I have a device (a vaporizer) which contains a rechargeable battery. The battery only takes a couple of hours to recharge, but sometimes I end up leaving it charging overnight. I have monitored the current drawn by the device when charging, and to my mild annoyance it still draws about 0.02A even when fully charged.
I don't know how to stop this small current draw. I also don't know whether I need to worry about this (i.e. whether it's decreasing the battery life). I have two choices when leaving the device charging overnight -- I can either use the mains, or a portable USB battery (i.e. use a second battery to charge the device). My portable USB battery turns off automatically when current draw is zero -- however the current draw of 0.02A pulled by the device even when fully charged stops my USB battery from switching off.
Is there something which I can buy, which has a USB input and output (or a micro USB input and output) and which stops conducting electricity if less than about 0.05A is flowing through it? Or is there a USB battery which turns off when less than about 0.05A is being drawn from it?
Some more details -- I know very little about the rechargeable battery in the vaporizer. There is no mention of what battery type it is in the manual; it's a portable vaporizer, so its job is to heat something up to 200 degrees celsius and keep it at this temperature. The specs on the device are that it wants a 5V input to charge and max power input is 10W; the charger that came with the device is 2A so this checks out. I bought one of these:
to monitor the current of the device whilst charging; it typically starts at 1.5A and then drops to around 0.02A when fully charged.
My main concern is that this constant drawing of a small amount of charge will degrade the battery in the device. A secondary concern is that leaving it to charge overnight represents a fire risk; most devices I have stop taking charge after some time and if I'm charging them with my USB battery then the battery switches off; this does not.
Am I fussing about nothing?