DC boost converter 3.7v -> 5v, chip + battery very hot

[Lycaon]

It's me again :p

I've got a simple power "bank" set up which currently consists of one 18650 battery holding about 1300mAh, a boost converter, and a micro USB cord.

I've got it all worked properly as far as I know (triple checked polarity all along the circuit with my DMM) and my phone is happy with the output, but both the battery and the converter get uncomfortably hot.  It's not quite enough to leave a red mark, but it is enough that you can't hold it for too long.

The chip on the converter is an MT3608 which I read over the datasheet for, but there was no info on temperature other than  155° C thermal protection cutoff.

Is the heat from such a small voltage boost normal?  I expect a lot of heat from higher voltage jump , but both the module and the battery are getting hot.  I wanted to be sure I wasn't misusing it.

[TorqueRanger]

It sounds like your phone is charging at high amps and making the chip hot.

[Lycaon]

That's what I thought at first, but its doing this even with no load attached.  I've checked for short circuits too.  No luck.

[Landrew2390]

I would start by measuring the actual current drawn by your phone.  If it's drawing a large current load (~1000mA), you would see temperatures similar to what you're observing on the boost converter.

I couldn't find a datasheet for a 1300mAh battery in the 18650 form factor.  Most of the ones I'm seeing are rated much higher, but the consistent variable is do not discharge them at temperatures above 60 degrees Celsius.  Changing to a larger capacity battery may help you stay under the maximum discharge temperature, but that's not a guarantee.  As with all lithium batteries, try to keep it as cool and comfortable as possible.

[TheUnnamedNewbie]

Is it perhaps possible that the boost converter is making such short pulses that the current during those pulses is quite high? What kind of capacitance do you have between the pusling output and ground? if the values are high enough and the boost converter switches fast enough, the current spikes might be seeing a short even though there is none at DC.