 04:53 PM
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San Pedro,Ca
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So what happens if I ran 8 reg AA batteries in it, which if you add it up is 12volts, So why would a lipo do any damage. I run lipos in all my Transmitters and ever once had a problem
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