Wouldn't applying load to any battery pull down its voltage ? What am I missing

This is a possible scenario I was getting at:

Suppose you have flown a couple - or more -days spaced over a "long time". How would one have an idea of the remaining capacity?
And, without that information, I would not feel safe.

Lipos discharge very very slowly.  I charge once a month or so on the lipo one.  Any time I turn it on, I look at the TX voltage on the display, for confirmation.

I decide on the field itself whether I need to recharge it for the next session.

When well within maximum ratings, the cell discharge curve is fairly flat until it starts to drop rapidly. In short, if the loading is not excessive, the drop will be gradual. A sudden drop or "pull down" as you describe it would certainly indicate that the currrent requirement and the battery capacity/type are mismatched. Try this experiment on your transmitter. Charge it fully and leave it aside (switched off) for a couple of hours. Switch it on, monitor the voltage and plot the results as voltage vs time.

I will,try and do this on my Tx and post the results. Let me know what you come up with!

I think a better test for how I understood the issue would be like this :

1.  Take two 3cell lipos, one low discharge (say 3C) and another high discharge (say 30C).

2.  Charge and balance them perfectly to 4.2v per cell / 12.6 volts total. (as much as possible, using a charger like the iCharger).

3.  Notice the voltage shown on the TX voltage monitor as soon as you connect each of the lipos to the TX as power source. 

Do not do this immediately after charging. Let them stabilise for an hour or more and THEN carry out your tests.

sushil any updates on the test?

The methodology of the  tests were suggestions to Anwar .  Without the precaution of waiting for some time after ANY charge, you could get a result that would lead one to an incorrect conclusion. I am aware of what the results would be!

If your are interested in transmitter lipo then its the right time. HK has re-stocked some transmitter lipo's which is just 8$ today.
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9787

I got one  .

Is it suitable for spektrum Dx6i?

This is 3s (over 12v).  I believe the DX6i users 4AA batteries, which mean 6v, so it would not work (without you adding some circuitry to bring the voltage down).  Even a 2s lipo may be too much, although some people seem to be using them.

Using rechargeable LSD NiMH cells seems to make more sense in this case. Even though they are 1.2v instead of 1.5v, many people are using these with their DX6is.

Looks like DX6i may now be shipping with NiMH cells :

http://www.horizonhobby.com/Products/Default.aspx?ProdID=SPMR6600

These are 1500mAH ones, you can get higher capacity LSD ones.

Thanks for the valuable input Anwar sir..

I conected my http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9787
Lipo to my turnigy 9x today. Soldered two 1A diode on one of the wires in series.
The diodes are reducing 1.7 V & my turnigy is detecting the voltage with .7V lesser then the actual.
so it sums up to 2.4 volt lesser then the actual volts
The manual tells that tx will start making warning sounds at 8.5V

volts at warning=>8.5+2.4=10.9
volt of individual cell =>10.9/3=3.63V
Is this ok. can the individual cells be at this volt(3.63).

Also the diodes are getting heated. Is this an issue?
What will happen if one of the diodes fail. Will it break the line or just pass the voltage directly?

Many people use 4 diodes in a parallel + serial combination for redundancy.

I have been using lipo, A123 for receiver but for my JR 10X the company dose not recommend using lipo batteries so i have dropped the idea.. but i have also found many using lipo in a 10X but that is on your own risk.. apart for this radio i have used lipo without any problem in transmitter.

Is there any small circuit which breaks the line when the current exceeds 1A for 12V.

Don't know but the company says the might get damaged. I know some are using Lipo in 10X but the official word is not recommended. I am using 2500 NIMH & they are the best.

Diodes seldom go "open". If at all they "short". A shorted diode will create a problem  even if you have another set in parallel. Current will flow through the path of least resistance, which now is the shorted diode.

The whole point is handling an "open" diode, since a shorted diode will only be just as bad as them not being there, as if the lipo is connected directly.  Lowering the voltage is only a "nice to have", so shorting is not really a concern.  It is "open"ing that matters, and that is why the parallel path seems like a good idea.

BTW, requesting everyone to vote in this poll !

True. But the odds of a diode going open are much, much less than shorting. From experience not connected to RC.

Hello friends,\
  :headscratch:I have been wondering since a long time why cant we use self assembled tx and Rx batteries.

A normal Tx battery costs around   750 at least
which is generally a combination of 8*1.2v AA size NiMh/Nicd batteries.

In contrary, a set of 4 NiMh/Nicd AA cell costs  :Rs:160.
We need 8 so:   160*2= :Rs:320 for eight cells

The rate of whole assembly is for 700mah. which is confirmed.

Hope everyone knows to connect cells in series to form batteries:(ie +- +- +- +-..)
To make it permanant, one can use soldering, or spring and slit arrangement. You can also get batteries soldered and connected by your nearest electronic shop, who doesnt know how to.

Rest all u need is a JR connector(if im not wrong due to weak terminology), at the remainig ends, to form a plug.
The output you get is nearly same in weight, power output, as well as dimensions.
Same can be done with Rx using AAA size cells(cost not confirmed)

Then why cant we assemble and use yaar . Atleast those who are good and interested at RnDs. Even i hope some might be using it too.
If there are any drawbacks, please let me know. Apart from the one created with poor workmanship while assembling.

Hope u understand my intensions > fly more at lesser cost

Hey sorry friends, regarding the name of brands present in pictures. My intension was upto demonstration itself.

Merged into existing thread... "self assembled" packs are discussed earlier in this thread.  Even the poll shows many people use them (like Sushil bhai).

PS: Requesting everyone to vote in the poll !