I think Vinay is talking fair here. Much has been already talked about Lipo. He is putting the LSD aspect as he originally wanted to use LSD than Lipo for all practical advantage (large shelf life, no fear of over discharging, in the box charging). Just that his idea of using individual Cell with Battery pack didn't work, he is going to Lipo, and he is earnestly accepting same and suggesting the pit falls to others.

Now between LSD and Nimh, I guess its more unanimous with even Sushil's opinion that given the negligible price difference, new investors in Nimh should go for LSD instead the aged Nimh. 300-400mAh difference is not deal breaking and charging Nimh at high charge rate is never a good idea. Nimh are not like 40C Lipos!!

Hope LHS are reading this and try to get LSD Nimh Tx pack for their next stock!! And do list them on thier site properly  

Anyone who is very particular about LSD Ni MH please do not go running to hobby city or tower hobbies, whole lot of 2.0 AH LSD Ni MH of reputed brand like Sony Cycle Energy or sanyo eneloop is available in ebay india for approximately Rs 180 to 200 a piece. My only reservation is it is 2.0 AH.

Please type NH-AA-B4K or eneloop in the www.ebay.in search field and press enter.

Though you will need a 8 cell battery case to use them with Futaba 7C type.

However in case of futaba 6EX there is no space in the battery compartment for a battery case. It can only take a flat type soldered battery pack since the battery case is already built in without the clips and spring. You can though modify the inbuilt battery case to receive the batteries by fixing it with springs and clips from flat battery case of toy cars or any other electronic equipment which has a similar spring and clips which I have done and shown in the photos posted by me earlier.

From the loose connect problems I faced, Yes! I strongly recommend People to goto soldered NimH - LSD/ Non LSD/Lipo rather than preparing their own battery packs.
The reason I am recommending Turnigy LSD over Non-LSD is for the people who still prefer to use that 8 cell Holder and to carry along a spare cells like you do/ and for the people who would want to use those cells for other purposes also, LSDs are better any time over Non LSDs.

I actually Chose LSD NimH, but after the problems faced, I had a chance to choose between Lipo and soldered LSD nimh. Personally I chose Lipo because It was cheap/Cool factor/More capacity.

vinay PS generally commercially available Nicd or Nimh or similar rechargeable battery packs are built using spot welding technique but not by soldering cells!

http://homepages.paradise.net.nz/bhabbott/straps.html

sahil

one can actually build a spot welder, its very simple (good DIY info on the net)

Oh is it? Sorry I was not aware of it. Was interchangeable using the words. Also there are few cells available with the leads given out for making packs, you mean even those have to be welded?

i was just talking about two different techniques, one can use any
method as long as the cells are not damaged in anyway  

vinay the cells you are referring to come with tabs right?, then i think soldering would be good choice! but the soldering iron has to be in the 50-65watt range and appropriate soldering wire has to be used !

Probably to avoid the melting of the solder at high temp I guess!!

i think that would be on the extreme side of the battery use   may be to prevent mechanical failure or something of that sort  

I have seen that even Lipos come soldered with these kinda high temp soldering lead. Last time I dismantled a lipo, I had tough time unsoldering the battery packs with the 25 W soldering iron, I finally had to use the 60 watts wala soldering iron to dimantle the lipos.

yep one should use higher watt iron as it heat things up fast and quicker to de-solder preventing damage to cells

Mr Anwar,

I personally have not been able to convince myself till date to go for a LIPO in my Tx for various obvious reasons brought out earlier here and other places. To list out some are

1.   Fully charged LIPO voltage of 12.6 Volts against a rated 9.6 Volts of Tx.

2.   Requirement to remove the LIPO from Tx for charging for safety of Tx. (When removing and re-fixing the JST connectors in the card of Tx with your fingers through the restricted space was not comfortable for me especially if it has to be done every time)

3.   It is also not comforting for me to charge the LIPO in the Tx knowing fully well it is not safe.

4.   As per Tx design the battery low warning goes off only at 8.4 Volts which is far less than the safe lower voltage for LIPO.

5.   I cannot leave the LIPO unattended in the Tx for more than two months without charging.

6.   I have two different transmitters whose LIPO requirements are different dimensionally.

7.   By far the most obvious is the setup in the both my Tx posted earlier which I have been successfully using for last year and half. I can use NiMH as well as LSD NiMH get all the benefits of extended period of usage as good as a LIPO without the hassles of LIPO enumerated above.

Many places people who use LIPO have been able to negate the problem of High Voltage of a LIPO; LOW Voltage warning problems of Tx with LIPO by use of a simple forward biased Diode just before the JST Connecters.

Fact that a forward biased diode has a voltage drop of 1.2 Volts, effective volts seen by the Tx is only 11.4 Volts which is very much comparable to the 11.2 Volts of the fully charged Nicd/ Nimh. Further when the Tx is seeing 8.4 Volts The LIPO is safely at 9.6 Volts. Has anyone has any experience in this direction?

Further Tx LIPO is available with built in balancing circuit as well as without. What is the cost difference between them? What are the benefits and disadvantages of both of them?

not true, suppose one is using a 8 cell battery holder with alkaline cells then the voltage would be above 12volts and more over the battery discharge curve to per cell voltages remains high upto 80% of the cells capacity which mean near 12 volts

can this voltage setting be changed ?


putting a diode is not a good idea, if the diode for some reason fails that's it end of story!

guys i have charged my SD-10G once and have been using it for simulator work! nearly 8 hours according to the radios internal clock and the battery still has some juice left in it  and according to my calculation full amp draw vs present battery capacity i should get 6.7 hours of run time which come to a week of flying before charge!

i seem to have lost my point 

None of these are practical issues, really.

1.  The NiCD cells and NiMH cells that are used routinely (instead of the lipo upgrade) have a fully charged no-load voltage of close to 12.5v; for the lipo it is 12.6v.  Newer TXes are working on the 2s range (Futaba 12FG, 8FG etc), and the full charged voltage of 2s lipos are often less than the fully charged voltages of the NiMH packs that come with them.  I use the NiMH pack itself on the 12FG now, but I have a 2s lipo which will work as a drop in replacement if I need it with me all the time.  The same 2s lipo works as both TX lipo, and as an RX lipo for my heli ! The reason I am using NiMH is because the amount of flying I am doing USING MY OWN helis/planes have come down, I end up flying others' aircraft more for testing/trimming/training.

2.  About removing and/or reconnecting the lipo for charging, there are two broad cases.

a) People who remove the lipo : They use a small servo extension which stay permanently inserted into the TX battery connector pins, and they plug their lipo into this. It is no big deal at all that you pull out the lipo 10 to 12 TIMES A YEAR !

b) People who charge the lipo without removing it :  Most TX specific lipos come with 3 connectors (one Futaba, one JR and one Balance).  If, for examaple, I have a Futaba TX, I will permanently connect the Futaba lead into the TX, cut of the JR lead and convert into something like JST connectors and use that along with the balance connector to charge the lipo.  There is no pulling out and pushing in of the lipo connector into the TX battery connector pins.

3.  Many people think that if you invest in a good lipo and take good care of it, then charging/using a lipo for TX is just routine and very safe.

4.  The low voltage cut off is the only default issue, which can either be mitigated by using voltage drop circuitry, or just by being a bit diligent about charging at around 10.5v.  Who amongst us wait for the TX to beep before we recharge again anyways ?  And with lipos, this is so infrequent, that it is never a bother.

5.  You can very well leave a lipo unattended with the switch turned off, is what I remember.

6.  Lipos are available in any of the sizes.

7.  NiMH versus Lipo is largely a personal preference.  I do see that lipos tend to last longer than NiMH. One things I noticed is that if you are small heli flyer  (or even foamies) and you are travelling, you can have a simple 2s-3s charger which can be used to charge both the TX and main batteries   This is no longer an issue with fully capable 6s chargers are available for $30 these days, but this was an issue couple of years back.

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.

All I can say is that it is NOT a small minority that is using lipos for the TXs.  The rest is a personal choice.

I am in total Sync with Anwar !!! 

Quote "not true, suppose one is using a 8 cell battery holder with alkaline cells then the voltage would be above 12volts and more over the battery discharge curve to per cell voltages remains high upto 80% of the cells capacity which mean near 12 volts"

As per manual is it not the recommended battery for Tx is 8 cell pack NiCd.
I think NiCd, NiMh, and LSD all are similar with respect to rated voltage of 1.2V and fully charged voltage of 1.4X something and 8 cell pack to give about 11.2Volts. However I see that people have been using higher voltage LIPO/Alkaline without issues.

I read this high voltage issue on long term use LIPO on an international forum.

"1.   Fully charged LIPO voltage of 12.6 Volts against a rated 9.6 Volts of Tx."

Even I was surprised.

Quote "putting a diode is not a good idea, if the diode for some reason fails that's it end of story!"

I don’t think, question of a PN diode failing does arise at all when the current drain required for a TX is only 170 to 200 Milli Amps which is far less than the rated amps of diode which is in Amps and not in Milli Amps. Further the Tx is as such full of diodes in the internal circuits. For that matter any diode can fail at any time due to any reason.

The diode in series in one of the wire of the JST connector was being used by him successfully. There is no issue in case of the diode fails as it is in series on the wire of the battery connector. If it shorts, the full voltage of a LIPO will reach Tx, which anyway is happening without the diode and if it becomes open junction no voltage will reach the Tx all you have to do is replace the diode or diode cable.

Yeah charging through the JST cable with diode is surely a big no go if you introduce it on the battery JST cable since it will be reverse biased for charging current. You have to rely on the balance connector only for charging. You can be obviating it by use of junction cable with diode, male and female JST.

I absolutely agree with you Mr Anwar. Though LIPO and Tx are not ideally compatible with each other most people have been able to use it successfully with various modification to the setup or the usage practice.

I am just bringing out some more modification which people are using in this direction with a querry for opinions of people who have tried them.

AFAIK, I read in some of the Airtronics forums that it was officially OK to use a 3S lipo. So i dont have to worry I believe as I use Airtronics radio.

I have built several battery packs for friends. Some are 5 cell units with a diode wired into the switch harness. Two packs are used in parallel for redundancy. The drop across the (silicon)  diode is typically 0.6V. Theoretically it should be 0.7V. I am unaware of 1.2V drop diodes.

Diodes are passive devices and would be as - or more - reliable than switches, connectors, etc.

I have seen several quotes, especially from Spektrum product support, who claim that the slight additional voltage can cause heat related RF section failures over longer periods of use.  But I have not seen anyone who have used it for 2 years (this is the longest duration I saw in people's posts) report anything wrong with their radios.

Added a poll, since we are on this topic anyways !

Anwar

You need to add the following options to your poll:

Self Assembled NiMh, NiCd packs for Tx and NiMh for Rx.

These are what I use and cannot cast my vote!

Updated.

It is interesting that all the voters so far use lipos with regulators on the receiver side !

Hi Sushil !!! 

Just wondering if you could throw some light on the linear regulator for Tx for Lipos.

Is there a possibility to build such a regulator  

They use two diodes in series to drop a total of 1.2v.