I did a search of The Crucible, and Google, and couldn’t find anything like this. I just finished installing a Desert Wanderer with the ECO-CC chassis and everything works; the crystal accent pixels light and behave according to the coded styles, the Shtok v3 connectors in the emitter and on the chassis light and behave as expected and the blade lights as expected. All functionality is present, but when the passive battery monitor displays on the blade, or when the battery level is checked it always reports that the battery is at 100%.
I did check voltage on the battery and across the BATT+ and BATT- pads on the board itself and get the same voltage (about 3.8V when it was measured). I tried multiple batteries that were known to not be at 100%, one was reading at 55% in its saber, but was reported as 100% in the Desert Wanderer. Conversely, the battery in the Desert Wanderer, when put in another saber, does get read as having been discharged to some degree, about 68% when the batteries were swapped to test.
As I said, the saber works in all respects, nothing else is really out of the ordinary, except for this strange behavior with the battery level reporting. Has anyone here encountered something like this? The biggest difference between this and my other five installs, which all correctly report battery level, is the crystal chamber, but I don’t see how that alone could be causing this.
The battery measurement circuit is very simple. It’s just a voltage divider leading to a pin on the CPU. Either the voltage divider has a short, or the CPU isn’t working properly.
The voltage divider is just two resistors: R3 and R4, both of which should be 410k Ohm. You can check them with a multimeter while the board is not powered.
You can find R3 and R4 using the Proffieboard part map:
I checked the resistors as best I could, my multimeter’s probes are quite large compared to the size of those resistors. I couldn’t get a good consistent read on them individually, but together (one lead on the left-hand side of R3 and the other on the right-hand side of R4, the side facing the pads on the board) I got a total resistance of about 358k Ohms.
I will also say that the board did eventually start reporting the battery level as being less than 100%, but I believe that the battery itself was likely around 25%. In another thread I saw here, if I remember correctly, you said that the voltage across them should be exactly half the battery voltage. My guess is that one of the resistors, at least, is bad so the voltage getting read showing 100% charge until the battery reaches a more advanced state of discharge. I know that it reports a battery that’s at 55% as 100%, I may try a battery I know to be less than 50% to see if that is the threshold for this board to indicate less than 100%.
I’m not going to worry too much about it since there are other visual indicators as to the battery being in an advanced state of discharge such as blade dimming that we can use to know when the battery should be charged. We may eventually replace the board, but since it works perfectly in all other respects I don’t consider it an urgent need. Thanks for your help.
So, if it’s reading the full voltage of an 18650 battery, that voltage can damage the CPU? Either way I’ll have to replace the board because there is no way I’d be able to replace the resistors on the board.
I think so, my understanding is that the input pins on the CPU are not 5v tolerant when in analog mode. It may be fine, but it is outside of the tolerances that the CPU is made for.
That’s good to know. The 18650 I’m using is rated for a maximum output voltage of 4.7V, so there’s a chance it may not reach that 5V threshold (as much as it’s a threshold). Hopefully it will be fine, but I’ll keep an eye on it for any other strange behavior. I will likely replace the board at some point in the future. Thank you again for your help with this.
The threshold isn’t 5v. I think it’s 3.6 or maybe 3.8 volts.
4.7 is a weird voltage for a li-ion battery though. Most have a nominal voltage of 3.7, and are charged to 4.2. Anything higher than 4.2 volts can damage a regular li-ion battery.
Oh, okay. LIke I said, I’ll make sure to keep an eye on it for any other issues that may arise from this and replace sooner if necessary.
Sorry, I meant 4.2V, I misquoted the specs on the battery. I think I had seen the 3.7 and 4.2 and conflated the two into 4.7, but you’re right the max rated voltage for the battery is 4.2V.