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Power Supply's upgrade 4AA baterries of my buggy receiver.

Discussion in 'Electronics' started by GreekRotorHead, Aug 17, 2017.

  1. GreekRotorHead

    GreekRotorHead Member

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    Hi guys, I want to change those 4AA batteries of the receiver. I m thinking of replace them with 2s lipo, , or with Nimh, without knowing how many cells Nimh must be. I'm running 9kg servos on throttle and steering. And if I use lipo at how many volts of battery do I have to charge it again?
     


  2. rdsok

    rdsok Well-Known Member

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    I'm going to start with some generic info and hopefully it'll lead you to finding out what you want to know... I'm doing it this way so you also will know this info for other things beyond just the receiver and can use the info for those also.

    AA refers to a battery size... not a type like alkaline for example... it's also known ( size wise ) as a 14500 size. So this will have a lot of info in it...

    A standard heavy duty or alkaline battery voltage is 1.5v per cell. A standard NIMH battery is 1.2v and a single LIPO battery cell is 3.7v nominal and 4.2v fully charged. Besides the voltage... each type of battery also has a capacity rating... ie it's mAH which equates to how long it can run at the voltage that is being used. Since each cell may have different mAH ratings, you'll need to also know what your batteries capacity rating is so you can estimate how long they will run for you. A typical alkaline AA cell will have about 2300-2500mAH of capacity but it can vary by brand a little.

    Since you are using 4 cells... you'd typically need to know how they are wired together... are they wired in series or parallel or a combination of both. In this case I can tell you they are in series which means their combined voltage is 6v and the mAH capacity is whatever your cells rated amount is ( in parallel the voltage would be the same as a single cell, 1.5v in this case and the capacity would by times 4 instead of the voltage being multiplied by 4 )

    A typical NIMN cell is as I mentioned... 1.2v per cell and can have somewhere in the range of 600-900mAH of capacity. So 4 cells would give you 4.8v with whatever rated capacity of the cells you were to use have.

    Now I'm going to switch to typical receivers and servo before going to LIPO info real quick....

    There are many different types of receivers and servos out there... The standard ones ( receivers and servos ) will operate in the 4.8v-6v range but because they differ.... you better first find out what the voltage ranges your receiver and servos can operate in. If you don't know... find out before deciding on what you are going to power them with.

    Now back to LIPO's as an alternate source.... Since the nominal voltage of a LIPO is 3.7v and fully charged cell is 4.2v... using a 2c LIPO battery will give you a nominal 7.2v and at full charge 8.4v. LIPO's voltage vary as they're capacity discharges... they start at 4.2v fully charged and can drop down to 3.2v fully discharged ( you never want to discharge to much less than 3.6v actually but that is another story for now ). If you are just using a standard receiver/servo... 8.4v will likely burn them out so you'd also need a BEC to power the receiver/servos so the voltage can be dropped down to something they can use without burning out. As I mentioned, there are different receivers/servos out there and some of them can also work at these higher voltages... so you first have to find out what voltages your's are capable of working with.


    Another little bit of info... If the car/buggy/truck is using an electric motor... I has to also use an ESC to provide power to that motor. It may be possible to get an ESC with a built in BEC in it to power your receiver/servos with. So that may be an option but again this differs a lot on different types/brands/makes of models.
     
  3. GreekRotorHead

    GreekRotorHead Member

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    Many thanks. As the receiver and the servos are stock, I can't find any information for their operation. For the servos I know that are 9,2kg, 0,13sec. Metal geared. The manual doesn't refer to their specification. I don't even know if servos are analogue or digital. So I assume that servos and receiver works at 6volts. So the 4 AA batteries in the receiver box must be connected in series. It must be. The buggy is the kyosho scorpion bxxl nitro version 2wd. 5,5 Kgs, with .32 engine. I haven't done the break in of the engine yet. So based on the assumption of 6volts operating voltage, I prefer to use some other kind of power source than the 4AA pack. What its better Nimh or Lipo?
     
  4. rdsok

    rdsok Well-Known Member

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    I don't do cars, trucks or buggies... so I'm not familiar with how good one brand vs another is...

    I'd probably suggest NIMH just because they come in AA sizes making it an easier conversion. Of course that'll drop the voltages down to 4.8v which will slow your servo response slightly.

    LIPO's have the potential of giving you more capacity than NIMH's but you'd need to also get a BEC and would need the room for them also. Most of the BEC's I've seen also output 4.8v but there may be a 6v version out there if you look.
     
  5. GreekRotorHead

    GreekRotorHead Member

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    Then probably I 'll get Nimh. But how many cells should it be?
     
  6. rdsok

    rdsok Well-Known Member

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    I'm going to make you re-read my original post since I already stated what voltage each cell has in that
     
  7. Admiral

    Admiral I Support Rc-Help! Rc-Help Supporter

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    Posted in error
     
  8. Tony

    Tony Administrator Staff Member

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    My headache is too bad to read all fo that, so I'm just going to post what I think you need to know. Both NiCd and NiMh are 1.2 volts per cell. If you have 4 of them, then that is 4.8 volts nominal. If you are running standard alkaline batteries, then those are 1.5 volts per cell or 6 volts for the pack. Without knowing what the max voltage is of the servos and Rx, I would just to with a 2s LiFe receiver battery. Very long run time and way less weight and still only 6.6 volts which should be fine with most electronics.
     
  9. GreekRotorHead

    GreekRotorHead Member

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    I just find out that the servo ks203 that I'm running has an operation voltage of 6V. I saw that from the spec sheet of kyosho servos. So I'm thinking that 6.6V may be too much for these servos. Probably I will try a 5 cell pack of 6V. Just to make sure the servos are not going to be burned.
     

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