With the January weather I quickly discovered that I couldn't sensibly go flying and worse still the workshop was so cold I couldn't go there either.

 I decided that the only useful thing I could do in modelling terms was to survey the multitude of NiCad and Nimh batteries that I have collected over the years.

 

So with my newly acquired Bantam BT6 charger I set too and cycled everything I could. The results were not too encouraging, at least half the battery stock was showing a capacity less than 85% of that stated on them.

 

Now that NiCad's are more or less unobtainable the choices are generally limited to Nimh or LiPo's. I guess I'm a bit of a stick in the mud, I haven't had good experiences with Nimh batteries and LiPo's frighten me.

 

 I know that  LiPoÕs treated correctly will give exceptional service which I've seen on many occasions on the field but I also have evidence from a close friend, of the damage that a wayward battery can cause. I'm not into electric flight so what I was searching for were flight batteries of about 2000MaH capacity.

An early attempt to solve the puzzle was, against my better judgement, to buy a FlightPower 2300 MaH LiPo , Oh! and a 5V regulator to get to a useable power supply.  Total cost about £47.  Not a very cash frugal solution when you've got lots of models and donÕt like swapping gear from one to another.

 I had been reading with interest, chatter on the American forums about cells that people were getting from DeWalt power tools that appeared to have the benefits of LiPoÕs but because they were hard cased like a NiCad had few of the possible deficiencies. These cells, called A123 cells are based on LiFePo4 technology whatever that is, but clearly a close cousin to the LiPo.

 The characteristics of these cells appeared to satisfy all my needs for a reliable replacement for my NiCads.

• Fast Charge
• Good current handling capacity
• Good battery life
• Safe, will not catch fire if overcharged.
• Direct replacement for 5 cell NiCad

The graph tells the story well. It shows that as a Rx. Battery, where current draw is unlikely to exceed 230 Ma. (the black line) the delivered voltage is virtually flat until the battery is exhausted.

The bonus to all this is that as I move to 2.4 GhZ where the minimum voltage is critical, this cell in a 2s format, will deliver 6.6 volts for most of the charge.

Never risking the dreaded  Rx. Reset.

A quick search revealed that a 2300MaH 6.6 volt battery was available from Puffin Models. Ordered two on New Years Eve, somehow they appeared two days later. That's service!

Once I'd located a suitable balancing lead to fit the battery we were off. A balance charge to 7.2 volts, balanced to within 0.01 volts per cell. Great!

 The next issue to creep up on was the thorny subject of running JR Rx's and servos at 6 volts. This has been reported by some people as a problem but I'd never had any concerns in the past.  The major stumbling block appeared to be the JR 591 servo, but once again, I'd never had a problem .

 I set up a test JR Rx together with 8 servos all driven by my Graupner/JR MC24. This Tx. has a servo test facility that avoids any need to twiddle the sticks, it does it on its own. The servos were all of known breeds and included two high torque digital examples. After an hour all the servos were slightly warm but still working perfectly.  

 I've flown this system in both 35Mhz and 2.4 Ghz configuration in my old wreck on wheels, sorry, my Astrohog and it was a total non-event.

I have concluded that with its safety, no memory effect and its ability to hold a charge when not in use these are the batteries of choice for me.

Acknowledgements:

 A123 graph – RC Group USA

Supplies:-

Bantam BC6 charger & Balance lead  :    Neville at  Andover Models

Batteries  :                                             Puffin Models