I have a 9.6V 1300mah Nimh battery pack meant for Optic6. I was wondering whether i can use this battery pack to power CF2822 motor with EMAX 18A ESC, because this helps me save money as i don't need to buy a separate Lipo battery pack and charger(I already have the 9.6V Nimh battery and the charger). Any help will be greatly appreciated.

i think it could be used as per the compatibility part but will not be so good to use as the model will become heavy
lets see what experts have to say

The battery packs used in Txs are designed for low current discharges only and they could not be used as Flight Battery Packs.Most Tx batteries are made with AA size cells and they could not provide the High Currents required by the plane motors. The AA cells are designed for Low Current applications like Toys,Torch Lights,Digital Cameras,Flash Guns etc.For Flight Batteries, high current discharge capable battery packs made of bigger size Cells like size A, and Sub-C which are designed for high current discharges should be used.

Rao

Thank You so much Rao uncle,
You explanation is very clear. On the other hand i do need to spend money on a new lipo battery.
Rohit.

You can call it shear luck but i managed to find 2 9.6V 650mah battery packs which are meant for Airplanes and helis. I want to join these two batteries is parallel and use it(as this increases the battery capacity keeping the voltage same) with the CF2822 and the Emax 18amp ESC. Will it work? Weight is not an issue, i guess because each battery pack weighs about 100gms so 2 will weigh 200gms and the motors are capable of 500-600gms.

Quote from: rohitgupta322 on April 09, 2010, 06:56:58 PM
You can call it shear luck....

Rohit, can you please share the source of your sheer luck ?
If you found some shop in Kolkata, then it will be awesome !

No no, Sethji i'm sorry, i didn't find any shop. It was sheer luck bcoz these batteries were used by my cousin for his rc plane and now that his plane has retired after multiple crashes, i procured the batteries from him(free of cost).
\
Coming back to the issue, as i had said earlier, will the two batteries work together in parallel with the EMAXCF2822 motor and the EMAX 18A ESC.

Don't try to connect two or more identical Ni-MH batterypacks in parallel to increase battery capacity.Only Li-Po battery packs could be used in such a way safely because each cell is monitored and all the cells in a battery pack are balanced while charging the battery pack,every time. Such balance charging is not possible with Ni-MH battery packs and also there are no such chargers available.

OH ok. Thanks so much Rao uncle for your help. I have decided to use the two batteries separately(Ill first fly with one and then after the battery runs out ill put the other battery and fly again). Can anybody give me an idea how long will a 9.6V Nimh 650 mah battery last with a CF2822 motor and 18 amp ESC(Model weight approx. 350-400g).

Quote from: Rao on April 10, 2010, 11:48:22 AM
Don't try to connect two or more identical Ni-MH batterypacks in parallel to increase battery capacity.Only Li-Po battery packs could be used in such a way safely because each cell is monitored and all the cells in a battery pack are balanced while charging the battery pack,every time. Such balance charging is not possible with Ni-MH battery packs and also there are no such chargers available.

Rao, Does is really matter connecting NIMHs in parallel? AFAIK it does not matter at all. One can connect any battery packs of any capacity in parallel as long as they are of the same discharge capacity (like 20C), same charge levels (say both are 90 % charged) and same chemical composition like you can connect 2 Lead acid or 2 NIMH or 2 NICD or 2 Lipos etc. Also when connecting in parallel the capacity need not be the same. One can connect a 600 mah and a 1600 mah lipos in parallel.

Here is what happens when discharging.

When you connect a 600 and a 1600 mah lipo and put it on load its common to assume that the 600 mah is discharging faster. But in reality if the 600 mah loses charge faster then its voltage drops below the voltage of 1600mah. Now since the voltage of 1600 mah is higher, it provides a floating voltage for the 600 mah to charge on the fly and the 1600 mah battery starts discharging faster. In simple words, the voltage across both the battery try to remain same.

Here is what happens when charging.

If you note that in a lipo like 3S2P. there are still only 4 wires in the balance terminal instead of expected 7 wires. That is because when charging, the voltage between the parallels never goes unbalanced. They try to balance themselves in real time.

The problem arrives when you connect different discharge ratings OR different Charge capacity (for example a fully charged 3000mah may damage a empty 500 mah when connected in parallel due to high current flow from 3000 mah to 500 mah battery.) OR when connecting different battery capacity and discharge capacity in series.

If I am wrong please correct me. I got the info from RCG 6 months back when I got into RC hobby. I am not able to find that thread. And I have never experimented with the above.

But its definitely OK to connect, use and charge batteries of same make and capacity in parallel. Just make sure you charge them or discharge them fully before you make the connection.

Quote from: rohitgupta322 on April 10, 2010, 01:40:32 PM
OH ok. Thanks so much Rao uncle for your help. I have decided to use the two batteries separately(Ill first fly with one and then after the battery runs out ill put the other battery and fly again). Can anybody give me an idea how long will a 9.6V Nimh 650 mah battery last with a CF2822 motor and 18 amp ESC(Model weight approx. 350-400g).

2822 is a hungry monster. It demands lipos or High discharge NICDs. Iam not sure if the current provided by the 2 650 mah batteries in parallel may be able to provide sufficient current. Instead invest in a small lipo and enjoy. Use those batteries for something else.

Well it might seem funny but to tell u the truth, " i am scared of using lipos by what i have heard and read in most threads" . I only got into this hobby last year. All of my RTF planes have had Nimh batteries and i had no probs with them. It is only this year that i have decided to scratch build my first airplane and by looking at the safety of Nimh i decided to stick to it. Luckily i also found two Nimh batteries from my cousin.Furthermore i dont have any separate place to charge and store lipos safely. Advice of more experienced people will be helpful here? What if im out of the house and the lipo suddenly catches fire. I will be thrashed by my parents.?

Dont worry my friend. Lipos dont catch fire easily. They generally catch fire if they are crashed or overcharged (happens with a bad charger w/o a balancer.) or shorted. I have over 4 to 5 Kilos of Lipos at home and nothing happened till date. Go ahead buy a lipo and a cheap balanced charger if budget permits. Nimh are so 1980s and heavy.

You also dont need a separate place to charge. I charge Lipos on my bed (a serious bad habit I need to break  ) and store them in my cupboard.

I am not sure that is sound practice/advise... as the saying goes "there is a first time for everything"   Do charge them at some place where they do not catch fire easily.  I have seen at least two cases where major fires were averted only because the lipo being charged was placed on a tiled floor and was away from anything easily combustible (carpets, curtains etc).

Lipos do no need to scare any one, but they can handle any amount of respect you throw towards them

I agree, I said - a serious bad habit I need to break   Probably center of the Hall is the biggest area I can find to charge.

This thread is going into wrong direction.The original question of this thread is whether two Ni-mh battery packs could be connected in parallel to increase the capacity of the battery pack?

My answer to that question is NO.

I still remember, when I first got into Hobby. I had ordered one lipo from HC. I somehow shorted it and burnt it. Then I decided to use normal eneloop nimh batteries(TX batteries) to run the motor and see. I wanted to desperately see how the outrunner works! After I tried and ran the motor, the voltage used to drop fast even w/o a prop on the motor and the ESCs used to cut off at half throttle - all these w/o a prop. TX batteries are no way good for powering motor, though you can power the receiver and servos I believe. but not motor and ESCs.

If you already have the motor, ESC radio etc, try connecting the ESC motor and the batteries you got from your friend and see if the motor can even achieve half speeds with a prop. If yes slowly throttle to full range and see. If there is a linear increase in speeds then the batteries are good. If the speed increase is not linear then you are overloading the cells.

Thank you so much everyone for your kind assistance. I will keep everyone updated as soon as i test the motor with the Nimh battery.