Large Model Association Forum

Hi All,

I have the top Flite 1/5th scale P51D Mustang fitted with about 10 servos. It's time to consider a receiver battery. Should I run Nicad, Nimh or Lipo, 4.8Volt or 6 volt and what kind of capacity will I need for a couple of 8 minute flights ?

Any thoughts of how I should go about deciding - any rules of thumb to be aware of ?

Regards All,

Steve

It depends on what the current draw is....if all the servos are digital then they'll probably draw a little more than if they were standard analogue servos. You are still not likely to get more than 5 amps (peak) and maybe 1-2 amps the rest of the time.

My Topflite P-47 has 6 digitals (about 10kgcm) and 2 standards and flies on a single 3700mAh NiMh. It used to have a 2000mAh....but the bigger ones are pretty cheap now so I thought..."the more (capacity) the merrier!" I'll get at least 4 'safe' flights before I think about a top up charge...and even then I've probably not used 1/2 the capacity of the battery. I would consider a twin battery set-up...for the redundancy, but it is by no means essential and in some ways just adds more complexity and possible points of failure....your call.

I wouldn't fit Lipos...purely because you really ought to remove them from the model the charge. If you have a big access hatch then it is not too bad....but unless you are desperate to save weight I wouldn't do it.

A123 cells are the new 'in thing'. I haven't any experience of them myself, but others seem to swear by them. At the moment they only come in 2300mAh or 2500mAh packs (I think) though they can be doubled up to 4600 or 5000mAh if you wish.

Hope this helps....

Steve

Steve,

many thanks - food for thought.... I'll probably look into the A123 cells.

Regards Steve

there is a great post in the latest journal from Dave Swarbick, where he goes into details of the A123 cells,

Thanks Alan,

Regards Steve

A123s are great. been using them for around 4-5 years now.

never had any issues with them.

plus they charge quick and hold the charge.

I use them for ecu packs, rx packs and ignition packs.

I do not like using Lipo packs as I have seen to many models set on fire whilst charging etc.

mike.

Thanks Mike,

are there any charging considerations for the A123 packs ?

Regards Steve

Hi mate

I have always used the fma multi cell 4 charger.

That one is basically a plug and play it charges at 4 amps.

It charges through the balance lead so every charge is a balanced charge.

I have been using these on a 40% yak with two 2300 packs in for a good few years and also 100cc aerobatic models

The yak has 13 hitec 5955 th servos in it which are high amp draw servos when in 3d flight and they are fine.

I will also be putting 4 of these packs in the nimrod I am building

Mike

Forgot to add they need a a123 or LiFePO4 specific charger.

Many Thanks Mike,

Steve