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Electronics => Repair => Topic started by: salil on February 09, 2015, 10:11:03 am

Title: HM1800 BT Headset refuses to run off 4v power supply instead of li-ion battery?
Post by: salil on February 09, 2015, 10:11:03 am
I removed the single cell li-ion battery soldered to the circuit board of a Samsung HM1800 bluetooth headset (http://youtu.be/jHOQLcOvhR4?t=17s) and replaced it with a 4.1v DC power supply.  Unfortunately, the device refuses to power on reliably.  I got it to power on once or twice, but it was performing erratically.  I put the included battery back and it of course works just fine.   I'm using a 5v/1A power supply and stepping the voltage down to 4.1v with an NTE956 regulator and some caps & resistors.  The current draw when using the battery has never exceeded 0.5A when I measured it.

Does anyone have any idea what could be going on here?
Title: Re: HM1800 BT Headset refuses to run off 4v power supply instead of li-ion battery?
Post by: janoc on February 09, 2015, 11:11:16 pm
4.1V looks quite high for a single Li-ion cell. Those are around 3.7V usually. Are you sure you are not giving it too high voltage?

Title: Re: HM1800 BT Headset refuses to run off 4v power supply instead of li-ion battery?
Post by: Alex Eisenhut on February 10, 2015, 02:59:20 am
Quote from: janoc on February 09, 2015, 11:11:16 pm
4.1V looks quite high for a single Li-ion cell. Those are around 3.7V usually. Are you sure you are not giving it too high voltage?

3.7V is the nominal voltage. Fully charged they go to 4.2V.
Title: Re: HM1800 BT Headset refuses to run off 4v power supply instead of li-ion battery?
Post by: Alex Eisenhut on February 10, 2015, 03:02:46 am
Quote from: salil on February 09, 2015, 10:11:03 am
I removed the single cell li-ion battery soldered to the circuit board of a Samsung HM1800 bluetooth headset (http://youtu.be/jHOQLcOvhR4?t=17s) and replaced it with a 4.1v DC power supply.  Unfortunately, the device refuses to power on reliably.  I got it to power on once or twice, but it was performing erratically.  I put the included battery back and it of course works just fine.   I'm using a 5v/1A power supply and stepping the voltage down to 4.1v with an NTE956 regulator and some caps & resistors.  The current draw when using the battery has never exceeded 0.5A when I measured it.

Does anyone have any idea what could be going on here?

What's with the unrelated video link?
Title: Re: HM1800 BT Headset refuses to run off 4v power supply instead of li-ion battery?
Post by: amyk on February 10, 2015, 04:18:49 am
Quote from: Alex Eisenhut on February 10, 2015, 03:02:46 am
Quote from: salil on February 09, 2015, 10:11:03 am
I removed the single cell li-ion battery soldered to the circuit board of a Samsung HM1800 bluetooth headset (http://youtu.be/jHOQLcOvhR4?t=17s) and replaced it with a 4.1v DC power supply.  Unfortunately, the device refuses to power on reliably.  I got it to power on once or twice, but it was performing erratically.  I put the included battery back and it of course works just fine.   I'm using a 5v/1A power supply and stepping the voltage down to 4.1v with an NTE956 regulator and some caps & resistors.  The current draw when using the battery has never exceeded 0.5A when I measured it.

Does anyone have any idea what could be going on here?

What's with the unrelated video link?
Apparently it's what he is trying to use the BT headset for.

It could be drawing far more current than 0.5A in brief pulses, which can't be seen without a scope.
Title: Re: HM1800 BT Headset refuses to run off 4v power supply instead of li-ion battery?
Post by: Alex Eisenhut on February 10, 2015, 05:14:58 am
Quote from: amyk on February 10, 2015, 04:18:49 am
Quote from: Alex Eisenhut on February 10, 2015, 03:02:46 am
Quote from: salil on February 09, 2015, 10:11:03 am
I removed the single cell li-ion battery soldered to the circuit board of a Samsung HM1800 bluetooth headset (http://youtu.be/jHOQLcOvhR4?t=17s) and replaced it with a 4.1v DC power supply.  Unfortunately, the device refuses to power on reliably.  I got it to power on once or twice, but it was performing erratically.  I put the included battery back and it of course works just fine.   I'm using a 5v/1A power supply and stepping the voltage down to 4.1v with an NTE956 regulator and some caps & resistors.  The current draw when using the battery has never exceeded 0.5A when I measured it.

Does anyone have any idea what could be going on here?

What's with the unrelated video link?
Apparently it's what he is trying to use the BT headset for.

It could be drawing far more current than 0.5A in brief pulses, which can't be seen without a scope.

Guess I'm not too patient. I see some unrelated video and I just closed it.

Yeah we'd need to see what this mysterious regulator with "some caps & resistors" actually looks like, how long the wires are, etc. Probably losing regulation because of poor transient response.

And how the current was measured, with what, etc...
Title: Re: HM1800 BT Headset refuses to run off 4v power supply instead of li-ion battery?
Post by: Seekonk on February 13, 2015, 02:12:01 pm
I would think the cap at the battery side needs to be a LOT BIGGER.  I suspect it can't handle the surge.
Title: Re: HM1800 BT Headset refuses to run off 4v power supply instead of li-ion battery?
Post by: Dragon88 on February 13, 2015, 06:40:11 pm
What's the dropout voltage of the regulator? Is it greater than 0.9V?

What's the measured output voltage of your regulator circuit with a 0.5A load?
Title: Re: HM1800 BT Headset refuses to run off 4v power supply instead of li-ion battery?
Post by: daveshah on February 13, 2015, 07:42:54 pm
I don't think that the regulator is an LDO - the data sheet doesn't even give a dropout voltage spec - so the dropout voltage is likely to be about the two volts or so. Have you measured what voltage it is actually outputting?