Hi everyone. My first post here, and my first post anywhere in the RC model community. Fantastic forums --- have been a lurker for a few months.

I am 50 years old. I bought an RC helicopter from Mustafa's in Singapore last year for my seven-year-old son. Nose-tip to boom is about two and a half feet. Total beginner's model, co-axial contra-rotating props, three-channel 2.4 GHz RTF set.

This year, when I took it out to take my son flying, the battery is not holding charge. I removed the canopy (four self-threading screws) and found what looked like two AA-sized cells wrapped in a shrink-wrap opaque blue plastic "skin". It has two leads with two quite different connectors, one for powering the helicopter (two wires) and one for charging (three wires). The "skin" has the following stuff written on it.

Li-ion BQP232
18500 1100mAH 7.4V

So I hunted around, and discovered that when people talk of 7.4V, they mean 2S Lipo, whereas this battery clearly says Li-ion. Typical Li-ion 2S would be 6.6V. I was confused, but found some solution. The "18500" was the real help. Apparently, there are Li-ion batteries from Samsung and others which are in the AA format, are Li-ion, and have 3.7V rating. For example:

http://www.gr8alt.com/1100mah-imr-3-7v-18500-battery.html#.VC9GQa13Qjh

All these sites seem to be related to e-cigarettes.

I then found the following pack which seemed to be the perfect upgrade to my existing battery:

http://www.all-battery.com/SamsungLi-Ion18650_7.4V_2800mAhwithPCM-31444.aspx

It has a much higher mAh rating, so should give me at least twice the flying time, and I am not feeling too concerned about matching the "C" rating, because I suspect my park-flyer type helicopter won't have too much current requirement.

The battery has raw leads, so I will need some connectors to use it safely. The original battery had two leads, this one has just one. I guess the same leads will be used here both for charge and discharge. To handle this battery, I am thinking of buying a new charger. I found this one:

http://www.all-battery.com/universalsmartchargerforli-ionpolymerbatterypack37v-148v1-4cells.aspx

I will also need to replace the connectors at three places:

• on the lead which comes out of the helo body, to receive power from the battery
• on the lead from the new battery I am going to buy
• on the lead from the charger which I will buy, so that it can charge the new battery

So, I read this article http://www.rchelicopterfun.com/rc-lipo-batteries.html and found this connector pack which seems to fit the bill:

http://www.hobbyking.com/hobbyking/store/__32960__EC3_Connectors_Male_Female_5_pairs_bag_.html

I have used a soldering iron on occasion, so I should be fine replacing the connectors.

Now for my questions:

• Am I on the right track? This is a life-first for me, messing with RC equipment
• Is there any replacement I can source from India anywhere? Would save me a lot of trouble

Thanks a lot for your guidance. As you can see, I need all the help I can get. And I have a very depressed son to bring back to his old chirpy self. 

You can replace the battery with a 2S lipo which are available at local hobby stores in different capacities. This will need a lipo charger.

Alternately, you can replace with a 6cell nimh pack. These are quite robust and can be obtained in different sizes and capacity. When I was in Mumbai I would get my NiMh battery packs custom made from Prime Products, syntofine estate, goregaon east. These are quite robust. They have a website also. This will also need a different charger which if you are comfortable, you can make at home.

Weigh the existing battery and replace with a 2S lipo of around same weight. The http://www.hobbyking.com/hobbyking/store/__7028__Turnigy_Accucel_6_50W_6A_Balancer_Charger_w_Accessories.html is a good charger and will serve you well in the future.
These chargers are available at local hobby stores in India.

+1 to Ashim.

Just weigh the existing battery, replace with almost same weight Lipo 2S from LHS. You can replace the connectors at Heli side to the more compatible ones used with Lipo. So it will be easy for you to charge with Normal Charger.

On second thought what were you using to charge the supplied Lion? was it a balance charger? if so you can use the same charger. Just replace the connector at the new battery compatible to the existing charger with the connector removed from the old Lion battery.

Hi Ashim and Sundaram,

Thanks a lot. Sorry about the late response. I could not log in, because of some problem with my account. Anwar sorted it out.

I am confused about switching from Li-ion to LiPo. Doesn't this require a complete change of the craft's control electronics? I was under the impression that these are not interchangeable...

Sundaram, I suspect my current (Li-ion) charger is a balanced charger, because it has three leads to charge a 2S battery pack.

I was thinking of switching to an ordinary Li-ion battery (as described above) with just two leads, which would mean I would have to charge without balancing.

Quote from: ashok baijal on October 04, 2014, 07:37:51 AM
You can replace the battery with a 2S lipo which are available at local hobby stores in different capacities. This will need a lipo charger.

I was under the impression that the craft electronics need to be different to manage Li-ion and Lipo batteries? Are they freely interchangeable? This really opens up alternatives...

Li-ion BQP232
18500 1100mAH 7.4V

As far as the heli circuit goes its not going to matter at all since the Lipo 2S is also with a similar voltage range  3.7 Volts to 4.2 volts fully charged. However some of the Lion has a fully charged voltage of 4.1 as against 4.2 of a Lipo. If that is the case the charger you have may not charge the lion to full capacity but will charge it to 95% only.

Most Balance chargers charge the Lion and Lipo battery in same category of selection in the menu IMHO that should be a reassuring confirmation that both are interchangeable. Its only Life batteries which are charged under different selection since thier final charged voltage is different from the Lipo/Lion.

Quote from: sundaram on October 07, 2014, 10:58:44 AM
Its only Life batteries which are charged under different selection since thier final charged voltage is different from the Lipo/Lion.

Great. This is very reassuring. Will look around for other options, then. Will these be good choices?

http://rcbazaar.com/products/1746-wolfpack-1800mah-25c-74v.aspx

http://rcbazaar.com/products/1747-wolfpack-3000mah-25c-74v.aspx

Both these RCBazaar items have a 2S structure, and two leads coming out -- one for balanced charging and one for discharge (the images are very low-res and unclear, but I am guessing). In that case, I may be able to get the benefit of balanced charging, compared to my earlier Li-ion choices I had seen in all-batteries.com.

Keeping in view that you had a 1100mAH earlier, You need to take care that you are picking up Battery of similar weight so that your CG of Heli does not gets shifted majorly.

Even if you use heavy lipo Your Heli should be able to haul the additional weight and you should have room to shift Lipo to a new location to get CG correct.

As long as you can manage above you can pickup those lipos.

Great. Will do.

Any recommendations about a balanced charger for these?

Skyrc imax b6 copy or original from rcmumbai.com.
Btw why don't you look at rcdhamaka batteries.

Quote from: rcrcnitesh on October 07, 2014, 01:39:16 PM
Skyrc imax b6 copy or original from rcmumbai.com.
Btw why don't you look at rcdhamaka batteries.

I have no idea about rcdhamaka... the first time I am hearing the name. Will definitely check them out. I had heard of rcbazaar from these forums, and the feedback was good, so I thought of them first.

Finished the surgery to the helicopter.

Used a LiPo 1800 mAh from RCbazaar instead of the original battery. This one is about 104 g whereas the original one was about 76 g in weight. It is also longer, so I can't place it in the cradle where the original battery was. Therefore I'm suspending this LiPo below the copter body using three cable ties. I will get self-adhesive hook-and-loop strips and do a better job sometime soon.

I also had to snip the original plug on the copter's power lead and replace it with Dean's Ultra connectors (called T-connectors quite often) connectors. Had some heatshrink tubing but it was too big in diameter, so the job was not as neat as I would have liked. Got the T connectors from RCMumbai

Needed a LiPo charger. Got a simple balanced charger from RCBazaar (costs less than Rs.1,000). It can charge 2S or 3S balanced LiPo batteries and is as simple as they come. It works.

Today, took out the bird and my son for the first trial flight. My son flew it happily. The battery has been placed a bit too far aft, and the CG has shifted a bit, so the helicopter drifts backwards a slight bit. More importantly, the helicopter has very limited inherent ability to penetrate a headwind, so it drifts to the edge of the field quite easily with even light wind. But the battery surgery has been successful.

Thanks for all the help. I did not have to import anything, and all your suggestions worked. AM thinking of getting a couple more batteries and the self-adhesive Velcro strips so that the batteries can be field-replaced, thus allowing for more flying time.