Transmitter lipo saver

[tungym]

I am using 3s lipo in my DX7 for 5 weeks or so. My kids (/myself) forgot to switch off the transmitter and killed 2packs of lipo.

Is it possible to use zenner diode at 9V or so such that it can cut the drain current when the lipo falls below 9V.
Is it safe as well, such that the transmitter is not automatically switched off?

Any opinion are welcome. THanks

[Miami Mike]

That's one of my many arguments for using NiMh cells instead of LiPo cells in a transmitter.

Still, it's an interesting problem. You don't want your transmitter to quit and crash your model to save your battery, yet you don't want it to kill expensive LiPo cells when it's accidentally left on. Maybe someone can come up with a tricky solution.

[cadmonkey]

Doesn't the Tx have a low voltage alarm? I left my Futaba T7 on a few weeks ago and fell asleep. In the middle of the night I was awakened by the squawk of the low voltage alarm of death - and I'm a pretty heavy sleeper.

[tungym]

Doesn't the Tx have a low voltage alarm? I left my Futaba T7 on a few weeks ago and fell asleep. In the middle of the night I was awakened by the squawk of the low voltage alarm of death - and I'm a pretty heavy sleeper.
no luck. It was killed inside my car.

[dleroi]

I am using 3s lipo in my DX7 for 5 weeks or so. My kids (/myself) forgot to switch off the transmitter and killed 2packs of lipo.

Is it possible to use zenner diode at 9V or so such that it can cut the drain current when the lipo falls below 9V.
Is it safe as well, such that the transmitter is not automatically switched off?

Any opinion are welcome. THanks

I think the answer is to use the same protection that is incorporated in any of the commercial (non-rc) lithium battery packs. If you don't have to share the TX batteries with the aircraft, the simplest way would be to use a 3-cell lithium-ion or lipo pack from a camera or some other device. Or, steal the circuit board from one and put it in the TX.

[vintage1]

It will take more than a zener..but its not impossible.

I've been thinking about a board that could be combined with a 3s LIPO pack to

1/. regulate it down a little to about 11v at the worst.

2/. regulate the charge so the standard wall wart chargers would actually charge the LIPO safely

3/. Shut down the battery in the event of it getting flat.


I think such a board would be a fantastic addition to the RC toolkit. I am fed up with flat TX batteries due to NiCd self discharge.

I'd probably use a reed relay to ensure total disconnection when wanted..resettable by switching the set off and on again. tho maybe a FET switch is cool, too.

I'll think about it.

[Miami Mike]

How about a motion detector that shuts the radio off, after sounding a warning alarm first, if it hasn't been moved for several minutes?

[vintage1]

How about a DNA sensor that gives anyone except you 11kv up the khazi if they pick it up? ;)

[dleroi]

I've been thinking about a board that could be combined with a 3s LIPO pack to

1/. regulate it down a little to about 11v at the worst.

2/. regulate the charge so the standard wall wart chargers would actually charge the LIPO safely

3/. Shut down the battery in the event of it getting flat.

I'll think about it.

Vintage,

I like your idea, but my point is that these already exist (except for "regulating it down") in all the lithium battery packs that are used in phones, cameras, pdas, etc. Take one apart and you'll find the little circuit board that is designed to protect us from ourselves.

- Don

[Reflex1]

Simple 1hr timer cct should do it
push switch on Tx starts timer, after 1hr Tx turns off.

push the switch at anytime (inc. during flight ) to reset the timer to the 1hr delayed turn off.

[Miami Mike]

How about a DNA sensor...I thought you were being serious about this. I am.

[z-matrix]

It will take more than a zener..but its not impossible.

I've been thinking about a board that could be combined with a 3s LIPO pack to

1/. regulate it down a little to about 11v at the worst.

2/. regulate the charge so the standard wall wart chargers would actually charge the LIPO safely

3/. Shut down the battery in the event of it getting flat.


I think such a board would be a fantastic addition to the RC toolkit. I am fed up with flat TX batteries due to NiCd self discharge.

I'd probably use a reed relay to ensure total disconnection when wanted..resettable by switching the set off and on again. tho maybe a FET switch is cool, too.

I'll think about it.

i am willing to design a board for tx under voltage protection and low voltage alarm/regulator for li-po in case of sufficient public demand

i bet many can fit in an airmail ...

[tungym]

I think Li-po using in Tx is getting popular in my locality. Manufacturers are making the same form-factor as a Ni-Cd, at the price of 20-30 USD. The run time and weight saving is significant especially for those who have neck pain like me.

[Zlatko]

tungym,

All jokes aside .... :) .... DNA sensor .... :)

I've seen this a while back but still haven't bought anything from them
http://www.batteryspace.com/index.asp?PageAction=VIEWCATS&Category=711

Cheers

[fhhuber506771]

Simple 1hr timer cct should do it
push switch on Tx starts timer, after 1hr Tx turns off.

push the switch at anytime (inc. during flight ) to reset the timer to the 1hr delayed turn off.


That to prevent accidentally leaving it on is a great idea, and should be easy.

The little board to regulate voltage down and to self-ballance and regulate charging should also be straightforward. (but not quite as easy...)

***********

The LiPo's voltage curve vs the typical TX low voltage indication... if you hit the low voltage alarm you already went too low for the LiPo pack (if using 3S direct... the regulator would hide low voltage even better...)

Most TX low voltage alarms that I know of are below 9.0 V Which at the low current draw of the TX will be essentially the same as the resting pack voltage.

What we need is for the TX makers to start incorporating the LiPo support in the less than $1000 TX's (Futaba uses LiPos in the 12MZ and 14 MZ.... $1k+ and $2k+ respectively)