The image I have is one provided by the Dev team. I don’t have any more information, that’s why I’m asking. There’s only one uConsole mainboard that i know of since the device just launched.
with all due respect, that was 4 paragraphs of generalizations with 0 new information.
you just told me what i already know.
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Yes J1 and J2 are identical headers (see attached image). With each connector presenting one 18650 cell to the main board after the basic protection.
Pin 1 & Pin 2 of J1 shorted together, so as to allow high current to flow through the small connector pins. Pin 3 & 4 shorted for the current return path. Same case for connector J2, which deals with the second 18650 cell.
So J1 presents 3.7v (pin1 &pin2 for +ve, pin3 and pin4 for -ve/GND) to main board from cell 1. Similarly, J2 presents a separate 3.7v to the main board from cell 2.
Since these connections are not just two cells in parallel, it is safe to assume that there is a some sort of battery balancing happening on the main board.
Like @Puddljumper90 was writing, it’s a good idea to wait for more schematics to get published.
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I was thinking as I read all that, it looks a lot like ChatGPT generated text to me. 
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If DevTerm and uConsole shares the same mainboard and battery module (which they should), the two 18650 cell is paralleled and not balanced, BMS is AXP228 on mainboard, communicate using I2C to core board and supported in Linux.
I’m considering using single battery to replace the battery module, but I’m not sure if the current is enough. a current measure is needed for picking right battery.
What do you mean by “they should” use the same main board and battery module? They don’t have to.
Are you saying that they are calling the main board “revision 5” for no reason? There can be design improvements 
My bad… I just realized it’s a new revision…
But DevTerm is still in produce, I still don’t think there will not be some big difference aside of smaller size and new layout, main component could be the same as old one to keep lower cost from design and inventory keep. Also, if a design is worked and tested on field, change it may have risk for themselves.
Let’s hope they got the “Loud “coil whine” noise” ruled out on uConsole…
Total capacity do not depend on on the battery are plugged.
Setting them in series or in parallel will change how high voltage, or oh much current you can drain from them
They use two connector to balance the load through the connectors, and if you want to know how it work on the other side, why haven’t you looked at the CPi mainboard schematic? It is clearly shown there how the batteries are connected:
The diodes are there to procect the DevTerm, not the batteries. Obviously there is a charger and monitor system on the mainboard, the battery board is just to connect them, nothing else.
The proper schematic is here:
PS: the mainboard on the uConsole and the DevTerm are identical.
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A small misconception… simply put Li battery in parallel is not balance, one BMS per battery is balance (or using a BMS that support detect and manage two cell)
(AXP228 in here is the BMS+PMIC, but it’s for one cell battery)
For DevTerm/uConsole, the easiest way to keep battery balanced is get two (almost) identical cell, this can be done by buying from same branch and do some test at home.
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ah, good to know they’re identical, thank you.
also thanks for the circuit diagrams, that’s super nice to have!
I’ve taken a look at it and it seems that the way they’ve set up the power circuity makes it interesting. there’s no hardware BMS per say, it goes though a USB fast charging IC (AXP228) which sends the battery voltage off to other integrated devices for their own power handling purposes as VBAT, then sends off the 3.3v and 5v lines for everything else.
given the devices specs, It’s possible to mess around with the power output to an extent, though im not sure if i want to trust the AXP228’s OCP to protect the board if i were to charge the batteries from another source.
whats interesting is that this chip supports LiPo charging, (like many 1S BMS boards) so it might be possible to change the system to run on LiPo instead of Lion which could give you more battery in a smaller space, and remove the potential for unbalanced cells.
Need to do more reading on the AXP228
tell me if I’m off my rocker; I ain’t an engineer, i just know enough to be dangerous 
here’s the spec sheet I’ve found:
http://www.enimac.si/images/pdf/AXP228.pdf
nope, no balancing at all!
VBAT connects directly from the charging IC to both batteries unbalanced.
im assuming the reason for that is because almost all balancing circuits require the batteries to be in series which would make the voltage too high to use the integrated charging IC OR the integrated battery level sense lines on the wifi module or the LPDRAM.
the more I look at this the more it looks like a LiPo would have been a way BETTER option from design standpoint, but due to global logistics and laws, Li-Ion would be more cheaply available for more users, so they went with Li-Ion.
As an electrical engineer, putting just two cells in parallel would force them to be balanced. If you put two cells in series, that is where you end up with a problem. During charging, the cell with the lower voltage would get less energy. That cell would then discharge faster and run out before the better cell. That would force the cells out of balance. Can’t happen on the uConsole or DevTerm.
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well, I learned something new today!
I guess i never deal with low enough voltage devices.
I learn new things all the time, but then I am old. Worked 25 years in manufacturing where we made battery chargers (big ones). While doing that finished a Masters in EE and also eventually a PhD. Switched to teaching in 2006, have been teaching EE for 16+ years now.
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I started out in Chemical Engineering - but had issues with the tedium of it (and make a mistake in lab and you have to start over) . I think electronics is the most challenging subject to teach. Especially electromagnetism … I found Mechanical subjects more easy to comprehend but my issue with mechanical design is that it must fit - electrical power it’s cut to fit paint to match - pull the wire and trim to fit 
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I started in Computer Science, got my BS in 1980. Took me 9 years to get my Masters in EE and another 12 years to get my PhD in 2001. Electromagnetic fields and waves are not one of the things I do well. Lucky for me, I don’t teach that class.
I have a BS in Controls and Instrumentation - , I’m a general in Amateur radio - electromagnetism made more sense when I started building antenna’s … build Arduino’s circuits, ESP32’s etc. , 12 volt boxes (lipo4fe’s) I feel better knowing others struggled with the subject…
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For processors, I have been playing with the RP2040. Done several designs with them and they do work really well. I have a few ESP32s sitting around, but don’t work with them much. The embedded systems class is using the MSP430 series and I have done a bunch of projects with those. Still do a few ATMEGA328 designs here and there, the first year students work with Arduinos and Juniors need to design and build a processor. I did pick up a pile of CH32V003 chips, in quantity they are like $0.10 each. These are RISC-V chips, but I just haven’t had time to get the tool chain up. My office is moving this August and I need to clean house.
I suppose all we can do now is wait and see what’s on the docs for the final version of UConsole when it ships (since Git is empty at time of post).
I know it’s SUPPOSED to be the same as Devterm, but “Supposed” and “Should” are dangerous words.
That is an assumption, but the power section of the DevTerm seems to work just fine so unless you can’t get parts you stay with it. In large volume manufacturing, you redesign it to save money. They just aren’t making enough units to justify the cost of redesign.
True, though in the present day availability problems are massive and parts cost fluctuates wildly. It wouldn’t surprise me if there were some revisions due to parts being hard to get or their cost quadrupling.
though i doubt the AXP228 will change as it seems to meet their spec of 2.2A USB charging at insanely high efficiency levels (claimed 98%) and seems readily available.
I just need to see if there’s anything i need to change to make it charge Li-Po instead.
I intend to make heavy modifications to the Uconsole. Im honestly buying it for the keyboard and track ball more than anything and the fact that i can run a CM4 core which brings me into ‘standard hardware land’ so I don’t need to fight with proprietary drivers out the ass (looking at you Mali).
but the first thing to be changed in the battery(s) for sure.