Estimating battery life with an instrument?

[mdredmond]

Hi folks,

I searched but didn't find anything...

I'm looking for an instrument that can help me estimate battery life for a device I'm designing.  This will be a sleepy device that spends most of its time in light or deep sleep, with occasional wake-ups to take sensor measurements and radio those to a server.   I think what I need is a "source measure unit" but I'm not familiar with these.  Ideally it would be something that powers my device and profiles current consumption and total mAh usage over time as the device does its thing.  My budget for such a thing would be sub-$10k USD.

Any ideas?

[tautech]

Welcome to the forum.

Joulescope is industry standard for this need.
https://www.joulescope.com/

[mahyarJbr]

Hi
you can use Fluke 289 True RMS Logging Multimeter you can buy it from Fluke website or websites like Amazon, mme-ae or aabtools

[Shonky]

What supply voltage and current do you need to measure?

At the very cheap end of the scale a Nordic Power Profiler can do up to 1A at 5V so for a single cell lithium coin cell or single Li-Ion kind of device it could do what you need. It auto ranges down to about 100nA precision.

Its under USD100 but might do what you need - you haven't really detailed your power requirements.

[pdenisowski]

https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_application/pdfs/Predict-the-lifetime-of-your-battery_ac_en_3684-0299-92_v0100.pdf

https://www.rohde-schwarz.com/us/applications/power-consumption-analysis-tool-for-r-s-ngx-power-supplies-application-note_56280-1171639.html

https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_application/application_notes/1sl380/1SL380_e_Power_Consumption_Analysis_Tool.pdf



An NGM should be sufficient (and cheaper than an NGU) for this application.

[Psi]

If you want something cheaper than buying expensive test equipment you can get a super cap, characterize its exact capacity and how much energy it loses in self discharge over a set time, then charge it up to a known voltage and connect it to your device instead of a battery. Use your device for a while to represent typical usage over a preset timeframe and then check the voltage again and calculate energy lost in the cap to work out what the average current draw was over that time. Then extrapolate how long your product will last on a battery of capacity X.

Obviously cap size will depend on how long you need the test to last, which will depend on your product and it's use case.

Its definitely not the best way to measure it, but sometimes you have to make do with what you have.

However, the Jouelscope is an awesome product if you can afford it

[Someone]

If you want something cheaper than buying expensive test equipment you can get a super cap, characterize its exact capacity and how much energy it loses in self discharge over a set time, then charge it up the a known voltage and connect it to your device instead of a battery. Use your device for a while to represent typical usage over a preset timeframe and then check the voltage again and calculate energy lost in the cap to work out what the average current draw was over that time. Then extrapolate how long your product will last on a battery of capacity X.

Big capacitor + current limited regulator and a coulomb counter is an another route. An integrated device that provides all that was recently posted on the forum: https://www.eevblog.com/forum/dodgy-technology/nexperia-battery-life-booster-for-iot/