Flamethrower

In theory, it's the same setup you were all suggesting

@RussellMcMahon No but they're not hard connected this time because each battery has its own charger module. Just instead of plugging two standalone chargers into a wall you plug two charger modules into the same power supply (through the Y cable).

On another note, would a 18 Ni cupronickel alloy be appropriate for the contacts on the robot's back?

@RussellMcMahon Actually, the diagram would be the same as at the beginning, just placing some lithium ion charger module before each battery. This wouldn't be a hard connection, right? After all, it's like just plugging two chargers into the wall

@RussellMcMahon I updated the wiring to include positive and negative, although I guess the power socket is an open factor for now because mine got fried haha

@RussellMcMahon No, I know, what I'm thinking is keeping the Y-division cable (the one that was hard-connecting the batteries before), fed by a power supply plug, but attaching a lithium ion charger module to each battery. But I don't know if this will work well or if it'll generate too much heat to be inside a robot.

I'm thinking of dropping the barrel jack and using a magnetic pad system instead, although in this case connecting the power supply to the dock's magnetic pads and dividing that into the two charging modules inside the robot would allow me to not have to use two different sets of pads. Is this a good idea? Do the charger modules generate a lot of heat?

@RussellMcMahon Although it's not really a single charger to replace the psu I'd be looking for, as I still need to get power out of the single DC barrel jack port into my robot. Would it be possible to use another psu, divide it with a Y cable like I was doing before, but then use a separate charger module for each battery at each of the two ends?

@Justme Is it really reasonable to blame such an unlikely phenomenon? Although it's true that it's weird since I had run lengthy stress-tests before with no problem.

@Justme And what might have caused it to stop "waiting" and suddenly burn up? Also, are you saying it was the lack of a proper charger, and not the connection between the batteries, that triggered this?

@RussellMcMahon It's just that I was trying to figure out the cause and what exactly happened (and I still am)... By the way, would you be able to provide some guidance about what to look for if I must keep the overall power input to a DC barrel jack? I looked for lithium ion charger modules but they all use USB-C and raw terminals, and some say they're BMSs but my battery already has a BMS...

@RussellMcMahon No, but the batteries were always connected like I showed in the diagram, they charged together and discharged together; I'm only isolating them now for testing.

@RussellMcMahon Done.

@RussellMcMahon That's the thing, nothing seemed to happen. What I was trying to do was to try and reproduce what happened because I still don't know which of the factors was the cause, of course ready to disconnect everything at the slightest sign of heat

It just would be nice to be able to reproduce this to find out what happened. The most I have is that, when charging my big battery with a power supply instead of a Li-ion charger and the divider cable in between (not necessarily also connected to the smaller battery), the divider cable heats up a bit, though I suspect this is just due to low wire gauge...

@SolomonSlow No, I did it just to test just what had gone wrong exactly; I was ready to pull it out if it got even slightly hot. I mean, I now know the best practices to avoid this kind of problem, but I don't know what caused it, why it was the bigger battery's cable that got damaged and not the other one, why it had worked perfectly so far and whether my servos, which heat up when idle, may have had anything to do.

@RussellMcMahon I just did a test and, after charging the small battery to 12.3V and measuring the other one to be at 11.2V (which is weird because I had also charged that one separately after the incident and it's basically the same voltage), when I connected them both with the divider cable, the voltage of the small one does slowly decrease, but no heat is generated.

@RussellMcMahon And if I charge both batteries at the same time with that, it'll be fine?

@SophieSwett Sorry, what "connector" and "device" are you referring to here?

@SophieSwett Oh ok, though what I meant with each line is of course a positive and negative pair. It's just that they're not separated in my real DC barrel jack cable either and the servos use dedicated servo cables so I just drew them as single cables.

@Hearth Isn't the charge controller part of the BMS? And otherwise, could you please provide some kind of link so I know what you're referring to? Thanks.

@Hearth Then how should I charge them? I read about placing a diode but that would reduce my voltage considerably...

@Hearth And, if I get a good one, can I charge them both with my Y-division cable?

@Hearth Then how can I identify a "good" charger? That one is like the one that came with my battery pack.

@Hearth But then what was the problem? The charger or the presence of a connection between the batteries? I also have a charger like this one. Will that do?

@RussellMcMahon Both batteries have BMSs, and I have 6 cells in the 18650 one and 30 in the 21700 one. I have two batteries because sometimes the current surge from the motors and servos starting up propagated to my Pis and they turned off. The only way the batteries are connected together is via the Y divider cable from the charging port. The psu is indeed dead, it gives no voltage. I think it got fried, because it was extremely hot. Though I'm not sure what you mean with it shorting + and - ...

@RussellMcMahon But I did include the link to the charger, please look at the module links list I've been adding (a.aliexpress.com/_EudXCLu). I say I think they're hard connected because the DC barrel jack y divider cable is going (positive + negative) from the charger to the battery pack and at the same time from the charger to my custom battery. Is that right? Although in that case I can't figure why they failed just now...

@RussellMcMahon But I did post links and update the diagram, I don't know what else to add; the batteries are connected by the DC barrel jack Y-divider cable, so I don't have some weird positive and negative setup. I have added the link to the adapter plug as well. I don't exactly know what a hard connection is, but I looked it up and I'm pretty sure they are hard connected.

@Justme Okay, I just added all the links, I hope they're helpful.

@Justme But the second diagram includes all the modules I'm using, there's nothing else I'm not showing. Is anything not clear or lacking?

@SolomonSlow It certainly isn't... But how could I prevent it from happening again, and why did it happen now that everything was mostly idle and after all this time? I'm still having trouble understanding exactly what happened...

@vir The rest of the modules are all buck converters, both for the servos (12V to 6V and 12V to 8.4V) to and the Pis (12V to 5V), apart from a PCA9685 which comes from somewhere else. The rest of the mess is just cables going to the servos. In any case, I'll add a more detailed schematic shortly.

Actually, I must correct myself: they were not charging. I've just gone to check the charger and found it dead (0V) and scorching. What I'm not sure of is if it happened before the incident (perhaps causing the voltage difference?) or as a consequence.

@WesleyLee But they had been working fine until now, and they were both charging when it happened...

@vir Sorry, I don't really know how to make that, I'm still a beginner in electronics. Is anything unclear? I'll happily update it if so.

So a single equation causes both time dilation and spaghettification?

@ACuriousMind Well of GR

@ACuriousMind But you can still look at the equations and see what effect each part of it has, right?

@ACuriousMind And can't you figure out what happens when you exclude spaghettification, just as we sometimes exclude air resistance?

Yeah it's true that that representation might have been a bit unclear, but say you throw the apple into a black hole. Time dilation will affect the part of the apple closest to the black hole before the other end. Doesn't that cause anything to the bonds between the molecules, as one part evolves faster than the other one?

@ACuriousMind No but just to half of it. Half of the apple would see the other half's clock as running slower than its own clock

No no not turn half the apple into a black hole but imagine just sprinkling it with neutron star-dense material

Like imagine one molecule seeing the other one as if it was falling into a black hole - something like that

@ACuriousMind Yeah but what if the proper time of two adjacent molecules is warped like that?

@ACuriousMind Through energy density warping spacetime

Does which form matter, though?

@ACuriousMind I mean you can heat it up, add a bunch of molecules, charge it electrically, excite its molecules... Just any form of energy

@ACuriousMind Well by giving it a load of energy, for example

What would happen if I let an apple drop but, during the fall, I froze only half the apple through extreme time dilation? Would it break in two? Would half the apple support the other half?

Also, a nothing cannot think (because an action requires an actor), so thinking about anything makes you not nothing = something