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Check your Transmitter Batteries!!!

Old 05-05-2014, 06:49 PM
  #26  
solentlife
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Denny ...

I use 4 cell pack of Grundig 2300mAh NiMH in my 61 powered Biplane .. it's running :

FrSky 8ch Rx
3 servos of 40gr HD 0.1sec - Bluebird
1 servo of 15gr for throttle.... an old JR from 1980's

You've seen the videos .. I get average 9 - 10 min flight before I land and stand her to one side.
I will think nothing of 2 - 3 flights that day .. and if its a meeting - another 2- 3 flights next day.

After a single days flying - I get home and plug her in ... 50mA JR charger .. how long ? Fully charged overnight. If I use my Prolux which charges at 1A ... then it's showing full after about 30 - 40mins .. indicating about 500mA. That also agrees with my being able to fly two days without worry... with just over 1 hr to recharge fully.

Blimey - even with yesterdays old 500 packs - I used to go flying all day with same model. If I did a weekend meeting I took a field charger and just gave a small boost on second day from the field box.

People tend to get carried away about capacity .. yes you can draw higher amps than some imagine ... but overall the total used capacity is less than most realise.

Nigel
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Old 05-05-2014, 07:23 PM
  #27  
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OK .... ti charge my 9xr LiPo Tx batts ... I quite often use this ... leaving my standard programmable chargers for flight packs :



I have a second one similar which came with an RTF ... same gear - different case.
Both shut of and go Green at about 4.15v .. not 4.2v - but that's fine as I feel safer with such not pushing the limits.

For my NiMH Tx and Rx packs ...

[media]http://pics.ebaystatic.com/aw/pics/viewitem/imgEndedCvi_96x96.png[/media]

(edit : Sorry seems it doesn't want to show it !! - It's a Futaba M series charger)

These come up on eBay every so often and are a good buy. They are rugged and deliver a steady reliable 50mA to both Tx and Rx outlets.
I've made my own leads to cover Futaba and JR of them ...

The Prolux is a faster charger and is about as high an ampage you can safely put through a Tx socket .. 1A ... it has auto-shutoff to trickle 50mA.
Unfortunately I don't have a picture of it or one I can pull of ebay ..

Nigel
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Old 05-05-2014, 08:59 PM
  #28  
thepiper92
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Originally Posted by solentlife View Post
Battery is a Battery .... if it aint charged - it's useless ... If it's old and on it's way out - it's useless ...

Life .. LiPo .. Nixx makes no odds .. they all go same way in the end and Kyles post only highlights the disregard some have for checking their Tx batteries.

Personally I don't see point of fitting a battery that you need to remove to charge .. except of course I believe Spekie now has provision for charging LiPo in it's later radios ?
So much nicer to just put Tx on bench .. plug in charger .. and KNOW your Tx will be full charged ready for next outing... without needing to actually check how much charge is left .. remove pack ... plug in balance and power leads to charger etc.

Nigel
I remember an old FM radio. The batteries were configured in a plastic bundle. A butter knife was necessary to pry them out. Getting tired of them, I found a cord that fit and charged it. I was only 10 at the time, not sure if it was too much for the plugin, or the radio which was already 12 years old just died. For my 9xr, I don't see the hassle or taking out the 2200 lipo pack. It isn't hard to remove, and I have to take the lipos out of my planes anyway.
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Old 05-05-2014, 09:04 PM
  #29  
kyleservicetech
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Originally Posted by solentlife View Post
Denny ...

I use 4 cell pack of Grundig 2300mAh NiMH in my 61 powered Biplane .. it's running :

FrSky 8ch Rx
3 servos of 40gr HD 0.1sec - Bluebird
1 servo of 15gr for throttle.... an old JR from 1980's

You've seen the videos .. I get average 9 - 10 min flight before I land and stand her to one side.
I will think nothing of 2 - 3 flights that day .. and if its a meeting - another 2- 3 flights next day.

After a single days flying - I get home and plug her in ... 50mA JR charger .. how long ? Fully charged overnight. If I use my Prolux which charges at 1A ... then it's showing full after about 30 - 40mins .. indicating about 500mA. That also agrees with my being able to fly two days without worry... with just over 1 hr to recharge fully.

Blimey - even with yesterdays old 500 packs - I used to go flying all day with same model. If I did a weekend meeting I took a field charger and just gave a small boost on second day from the field box.

People tend to get carried away about capacity .. yes you can draw higher amps than some imagine ... but overall the total used capacity is less than most realise.

Nigel
Agreed:

Nice thing about those LiFe or A123 cells. When you discharge say 1000 Mah out of them, it takes 5% more or 1050 Mah to recharge them. That said, a number of my club members have gone to the A123's and are finding that they are using about 200 Mah per flight. And, that 200 Mah also includes running the ignition system for the gasser up front.

Yesterday, one club member indicated his dual A123 pack is delivering 350 Mah per flight, NOT including the ignition. But this is a giant scale model with a big engine up front, plus some 10 or 12 digital servos. That model weighs some 30 or 40 pounds.

Years ago, we had those Nicad "AA" receiver batteries. The newer Nih AA cells can't put out the same current at the same voltage as those old units. I'd NEVER use a four cell AA receiver battery in any 2.4 Ghz radio. Just to marginal in operation. Or, never use a 5 cell AA receiver battery in any higher powered model like a 30 cc gasser.
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Old 05-05-2014, 09:21 PM
  #30  
solentlife
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My mate explained about the differences ... the old NiCD's were a lot lower in capacity and they could deliver quite a jolt in amps .. I have a burn on my leg from one AA .

Later as the capacity went up - the amps max came down ... NiMH are less able to deliver high amps - BUT they can still deliver a punch ... You can still light a fire with a NiMH and a ball of steel wool.

He talked of "Charge density" .. but to be honest most of what he said went over my head ... but I understood that basically to get so much charge capacity - the trade of is high amps.

As to using 4 cell ... I have never had any indications of any glitches, problems, voltage drop to cause me any concerns. I've even after reading posts such as yours put meter in the system to measure the amps load when waggling all sticks and stalling servos ... I never got over 1.5A on even a badly stalled set .. and that was TOTAL across the whole model .. the 3 x 40's and 1 x 15 .. that's 4 reasonable size servos ..

Nigel
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Old 05-06-2014, 12:17 AM
  #31  
kyleservicetech
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Originally Posted by solentlife View Post
My mate explained about the differences ... the old NiCD's were a lot lower in capacity and they could deliver quite a jolt in amps .. I have a burn on my leg from one AA .

Later as the capacity went up - the amps max came down ... NiMH are less able to deliver high amps - BUT they can still deliver a punch ... You can still light a fire with a NiMH and a ball of steel wool.

He talked of "Charge density" .. but to be honest most of what he said went over my head ... but I understood that basically to get so much charge capacity - the trade of is high amps.

As to using 4 cell ... I have never had any indications of any glitches, problems, voltage drop to cause me any concerns. I've even after reading posts such as yours put meter in the system to measure the amps load when waggling all sticks and stalling servos ... I never got over 1.5A on even a badly stalled set .. and that was TOTAL across the whole model .. the 3 x 40's and 1 x 15 .. that's 4 reasonable size servos ..

Nigel
Charge Density? Could be that is an indication of how many Watt Hours your battery can put out. Watt Hours is Milliampere Hours times the milliampere load being applied to the battery. That's where those LiPo and A123 cells have higher Watt Hour capability. Roughly the same milliampere hour rating, but at three times higher voltage. My Astroflight Wattmeter shows both Mah, and Watt Hours. So, if your battery measures 2060 Milliampere Hours on a battery test operation, that would be ABOUT 2.06 times 1.2 Volts or 2.47 Watt Hours. About, because the battery voltage is not consistently at 1.2 Volts DC. On an 2300 Mah A123 cell, the Watt Hour capability would be about 7.6 Watt Hours. Lipos are even better.

Bottom line, if you don't use more than perhaps 50% of your receiver battery on any particular flying day, this stuff is needless info!

As you've indicated, when the battery mfg's cram in more and more milliampere hour capacity into a "AA" sized battery, something has to give. Ain't no free lunch. What gives is thinner plates inside that battery for more surface area. Thinner plates means higher internal resistance. Higher internal resistance means lower ability to put out high currents. Kind of like a 1 inch diameter garden hose, versus a 3/8 inch diameter garden hose.

That works just fine with our transmitters, that pull perhaps 200 Milliamperes or so. But those digital servos used in the giant scale airplanes, or even the high torque servos also used are a whole different breed of animal.
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Old 01-05-2022, 08:17 PM
  #32  
Rhondas
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Talking checking transmitter batteries

Originally Posted by kyleservicetech View Post
I've got a Spektrum DX8 transmitter that normally would run over 7 hours on its internal battery. A few weeks ago, that DX8 undervoltage battery alarm went off after only three 6 minute flights.

A quick test on my Western Mountain CBAII battery analyzer showed the battery only had 70% of original capacity. Worse, that battery dropped to 1.05 Volts per cell at the load value of the transmitter. A new battery fixed things.

But, much worse, today a fellow club member lost his giant scale 50 cc gasser one minute after take off. The resulting crash wrecked the 50 cc engine, most of the receiver and servos. The transmitter LCD display was flashing on and off, and absolutely no control of the model was present.

That was the members first flight of the year on that JR radio. The radio was also about a year and a half old.

Another quick check on the battery pack in that JR transmitter showed what happened. The battery voltage measured 10.8 volts at no load. But with a load test of 400 milliamperes, that voltage dropped below 8 Volts DC in less than 5 seconds. Every cell in that pack was That battery died so fast, the transmitter low voltage alarm didn't have enough time to warn the pilot. Very strange.

So, what to do
Nice thing about transmitters, they present a constant current load to its internal battery. So, after a transmitter has sat idle for a long period of time, charge it up.

Then turn it on, and do something else for four or five hours. If your transmitter quits in 4 or 5 hours, time for a new transmitter battery.

IMHO, that's a good thing to do once or twice a year. If you have a 72 Mhz transmitter, be sure to do this test with the antenna fully extended.

If this thread saves one model from disaster, its been worth while.
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why must I ~~~~If you have a 72 Mhz transmitter, be sure to do this test with the antenna fully extended. ?

Last edited by Rhondas; 01-05-2022 at 08:25 PM. Reason: changes numbers
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Old 01-07-2022, 01:43 AM
  #33  
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Because extended operation with the antenna collapsed is not good for the final amp in the transmitter circuit.
It is fine for a short time range test but not for several hours.
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Old 01-07-2022, 10:58 AM
  #34  
solentlife
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Old thread revisited ... but a good one.

More and more people are using LiPo / LiIon cells in their Tx's - this brings in a whole new ball game ...

NiMH are fine to charge up and leave ... but we all know that LiPo / LiIon lose out if we do same. But what to do ? Tx does not have discharge function .. leaving on is not good ... so its remove packs and connect to charger to storage them.

BUT then when you want to use the TX .... you have to charge up the pack ...

If anyone has a solution to this - I am all ears !!
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