Pololu Robotics & Electronics
Menu
My account Comments or questions? About Pololu Contact Ordering information Distributors

Pololu Forum

Pololu 5V Step-Up Voltage Regulator U3V50F5 with Lifepo4 3.2

Hello,

I am looking to use a Calb 100ah Lifepo4 cell to run a raspberry Pi project remotely. The cells have a nominal voltage of 3.2v. The pi will be using c.500ma but will occasionally pull up to around one amp. The voltage curve of the Calb cells can be found here - Calb but they drop from around 3.4 to 3v through their use.

Will the U3V50F5 U3V50F5 Step up convertor be suitable. Will it output sufficient current at these voltages?

Many thanks,
Sam

Hello.

The U3V50F5 would probably be fine for your application. Just in case you are not aware of it though, you might consider our U3V70F5 instead. We recommend our newer U3V70x family of boost regulators over the older U3V50x regulators for applications that require 20 V or less since the newer regulators are smaller and can deliver more current.

- Patrick

Hi Patrick,

I’ve bought and tried both the U3V70F5 and the U3V50F5 regulators with the battery. My setup is using c.0.6 amps with these step up regulators.

When I use the same setup with the S7V8F5 and a 6v battery it runs on c.0.3 amps (comparable to how it runs directly off a 5V USB).

Is there a reason that these step up regulators seem much less efficient than the step down regulators? The stated efficiency shown for all of the regulators at these voltages/ currents is over 90%.

Many thanks,
Sam

Presuming that the load is the same in both cases and that you are using the 3.2V battery you mentioned before with your step-up regulator, the efficiencies for the two cases you described are actually pretty close. It sounds like you are thinking of your efficiency only in terms of current rather than in terms of power (current times voltage). If your step-up/step-down regulator is drawing 0.3A from your 6V battery, then the system is drawing 1.8W, and if your step-up regulator is drawing 0.6A from a 3.2V battery, then the system is drawing 1.9W, so the difference in power consumption is only 0.1W.

- Patrick

Thanks so much, you are indeed right, I’m still getting my head around battery operations. That has been really useful, I appreciate your help,

Many thanks,
Sam

1 Like

Hi Patrick, sorry for the long gap between messages. Do you think I will need a heatsink with either of these boost converters for this wattage?

It sounds like your application is only drawing currents on the scale of a few hundred milliamps which is well below the maximum current these regulators can handle, so I do not think you will need a heat sink.

For future reference, all of the performance ratings on our regulator product pages are for operation in an open, room temperature environment without additional cooling measures like heat sinks or forced airflow. In general, heat sinks should not be necessary unless you are pushing the performance limits of what the regulator can do or operating in extremely adverse conditions (e.g. a tightly confined space with no air flow and a high ambient temperature).

- Patrick

Thanks Patrick, that’s really useful

1 Like