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Powering a Rover 5 with a Lipo?

After reading these forums the last months, finally my first post :)

I've just received a Rover 5 (4 motors/encoders), red back spider and 4 channel motor controller from Yourduino. The Rover 5 comes with a case for 6 AA batteries, when I fitted 6 GP NiMH batteries the case nearly broke. It's a bit to tight. I would prefer to power it with a Lipo battery. I have no experience with these batteries, but they seem like a good solution. The question is which one should I buy, 7,4V or a 11,2V version? The red back spider manual says that it will work with a 7V source, but it is fitted with a LM2676 5V regulator. The datasheet of these regulators says that it needs 8V? Will the red back spider work with a 7,4V (800-1200mAh) Lipo? The red back spider will control and power 4 mini servo's, 2 SRF06 modules, a bunch of IR leds, and control the 4 channel motor controller. I'll use the 5V from the red back spider to power the logic for the 4 channel motor controller. And use the 7,4V from the Lipo to power the 4 motors. If I would use a 11,2V Lipo I would need a powerfull regulator to get the 11,2V down to 7,2V for the motors. I'll also use a LM1117 3,3V regulator to power the nRF24L01 module. Which connectors do you guys use to get the power from the Lipo to the different devices? Is there a name for these connectors? So I can start searching on ebay :) Any tips or comment are welcome...

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Thanks for the comments. I don't think I will ever come near a 3A load. I have not bought a Lipo yet, I'll visit the local RC shop later this week to see what they have to offer. Else I order one from Hobbyking.

Yesterday I connected the 4 motors to the motor controller and the red back spider. With a very simple sketch I was able to spin the 4 motors :) I did have to change the polarity of 2 motors to make them spin in the same direction. I currently have everything powered from my lab power supply.

When I wrote the specifications for the Spider controller I tested the switchmode powersupply with a 3A load. I had it down to about 6.8V and still had a steady 5V output. I then rounded up to 7V. If you're load on the 5V output is less than 3A then you can maintain a steady 5V output at even lower input voltages.

A 7.4V LiPo will actually have 8.4V when fully charged and 6V when completely flat. This is fine. Do not use a 3 cell LiPo as the voltage is too high for the Rover 5's motors.

As there is more than 1 type of connector used for LiPo batteries and you haven't posted a photo of the battery we can't help you with connector names.

My LiPo has two bannana jacks. Other Lipo's use a T shaped connector.

If it already has the regulator in the circuit then there's no way 7.2v will underpower it if 6v or 4.8v will do it. Make sure you're putting it in the same feed circuit as the battery pack and not in a separate circuit though. Regulators are often tricky and each has a personality in my experience. Some need the professional heatsink and some you can just put a long bolt through or leave naked if you're cascading them. Also make sure you're in the right current range with that battery. If the LIPO puts out too much, figure out a resistor value to put in between Vcc after the regulator and the circuit.