Large Model Association Forum

Can anyone recommend what diodes are the best to use in making twin battery set ups for receivers please.

Simon

Simon,

I can recommend 2S A123 packs and no diodes, just plug them into opposite ends of the receiver.

please explain what is a 2S A123 PACK

RON

I make my own, but this should explain what they are...

http://www.electricwingman.com/a123-life-battery-packs.aspx

Thank you Rob. But I do not see how this avoids the need of diodes .unless you make a break in the receiver + connection inside the receiver and so split the output.

Ron

I have been using a twin battery set up without diodes for quite a while now. Two batteries, two switches into spare RX ports. Works for me.
stu k

what happens though if one battery develops an internal fault, will it not pull down the voltage of the other battery if theres no diodes?

Do batteries develop internal faults? or do they loose capacity and go flat. There is a battery docter web site somewhere which indicates that the situation that you describe is highly unlikely.
In the end, you pay your money & make your own decision . I prefer the most simple set up with the fewest part count and connections.

Could a battery backer be used? I was thinking of using two Rx batteries in a large plane in the future.
I was thinking of a battery backer...something like the Jomar/EMS unit. Has anyone had any experience of using such a unit?? There are several good reviews in the US where they are quite popular

Peter, using two batteries and having one of them which will almost certainly be redundant
most of the time just does not make sense. With two batteries both being used you will
have the benefit of both extra speed and power, [Greater capacity equates to less voltage drop you see] I thought battery backers went out with Noahs ark and 4.8v systems. Incidently, two batteries being used in parallel to power the same unit should ALWAYS be isolated. In the event of one battery or associated switch/wiring harness developing a problem it can adversely affect the supply of whatever it is powering. While both are good you are fine, but any battery can fail at any time. Why take a risk when it could cost you a model and possibly someones life.
Hope this clears things up for you.

Tony.

With over 20kg models it is mandatory to have two separate radio systems. This means two batteries powering two systems. If one battery fails or anything else in the system stops working, the model is still safe and operable on the remaining receiver. If you know your model, and you should, you will sense that something is not quite right and be able to land the model safely. In this case why have batteries doubled up? you will not fly again, hopefully, until the dud battery is replaced. The chances of two batteries failing simultaneously in a dual receiver system is pretty remote. The worrying thing, of course, is however much the aircraft electronics are safeguarded you are using only one transmitter, rare for them to go faulty but it has been known.

I understand from the last posts that the larger the model the greater the responsibility to other pilots, yourself and the general public.
Though there comes a point where the responsibility goes up exponentially. Living down in Cornwall it's not easy just to "pop" over to get some advice or show an LMA member a problem.
I want to get this right so it's safe as possible.

Simon , I thought I would add my thoughts , many years ago I was demonstrating my half size Sopwith Tabloid at a Woodvale event . I finished a long solo display to a very large appreciative crowd and safely landed the model.
In the pits area I could smell something burning and on removing the cowl , found that one of the two radio batteries had managed to destroy itself . I had fitted two 8amp diodes and a total of four battery leads after the diodes so that each receiver had two battery inputs, one from each battery and as such I was able to complete my flight with no problems despite the meltdown of one battery.
Its a system that I always use on my many large models and it has been 100% reliable.
The key issue is redundancy and with this system you can loose a battery lead , diode, switch or battery and your radio will still work. Would recommend the industrial Apen double pole 6volt 8amp switches from Farnell
Regards Ian Turney-White