Spektrum 2.4 multi batteries

[Mike Ellis]

Can anyone advise as to what size batteries I can use with my Spektum DX7 outfit. I like to use 2 batteries if poss for safety and also I prefer 5 cell 6v types. I wish to move over from 35mgz for purly safty reasons. I dont fly over 20kgs models at all.
How are the batterries attatched to the reciever ?? Would I need some sort of module to connect them through and then a lead to the reciever from that or what, and if so,where would I get the so called "module from ????
I have been led to believe that 6 volt batteries are not compatible with Spektrum?
May sound basic to some people BUT when you have a peanut for a brain where electrics are concerned I need all the help I can get ! lol

Many thanks

Mike

[Simon Willey]

You have opened a can of worms with that question as everyone will have there own view on the matter.
I run 2 x 5 cell packs sub C size in my bigger models each fitted with its own switch plugged into different ports on the RX .
On my smaller petrol models I run one 5 cell pack with two switches in parallel again plugged into different ports on the RX.
There is no problem running Spektrum on 5 cell packs. The only issue you may have is some servos do not like 6v but I have not had this issue, though I mainly use Hitec and JR.
Works for me.

Simon

[Phil Clark]

I've been running 6v packs on Spectrum AR7000, AR9000 and AR9100 RX's for the past 9 months....no isues what so ever (all Sub C size packs from 2,400Mah to 4,600Mah)

I have recently switched to using the Powerbox 'Smart Switch' instead of regular heavy duty mechanical slide swithes........these are an electronic rather than mechanical component, so less prone to vibration failure.......but if they do fail, they fail 'On' rather than 'Off'...................worth looking at. Due to this, I now run 1 Smart Switch rather than 2 slide switches in parallel.

Phil

[Martin Waller]

You should not put Nicads, NMHi, Lipo or for that matter I think LiFer batteris in parrellel. They all have a very low internal resistance and if a cell in one goes down the battery with all good cells will back feed the wek battery by 30 to 35 amps for a NMhi or even 70 amps in the case of a high quality lipo. This current will be limited by the wiring and switch impedance and all are likely to melt down as will the receiver input rail.

These batteries must always only be parelled by one way systems such as a diode although this is not recommended for 2.4GHz as a diode is a none linear device and will cause varying voltage regulation on the receiver as the current spikes are produced by the servos.

A power box regulator is a most sensible option and the one I always use either Competition, Evolution for over 50cc models and jets and the smaller Gemini for two batteries using JR ribbon cable only rated at about 2.5amps if the heavy goldtech is used. For large digital servos like the DS8411 the Evolution with 4mm silicon cable would be my minimum choice. (40amp to avoid voltage regulation, ie very low impedance)

The Power box digiswitch is great for one battery and 5 standard or 9202 NON DIGITAL servos. I have used the Gemini with two wires from a single battery plugged into both battery inputs to reduce the volt drop regulation on the JR ribbon cable which I think is on its limits with 2.4GhZ. 2.4 GHzSystems use computers which do not like voltage fluctuations. 35Mhz systems will stand huge voltage fluctuations and work perfectly. Put a scope on the receiver and see. I never use mechanical switches with 2.4Ghz as tests show them to have varying impedance across the contacts and these can gradually get worse with time. I have known over a volt to be dropped over a dirty switch. Vibration aalso affects mechanical switches. Only self cleaning swicthes should be used even with 35MHz.

I was mainly prompted to reply in this forum when I noticed people were parrelleling batteries with such low internal rsistance and huge current delivery capabilities. A Lipos treated such would certainly explode if a cell went down and with the others the wiring would all melt dwn or if heavy wire is used then they too could explode. This is most dangerous.

Regards

M J Waller