Is using Lipo batteries for Transmitter safe?

[Duffy]

Hi:

Probably with the exception of Hitech Aurora, it appears most companies discourage people to use lipo batteries for transmitter. Yet I see a lot of these 11.1 volt 3C lipos sold specifically for transmitters. The Nicad battery is only 9.6 volt. Fully charge lipo can easily go up to 12.5 volt.

I read some JR manual specifically say not to use Lipo for their transmitter.

There are some discussion on helifreak that people either add diodes to step down the voltage, or simply don't charge beyond say 11.5 volt. Others say full charge still okay.

Of course, the benefits of using lipo is that it's cheap and can be used for probably weeks on one charge.

So more confusion for newbie like me.

Can anyone share experience with using these lipo batteries on your transmitter?

Thanks

[foxkilo]

There are usually voltage regulator circuits within the transmitter that can step down the voltage of a fully-charged lipo to a level that can be accepted by the transmitter. Personally I find no problems so far using lipo for transmitter, except that the frequency module can feel a bit hotter than usual. Overall it's not ideal for the circuitry, but then for the convenience of not having to charge the transmitter battery so often, it might be worth it?

Downside of lipo is that you can no longer rely on your transmitter's low voltage warning (usually 8.8 - 9.0 volts (?) for those that use 9.6V NiMH or NiCd) If you're using 3s lipo, in this case, and you wait for the low voltage warning to appear - by then your lipo is possibly overdischarged...

Using a diode in series to absorb the excess lipo voltage is a good idea, but I've not tried it.

Nowadays you can also buy a 9.9V LiFePO4 TX battery which is more suited for this purpose than ordinary lipos.

[baby_zyklon]

Been using a 3cell lipo on a 9c super for almost a year. No problem with voltage.

I prefer eneloop though. Can plug into wall charger and doesn't self discharge, even after many cycles. The hobby city lsd nimh also work equally well.

[Crafter]

I vote for Lipos

After my experiences with NiCD and NiMH, I got a Tx-specific Lipo battery pack from Hob-- city, and have never looked back.

Firstly my bad experience with the stock Hitec NiCD pack that came with my Eclipse7. (See http://www.daddyhobby.com/forum/showthread.php?t=33556).
I was about to switch to Eneloops when the above-mentioned Lipo became available. Anyway I'm not sure if LSD (Low Self-Discharge) cells like Eneloops still gas off or not, which usually has a corrosive effect on bare metal surfaces like battery holders. My Lipo-pack actually cost less than 8 Eneloops too :> Anyway the confidence that Lipos gives me is well worth it.

While a fully-charged 3S Lipo will have a voltage above 12V, I think it's OK as most Tx are designed to work off 8 Alkaline cells, which when brand-new would also produce more than 12V together. Placing a suitable diode in series with the Lipo leads as mentioned above would have 2 good effects. Firstly, it will drop the voltage by about 0.7V, bringing the voltage of a fully-charged Lipo down to about 11.9V. Secondly, the voltage that the Tx 'sees' is always 0.7V lower than what the Lipo is supplying. So when the Tx finally sounds the 'Lo-Batt' warning at about, say, 9V, the Lipo should actually be at about 9.7V, which I believe is not over-discharged yet.

A 'suitable' diode would be a power-diode that can comfortably handle the typical current drawn by the Tx in full operation.

While I mentioned the diode thing above, I've not actually applied it myself. Hmmm, maybe something I should look into this also ...... though there's no urgency :>

Cheers!

[Jack_Chen]

used a lipo for Hitec Optic 6 and Futaba 9CAP.

Charge once, can fly for a few weekends. don't charge so high if you want longevity.

[Duffy]

Thanks a lot for your suggestions

[zxyong]

Havent charge my tx lipo since last year, took out and used it on simulator last week, voltage same as last year.

[VinCopter]

Been using lipo in my 9XII for three years, now on my second pack. No problem.

[hallobaby]

im using full charge is fine.....
still using now... being using 2 yrs liao!!

[etman]

Using Lipo for TX is the best upgrade.
Now I only need to charge once a week.
And the voltage does not drop like NiMh.

But you must be careful not to leave the TX on.
One Lipo died that way. 50 bucks gone.

[Super-Hornet]

...
Downside of lipo is that you can no longer rely on your transmitter's low voltage warning (usually 8.8 - 9.0 volts (?) for those that use 9.6V NiMH or NiCd) If you're using 3s lipo, in this case, and you wait for the low voltage warning to appear - by then your lipo is possibly overdischarged...
....

Not really. It depend on the TX. Take example Hitec Aurora 9. It support LiPoly. And when u put LiPoly, set the battery type to LiPoly, u will have new low voltage level warning.

SH

[yacsf]

I have been using lipo for my JR DSX9 for about a year, so far so good. Added a diode in series and set my TX warning voltage from 9V to 10V. When my TX voltge display 10.6V. It lasted very long time.

[kelvinlow]

I have been using lipo for my JR DSX9 for about a year, so far so good. Added a diode in series and set my TX warning voltage from 9V to 10V. When my TX voltge display 10.6V. It lasted very long time.

Hi yacsf,

how do u set this TX warning from 9v to 10v ?
i cant figure out how to do it on my radio :rolleye
appreciate yr help

thank you.