Of FEZ and Batteries

Mini review time…and the news is good! :slight_smile:

Armed with a 3D printer, entirely too much GHI gear and the latest power module from SolderMonkey I set out to create an all-in-one diagnostics kit for Skewworks. The device had to do double or even triple duty as it would also be the device my oldest son would use to work on his programming skills.

Before I get to the breakdown of the power module and the battery performance let’s check in on the hardware: FEZ Hydra, T35, Bluetooth, uSD, USB Serial, 6 Button module, LED7R and Tunes module.

All of the hardware was connected the entire time for this test. The screen refreshed every second and every second data was dumped to the uSD so I could see the final dropoff voltage.

While I’m disappointed the module from SolderMonkey requires the D slot (ruling out using it on the Cobra II which has none) it’s a fantastic module. The battery percentage always read zero, but hey it’s a beta driver. What did work was the temp and voltage readings.

I started the test with a fully charged 2600mAh LiPo which read at just above 4.2 volts. I let it run continuously for 5 hours until I had to turn it off since it was 1AM. I had a stop watch running to make sure I kept proper track of time, so I paused that too. In the morning I turn the board back on and resumed the timer.

During the entire run the voltage dropped down in the most steady and beautiful way. Making a battery gauge with this would be most simple (and was actually the point of the test, to find the end dropoff voltage)

The board [finally] gave up the ghost at 3.24724197volts after 8hrs 27minutes and 33seconds! Can you imagine if I’d actually done, literally anything at all to conserve battery life?

So, yeah. FEZ + SolderMonkey + LiPo = GOOD. You should invest in this setup.


Thanks for doing the test! Sounds great I will be ordering the module. What battery did you use?

I’m sure you can find the exact battery elsewhere. I grabbed it from Adafruit because I was also ordering other things at the time. Including their battery charger, which is what will probably end up powering my cobra. Sadly, I’ll have to add hardware to it to get the same data as the SolderMonkey module gives me.

Great test! i would be interested to see the same test run on a Cerberus and a spider to see what the difference is?

I don’t have a spider available bit I do have a Cerb handy. What kind of load (modules) would you like on it?

I guess whatever modules you feel would make a good test :slight_smile:

maybe the conditions using a gps module

Well this http://www.adafruit.com/products/328 is not really a battery, it’s a lipo pouch cell, you still should to add a bms chip and temp censor to charge and handle it safely.

And then there are some serious down sides to this technology, if you complete discharge it, you kill it… even with a bms chip that switches the power off at a safe level you still need to apply a charge before it’s to late.

The module from SolderMonkey does have temp sensor and bms. :wink:

@ Skewworks - Ahaaaa !! you used this one :


Yes indeed, a good marriage :stuck_out_tongue: (still divorces happen, discharge it complete and it’s dead, but then again, if you need compact power at the moment, you don’t have a choice)