17338Views10Replies

Author Options:

converting 9 volts to 6 volts? Answered

i have a small r/c tank that is 6 volts  .the problem with it is it is made to take CR123A 3 volt camera batteries  .which run about 5-7 dollars each  .i could by rechargeable ones for 50 but i thought it would be easier and more cost effective to convert it to run on a nine volt rather then four AA or AAA  .not just do to the cost but also because the space limitations

i know how to solder and built circuits if i have a schematic provided .so could anyone provide me with a small circuit schematic or is it just in need or putting a resistor in between the terminals?

10 Replies

user
PolymorphBest Answer (author)2009-12-29

A standard 9V battery has a very low energy density. Four AAA batteries take roughly the same space but carry a lot more power.

And a 9V battery has a very low maximum current draw, not suited to devices with motors in them.

Plus if you use a linear LDO regulator to drop from 9V to 6V, all the power dropped in the regulator is wasted energy.

And one alkaline 9V battery costs more than four alkaline AAA batteries. Same for NiMH.

The 78xx series of regulators requires a minimum of 3V above the output, so for a 7806 it requires 9V minimu, so a 9V battery will quickly drop below 9V.

So if I were you, I'd use four AA or AAA batteries to replace the CR123A

Select as Best AnswerUndo Best Answer

user
luxstar (author)2012-09-02

Here is an instructable using a DC to Dc converter:

 

 

 

https://www.instructables.com/id/93-efficient-DC-to-DC-Converter/

The data sheet says the input voltage can be 4.5 to 14 volts. The output can be adjusted from one half volt to 6 volts. Murata makes several different devices for different current / wattage requirements;

 

 

http://www.futureelectronics.com/en/Search.aspx?dsNav=Ntk:PlainTextSearch%7coktr%7c3%7c,Ny:True,Nea:True

Select as Best AnswerUndo Best Answer

user
lemonie (author)2009-12-30

9V batteries these days tend to have 6 x AAA inside them. If you want to go this way you may be best taking the 9V apart.

L

Select as Best AnswerUndo Best Answer

user
Polymorph (author)lemonie2010-01-01

 Slight correction - some 9V  batteries have AAAA quadruple-A batteries inside them. I suspect that is what you meant to say.

That is a good point- if space is really precious, don't waste 3V out of 9V in a regulator, just use smaller batteries. I'll bet there is more free space inside the tank, though.

If you want to put rechargeable batteries in there, you could pick and choose from some of the many flat and odd-shaped Lithium-Ion batteries, but you'll need to build a custom charger. Google is your friend...

Select as Best AnswerUndo Best Answer

user
lemonie (author)Polymorph2010-01-02

Yes thanks, that is it. Not having touched AAA / AAAA for a long time I blurred the sizes in my head.
I've got some of those Li-Ion batteries, but done nothing with 'em yet - any help?

L

Select as Best AnswerUndo Best Answer

user
Sandisk1duo (author)2009-12-29

nine volts don't provide enough amperage to run the tank

Select as Best AnswerUndo Best Answer

user
Re-design (author)Sandisk1duo2009-12-30

How much power do you think the CR123A 3 volt camera batteries that the tank runs on has?

Select as Best AnswerUndo Best Answer

user
gmxx (author)2009-12-29

 the problem with this is, a 11v will not give enough amps to go through a lm-7806 voltage regulator. nor will enough amps be available. the best wau would be to get one of those rechargeable packs for rc cars. 

i actually just modified a controller for an rc robot to use a wall outlet, because it would suck a 9v down to nothing relatively fast.

Select as Best AnswerUndo Best Answer

user
Re-design (author)2009-12-29

You need to use a voltage regulator circuit.  Google voltage regulator and you will get a list of circuits that will work.  It's a 78 something or other chip.  You need a chip and a resistor or two maybe a heat sink and bam your're fixed up.

Select as Best AnswerUndo Best Answer