Li-Ion battery pack for Tektronix 222 and 224 - Page 1
Forum section: electronics / projects

author: kitsune-denshi
author_rank: Contributor
timestamp: May 30, 2016, 02:47:43 pm
content: A few months ago I acquired a Tektronix 222 oscilloscope, and as expected the SLA battery was completely dead. It also didn't look like there was much in the way of a direct replacement, so I thought it would be a nice challenge to build a module that will allow to use the scope with standard 18650 Li-Ion cells.Well, here is the result:It's quite a simple circuit in principle: There is a battery charger to charge the Li-Ion cells, and a boost converter to step up the battery voltage to the 8V required by the scope. When the scope is plugged in, it will output 9.5V on its battery connector to charge the battery. The circuit simply detects this voltage level, and switches between the charger when the scope is plugged in, and the boost converter otherwise. On a high level, it looks like this:There are obviously a few other little additions like cell protection, and quite a few interesting design trade-offs along the way. Being well aware that this is a shameless plug, I have written up a rather more detailed description on my website (http://kitsune-denshi.net/projects:tek222bat), where you can also find the schematics, BOM and everything else you might be interested in. Component cost for the circuit was around £20, plus boards and laser cut acrylic for the case. Not too bad in my opinion to make the scope battery powered again.When doing my initial research, I came across quite a few people who seemed to have similar difficulties with finding replacement batteries - so maybe this module will be of interest to someone else tooIf you do want to build your own, I have a bunch of bare boards left over and would be happy to send them out to people. Be aware that some minor bodges are required to get the boards working, though.Let me know that you think, I'm keen to hear some opinions on this project.

author: aix
author_rank: Regular Contributor
timestamp: January 24, 2020, 07:12:13 pm
content: Just wanted to say thanks to the OP on behalf of my two 224 scopes, which are now very happy.One trap for young players is that Diodes Inc makes AP9101C in both SOT25 and SOT26 packages,with incompatible pinouts. Wasted more time on figuring that one out than I'd care to admit.

author: n0dyjeff
author_rank: Newbie
timestamp: May 27, 2020, 06:09:02 pm
content: I wanted to let folks interested in this project know that a kit is now available. The kit consists of one assembled and tested battery charger circuit board, one 3D printed case, and some miscellaneous parts such as light pipes to bring the LED indicators to the front of the case and a jumper cable to attach to the scope's battery connector. The kit does not include rechargeable 18650 lithium batteries (required for operation).It's available on eBay (search the SLA battery P/N 146-0075-00) or via my web sitehttps://www.n0dy.com/product/tekcharger/Full attributions and credits are on those sites.

author: pivous
author_rank: Newbie
timestamp: May 10, 2023, 09:00:24 am
content: I'm building a brilliant "Tektronix 222 Battery Adapter," and I've found a discrepancy in the values of two resistors. The first question is regarding resistor R29. The schematic shows a value of 560 Ohms, but the component list states 1 Megaohm. The second question concerns resistor R9, which has a value of only 330 Ohms in the schematic. However, identical resistors R11 and R13 have a value of 390 Ohms. Does anyone know what is correct?

author: wasedadoc
author_rank: Super Contributor
timestamp: May 10, 2023, 04:59:08 pm
content: Quote from: pivous on May 10, 2023, 09:00:24 amTypo or some other error in what you wrote there.

author: tooki
author_rank: Super Contributor
timestamp: May 10, 2023, 05:30:06 pm
content: Quote from: n0dyjeff on May 27, 2020, 06:09:02 pmVery cool.Just a lil tip though: maybe not use a picture that shows a unit with the inductor snapped off!Also, kitsune denshi’s website appears to be gone.If you have an alternative link or source for the schematic, that’d be cool!

author: pivous
author_rank: Newbie
timestamp: May 11, 2023, 06:01:14 am
content: Thanks, I corrected the post. R9=330, R11=R13=390 in the original schematic. I added the schamatic as attachement

author: hiwi
author_rank: Newbie
timestamp: June 26, 2025, 03:36:48 pm
content: Although it is an old post, i have parts to build this charger.So is the question about the resistors answered?Looking into the datasheet, 1 MOhm for the shutdown line is the correct value not 560 Ohm. This is a typo in the schematics. The value for R9 as 330Ohm instead of 390 make no sense for me, but I assume the value is not that critical. See datasheet of th LiIon protection ic.The kits are not available nay more and some parts are obsolet.Ralf

author: edavid
author_rank: Super Contributor
timestamp: June 26, 2025, 04:52:12 pm
content: Quote from: tooki on May 10, 2023, 05:30:06 pmThe current location is:http://kitsune-denshi.net/doku.php?id=projects:tek222bat