My DSO138 battery mod (fit 3000mAh Li-Po in existing case, $7 total) - Page 1
Forum section: electronics / projects

author: John_doe
author_rank: Regular Contributor
timestamp: May 13, 2019, 06:08:12 am
content: Before I even start, here are some photos:Parts list:1. 3000mAh 357095 Rechargeable li-Po Battery [$4.35 @ Aliexpress] (was $3.38 when I purchased it)1a. (Optional) 1800mAh 306070 Rechargeable li-Po Battery [$4.00 @ Aliexpress] (was $3.03 when I purchased it)2. MT3608 DC-DC Adjustable Step Up Module 2A [$0.39 @ Aliexpress]3. TP4056 1A Li-po Battery Charger Module (Clone) [$0.25 @ Aliexpress]4. 1S Lithium Battery Capacity LED Indicator Module [$0.76 @ Aliexpress]5. SS12F15VG4 SPST Slide Switch [$0.68 @ Aliexpress]6. 50PCS M3 Nylon Hex Nuts [$0.60 @ Aliexpress]--------Total cost: $7.03 USD.Used but not included in the cost:- DSO138 "toy" oscilloscope (clone, not by JYE) [~$13 assembled]- DSO138 acrylic enclosure [$3.91 @ Aliexpress]- M3 washers [$0.69 @ Aliexpress]- Some resistors- 2 pin female header for the J9 connector (2.54mm pitch)- Tools (Wire cutter, soldering iron, cordless drill, drill bits, etc)- Materials (Wires, solder, various adhesives, etc)Hello everyone, I just finished this modification and I thought I'd share it here.I had a DSO138 and an acrylic enclosure and I noticed there was a 5mm gap in the bottom. I thought I'd try to fit a Li-Po battery in there so I bought 2 batteries: 3000mAh 357095 (95mmx70mmx3.5mm) and in case it would be too big I bought a smaller battery as a backup - 1800mAh 306070 (70mmx60mmx3mm). I planned to put everything on the bottom but when the batteries arrived I realized that that would be easy for the 1800mAh battery, but I was curious if I could fit the 3000mAh battery on the bottom and all the modules elsewhere (Spoiler alert: I could).I started by cutting all the solder joints on the underside of the PCB with a $1.4fakePlato 170 wire cutter, the plan was to then sandpaper it to flatten it more but the fake Plato did such a good job that I didn't have to.Next I cut a piece of thin (~1mm) plastic from a food storage box (Polypropylene) and attached it to the now-flat PCB underside to protect the battery. I attached the battery to the case with some double-sided adhesive tape. Then I attached the slide switch to the PCB with some E8000 glue. I had this slide switch for many years so I don't know the exact model, but the one I linked in the parts list should work just as well, I believe.I googled and found a post by someone from JYE Tech saying that the on-board mini USB connector is unused and can be used for battery charging:https://jyetech.com/forum/viewtopic.php?t=697So I soldered wires to Vbus (Test Point 33 in the manual) and GND:I used 2 nylon nuts between each layer of the acrylic enclosure. On the 1st layer I've put both modules (TP4056 and MT3608) with double-sided adhesive tape. I had to modify both of them.TP4056:The module comes with Rprog value of 1.2K ohm for 1A charge current, but this makes it very hot. I changed Rprog to 1.5K ohm for 780mAh current to reduce temperature:MT3608:The potentiometer (trimmer) is too big to fit in the case. I removed it and replaced it with a voltage divider of 47K and 3.3K which gives me exactly 9.3V.See the MT3608 datasheet for Vout calculation (my Vref is 0.609V):I used 0.25W resistors, they do fit but just barely so. 0.125W or SMD resistors will do better.I drilled two holes in the enclosure, one for the slide switch and one to pass the wires through to the battery capacity indicator.Finally, I attached the battery capacity indicator to the side with some hot glue.Note: The nuts (and washers) are necessary to space the acrylic layers correctly, they don't have to be made of plastic, metal nuts can be used as well.The original acrylic enclosure has 2 identical layers, one of these is used only as a spacer and can be safely discarded (the nuts are used in it's place):Afterthoughts:1. I connected the slide switch directly to the battery because I wanted to minimize leakage current but this poses 2 problems: The battery capacity indicator can only work when the device is turned on, but more critically, the battery can only be charged when the device is turned on and that is a big problem because around 500mA of the 780mA charge current will be wasted on running the DSO138.After completing this mod I checked the components for leakage current and the TP4056 module gave around 600nA while the battery capacity indicator didn't even register any current on my UT139C.So in hindsight that was a big mistake. I should've connected the slide switch between the TP4056 and the MT3608 like so:When I can be bothered, I'll re-open the case and rewire the switch.2. I haven't charged the battery yet (because it's still full) but I suspect that 780mA will get the TP4056 module warm enough to soften the double-sided tape and detach it from the case. Sure, it was cool enough in the winter open air but inside the case it'll probably get hotter. Maybe I should've put a 2K resistor for 580mA charge current.That's all, I hope this helps someone else who's thinking about making their DSO138 portable.