Products > Test Equipment
Battery simulators NGM202 vs BCS6401
pdenisowski:
--- Quote from: Geofrey on June 15, 2024, 09:33:22 pm ---By bandwidth I meant like for scopes, which typically have a bandwidth lower than the sampling rate to avoid aliasing. I would like to know if fast log mode is susceptible to aliasing. Or maybe that is not applicable to the logging of a PSU, or the values logged are the average since last log point, can you clarify ?
--- End quote ---
It's a good question: I haven't seen power supply logging specified in terms of bandwidth - it's basically simply taking N samples per second and as long as Nyquist is being observed (and I'm sure it is), then there won't be any issues with aliasing. In the specification sheet we specify logging rate and voltage / current measurement accuracy (which is the same as the readback accuracy), so this would necessarily include any other effects as well.
*I did some looking around and I couldn't find a benchtop power supply manufacturer who specifies logging accuracy in terms of bandwidth - most also seem to say it's the same as readback accuracy (and several don't specify it at all).
Geofrey:
So I finally went with the BCS6401. Sorry @pdenisowski, the NGM202 looked really nice, but the price and 3+3A max instead of 5+5A definitely played a part in the decision.
I did also consider a pair of Otii Ace Pro. I had a nice demo from Qoitech. This seems quite capable also, but the extra software licensing model broke the deal. At least it is quite usable without extra license (that was not the case on the non Pro models) and there is a perpetual licensing scheme available, but the battery simulation software is one of the extras, automation is the other. The battery part I can understand, even if that puts the solution right between the BCS6401 and the NGM202 in terms of cost, but 50€/month or 2500€ perpetual for automation which is something you can relatively easily achieve through SCPI commands on every other instruments is a bit meh. The Otiis also need to be tethered to a PC to work, that can be an hindrance.
About the BCS6401, it's not really perfect : ergonomics and usability could be improved. A small non touch screen is not the best. The UI is responsive enough but quite slow to navigate. The worst part is that there is no way to set an arbitrary SoC to go to on your battery profile, neither you can freeze the profile to that SoC. The only option is to reset to the first point of your battery profile. So if you want to simulate end of charge, you need to import a profile starting at 90% SoC and going upwards. If you want to do a full discharge, another profile starting at 100% and going downwards. Want to do a full charge ? Another profile. Work at mid SoC : yet another one. I find that pretty insane.
It's also not silent. Okish at low currents but loud as soon as the first fan speed step up, which happen when one of the channels cross 1A.
The crossover between low and high current ranges is at 5mA, and it's a 1000x step in current readback resolution. Given that, the readback resolution is a bit poor in the 5 to 100mA range.
All being said, I decided to keep it. Having the source+sink capability is really nice, and SCPI commands should let me use some scripts to improve on the usability.
I did manage to connect it to HKJ's TestController software. For the moment I did the configuration files for basic readback only. I will push it as soon as I get the time to make it a bit more complete.
Kean:
Congrats on the purchase. Let us know how you find it after you get to know it better.
Just for reference, BK Precision products are almost always rebadges. I believe that the BK BCS6401 is a rebadged ITECH IT6412.
See https://www.itechate.com/en/product/dc-power-supply/IT6400.html
I looked at a few options over the last few years, but all were out of my price range. I almost bought a refurbished Keithley 2281S, but missed out after overthinking the purchase.
Early last year I managed to snag a 2nd hand Keithley 2306 on eBay at a good price, and I could not get it to reproduce the described fault (over temp warnings). It just needed recalibration, which I did myself. The fans are horribly noisy though, and I've yet to write any scripts to properly simulate battery SoC.
On a day to day basis, I use a pretty simple "battery simulator" (2-quadrant PSU) that I designed myself - although that is limited to 9V 1A source, and 300mA sink. It has a SCPI-like USB serial interface, and no other UI other than a couple of status LEDs. Accuracy is pretty low, but it is more than good enough for my typical "long term" testing, and more importantly for automated firmware and manufacturing testing. And it is very cheap to build, so I have half a dozen or so.
Geofrey:
Thanks Kean. The ITECH IT6412 certainly looks very similar, and the series shows interesting different combinations of voltages/currents. And yeah, when you need a fleet of device and have the time for a side project, DIY is compelling. Actually the first electronic project I did was a high current (60A charge, 40A discharge) battery tester/cycler, with the ability to set arbitrary current cycles, to evaluate cells on a realistic use case, including high power regen peaks. Full of flaws, which is not surprising considering it was my first ever electronics design and was self taught on this field. No way I could afford anything off the shelf at that time. I'm still using 25A/25A cheaper BOM derivatives now, 10 years later, 24/24h 7/7d for more basic cycle life assessment of cells following different use profiles.
I completed the device file for HKJ's TestController, with enough stuff to do SoC and iR curves with it.
Note to users : as is, the 4th command in a row in a script get ignored, unless a delay is added after the 3rd command. For example :
--- Code: ---=setVoltage(ps,4.2)
=setCurrent(ps,1.5)
=setResistance(ps,0)
#delay 0.5
=setOn(ps,1)
--- End code ---
is ok, but without the #delay 0.5, =setOn(ps,1) is ignored.
makahdz:
Hi Geofrey,
Maria, Product Specialist at Qoitech over here. Thanks for your feedback and for considering Otii Ace Pro in your evaluation! I wanted to clarify a few points regarding Qoitech licensing model, as I noticed some of the concerns you raised might be based on previous conditions.
First, even though the “Pro” naming is still used (which is simply meant to indicate “professional”), the software licenses you mentioned are no longer required for basic use. Now, all Otii instrument versions—can be used completely free with the Otii 3 Desktop App. This includes using the app for tasks such as power profiling and measurements, debugging over UART (RX/TX), and battery life estimation with no restrictions on the number or duration time of recordings.
Additionally, if you don’t have your Otii instrument at hand but want to analyze an existing .otii3 project, you can easily do so by downloading the app for free, opening the project, and navigating through the data without any limitations.
The Otii Toolbox features (like Battery, and Automation) are specialized add-ons designed to enhance the software’s capabilities for more complex tasks. These tools are managed under a subscription-based model—offered monthly, annually, or as a perpetual license. They’re optional but can significantly streamline your workflow when working on in-depth battery emulation and automated testing.
If you’re interested in more details about the latest changes to the license model, feel free to check out this post for all the updates: https://www.qoitech.com/blog/license-model/
I hope this clarifies things a bit more!
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