LiPo Battery 11.1v with a mosfet at 4.0v output?

[caesar]

I used it as a car adapter, but I completely forgot about it until I saw this post.
Sadly it is to big to put it into a nicobox mod.

Still a home-made 4-5-6V 1.5A version could be made using a PIC, coil, mosfet, diode and capacitor.
The above product is just rugged and easier to use. I'll order a few more myself

PWM to a large capacitor; monitor voltage to adjust pulse width. So a voltage controllable duty cycle oscillator, big capacitor, opamp and a MOSFET would do the trick.

You forgot a coil and diode

 

[kinabaloo]

You forgot a coil and diode

My way doesn't involve those

The coil is to supress rf noise; maybe need it.

But no need for a diode in a transformerless converter.

Op amp comparator monitors output voltage (in the capacitor) with respect to the desired voltage and instead of adjusting the current as in a normal voltage regulator, adjusts the duty cycle (pulse width) of the oscillator; to keep the capacitor suitably charged as the load drains it.

 

[RayJ1]

This is a 3s lipo battery. In order to properly charge this battery you will need a rather expensive charger. It will require peak detection charging, and a balance port adaptor to properly balance charge the 3 lipo cells inside that are hooked up in series. The battery packs themselves are also on the order of $50.00 +, and chargers at a minimum of $50.00 +. This unit will be the size of a TV remote.

 

[DaMulta]

The airsoft 11.1V ones come with their own chargers, and some are smaller than others.

 

[caesar]

Found two cheap batt packs too:

DealExtreme: $14.79 1500mAh 11.1V 15C Rechargeable Lithium Battery Pack
This can be dismantled and put in parallel.
Nice batt pack, can deliver 15x its rating (15C) so it's good for 1A.

and this one:

DealExtreme: $26.27 Mystery 4.2V 2650mAh 25C Lithium Polymer Rechargeable Battery for R/C Helicopters

It's smaller and already wired in parallel. 2.4Amps at 25C, good for attys too.

Have ordered them and will post dimensions when they arrive. Should be pretty small and light, fitting an AA nicobox I hope.

 

[kinabaloo]

Found two cheap batt packs too:

DealExtreme: $14.79 1500mAh 11.1V 15C Rechargeable Lithium Battery Pack
This can be dismantled and put in parallel.
Nice batt pack, can deliver 15x its rating (15C) so it's good for 1A.

and this one:

DealExtreme: $26.27 Mystery 4.2V 2650mAh 25C Lithium Polymer Rechargeable Battery for R/C Helicopters

It's smaller and already wired in parallel. 2.4Amps at 25C, good for attys too.

Have ordered them and will post dimensions when they arrive. Should be pretty small and light, fitting an AA nicobox I hope.

The second one, at 4.2v, is obviously the best choice. Pricey but presumably light Comes with charger?

 

[Laredo7mm]

...Should be pretty small and light, fitting an AA nicobox I hope.

According to the specs listed on DX, they will not fit in an AA battery box. One is 23mm thick and the other is 25+. I think the AA boxes are about 19mm thick, IIRC.

 

[caesar]

They are spaced for ventilation (25C and 15C can get them hot).
I plan on reducing that space, an atty will not draw more than 1C anyway so it should make them around 1.5cm less thicker.
I am thinking around 5-6mm per battery times 3.

 

[funkybozu]

could not a 11V batt be perfect for a twin(in parallel)atty set up?

 

[caesar]

in parallel they will both get the full 12.6V (when fully charged) so that's a no-go.
in series there will be problems with different atty resistance.

But 2 attys on a step-down converter at 5V or 6V would be great.