dc motormotorvoltagevoltage-regulator
I have a 4S LIPO battery 5800mAH at 14.8V and I want to use it to power some 7.2V motors I have.
The Rover 5 Chassis to be exact (https://www.sparkfun.com/products/10336), the only problem I have is I don't know the most efficient way to step down the voltage. I bought this battery to use with a quadcopter and I realy don't want to buy another one is there any way I can use this?
I know about regulators but that must be really inefficient.
Arduino Leonardo, like the Uno, uses an NCP1117 linear regulator (LDO), which can supply 800 mA, but at 11.1 V input that would be 4.88 W, so thermal protection will set in much earlier.
Using USB is a possible solution, but keep in mind that USB doesn't have to supply more than 100 mA, you'll have to negotiate for 500 mA. And Arduino is not designed for low-power, I don't know what the Leonardo consumes, but I guesstimate the Uno's supply current at 50 mA, so powered from USB that may leave too little for for instance a series of LEDs.
Your own switching power supply looks like the best solution. Bypass the NCP1117 and supply it directly with 5 V. A 12 V to 5 V buck converter should be able to have a near 90 % efficiency. If the dingus would need 50 mA it can run for more than 48 hours on the LiPo battery.
Further information
Arduino Leonardo schematic
As m.Alin suggested, you could you boost regulators. Look at the following example from LTC
You can input your input and output parameters and regulator suggestions will be provided.
Choose the best one that suits your need.
Here is a schematic of a boost regulator, one of the cheapest regulator chosen from the list.
Another power products manufacturer is TI. You can use their webbench (online software) to adjust lot of parameters and choose the best regulator for your needs. TI products may be cheaper than LTC.
Edit: If your requirement is one off only, then you may go with Jippie's suggestion and look for a ready built boost regulator. Pay special attention to the wattage as some of the cheap modules do not include a heatsink. They expect the user to add a heatsink for prolonged operation.
Best Answer
As @brhans says in his comment, the answer is a buck style regulator. Those can be 90%+ efficient. They are a type of switching power supply that also uses an inductor. A buck/boost power supply can even raise the voltage, but you don't need that in your application.
Buck regulators are quite common in motor circuits, so you should be able to find a 7.2V buck regulator as an inexpensive off-the-shelf part.
In the RC world, such a supply is called an UBEC (which stands for "Universal Battery Eliminator Circuit"). A quick Google search on "7.2V UBEC" found lots of results, including this one:
7.2V "UBEC" regulated power supply