will adding another battery to my smartwatch double its battery life?

[Legolessed]

i have a U8S smartwatch and i decided to open it up today to see if i could increase the battery life of it. I found the power delivery circuit and was wondering if the battery life would double if i added a second battery. The battery already inside is a 230mah battery and the battery i want to add is a 250mah battery.

[Hackentosher]

Are you replacing the battery or adding in a second battery? 

[Legolessed]

1 minute ago, Hackentosher said:

Are you replacing the battery or adding in a second battery? 

adding a second

[BenoitWW]

6 minutes ago, Legolessed said:

i have a U8S smartwatch and i decided to open it up today to see if i could increase the battery life of it. I found the power delivery circuit and was wondering if the battery life would double if i added a second battery. The battery already inside is a 230mah battery and the battery i want to add is a 250mah battery.

depends if there is space inside. If you wire in series or parallel.I would recommend parallel as that would "double" battery life.  

[BenoitWW]

and if you screw it up the watch is only $12 so just buy another one

[Legolessed]

1 minute ago, Hackentosher said:

Are you replacing the battery or adding in a second battery? 

one of my worries is that would the voltage be 7.4 volts? i dont know if the board can handle that. I was planning to wire it at the same solder points as the previous battery

[Legolessed]

1 minute ago, BenoitWW said:

and if you screw it up the watch is only $12 so just buy another one

thats why im doing it  i got it for $6 when it was on sale

[Legolessed]

2 minutes ago, BenoitWW said:

depends if there is space inside. If you wire in series or parallel.I would recommend parallel as that would "double" battery life.  

i was going to wire it to the band. the battery i have has a couple centimeters of wire to work with

[BenoitWW]

1 minute ago, Legolessed said:

thats why im doing it  i got it for $6 when it was on sale

just make sure that the voltage of the 2nd battery is the same as the 1st. otherwise, expect some magic smoke

[tlink]

its a bad idea, especially since they are different mah. its better to replace the battery as a whole with a higher mah rating that has the same chemistry. if you're going to do this, make sure the battery's are both the same spec and the same mah, otherwise its pretty risky especially if you don't know what you're doing. what can happen for example is that you overdraw the smaller battery resulting in it simply dying. its not an exact science though so i really am not sure especially since we don't know the exact specs and brand of both battery's.

[Legolessed]

1 minute ago, BenoitWW said:

just make sure that the voltage of the 2nd battery is the same as the 1st. otherwise, expect some magic smoke

they are both 3.7 volts. magic smoke  i have been refreshing my knowledge of parallel circuits and i was wondering if  this circuit would be parallel. i linked my beautiful ms paint picture  

[Legolessed]

4 minutes ago, tlink said:

its a bad idea, especially since they are different mah. its better to replace the battery as a whole with a higher mah rating that has the same chemistry. if you're going to do this, make sure the battery's are both the same spec and the same mah, otherwise its pretty risky especially if you don't know what you're doing. what can happen for example is that you overdraw the smaller battery resulting in it simply dying. its not an exact science though so i really am not sure especially since we don't know the exact specs and brand of both battery's.

they are so close in mah that i think the bigger battery would die long before the smaller one got to dangerous voltages

[tlink]

5 minutes ago, Legolessed said:

they are so close in mah that i think the bigger battery would die long before the smaller one got to dangerous voltages

from 230 to 250 is an 8% difference. the cutoff point of lithium ion cells generally is at 92% to 98% depletion. if its cut off point is at best at 92% than there is exactly 230 mah drained from the 250mah cell.

 

EDIT: this is rough math, i also am not a battery expert just a hobby electronics human.

[Legolessed]

2 minutes ago, tlink said:

from 230 to 250 is an 8% difference. the cutoff point of lithium ion cells generally is at 92% to 98% depletion. if its cut off point is at best at 92% than there is exactly 230 mah drained from the 250mah cell.

i dont know if this is the same thing but when i use 1s lipos for rc stuff they only go down to around 3.6v about and they start at 4.2v. lipos start dieing around 3v.

[Hackentosher]

What about charging?

[Legolessed]

22 minutes ago, Hackentosher said:

What about charging?

the micro usb port is still free

[Hackentosher]

14 minutes ago, Legolessed said:

the micro usb port is still free

I mean keeping your two cells balanced. You don't want your wrist to blow up, now do you?

[Legolessed]

1 hour ago, Hackentosher said:

I mean keeping your two cells balanced. You don't want your wrist to blow up, now do you?

what does that mean?

[Legolessed]

1 hour ago, Hackentosher said:

I mean keeping your two cells balanced. You don't want your wrist to blow up, now do you?

is the circuit i drew a parallel circuit? 

[KaminKevCrew]

4 hours ago, tlink said:

its a bad idea, especially since they are different mah. its better to replace the battery as a whole with a higher mah rating that has the same chemistry. if you're going to do this, make sure the battery's are both the same spec and the same mah, otherwise its pretty risky especially if you don't know what you're doing. what can happen for example is that you overdraw the smaller battery resulting in it simply dying. its not an exact science though so i really am not sure especially since we don't know the exact specs and brand of both battery's.

Since it's a parallel circuit, that shouldn't actually matter at all. You can add as many batteries as you want, and they'll all draw down to the end voltage at about the same time. 

4 hours ago, Legolessed said:

they are both 3.7 volts. magic smoke  i have been refreshing my knowledge of parallel circuits and i was wondering if  this circuit would be parallel. i linked my beautiful ms paint picture  

Yes, that's a parallel circuit.

16 minutes ago, Legolessed said:

what does that mean?

Balanced charging is where you charge the battery cells individually, rather than both at once. It's a very important thing to do with Li batteries. 

 

To give you an example, if one battery were at, say 3.2V and the other were at 4.0V, but you're charging both at the same time, you would end up blowing up the battery that's at 4V because you would be attempting to over charge it. balanced charging means that you charge each cell to the appropriate voltage individually, to avoid that.

 

You should read this: http://www.instructables.com/id/Lithium-Polymer-Etiquette/step5/Balance-Charging-Setup/

[Legolessed]

6 minutes ago, KaminKevCrew said:

Since it's a parallel circuit, that shouldn't actually matter at all. You can add as many batteries as you want, and they'll all draw down to the end voltage at about the same time. 

Yes, that's a parallel circuit.

Balanced charging is where you charge the battery cells individually, rather than both at once. It's a very important thing to do with Li batteries. 

 

To give you an example, if one battery were at, say 3.2V and the other were at 4.0V, but you're charging both at the same time, you would end up blowing up the battery that's at 4V because you would be attempting to over charge it. balanced charging means that you charge each cell to the appropriate voltage individually, to avoid that.

 

You should read this: http://www.instructables.com/id/Lithium-Polymer-Etiquette/step5/Balance-Charging-Setup/

ok so do i have to charge both batteries seperatly and then build a port that i can plug the battery into or what should i do? do i cant just use the micro usb port to charge the smartwatch if i do this?

[KaminKevCrew]

4 minutes ago, Legolessed said:

ok so do i have to charge both batteries seperatly and then build a port that i can plug the battery into or what should i do? do i cant just use the micro usb port to charge the smartwatch if i do this?

I mean, you can use the micro USB port, but I would be prepared to charge the batteries separately every ten charges or so.

[Legolessed]

4 minutes ago, KaminKevCrew said:

I mean, you can use the micro USB port, but I would be prepared to charge the batteries separately every ten charges or so.

is there any way to do this where i dont have to not use the micro usb port?

[KaminKevCrew]

3 minutes ago, Legolessed said:

is there any way to do this where i dont have to not use the micro usb port?

I mean, you could buy one of the (significantly) more expensive batteries that has its own protection circuit that will prevent overcharging.

[Legolessed]

11 minutes ago, KaminKevCrew said:

I mean, you could buy one of the (significantly) more expensive batteries that has its own protection circuit that will prevent overcharging.

is there any way to do it without one of those?