8.4 volts sounds like exactly 2 cells (they go to 4.2v max each), meaning one out of three is not connected or has gone bad. Like I said: measure each individually, measure the sum of the raw cells, measure the output of the BMS, that way you can tell what has gone bad.
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You got it. Looks like one of these wonât take a charge. Well, at least Iâm learning a lot about the fine art of making battery packs. Thanks again!
yeah, any one here open up a MK1 to see if theres room inside?
Iâm pretty sure the layout in Octatrack MK1 is the same as inside MK2 and 18650 batteries would fit (not 20760 though).
But thereâs another problem, MK1 uses exotic 6V power, so the same 3-battery configuration wonât work. Maybe you could go with AA-sized batteries, as they deliver around 1.2-1.5v, but I have no clue what stock BMS you could use for that.
Rytm has a 12V 2.5A output power supply
ive got a 3 x 21700 (5000mah) battery pack and wanted to see if its worth opening my rytm for
Hereâs my semi-simple solution. Itâs bit more âoff the shelfâ if you donât have a 3D printer, and keeps you from soldering right to cells, which I found out you should never do - and I did do with my first failed pack. You will need a soldering iron though for the BMS.
I bought some premade 18650 pair holders on the Amazon, fused and glued them together to make a small pack, then wired everything up. The nice thing here is that you can replace the batteries very easily. As newer, higher-capacity packs come out, you could just grab new cells.
Iâm using some cells that are maybe 2200mAh or so and Iâm getting about 2 hours of play time. Not stellar, but enough for some couch play time. I ordered up some 3500mAh capacity cells to see what I getâŚthree hours would be quite nice. Six cells would be better, but 3 is doing the trick for now.!
These are the holders I bought. I think they came in a 10 pack.
Glued them together into a 4 pack and fused in between them with a soldering iron.
The reverse side has pegs so you can wire them in series very easily. I bent these down and soldered right to them.
The pack in place with extra room. Not enough for another holder. Wrapped things up and used a little VHB tape to secure it to the front face. Be sure to wrap your pack very carefully to prevent shorts. And of course, Iâm sure this will void your warranty.
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Very interested in this!!
And a speaker so you can really piss people on the plane off
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Say I didnât mind making holes in the metal frame of the digitakt,
Would this work as an alternative if I used a 12v ripcord? Wouldnât mind charging the OPZ at the same time
Nice work man. Easier than what I do for sure. Youâre right that soldering on 18650âs is not recommended, spot welding is the only way to go, but you can do that cheaply with a motorcycle battery and a solenoid (i do it).
Some thoughts on your design:
-You really donât need such thick gauge wire. Those batteries will charge at 2A max, and the Digitakt peaks at 1.2A draw on startup. Similarly, no need for those super-beefy XT60 connectors, simple red JST ones do just fine, those are rated up to 3A.
-I wouldnât trust just the VHB to hold that pack in place. Itâll come loose eventually. Iâd squeeze a piece of foam above it, against the controller board, or something similar.
My DIY pack failed recently, looks like the cells totally went out of balance, not sure how that could happen, the BMS must not be doing a decent job. Iâm manually recharging them to see if I can bring it back.
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Thanks! I was inspired by what youâre doing. It actually led to a whole odyssey of learning about 18650 cells, and BMSs and powerwalls and all this crazy stuff. Itâs been an interesting summer TSTL.
Looks valid. I donât know if youâll be able to use this holder though, you may need to mod it slightly. Other then that, should work.
Try first putting batteries in the holder, put the whole thing into Octa and see if thereâs enough space. Vertically there might be not enough due to crossfader placement.
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200g is the amount of cheese I eat in a sitting. a reasonable amount.
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These look more flexible, yes. Youâll need 6 of these though, I assume. Three on each side of the pack.
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Yes. Thanks a lot!
What happens when the battery runs out. Does it shut off immediately or does it sort of fade out when the battery gets low? 
It freezes. If you try to restart it, it doesnât go past loading screen.
I assume thereâs underpower protection and this is how itâs implemented.
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Ah ok. And if you plug in the power, does it unfreeze?
Thanks