I've been building and tweaking a raspberry pi based timelapse camera and have things pretty optimized at this point. I'm looking for some advice on how I might get some real numbers on how much power the Pi is drawing while on battery power though.
I have a cheap USB-C multimeter and while running from wall power providing 5v to the whole setup, it draws about 130mA on average. It idles around 95-100mA and jumps up to 160mA or so during periodic higher activity. I don't know if this number translates to the draw from battery however. I assume the Pi itself is drawing the same current, but what I mean is that I'm not sure what current is actually hitting the batteries on the input side.
While on wall power and battery power both, I am running power into a Pi-UPS 2.0 hat that provides 3.3v and 5v to the Pi regardless of the input power. From the wall of course, there is a steady supply of 5v coming in so the Pi-UPS only has to pass through 5v and buck down to 3.3v. I am using a cellular hat and a camera, but unsure exactly what those are running on so I don't know what the mix is for the two voltages, but that may not matter.
While on battery power, the Pi-UPS board gets battery voltage in that ranges from 4.1 at the start down to 2.6 before it cuts off (Li-Ion packs). All the while, it boosts that to 5v and there is loss there, but I don't know exactly how much. (I've been estimating 80-85% efficiency, but no idea if that's reality)
I've done dozens of real world tests now and I've put together battery packs that give me a week of runtime, which meets my needs well. All I'm trying to do at this stage is document exactly what my packs are so I can vet them against other power options in the future.
For example, the battery pack I'm currently using is an 8-cell 21700-based pack that is rated at 39,200mAh (4900mAh for each cell). I'm about to know exactly how long that pack powers my Pi in the next few hours but it looks like it will land around 146 hours. The only way I get the math to math while using the 130mA current draw number is with an efficiency number of 65%, which seems very low or by adjusting my per-cell capacity down to 4000mAh for Samsung branded cells from a reputable seller that are listed as 5,000mAh and marked as 4900mAh.
Without knowing for sure what the current draw is that is actually hitting the battery though, there's a lot of doubt left to sort out.
I guess the obvious answer is that I need to get a DC current meter of some kind that will measure as low as 2v and 100mA. If anyone can point me to one that isn't a five thousand dollar lab-grade power supply that would be appreciated! (or if there is another way to get what I need, I'm all ears).
Thank you in advance for any input!
I have a cheap USB-C multimeter and while running from wall power providing 5v to the whole setup, it draws about 130mA on average. It idles around 95-100mA and jumps up to 160mA or so during periodic higher activity. I don't know if this number translates to the draw from battery however. I assume the Pi itself is drawing the same current, but what I mean is that I'm not sure what current is actually hitting the batteries on the input side.
While on wall power and battery power both, I am running power into a Pi-UPS 2.0 hat that provides 3.3v and 5v to the Pi regardless of the input power. From the wall of course, there is a steady supply of 5v coming in so the Pi-UPS only has to pass through 5v and buck down to 3.3v. I am using a cellular hat and a camera, but unsure exactly what those are running on so I don't know what the mix is for the two voltages, but that may not matter.
While on battery power, the Pi-UPS board gets battery voltage in that ranges from 4.1 at the start down to 2.6 before it cuts off (Li-Ion packs). All the while, it boosts that to 5v and there is loss there, but I don't know exactly how much. (I've been estimating 80-85% efficiency, but no idea if that's reality)
I've done dozens of real world tests now and I've put together battery packs that give me a week of runtime, which meets my needs well. All I'm trying to do at this stage is document exactly what my packs are so I can vet them against other power options in the future.
For example, the battery pack I'm currently using is an 8-cell 21700-based pack that is rated at 39,200mAh (4900mAh for each cell). I'm about to know exactly how long that pack powers my Pi in the next few hours but it looks like it will land around 146 hours. The only way I get the math to math while using the 130mA current draw number is with an efficiency number of 65%, which seems very low or by adjusting my per-cell capacity down to 4000mAh for Samsung branded cells from a reputable seller that are listed as 5,000mAh and marked as 4900mAh.
Without knowing for sure what the current draw is that is actually hitting the battery though, there's a lot of doubt left to sort out.
I guess the obvious answer is that I need to get a DC current meter of some kind that will measure as low as 2v and 100mA. If anyone can point me to one that isn't a five thousand dollar lab-grade power supply that would be appreciated! (or if there is another way to get what I need, I'm all ears).
Thank you in advance for any input!
Statistics: Posted by archaic0 — Sun Nov 02, 2025 6:02 am