Spare Tx battery pack made from Blackberry batteries x 2

[PhantomFan]

Several years ago both my son and daughter had Blackerry devices. Now they have IPhones and their old devices are considered junk. They each have a 3.7 volt 1080mAh "Li-ion" battery in them that still take and hold an excellent charge. I wrapped the two of them together TIGHT with electrical tape, wired the them together in series to give a nominal 7.2 volts. I soldered on a spare JST connector and charged them up and with my Tenergy charger to a total of 8.1 volts. Together they have over 2000mAh of juice. The battery pack fits easily inside my Futaba transmitter.

When I plugged this into my Futaba transmitter, it worked just fine. I was thinking of using this as a back-up power pack for my transmitter. Is this an OK thing to do??? I'm not sure of the rate at which the current will dip, but the Futaba DOES monitor battery voltage and has an alarm.

Comments from those who are familiar with batteries and/or this proposed usage???

TIA.

PF

 

[Driffill]

You have made a rookie error!

Have you connect two batteries together, you either add the voltages or the capacity, not both . . If you have increased the voltage to 7.4 then it would essentially be a 7.4v 1080mah battery pack.

With that said, smart idea to use other batteries that are about

 

[PhantomFan]

That's why I invited commentary. I had a feeling I was wrong about SOME aspect of the arrangement, but I couldn't put my finger on it.

I just ordered Realflight 7 and plan on using my own transmitter, a Futaba T8J. I know there is some sort of dongle that connects my Tx to the computer to use the simulator, but I'm not sure it provides power, hence my search for a less important battery pack than the one I use for legitimate flying purposes.

Thanks for helping with my understanding. +1 !

PF