I've been asked many times how the HP Prime G2 compares to the Nspire CX. Although the battery life of the HP Prime G1 has already been documented by Erwin Ried, no one has tried the G2 yet and I never had a Nspire to test it against until recently.

Testing method and code:
Since I don't have a robot that can replicate the battery test used for the HP Prime G1, I wrote a program that I could simply port to the Nspire. Instead of having the calculators constantly crunch numbers, I wanted something slightly more realistic so I had the calculators increment a number by one, display it, then wait one second. This is the psudo-code I settled on:

Code:
int c=0;
while(true)
{
 c++;
 print(c);
 wait(1);
}

Here's the code I actually wrote:

(Click for full size) I'll address the extra if statement on the Nspire side below.

The results!
The results were very impressive, both exceeded my expectations. The HP Prime G2 died first at 16 hours and 55 minutes, so close to 17 hours! The Nspire CX lasted roughly (I'll explain below) 18 hours and 21 minutes!



Since the HP Prime updates the battery indicator even while the program is running, I was able to see exactly when it dropped to 75%, 50%, and 25% battery. Unfortunately, the Nspire only refreshes the battery indicator when the program stops so I only got times for 100% and 0% battery for it.



All the imperfections that occured:
First, the battery health on the calculators. My HP Prime is about 2 years old at this point but the battery is relatively new and I'm confident the battery health is at least 97% so add about 30 minutes to the HP Prime's final time (I did not reflect this in the chart because I don't know what the exact health is). On the other hand, I have no idea what the Nspire's battery health is but I do know my TI-84 Plus CE's battery health is at 80% from a test I did a while ago. Since the batteries are compatible between calculators, I used that one instead (I don't have a newer battery to test unfortunately). This means the Nspire actual time was only 16 hours and 1 minute, but since the battery health was so significant, I reflected the 20% change in the chart above.

Unfortunately, I discovered a major issue which basically invalidates my HP Prime results. I was confused why my chart looked so different from Edwin Reid's HP Prime G1 results. I couldn't figure out how HP managed to stretch the last 25% of the battery so much longer than the rest of the test. After looking though my footage, I realized the calculator stopped counting at 14 hours and 34 minutes. My guess is that's when the 'Battery Critically Low' message was suppose to appear, but instead it just froze the program (and probably would have turned off if I had the default off settings). My guess is that the HP Prime would have died within the next hour but I really have no idea, I'll have to come up with a better battery benchmark next time. Crying

The other problems weren't nearly as significant. The Nspire inexplicably can't display the number 14,324 so it broke the program and turned off for 24 minutes. No big deal, I changed the code so it would restart at 0 if the number got to 14,000. I just chopped off 24 minutes from the Nspire's final time (this is reflected on the chart).

For some reason the HP Prime still dims the screen even if a program is running unless you manually tell it to not. I sort of expected this so I caught it only 2 minutes after the screen dimmed. I figured this short amount of time was negligible so I didn't reflect it in the chart.

My observations:
Just for fun, I threw in my TI-84 Plus CE into this test and, predictably, the lower powered processor lasted several hours longer than both the HP Prime and Nspire coming in on 26 hours and 6 minutes! Remember, it was running on the Nspire's battery which I don't know the health of so this number means very little. Nevertheless, I thought it was fun to add in. Amusingly, it was the only calculator that I didn't have to restart the battery benchmark program on so it ended up counting higher than both the HP Prime and Nspire!

I'm working on compiling all my footage of this test. I'll hopefully upload it within the coming days. I know this test is super inaccurate, but I spent so much time working on this post before I realized the big issue, I've decided to post it anyways,
  
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