Equipment advice: Battery lifetime testing - Page 1
Forum section: electronics / testgear

author: tszaboo
author_rank: Super Contributor
timestamp: February 18, 2019, 11:29:15 am
content: Do you know equipment, that measures the power usage of some DUT? I know this is typically very simple, however I have some requirements.The sleep current is around 20uA, with occasional RF transmission, up to 2A pulses should be measured.If it simulates battery behaviour, with internal resistance it is better.The mAh or mAs is important.We used a bench multimeters to do this kind of testing, but the overhead for calculating the actual usage is too long. We want to do this testing each time a new firmware is released, so the less time we have to spend on it the better.And the drop on internal shunts is not really acceptable. And there is also the problem of slow sample rate.One candidate I'm looking at is the Keithley 2281S-20-6 Precision DC Supply and Battery Simulator. We have it's small brother, the Keithley 2280S. I think the difference between them is mainly software, maybe it is the extra battery discharge unit? Doesnt matter that much, it is a nice equipment in theory, slightly inconvenient to use in practice. To be honest, all the recent Keithley equipment was a slight disappointment, and I'm somewhat reluctant to spend more money at them.At this point I can convince management to spend a few thousand euros on this equipment (that is a few+1 thousand USD).Do you guys know anything else that can be used for such purposes? I never had an SMU, is that something that can do these tests? Or probably an overkill.

author: Kean
author_rank: Unknown
timestamp: February 18, 2019, 01:31:56 pm
content: Qoitech Ottihttps://www.qoitech.com/A couple of forum discussions here about it - the big negative for most is the annual licensing model for the softwarehttps://www.eevblog.com/forum/testgear/qoitech-otii/https://www.eevblog.com/forum/testgear/battery-energy-consumption-how-to-measure-it/

author: genghisnico13
author_rank: Regular Contributor
timestamp: February 18, 2019, 02:00:00 pm
content: This previous thread has a couple of options:https://www.eevblog.com/forum/testgear/battery-energy-consumption-how-to-measure-it/

author: tszaboo
author_rank: Super Contributor
timestamp: February 18, 2019, 03:10:41 pm
content: Quote from: Kean on February 18, 2019, 01:31:56 pmOtti: Looks interesting, though the sample rate is not great. I think I visit them for a demo next week in Nürnberg.Also, to cover all the equipment we sell, it would need 15V output.Lots of good info in the thread, the Rhode equipment is also interesting, though probably obsolete. I will pay them a visit also anyway.

author: Kean
author_rank: Unknown
timestamp: February 18, 2019, 03:57:57 pm
content: Great, please come back here and let us know what you discover - good and bad.I'd also like more than 5V capability to cover my various projects (in particular 2S LiFePO4 and maybe 4S LiIon).I've been considering the ITech IT6411 which is similar to the Keithley 2281S.

author: tszaboo
author_rank: Super Contributor
timestamp: February 19, 2019, 09:24:58 am
content: Quote from: Kean on February 18, 2019, 03:57:57 pmThose Itech units seem to be OK on first sight, but if you go into details, it falls apart.It has two ranges, on the high range (5A) the resolution of current is 1mA, that is 13-14 bits. Not very promising. And it doesnt say anything about range switching. This is from the user guide:Sample Rate Sample rate: 30KHZ at maximumSample Count: Sample count: 600 points at maximumSo what happens after the 600 samples? Anyway, the soft specs seems to be quite lackluster.That being said, I was designing similar equipment in the past, it is not easy to do high accuracy high and sample rate at the same time.

author: jeremy
author_rank: Super Contributor
timestamp: February 19, 2019, 10:56:31 am
content: Best one I’ve found is Keysight N6781A. 20V@1A (or 6V@3A), 200kHz, unlimited sample streaming. Only downside is the pricebut I have one and it does the job.I have an older Keithley as well, but it’s very limited in sample rate.

author: mliberty
author_rank: Contributor
timestamp: February 19, 2019, 06:53:42 pm
content: I know the perfect test instrument for measuring energy consumption, Joulescope, and I justposted about it. (disclosure: I am the creator of Joulescope).Joulescope does not do battery simulation (it's not a power supply), but you can use it with a real battery or battery simulator. I created Joulescope because I faced this same problem! Existing gear is too expensive or not good enough (usually too low bandwidth and too high burden voltage).What do you think?

author: tszaboo
author_rank: Super Contributor
timestamp: February 20, 2019, 09:10:27 am
content: Quote from: mliberty on February 19, 2019, 06:53:42 pmIt is a smart device. Looks to be perfectly tailor made for such projects.Are you planning on operating a webstore after the kickstarter? I might purchase one or two, because this would suit our needs perfectly.

author: mliberty
author_rank: Contributor
timestamp: February 20, 2019, 12:55:58 pm
content: I am planning on having preorders and then a full webstore after general availability. The Kickstarter is a great discount off the retail price, so it's worth considering! If you want to wait, I recommend that you visit theJoulescope websiteand sign up for the newsletter. As details become available, I'll send ordering information through the newsletter.

author: BitWrangler1001
author_rank: Contributor
timestamp: February 20, 2019, 02:50:22 pm
content: Quote from: mliberty on February 20, 2019, 12:55:58 pmDoes the joulescope do real-time 2Msample/s to RAM or HDD?Thanks

author: mliberty
author_rank: Contributor
timestamp: February 20, 2019, 02:56:13 pm
content: Quote from: BitWrangler1001 on February 20, 2019, 02:50:22 pmYes!Joulescope captures to a 30 second RAM buffer by default. In the user interface, you can press the "record" button to simultaneously record to HDD/SSD. The recording size is only limited by your storage. Full rate captures are about 8.5 MB/s, which gets big pretty quick. We will add a downsampling feature (for when you don't need full rate data) before July to enable longer captures that take less storage.

author: tszaboo
author_rank: Super Contributor
timestamp: February 20, 2019, 03:01:58 pm
content: Quote from: mliberty on February 20, 2019, 12:55:58 pmThanks. I wish you success, but I hope you understand that I am getting this for a company.So invoice, delivery and payment terms, all the boring things are necessary.

author: BitWrangler1001
author_rank: Contributor
timestamp: February 20, 2019, 03:05:29 pm
content: Quote from: mliberty on February 20, 2019, 02:56:13 pmThat's great, also, is there some interface so I can stream data into a python program? Or will the program have to read the data from a file instead?Thanks

author: mliberty
author_rank: Contributor
timestamp: February 20, 2019, 03:17:50 pm
content: Quote from: BitWrangler1001 on February 20, 2019, 03:05:29 pmJoulescope is made to be integrated into your own python program! The Joulescope "driver" in python is open source onGitHub, and you can install it using pypi:Code:pip install joulescopeLook atthis example scriptwhich finds a Joulescope, opens it, and records to a file. If you want to deal with streaming data, like the UI does, you can do that, too. You have a few options, but the easiest is to periodically poll the stream buffer for new data.

author: BitWrangler1001
author_rank: Contributor
timestamp: February 20, 2019, 03:23:32 pm
content: Quote from: mliberty on February 20, 2019, 03:17:50 pmWow! 1us range change time, seems to good to be true, makes me suspiciousI look forward to trying it

author: mliberty
author_rank: Contributor
timestamp: February 20, 2019, 04:19:43 pm
content: Quote from: BitWrangler1001 on February 20, 2019, 03:23:32 pmYou are right to be suspicious, and it's great to hear! Makes me feel better about taking 2 years to develop JoulescopeI have a custom load board that has a 1 mega-ohm resistor in parallel with a 1 Ohm resistor. The 1 ohm resistor can be switched on/off by a fast MOSFET and gate driver in under 200 ns. I set my power supply to 1V with a 2A limit and captured the attached plots going from 1 microamp to 1 amp. Notice that the total duration between the markers is the two images is 4 microseconds. Joulescope goes from the 18 microamp range with a 1000 Ohm shunt to the 2 amp range with 0.01 Ohm shunt about 1 microseconds (it's actually very hard to measure on the Joulescope output - but it's more fun to see here!). Note that the voltage drop is between IN+ and IN- and has nothing to do with the Joulescope shunt resistor - this is cable inductance!Questions? Still suspicious?

author: BitWrangler1001
author_rank: Contributor
timestamp: February 20, 2019, 05:02:29 pm
content: Quote from: mliberty on February 20, 2019, 04:19:43 pmIt's very impressive, and certainly fills the void that has existed for a while in the IoT space.Can the UI zoom into that current edge? Perhaps just view 10 pts so we can look at the glitches?Have any more kind of real-world examples, like a SoC BLE chip profile example? The 18mA is the sweet spot when RF circuitry activated for many of the BLE devices I've used.Would be nice to see a shot of a BLE SoC in polling advertise mode, then to an active data send mode, and then back to idle advertisement mode.Always suspicious

author: mliberty
author_rank: Contributor
timestamp: February 20, 2019, 05:22:03 pm
content: Thanks! It's been great to hear stories from lots of other people that have struggled with energy measurement & optimization!The UI zoom is currently limited to 1 sample per pixel. If you want to really see the glitches, you really need multiple captures since timing varies. I'll see what I can do...I don't have a BLE example, and I haven't worked on BLE recently. Do you have a specific dev board + example code + system setup that you would like to see?

author: mliberty
author_rank: Contributor
timestamp: February 26, 2019, 11:25:40 pm
content: Quote from: BitWrangler1001 on February 20, 2019, 05:02:29 pmI measured the Joulescope step response in a way that can be replicated with reasonable ease, and I posted theresults. Comments?

author: tszaboo
author_rank: Super Contributor
timestamp: February 27, 2019, 07:44:37 pm
content: Quote from: Kean on February 18, 2019, 03:57:57 pmOK, so I visited them and spent like 20 minutes talking to the guys, and checking out the equipment.It seems to be quite OK for the price, like it has the same capture window for the UART as the power measurement, so you can just send log messages on UART, synchronize the power measurement with it, or capture GPIO. It is a powerful unit, even without the battery capabilities. I think we will buy one to test, because honestly, the price is really good. I mean we pay something like 350 EUR for the TTI power supplies, for about 100 EUR extra, you get UART, ADC and a very easy to use software. OF course the power supply has more voltage and current, but I dont think it matters if your device is a battery powered microcontroller project. And then see how it goes from there, probably I have to convince the software guys that this is useful, use it.

author: supriyala
author_rank: Newbie
timestamp: February 28, 2019, 10:40:59 am
content: Excellent topic! I got lots of valuable information from here. Thank you.

author: Kean
author_rank: Unknown
timestamp: February 28, 2019, 04:55:14 pm
content: Quote from: NANDBlog on February 27, 2019, 07:44:37 pmThanks. Just to clarify... you are talking about the Otti here?

author: tszaboo
author_rank: Super Contributor
timestamp: February 28, 2019, 08:24:27 pm
content: Quote from: Kean on February 28, 2019, 04:55:14 pmyes

author: kaz911
author_rank: Super Contributor
timestamp: March 03, 2019, 09:46:40 pm
content: Quote from: NANDBlog on February 27, 2019, 07:44:37 pmI have the Otti and the weakness are1. Sample rate2. The annual charge for the premium "features" (Battery profiling; Battery simulation; Scripting & Automation; Importing debug logs. ) (Euro 400/year + VAT)Which is why I have pledged for Joulescopeas I will never subscribe to a set of product features on an annual basis.But apart from that the Otti is good even without the premium license but spec wise Joulescope is better. And I like the re-replaceable front panels. I just hope for USB-C connector vs the old type A. (Not USB-C PD but just normal "usb" power delivery just via the USB-C connector. I like them better than USB-A/B/Micro.

author: tszaboo
author_rank: Super Contributor
timestamp: March 04, 2019, 06:26:08 pm
content: Quote from: kaz911 on March 03, 2019, 09:46:40 pmWell, the guy explained that the sampling method they use (probably delta sigma) integrates the current, so if you have some short events, like short RF transmission, while you dont see the actual hight, it will still calculate the mAh used properly.Yes, the Julescope looks nice on paper, but it is not a final product, and it is something that you need with a power supply.Well, it is still far from Keysight, who told me that I should buy a N6705C, with some plug in modules for 8000. Or Rhode and Swartz, who said, buy all this:5000 only for the probe.

author: nctnico
author_rank: Super Contributor
timestamp: March 04, 2019, 10:40:31 pm
content: I think the point about integrating short spikes is a good one. A filter will just suppress short spikes giving a false reading.

author: mliberty
author_rank: Contributor
timestamp: March 04, 2019, 10:58:22 pm
content: Quote from: NANDBlog on March 04, 2019, 06:26:08 pmNot sure I get this point. That's like saying multimeters, oscilloscopes and logic analyzers are not final products. Joulescope is a measurement instrument that doesn't mess around -- it's easy-to-use and affordable with the performance you need.

author: tszaboo
author_rank: Super Contributor
timestamp: March 06, 2019, 05:29:34 pm
content: Quote from: mliberty on March 04, 2019, 10:58:22 pmCan you send me a Digikey link to buy it?

author: mliberty
author_rank: Contributor
timestamp: March 06, 2019, 06:47:36 pm
content: Quote from: NANDBlog on March 06, 2019, 05:29:34 pmDigikey, no. But if you or your company wants to buy a Joulescope beta unit at the full retail price, we have 1 left. Send me a direct message. Jetperch does provide an invoice and payment is by credit card. We have already sold some to companies who could not wait for the Kickstarter or July general availability. Ships within 2 business days upon receipt of payment using your choice of service from UPS, FedEx or USPS.Otherwise, we will have Joulescope preorders immediately following the Kickstarter for delivery in July, and we will have normal purchases in July. EU distribution still TBD (plan to have something by July), but you can always order for shipment from the USA.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: May 01, 2019, 09:25:08 am
content: Folks,There is a similar product already out on the market. ZS-2102-A from ZSCircuits. (Disclaimer : I'm the designer for this product)This USB powered unit has -1A to 1A range with better than 100nA resolution. (With averaging, the resolution is close to 1nA)With an accuracy of better than 1% +/- 1uA across the full range of -1A to 1A, the step response time is well within 2uS. So this can respond to fast transient currents common in WiFi devices.The current sampling rate is 1Msps, wheres the voltage sampling rate is 50Sps.It has a burden resistor of only 0.1 Ohm and there is no range switching.It sends data real-time to the PC over a USB bus and can capture profiles for more than 20 mins. (Actually tested for 1 hour)More info atwww.anglercircuits.com

author: cgroen
author_rank: Unknown
timestamp: July 01, 2019, 06:15:28 pm
content: NANDBlog,did you get any further with this (like buying some equipment) ?I'm also looking at the 2281S, it fits my budget nicely and I can't seem to find something similar (battery simulation) out there.Also ordering a Joulescope in a couple of days

author: tszaboo
author_rank: Super Contributor
timestamp: July 02, 2019, 03:47:01 pm
content: Quote from: cgroen on July 01, 2019, 06:15:28 pmYeah, I had the 2281S for a demo for a week. So alone it cannot create the model, you need an SMU for that. I wasnt satisfied with it, because in battery simulator mode, the current resolution is really low.In power supply mode, it has many ranges and it shows 3uA load perfectly, but in battery simulator, it is locked in the highest range (6A) and your resulution is 10uA.Also, by the looks of it, the ESR is simulated, so it takes a current measurement, and adjusts the voltage accordingly. Which is slow, hovewer probably an OK model if you have high currents for a long time.I think their target market is phones and other equipment with rechargeable battery. Definitely not my use case, I have devices with 10 year battery life.The salesman suggested buying a 2461 SMU, which has 1MSPS, the required range for current measurement, and spending a bunch of time writing scripts. But then again, that is already an expensive equipment.At this point, I think "two boxes" would solve the problem a lot easier than 1 box. I am talking about a power supply with sense lines and a current measurement device (probably multimeter). If it can compensate for the burden voltage, then it should be fine, and the statistics on multimeters should be enough.For sure, the Julescope would be interesting when it is available. Also, I guess mAh reading could be added. Otherwise I will ghetto-rig something together.

author: mliberty
author_rank: Contributor
timestamp: July 02, 2019, 04:04:33 pm
content: Quote from: NANDBlog onTodayat 01:47:01 amJoulescope is available, in stock and shipping now! You can purchase one athttps://shop.joulescope.com/. We have already shipped to all of our Kickstarter backers and preorder customers. We are shipping orders placed on the shop as of today.Disclaimer: I am the creator of Joulescope

author: cgroen
author_rank: Unknown
timestamp: July 02, 2019, 06:16:29 pm
content: Quote from: NANDBlog on July 02, 2019, 03:47:01 pmThanks NANDBlog,As far as I can tell, there are a number of csv files of "known" batteries for the 2281S, I hope I can cope with that and/or find someone with a 2450 that can get the data from a specific battery.I need something to act as a battery for some of the stuff I do, normally it is with LiIon (1S) around 2000 to 3000 mA/H and current drawn is usually around 20 mA when active and down to maybe 50 uA when sleeping.Quote from: mliberty on July 02, 2019, 04:04:33 pmI actually placed my order for a Joulescope today, so looking forward to getting my hands on it

author: tszaboo
author_rank: Super Contributor
timestamp: July 02, 2019, 07:23:17 pm
content: Quote from: cgroen on July 02, 2019, 06:16:29 pmThat might work, because the sales rep said that it still accumulates the data for low currents, just doesnt show it.Basically you have a CSV for a battery, for every % of SOC they measure an ESR, and votlage, and that's it. I would need to have at least a 3rd dimension, temperature. The voltage and the ESR of a battery changes a lot with temperature, and a 3.6V battery could be 2.4V at -40, with 3x the ESR. And my average current is below 10uA, so it showed 0 on the screen. Not very useful.But probably it is fine for consumer stuff with pouch cells, AAs or 18650s. Those dont last that long on their own anyway.

author: Kean
author_rank: Unknown
timestamp: July 03, 2019, 05:31:16 pm
content: I put off buying anything (apart from the Joulescope) for now. Nothing beats testing with real batteries, but it does take time.