Electronics > Beginners
Why would an Arduino kit specifically ask to use unprotected 18650 cells?
beanflying:
Cruddy Chinese 18650's not able to deliver the current needed causing the protection circuitry to kick in when firing up a motor under load as has been mentioned.
A quick look at the manual and maybe some heavier wire from the battery holder to the DC-DC converter would be nice too.
Within reason don't be to worried about the cells going down to 3V the LM2596 will fall out of regulation so you should be able to pickup a slowing of the vehicle. You could as an extra do a little trickery on Pin 5 of it to provide low voltage cutout of the regulator and that would switch it off. It is shown tied to ground (on) but if the voltage on that pin is 1.3 or up it turns off. http://www.ti.com/lit/ds/symlink/lm2596.pdf
KL27x:
I have encountered the problem, before, in a battery powered ICSP programmer. The battery I used has an internal current limiter, and it trips when one of the circuit's outputs gets shorted. Good? Well, the circuit has its own short-circuit detection and cutout which would kick in a few mS later. But once the battery protection trips, then you have to put a float voltage on the leads of the cell to turn it back on, again. Due to the purpose of the device, some short circuits occur, now and then.
Kilrah:
--- Quote from: beanflying on January 03, 2019, 10:51:41 pm ---Cruddy Chinese 18650's not able to deliver the current needed causing the protection circuitry to kick in when firing up a motor under load as has been mentioned.
--- End quote ---
Not the same thing at all. That's supposing the cell's IR is so bad the voltage sags. But the likely problem has nothing to do with voltage, just the overcurrent/short circuit protection being set too low for what the motor draws when starting.
--- Quote from: beanflying on January 03, 2019, 10:51:41 pm ---maybe some heavier wire from the battery holder to the DC-DC converter would be nice too.
--- End quote ---
In both these scenarios heavier wire would actually make it worse. The wire is after the protection, so thinner one would reduce both the voltage sag in the cell and the max current draw from it.
beanflying:
That wasn't meant as a resolution to protection or lack of it, the wire from the holder just looked cruddy ;) Give me decent known LiPos over random 18650's any day too.
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