http://heli.brixtonjunkies.com/2009/07/02/transmitter-lipo-3s-11-1v-stepdown/

http://www.wattflyer.com/forums/showthread.php?t=1213

Basically, add the diodes if you want added safety, preferably on a servo extension type setup, and charge the lipo outside of the diode setup.

Not recommended at all, but some Spectrum folks have been updating the voltage alarm using the service menu.



Watch 2:46.

Again, not recommended.  Just do the diode thing if you have to.

Mr Anwar,

Still none have comented on use of LIPO with built in "Balancing circuit" and the LIPO without the balancing circuit and the cost difference vis a viz the benefits.

Are none of the forum members are using the LIPO for Tx with built in balancing circuit?

I thought "built in Balancing Circuit" is a vital componenet for a LIPO used in TX for extended durations, especially when charged LIPO left idle in the long run is bound to get unbalanced voltages.

Looks like you missed this part of my earlier post.

Quote from: anwar on March 07, 2010, 11:06:03 AM
The lipos with balancing circuitry inside (I used such a TX lipo for a while) is convenient for people who want to charge using the regular charging leads (not opening the battery compartment at all).  But if you are charging 12 times A YEAR, all this is cosmetic.

There is some discussion of a TX lipo here too : http://www.rcindia.org/batteries-and-chargers/battery-voltage-measurement-reliability/

Regardless of all of this, using low "C" TX lipos with balance connectors is more than enough, as you will be charging them once a month or so.  The built-in-balancer one is just "bling" for the most part.

QuoteIs there a possibility to build such a regulator

Very simple actually. Will do a bit of spadework on a few, accessible transmitters, to measure the current drawn. Don't expect it to exceed 300mA.

Thanks Mr Anwar,

I had actually missed that. From what I understand, further you cannot use LIPO with built in Balancing Circuit to charge fitted in the Tx from built in charging circuit of Tx if you are using Diode modification.

What might be the cost difference between the one with balancing circuit and the one without say for 11.1V 2200mah?

I am with Vinay, Ujjwana and Sunderamvelar on the preference of LSD NiMh over LiPo for Tx use. A set of 8 LSD cells cost less than the cheapest TX LiPO of similar capacity, in India. No further hassles of charging issues, safety, etc. They will last as long as the Lipo  under the same conditions.

In case of Rx packs, I think a 2 cell LiPo + Bec would cost significantly more than an LSD NiMh pack.  

So, other than the "in/cool" factor, practically, NiMh would/should be the preferred choice.

I agree that with current LSD NiMH availability, lipos may not have the advantage anymore.  Their advantage is pretty much limited to charging time now, which is not an issue for infrequent charging.

I guess the writing is on the wall, when most of the latest models of radios now come with NiMH packs, wish there were all LSD though.

With the present advancement of technology it is only in the near future, not far from now when LSD Ni Mh Batteries are going to be available aplenty at 2.8 AH to 3.0 AH further with Plus 1C charge rate which will reduce you're charging time to about to an hour. Then the charging time advantage of LIPO is also going to be non existent.

Presently some of the 2.1 AH LSD Ni MH batteries of Sanyo are available at 2.1 Amperes (1C) rate of charging ( Only that it is not available so commonly) which has a charging time of about an hour and a battery pack of 2100 mah 9.6V can be easily created with them.

Bump   Reminder for everyone to vote !

Can i use a 3s 4400 mah battery with 15c on my tx with diode to reduce the voltage to 11.0. I can fix the lipo outside just like dave of rcpowers do . my doubt is can i use it on the tx so that it gives more time for my next recharge.

Anyone has experience with a 6.6v LiFe hump/straight pack for receivers? I would like to get one.

I use 6.6V LiFePo4 A123 batteries all the time for my Futaba FASST Rxs. Works wonderful !

Where is the best place to order the LiFes? The hump packs are not very common.

Quote from: azhaguvel on November 01, 2010, 10:59:33 PM
Can i use a 3s 4400 mah battery with 15c on my tx with diode to reduce the voltage to 11.0. I can fix the lipo outside just like dave of rcpowers do   my doubt is can i use it on the tx so that it gives more time for my next recharge.

Yes, many people do that.  The only concern is that even at 15C these have high discharge rates as compared to dedicated TX lipos (usually around 3C).  The high discharge may cause issues while plugging in to radios whose plugs are not designed for the same.  But in practice this seems to be rare enough that many people are doing it.

Quote from: azhaguvel on November 01, 2010, 10:59:33 PM
Can i use a 3s 4400 mah battery with 15c on my tx with diode to reduce the voltage to 11.0. I can fix the lipo outside just like dave of rcpowers do . my doubt is can i use it on the tx so that it gives more time for my next recharge.

See the earlier posts. The current consumption of "8 cell" Txs is of the order of 300 mA. A fully charged battery would last at least 4-5 hours of flying time. Can't see why you would need more than that for any session. Besides, what you would use for the Rx battery to get proportional time.

Quote from: anwar on November 02, 2010, 11:30:05 AM
Yes, many people do that.  The only concern is that even at 15C these have high discharge rates as compared to dedicated TX lipos (usually around 3C).  The high discharge may cause issues while plugging in to radios whose plugs are not designed for the same.  But in practice this seems to be rare enough that many people are doing it.

Anwar
The discharge rate is determined by the TX current draw. The capacity of the battery will not influence that in any way.

A good example is your mains supply. It may well be CAPABLE of suppling several kilowatts for, say, several air conditioning units. Yet you may use a phone charger with the same supply which will draw a few watts, at most.

Yes, that is clear.  The issue is "connection sparks" (for lack of a better word) . This is documented in many locations. Basically every manufacturer lists this as the reason why they came out with special "low discharge" lipos for use as TX lipos.

Quote from: mail4ajo on November 02, 2010, 10:29:48 AM
Where is the best place to order the LiFes? The hump packs are not very common.

Try SDSHobby.net for A123 packs, or if you want branded more expensive oned - try HobbyKings for A123 racing genuine cells or Readyheli.com for Hyperion ones.

I have used all of them and they work great !.

I cannot buy that theory. A spark will only occur when high current is DRAWN. It is not possible to FORCE current into any device as I have clarified.

ya i accept a normal battery last for 3-4 hours. but think of the advantage 4400 mah lipo & the transmitter gets only 300 mah, it last for 14.6 hrs. i can forget about charging them for a long time. About discharge rate,that is what i was wondering, anyway the tx is going to withdraw only the amount it wants (300mah). so why should i care about the c rating?

Hmmm... I thought arcs are possible when connectors are close enough.  This is how the Rhino lipo folks put it.

http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=7346

QuoteIt is a low discharge Lithium Polymer pack, designed specifically for R/C Radio use. We do not suggest you to use a standard Lipoly pack with Tx power plugs in your radio system as standard Lipoly are capable of a rapid energy release which can harm sensitive radio electronics.

Not sure if this is more of a marketing talk than it is a real life possibility.  

Another reason I have seen discussed is that a lower C rating pack's output voltage is pulled down more under load, as compared to a higher C pack, thus making their use without diodes easier on the TX.

Yes. You do not need to worry about the C rating. But I have a point to make about "I can forget about charging them for a long time". How would you know the state of the battery "after a long time"? What if it was on its last legs?

For safety's sake it is prudent to ensure that the Tx and Rx batteries are charged before  each flying session. And if one follows this rule, it really makes no difference as long as the battery can survive your days session. It is no effort and, in return, I (at least) get peace of mind.

Quote from: anwar on November 02, 2010, 12:43:30 PM
Hmmm... I thought arcs are possible when connectors are close enough.

Another reason I have seen discussed is that a lower C rating pack's output voltage is pulled down more under load, as compared to a higher C pack, thus making their use without diodes easier on the TX.

Sorry to be pedantic but "sparking"is between , say the male and female, connectors. Arcing is sparking between 2 (or more) terminals with different potentials.

If the current draw of a Tx or, more so, Rx is causing the supply to pull down , it would indicate insufficient battery capacity and a "no-no" in my book.

The display on the TX is a good indication, and recharging around 10.5v is what I have been doing.  Do NOT trust (and wait for) the TX lipo warning (unless you use 2 diodes).

If we charge the TX every time, that defeats the purpose of using a lipo in the first place.