Hello everyone,
i have a query regarding batteries for fuel powered planes.
I have a 46 size plane and i am using 5 servos with it.


Now what battery do i require to run these servos and the receiver??
I currently have 2 NiMh packs(8.4V each), can i use these? Will i require a BEC with this system?
What other options do i have?

Regards
Ayush

Most receiver power setups (especially servos) are rated only to 6volts.  So you will have to use a BEC.  Another more drastic option is to repack the batteries closer to 6v.

i was thinking about soldering and connecting 5 NiMh cells together and make a pack, can this be used for the rx??
will a BEC be required with this pack??

Yes, that will give you a 4.8v pack that will nicely power the plane (without the need for any BECs).

Caution/care is urged when you build the pack, especially in soldering and tightly binding them all together as a single unit.

Anwar, 5 NiMH = 5 x 1.2 = 6V, He told for 5 Cell in series.
But Max voltage of 5 Cell = 5 x 1.35 = 6.75 Volt.

You have to add 1 1N4007 in series to drop out the voltage about 6 volt.
And 4 cell also should work that give 4.8 volt.

Thanks alot Anwar and KALYANPRODHAN

The servos i have are rated for operation under 4 to 6V, so if i just use 4 cells that will be good enough for this setup.
What about the total capacity of the battery pack??
What is the capacity of 1 NiMh AA cell?? How much battery capacity will i get out of a 4 cell pack?

Cells range from 1000 mah to 3000 mah.If you hook up 4 1000 mah NiMHs in series,the final capacity will be 1000 mah.So,in series,the capacity depends on the cells you use.

Putting some identical cells in parallel will give you a better mah and a better flying time with same voltage the added weight will be a compromise you can live with on a 46 size plane

Quote from: KALYANPRODHAN on March 20, 2011, 01:54:15 PM
Anwar, 5 NiMH = 5 x 1.2 = 6V, He told for 5 Cell in series.

Oops... thought it was 4.  He could make multiple 4.8v RX packs.

Quote from: KALYANPRODHAN on March 20, 2011, 01:54:15 PM
But Max voltage of 5 Cell = 5 x 1.35 = 6.75 Volt.
You have to add 1 1N4007 in series to drop out the voltage about 6 volt.

Anything rated to 6v should work on 5 NiMH packs without issues.  I believe manufacturers do consider the fact that any 4.8v pack will have higher volts at full charge (and similarly for the 6v nominal voltage packs).

Quote from: lynxheli on March 20, 2011, 06:10:58 PM
Putting some identical cells in parallel will give you a better mah and a better flying time with same voltage the added weight will be a compromise you can live with on a 46 size plane

i am really asking questions on basics, but please clear me out before i try this.
According to you, if i connect the batteries in series then the overall capacity will remain same as of an individual cell, but if i connect them in parralel i will have a higher mah but the voltage will remain same. 

So in order to get 4.8~6V from these cells plus higher mah, i should connect 4~5 cells in series for high voltage plus 1 or 2 cells in parallel for higher mah??

i can compromise extra cells with weight easily

Quote from: anwar on March 20, 2011, 09:32:55 PM
Oops... thought it was 4. 

Anwar sir i have 2 X 8.4V NiMh packs of 400mah with me. its a ready made pack i took out from a small toy helicopter.

Now can i salvage the cells from these packs to meet my requirements of ~6V and a good enough mah??

Hey Ayush,
i have made a battery for myself by repacking 4 Nimh cells(of a six one from chinese heli battery). its working fine. I u need further details, i can mail you pictures stepwise.
I made a post earlier but it was deleated by anvar sir.
I have made my Rx battery similarly by adding eight brand new cells.

Instead of going for a 4s2p configuration using 8 cells (which will give you 4.8v at 2x the mAH/duration), it would be better to make TWO 4s1p (just 4 cells in series) packs.  If you are low on one pack, use the second pack and fly ! 

I haven't seen people using 4s2p (i.e. make two sets of 4 cells in series, then connect those two sets in parallel) configuration using NiMH cells, although it sounds feasible.

Quote from: abhay1290 on March 21, 2011, 12:09:25 AM
I made a post earlier but it was deleated by anvar sir.

Wondering why I would do that   Did I PM you any reason for the same ?  Sorry, I am getting YOUNGER, can't recall the incident !

I don't exactly know how much flight time 400mah can give me, so i was trying for scavenging as much mah as i can from these 2 packs.

Although if 400mah is enough, i will be glad to make 2 simple series connection packs instead of a single 4s2p pack.

Quote from: abhay1290 on March 21, 2011, 12:09:25 AM
i have made a battery for myself by repacking 4 Nimh cells(of a six one from chinese heli battery). its working fine. I u need further details, i can mail you pictures stepwise.

Please do send me the pictures for this procedure.
It would be really helpfull.
Thank you very much.

400mAH is kinda small, depending on the load of the 5 servos etc, they may last only one flight. Can't say with certainty.

Even im confused.
You didnt sent any pm or mail. It was deleted without notification..

http://www.rcindia.org/batteries-and-chargers/you-experience-with-lipos-for-receivers-and-transmitters/msg46724/#msg46724

It is still here... so I must have deleted a duplicate post !  When I delete posts, there is usually a very valid and strong reason

Thanks Anwar sir, for misunderstanding you. but i didnt get any notification regarding it getting deleted.
I wonder about other pictures did i post or not.
I misunderstood you. U are such a cruel guy i thought, and u know. but since u r the moderator, i considered that i might have been done for a genuine reason..

Thanks

dear ayush,
i have deleated the pictures from system as well, i will try to recover from hard drive if possible... however the pictures only showed soldering and laminating via electric tape. And fixing them togather..
for other details, u can contact me directly on my no. i will pm it to u..

here are a few pictures i was able to recover...

two more..

the tx battery perfectly fits the battery cavity on tx.

Dissambling photos has been permanantly deleated..

Thank you Abhay, these are very helpfull   

Quote from: anwar on March 21, 2011, 01:38:16 AM
400mAH is kinda small, depending on the load of the 5 servos etc, they may last only one flight. Can't say with certainty.

Anwar sir, by a single flight how many minutes do you mean this would last??

That is one of the variables, because of which we cannot really say how many flights you can SAFELY have with a 400mAH RX battery.  Also, the current drawn by various servos differ, that is another factor.  There are many other factors, like your style of flying, whether there is any binding of servos in your build etc etc.

The average duration of a 46 size model depends again on many factors, like how well your engine is tuned, what average throttle range do you fly at, the size of your fuel tank etc etc.  It is common to get 10 to 15 minutes of flight time per tank of fuel.

Quote from: ayush29k on March 21, 2011, 01:30:58 AM

I so i was trying for scavenging as much mah as i can from these 2 packs.

Ayush.

The cells used in most of these cheap Chinese products are of rather dubious quality. After even a few cycles the capacity drops dramatically.  Somehow, I would not risk a decent sized plane for saving a very small amount - the cost of a new pack  By all means make up packs top be used in less critical applications, though.