Two batteries in a plane?

[Craig Spence]

Hi all,

 

im currently building a Brian Taylor DH Mosquito and I am pondering whether to use two batteries or not.

I know about battery backers but I was reccommended to use two battries (without backer) going direct into the receiver.

 

I belive this would provide a constant power and longer flight times but could also unbalance batteries.

 

So do you get battery Y-Leads?, then just connect them up to the receiver?, do you get battery extension leads?.

 

I need a little help here.

 

The plane will be set up as this.

 

x2 digital Futaba S3152. (Elevator and Rudder, already installed)

x2 retract servo's.

x2 Flap servo's.

x2 Aileron servo's.

x2 Throttle servo's.

 

So ten servo's all in all.

 

The plane itself is 71" and powered by two SC52FS.

 

The flight  battery will be a Sanyo Eneloop 6v 2000mah, these batteries are fantastic as well.

 

So would I need two?, will I need an opito isolater?, are there any special switch harnesses I should consider.

 

Any help would be greatly appreciated.

 

Cheers all. 

 

[Tim Mackey]

Id use either a good switch mode UBEC and Lipo or perhaps 2s A123 cells.

Have you considered the stuff from powerbox such as the digiswitch?

[Craig Spence]

Hi Tim,

 

Thanks for the quick reply there, Im not going to go the lipo route for various reasons which I wont get into in fear of opening up a can of worms lol!.

I have heard of these A123 cells though, could you elaborate on what sort of set up I would need for these and would I need a specific charger etc...

 

Ill have a look on Powerbox now.

 

Cheers Tim.

[Craig Spence]

Hi Tim,

I think thats the quickest awanswer ive had on here that im completely happy with, I have found this switch which is more of what im after, whats your thoughts on this product.

PowerBox 12 The Power Switch. It is basically what I want the use of two batteries.

Thanks Tim, Very usefull indeed.

Craig.

[Martin Harris - Moderator]

I've used the 2 battery, 2 switches, 2 connections to the receiver methd without any diodes etc. method successfully. The only requirements are that the batteries are the same technology and cell count and that they are charged seperately. You can add a diode to each pack if you use 5 cells if you want to but it isn't essential.

 

In my opinion, introducing a power box with multiple components and connections introduces an excessive number of potential failure points but some form of back-up is always a good idea in a largish or expensive (in monetory or work terms) model.

Edited By Martin Harris on 07/10/2010 13:04:26

[Tim Morton]

Craig
I'm no expert but saw one of our club members P51 with retracts a week or three back - he had the retracts only on a seperate battery in case of a malfunction (e.g. it didn't quite retract properly and was continuosly drawing current) - seemed very sensible to me.

 

I can't quite remember the wiring setup but I'm sure if you give one of the better shops a call they'd be able to help you out.  There was a seperate switch but it wasn't very complicated.

Tim 

 

 

 

[Martin Harris - Moderator]

Highly recommended method for electric retracts in case the servo stalls.

 

You need a Y lead and to remove the power feed from the receiver (Futaba red lead) on one leg and connect the battery to the other.  I think Timbo has a diagram somewhere...?

Edited By Martin Harris on 07/10/2010 13:17:18

[David Ashby - Moderator]

Posted by Martin Harris on 07/10/2010 13:03:57:

I've used the 2 battery, 2 switches, 2 connections to the receiver methd without any diodes etc. method successfully. The only requirements are that the batteries are the same technology and cell count and that they are charged seperately. You can add a diode to each pack if you use 5 cells if you want to but it isn't essential.

 

In my opinion, introducing a power box with multiple components and connections introduces an excessive number of potential failure points but some form of back-up is always a good idea in a largish or expensive (in monetory or work terms) model.

Edited By Martin Harris on 07/10/2010 13:04:26

 

The Powerbox Digiswitch reduces complexity

 

1. it's not a mechanical switch so removes a potential source of problems in higher current applications

2. It has a built-in regulator so saves space and wiring.

 

It's a beautiful thing   

 

Edited By David Ashby - RCME Administrator on 07/10/2010 13:10:56

[Martin Harris - Moderator]

Posted by David Ashby - RCME Administrator on 07/10/2010 13:09:28:

The Powerbox Digiswitch reduces complexity

 

1. it's not a mechanical switch so removes a potential source of problems in higher current applications

2. It has a built-in regulator so saves space and wiring.

 

It's a beautiful thing   

 I'm not sure how introducing a regulator and electronic switching can reduce complexity but I'm sure it's a clever bit of kit. However a GOOD QUALITY switch of sufficient rating is unlikely to fail and is backed up anyway in my favoured system.

Edited By Martin Harris on 07/10/2010 13:23:42

[David Ashby - Moderator]

Posted by Martin Harris on 07/10/2010 13:16:08:

Posted by David Ashby - RCME Administrator on 07/10/2010 13:09:28:

The Powerbox Digiswitch reduces complexity

 

1. it's not a mechanical switch so removes a potential source of problems in higher current applications

2. It has a built-in regulator so saves space and wiring.

 

It's a beautiful thing   

 

Edited By David Ashby - RCME Administrator on 07/10/2010 13:10:56

 I'm not sure how introducing a regulator can reduce complexity but I'm sure it's a nice bit of kit. However a GOOD quality switch of sufficient rating is unlikely to fail and is backed up in my favoured system.

 

That's because you don't seem to know what they look like by the sounds of it Martin. The Sensorswitch would be a good option as it allows two packs to be connected, again, with minimal wiring. Have a look here Craig - not the cheapest option mind...You'd have the option of using Lithium as Tim suggests too. 

[Martin Harris - Moderator]

I do recall reading about them in the magazine and yes, they do look very tidy but I'm talking about electrical and electronic complexity. If something should get hot in that little box it could potentially fry the whole thing - then where are you?

Edited By Martin Harris on 07/10/2010 13:27:49

[Ed Darter]

Craig,

I've recently been through an almost identical issue with my Kyosho Spitfire which has 8 servos in total. In the end I fitted 2 Eneloop packs like you are suggesting. One powers the primary flight controls as per a standard model (ie 5 servos) and the other battery powers the retract servo and the 2 flap servos. There are two normal switches involved, one for each pack and as mentioned above, if the U/C one stalls you are not draining power from your primary flight surfaces.

 

I worked out a way of doing it non destructively as well for most of the extension leads, the only sacrificial one was a Y lead. Have attached the diagram I drew at the time to help figure it all out in my head ! colour codes are for JR but I'm sure you can work out Futaba equivalent if required ;o)

 

HTH

Ed

[Tim Mackey]

Sorry Craig, been out

However you seem to have a few responses, and I guess at the end of the day, you have to make your own mind up. The powerbox system stuff is top quality, and is used by many of the top fliers in all sorts of models right up to 1/3rd scale  and so on.

I have yet to read of anyone with any complaints whatsoever.

Even their simplest digiswtich is a lovely bit of kit.

[Craig Spence]

Hi all,

 

well thats some fantastic feedback there. Ive got alot to work with but I think I will be going with my original choice I think.

I have a few things to clarify though if any one would like to comment.

 

Hi David,

 

the link you gave me, what is the difference between the powerbox 12 switch and the powerbox sensor switch (the link you sent me). They look very similar.

 

Also with these set ups, how do they work I have read the detail on them but am still pondering it.

So does the switch draw off of both batteries?, or does it draw from one and then the other when the master battery voltage dies down?.

 

Alot of people have said in this topic that they use different power systems for the undercarriage should there be a malfunction and they draw too much current/ continue to draw current whilst no in use.

Would the set up im thinking of be sufficent if such a malfunction takes place?, I personally would have thought so due to longevity and voltage of two packs.

 

Thanks all, very happy with the response and the pictures.

 

Craig.

[Vecchio Austriaco]

I use the digiswitch already on 3 models, it combines switch and voltage regulator and shows you the state of your battery by 3 colour leds. Can be used also with NiCads if somebody dislikes LiPos. No extra wiring -no cable mess (working in the cable industry I shouldn't say that). No accidentally switching possible.

Only disadvantage is that it costs a bit of money.

 

VA

[Craig Spence]

Hi Vecchio,

 

can you use this switch with two batteries or would you need two of them?.

 

Cheers.

[David Ashby - Moderator]

The Sensorswitch is the next one up in the range after the Digiswitch and has 2 batt leads - it's 2 Digiswitches in one unit basically. See my link above.

[Craig Spence]

Hi David,

 

so can you tell me the difference between the PowerBox Sensorswitch and the PowerBox 12.

They look the same, have the same leads but are priced differently.

 

Also will two batteries power the receiver, or one and then when that one battery drops below a certain voltage it switches over to the one which was not in use.

 

Cheers David.

 

Craig.

[David Ashby - Moderator]

Well the '12' is a mechanical switch (a darn good quality one of course) while the Sensor and Digiswitches are electronic switches (so no moving parts or contacts).

 

The '12' doesn't handle Li-Pos, just 4-5 cell Nixx packs. These packs can be charged in situ directly through the unit. Yes you have dual batt safety/redundancy in case one fails, hence the two leads to the Rx. 

[Vecchio Austriaco]

Craig, 

 

David gave you the answers while I was at dinner. Thanks David!

VA - enjoing German cusine today (If there is something to enjoy on it...)

 

[Craig Spence]

Hi David,

 

thanks very much for the help again, if you did post an awnswer earlier (as Vecchio has pointed out) im sorry that I never saw it (probably didnt fully understand).

 

I think im ineterested in the PowerBox12, it is just an on/ off switch on it isnt it?, this would be the only mechanical part right?. Also why would electrical be better than mechanical?, is this because of movement or high g's.

I just had a quick read of the user manual and it sais that you can use nimh batteries as well, sorry but what are Nixx packs?.

 

So basically David what are the pro's and cons between the two switches and which one would be suited to my plane and set up?.

 

David, thanks very much for your help its really appreciated.

 

Craig.

[Ultymate]

The electrical switches used by Powerbox are all as far as I know fail-safe that is if they do fail your gear will stay switched on until the battery is disconnected. 

[David Ashby - Moderator]

Nixx - an abreviation for NiCD or NiMH, sorry being lazy

 

Well, mechanical switches mean moving parts which may/will wear over time. The thinking is that big expensive models shouldn't die because a £2.50 switch fails to carry the current due to it having muck, dirt and fuel affecting the quality of the contacts, or the contacts themselves being poor quality, or indeed if the level of current being too much for the unit.

 

That said, many models fly for years with simple mechanical switches of course but the electronic switches provide a level of assurance for those who want to pay a bit more. You can be sure that the Powerbox mechanical switches will be some of the very best mechanical switches you can buy so I wouldn't worry about that aspect if you're planning to get the '12'.

[David Ashby - Moderator]

Just nipped off to take a look at the '12' spec again and read your first post. I think you'll be fine with the 12 but I would suggest you give someone like Dave Wilshere at Motors and Rotors a call. he's a Powerbox main retailer and knows 'em inside out - I always run the scenario past him before settling on the correct unit.

[Craig Spence]

Hi David,

 

thanks very much for your help again, ill give Dave an email to see what he sais.

 

Thanks very much.