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[sentry]

Hi  Gents, Would it be ok to use a PP3 8.4V rechargeable to power my receiver  a Spektrum DX5E as am building the Revell landing craft and don't have a lot of room also would 4 or 5 AA battery's made into a long stick work as i would like to put these down the side's between the hull and the cargo well  one each side for each motor with a mtronic 10a speed controller on each stick and the RX having it's own battery and would I get much sailing time with this set up think sticks would be 2600 mah each and hav,nt a clue how long a pp3 on the Rx would last if its possable.
                                                    Regards Sentry. 

[Prophet]

have you got a photo of the available area where all your components will fit there may be other alternatives maybe a slim line receiver pack for the Rx.
What size motors are you looking at using?

 I see a 10A esc that sounds fine, maybe with limited space you may be best off utilising the BEC of the esc saving on Rx battery pack.

Some more info on motors and photo of the space Will help work out your best solution, as well as the dimensions of the craft (you may have options to use 1 esc or an Action Product which will help in reducing the use of space, I'm sure many will agree.

Options to create your own battery pack is pretty simple, exact same process to creating the RC cars battery cells. 

[DickyD]

As Prophet said, forget the Rx battery and use the Bec in the speed controller. 

[Prophet]

That will only eliminate the use of a Rx pack, he's wanting to use twin esc's my feeling is using a single 25A esc or similar and connect both motors to it eliminating the need for two powering two esc on a few pencells isn't going to give a long running time litrally 2 -3 Min's, there are expensive options like th eP94 from action that would do the trick for the all in one function. but at £80 with p&p its a real expensive option.
Hence the reason why i want to see photos to establish what room there is and see what options he really does have.
I always work on the idea that most people want to spend as little as possible just like me LOL

[barriew]

This is a plastic model - I can't believe he is putting MMB900's in it More like 385's or less, so the pencells should be OK. I run a Speed 400 in my Deans RAF fireboat and get 20 mins plus on 6v NiMh pack, with separate Rx pack. As most BECs need at least 5 v, running off a 6v pack is a little risky in my book.

Barrie

[Prophet]

Not sure if anyone ever recalls the program 'model mania' in discovery some years back they built the a semi submersible frigate that then had a model landing craft come out of it. then had a model tank able to drive off it. cant remember the ships name ' must be age' but from what i remember he used 2 small motors i forget the size connected to a 2mm shaft. the boat travels quite slow and he never used a esc due to the speed of the craft just ran it of the TX sticks (simple forward/reverse system) through the receiver using a receiver pack, steering was established via speeding up one side to the other,  and used a micro servo to open and close the bow ramp. anyone remember this?

[sentry]

Sorry Gent's my last reply looks like its floating around in cyber space. What I forgot to say was  I have area 110mm x100mm x 35mm am not going to use any servo's as am fixing the rudders and driving it on both sticks tank style so I have two motors which are mfa 457RE140/1 3-9volt about 25mm x 25mm with 2mm shafts two 10A mtronic esc's and a AR500 RX,I have a small gap between the hull side's and the well bay about 16mm x 18mm which I could get 5AA in-a-line battery's down one for each motor and esc  which was why I was hoping I could use a pp3 8.4v  on the RX as I think you can go up to 9v on the Spektrum DX5e RX all battery's rechargeable and by using this setup hoped to get maximum  time on the water if it will work   
                    Regards Sentry.

[RaaArtyGunner]

I always work on the idea that most people want to spend as little as possible just like me LOL

Prophet,
Ten out of Ten 

[Prophet]

well to be honest i think you solved your own question with your plan, its possible to do what you want with the space you have im just not sure on the running time. i still think 2 -3 mins tops even with the use of a rx battery pack, just remeber to disconnect the BEC (central cable from the plug) from each of the esc before you plug them in or you will over power the rx, other options may be to add a battery pack in say a 'container' on deck hidden.

other options may to be to use a 9v cell they are pretty good in small crafts and there light weight you could possible slide 2 up the sides of the hull (there about 16mm in width i think, but check!) connect 2 in parallel giving you a longer running time possibly up to 15mins

 you could look at the micro esc serise bit pricy but well worth it i have used 2 to move a revell panza tank trust me when i say that little thing goes like a bat outta hell!

380 motor & esc set
http://www.modelsport.co.uk/?CallFunction=ShowSpecification&ItemID=33281

micro esc only cheaper make but will do the job
http://www.modelsport.co.uk/?CallFunction=ShowSpecification&ItemID=32248
http://www.micronradiocontrol.co.uk/micro_esc.html   <--- sweet link just found that esc's as tiny as your finger nail.. and for £10-£15 for a 3A, 7A or  10A!! look at the bottom brushless section, they also have micro motors... incase that helps.. smaller motors draw less giving you longer run time!!

 using A  micro esc will free up more space allowing for more batterys giving you more run time or less weight for a faster boat

[FullLeatherJacket]

http://www.action-electronics.co.uk/pdfs/P82.pdf
Full motor mixing from 2 channels. One 4-cell battery powers everything. Rudder servo is optional. £60 total incl P&P (£5 cheaper if you use P52 ESCs).
Suit yourself.
FLJ

[barriew]

I was just going to ask if you already had the ESCs as otherwise take a look at ACTion micro ESCs which work entirely off the main battery pack. I still think Prophet is being very pessimistic on run times if you get high capacity AA cells.

Barrie

[sentry]

Thank you for all the replys, FLJ  I already have the ESC,s  which I cant see me using them in any thing else but  all my other builds will be bigger so think it will be ACTion next time.
                                Regards, Sentry.

[FullLeatherJacket]

OK. BTW those motors are rated at 0.2A on 6v at maximum efficiency, so a 2600MAH pack running both motors flat out will last in excess of 6 hours. I think maybe our mate Prophet got his decimal point in the wrong place 
FLJ

[Prophet]

maybe.. but im still thinking only a few mins run time, i guess the only way to find out is to wait and hear what happend's

[DickyD]

I'll put my money on Daves calculations 

[malcolmfrary]

This is a plastic model - I can't believe he is putting MMB900's in it  More like 385's or less, so the pencells should be OK

Not only a plastic model, a SMALL plastic model.  One 385 would probably sink it.  
For batteries, a stick of 4 AAA rechargeable, for control a pair of Action's micro ESCs and matching mixer will do the job and power a pair of matching mini motors from the same supplier or servo motors if connecting to a very short stubby shaft is not a problem.  Should be good for an hour or so.  I suggested the mini ESCs because finding a home for the all-in-one unit might be a problem in a SMALL model.
The pessimistic run time could be due to the assumption that a 25A ESC will use 25A.  This is not so, just because it can does not mean it will, the current depends partly on the motor, and upon the load imposed on the motor by the prop.  After that, its down to Ohm's law and battery voltage.  While an ESC that can handle a lot will control a little equally well, the big 'un will probably need more current to drive the output stages, so matching is a good idea.