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3 cell Lipo's in 9.6 v Transmitters

Old 02-25-2018, 08:09 PM
  #26  
Wildflyer
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Guys will you stop fighting! You sound like you are on RC groups.

I meant this as a cautionary advise.

My TX on Ni/cd would show around 9v while operating, on Lipo it showed about 12.4 dropping to 11.

Since it has a linear voltage reg. the excess voltage must be converted to heat.
That is why we can pull more servo power when using a 2s battery that a 3s or 4s, when using an ESC with a linear BEC.

Tomorrow I will ask admin to remove this entire post. This has gone too far.

I know both of you are smart, and I value your advise. Please end this bickering.
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Old 02-25-2018, 09:28 PM
  #27  
dereckbc
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Originally Posted by Wildflyer View Post
Guys will you stop fighting! You sound like you are on RC groups.
My apologies, but I did not start it. At least on RCG they have a lot more traffic.

Originally Posted by Wildflyer View Post
I meant this as a cautionary advise.

My TX on Ni/cd would show around 9v while operating, on Lipo it showed about 12.4 dropping to 11.

Since it has a linear voltage reg. the excess voltage must be converted to heat.
I was backing that up with WHY and HOW. What bothers me is why a manufacture would design such a fragile VR to save 5-cents on a heat sink or more durable VR. Other than a passive electrical device like a flashlight, just about any electronic (note there is a difference between electrical and electronic) will use a voltage regulator. Anything with a microprocessor will likely use 3.3 volts, and the analog radio parts can be anything from 5 volts up.

NiMH and NiCd are pretty much antiquated. They do have some niche applications, but radio, controls, and traction motors are not one of them today, especially in our hobby. Brushed DC motors and NiCd are dead in RC hobbies. NiCd/NiMH $/wh cost are roughly the same as Lithium counterparts. Couple that with lithium having 2 to 4 times the energy densities, higher specific power, and longer cycle life made Nickel batteries 8-Track tapes. OK for a power tools, but not much else.

Once again Wildflyer I apologize too you.

Dereck
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Old 02-25-2018, 10:07 PM
  #28  
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All that is true, but for a transmitter that was designed maybe 15 years ago, for a 700mah Ni/CD pack, long before Lipos were available. They were NOT thinking of handling any more voltage that a Ni/cd pack would deliver.

I understand electronics more than you think I do. Thanks the the Army screwing me out of the Navy (long story) I was inline to have a very high end electronics career. I hold a valid FCC general class lic and a ham lic. I have done some design work, although it was a long time ago. I have tried to sort of keep up with some parts. I know many people don't think much of a FCC general anymore, but it 1970 it was the golden ticket, and it took a lot of study to get it.

My Tx drew 200ma, at 2 volts extra that would be 0.4 watts additional power to dissipate, not much I know, but I don't know the specs of the VR they used or the amount of power they figured it would be wasteing. A little bit more, over time MAY have been the straw that broke the camels back. I am just glad that it failed while the plane was on the ground.

Put an extra cell in your car battery and see how long the computers and radio last. It would only be an extra 2v as we call it. Odd that we car a car batter by it's totally discharged voltage. In my little joke here, the car battery would go from 13.6. up to 15.86, that might be fine for the starter, but something might fry. So it would not be a good idea.
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Old 02-26-2018, 01:42 AM
  #29  
hayofstacks
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I ran with a blown diode in my car forever, didn't realize it. It was sitting at 14 volts at idle (barely within range) and 17 volts at 2k rpm. I have a habit of flooring it on on ramps. Neger blew a fuse or the radio. The battery just kept eating itself. Felt kinda dumb when I finally hooked a volt meter up and checked it.
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Old 02-26-2018, 08:57 AM
  #30  
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Wildflyer - apologies that Ego's and Pride took over ...

Hang in there - WF is better than what happened here.

On subject of blown diode in a car ..... my boats alternator blew one of the bridge diodes ... that was KAPUT to various items and the main starter battery !! Contrary to design - where its supposed to fail and open circuit ! Basically it shorted and full whack out of a 120 Alternator to the system.
Myself and the Auto Electrics guy called to sort had never seen anything like it before.

As to voltage reduction in radios : Its not just old radios that carry on the regulation by dissipating heat ..... many budget radios still do it. Its cheap and simple.

Nigel
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Old 02-26-2018, 05:28 PM
  #31  
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I think hayofstacks, and Nigel have just proved my point.

If the VR which is just a 3 lead device in many cases, works then no problem.
If it fails open, no radio but not much damage.

If it fails shorted then all heck might happen.

It will cost about $85 for shipping and repair of my JR 9303, plus the cost of the battery I won't use again. Haven't decided yet.

I do not want more fighting about the exact voltages of the different chemistry's of batteries.

So PLEASE TAKE THIS AS AN ADVISORY and think if your radio can handle a Lipo.
We can get the same mah capacity in Ni/mh and LifePo4 batteries both at a voltage that older Tx's can handle.
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Old 02-26-2018, 09:47 PM
  #32  
solentlife
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My 9x .. which is based on JR design ... is an 8 cell NiMh radio.

I have 2 of them ... one is still with NiMh (Grundig brand 2300 mAh and LSD as good as more expensive Enerloops) .... other has a LiFe battery in.

So my opinion is that NiMh may be old hat - but it works. Most NiMh other than cheapo crap - are now LSD - so charge and enjoy ... why change to another format ? NiMh are available over supermarket counter ... Each year - I do a discharge check maybe 2x of the NiMh ... just to make sure the cells are good. They are still good for over 9hrs Tx use even though they are that old I can't even guess when I put them in ! It has to be more than 6 or 7 years ...
I use an old Futaba 50mA charger ... which can literally stay connected indefinitely.
Or go for equivalent LiFe pack - the question then is whether it fits in the space in radio.

I know my JR Propo with banded 8 cell NiMh pack - to fit any other battery form is difficult due to the space allocated in the radio. The cells are arranged in a non-uniform shape to fit.

Nigel
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Old 02-27-2018, 12:05 AM
  #33  
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Is there a question?

Last edited by dereckbc; 02-27-2018 at 03:12 PM.
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Old 02-27-2018, 03:17 AM
  #34  
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