Question about making a wireless keyboard rechargeable?..

[shugz117]

This might be sort of a silly question but... I have a Labtec wireless keyboard and a spare cheap-o xbox 360 rechargeable battery pack. What i want to know is if it would be somehow possible to wire the pack up to the keyboard making it rechargeable? the pack says '1200mAh 2.4V' and on the back of the keyboard it says '3V 8mA'. If it is at all possible would anyone have any ideas on how to do this:think:?

[Trace]

The battery pack is not high enough voltage.

[shugz117]

ahh should have seen that :facepalm:does anyone have any other alternative ideas or seen something similar done before?

[x88x]

Yeah, probably not, but you could always try wiring it up and see what happens. Sometimes manufacturers build in a buffer zone, especially if it uses standard batteries where you can only work in multiples of 1.5V.

[billygoat333]

can always just buy rechargeable AA batteries. :)

[shugz117]

Yeah, probably not, but you could always try wiring it up and see what happens. Sometimes manufacturers build in a buffer zone, especially if it uses standard batteries where you can only work in multiples of 1.5V.

I might give it a go anyway just too see:think: thanks for the reply!


can always just buy rechargeable AA batteries. :)

haha yeah I know i am being cheap but I want to try something like this for when the battery power needs recharged all i have to do is plug in the usb cable and away i go :)

I will post back with results!

[shugz117]

Well it didn't work:down: some smoke came off it it :facepalm:but i am typing this reply on the keyboard now so no harm done thanks for the replys!

[x88x]

Hmm, smoke came off the battery? Crap, looks like it was actually pulling 3V after all. :(

There is a way you might be able to pull it off, but I'm not sure how well it would work...with that small a voltage difference, it might work..though it would kinda blow your 'being cheap and using what you have lying around' theme out of the water. :P

Basically, you would build a circuit a lot like my capacitor charging circuit for my coilgun project (link in my sig), but use a 3V capacitor, preferably with a pretty large capacitance. Basically, your charge rate to 3V would have to be at least as fast as the power draw rate, so the capacitor charge stays at 3V. You would also have to figure out a way of making the charging stop once it reaches 3V, something I haven't looked at (well, it would be more like 450V in my case, but same principle), but in theory it might work, especially since you're only boosting it 0.6V.

[Konrad]

Lithium-ion/poly cells will actually discharge at a sustained 4.2-4.3V if they are not regulated. They are always regulated at 3.6V (nominal cell rating) or even a bit less (if intended for lower-voltage applications) because at full discharge rates they get dangerously hot very quickly. Almost every li-ion/poly battery actually contains a voltage regulator IC inside the casing; the few that don't require that these regulators are designed into the powered device.

When they get hot they degrade at an accelerated rate, they won't charge to "full" capacity (as far as battery-status software calibrated to normal parameters can tell), they won't last as long per charge (lower capacity), and won't last through as many charge/discharge cycles before end-of-life.

When they get dangerously hot they actually explode. Most often this is just characterized by hissing noises as gasses are vented (permanently derating the battery). Sometimes this "explosion" is more of a swelling expansion that undramatically splits the battery case open and leaks charged corrosive chemical goop all over the inside of the device (can be ugly). On rare occassions the battery will actually spontaneously ignite and/or explode with violent force.

Multiple safety mechanisms, including the regulator IC, are engineered into these batteries to minimize the risks.

If you saw smoke while using this battery with the keyboard then you were drawing ~4.2V (assuming full charge). As mentioned, your battery would get very hot very quickly. Your keyboard electronics might have been damaged. I'm assuming no electrical safeties (transformers, fuses, diodes, etc) before the fragile semiconductor circuitry would be present in the keyboard, simply because the engineers never thought your usage model was very likely. The fact that it's rated at 8mA suggests the circuitry isn't very electrically robust.

Your battery will be able to put out 3.0V (or even 3.6V, though the label says otherwise). You should be able to use it safely if you use a 3.0V regulator, preferrably one that can handle decent (>500mA) loading.

[slaveofconvention]

This is kinda confusing. The simple fact of the matter is, the XBOX controller will quite happily run on 2 AA batteries, the rechargeable battery pack is little more than a pair of 1.2V rechargeable AA's. Fact of the matter is, if you have ANY rechargeable AA's lying around, you'll almost certainly see that they are 1.2v. There really is no reason this shouldn't work just fine.... *confused look* Let's face it, you could pop rechargeable AA's in the keyboard I'm sure, and they'd only be 1.2v each too....

[shugz117]

Hmm, smoke came off the battery? Crap, looks like it was actually pulling 3V after all. :(

There is a way you might be able to pull it off, but I'm not sure how well it would work...with that small a voltage difference, it might work..though it would kinda blow your 'being cheap and using what you have lying around' theme out of the water. :P

Basically, you would build a circuit a lot like my capacitor charging circuit for my coilgun project (link in my sig), but use a 3V capacitor, preferably with a pretty large capacitance. Basically, your charge rate to 3V would have to be at least as fast as the power draw rate, so the capacitor charge stays at 3V. You would also have to figure out a way of making the charging stop once it reaches 3V, something I haven't looked at (well, it would be more like 450V in my case, but same principle), but in theory it might work, especially since you're only boosting it 0.6V.

Hahaha yeah i disconnected it as quickly as possible once i seen the smoke :rolleyes.:I would love to be able to try that out but i wouldnt know where to start :redface: I will be learning electronics this year now coming starting next month so i might look into your work and see what i can do:D.


Lithium-ion/poly cells will actually discharge at a sustained 4.2-4.3V if they are not regulated. They are always regulated at 3.6V (nominal cell rating) or even a bit less (if intended for lower-voltage applications) because at full discharge rates they get dangerously hot very quickly. Almost every li-ion/poly battery actually contains a voltage regulator IC inside the casing; the few that don't require that these regulators are designed into the powered device.

When they get hot they degrade at an accelerated rate, they won't charge to "full" capacity (as far as battery-status software calibrated to normal parameters can tell), they won't last as long per charge (lower capacity), and won't last through as many charge/discharge cycles before end-of-life.

When they get dangerously hot they actually explode. Most often this is just characterized by hissing noises as gasses are vented (permanently derating the battery). Sometimes this "explosion" is more of a swelling expansion that undramatically splits the battery case open and leaks charged corrosive chemical goop all over the inside of the device (can be ugly). On rare occassions the battery will actually spontaneously ignite and/or explode with violent force.

Multiple safety mechanisms, including the regulator IC, are engineered into these batteries to minimize the risks.

If you saw smoke while using this battery with the keyboard then you were drawing ~4.2V (assuming full charge). As mentioned, your battery would get very hot very quickly. Your keyboard electronics might have been damaged. I'm assuming no electrical safeties (transformers, fuses, diodes, etc) before the fragile semiconductor circuitry would be present in the keyboard, simply because the engineers never thought your usage model was very likely. The fact that it's rated at 8mA suggests the circuitry isn't very electrically robust.

Your battery will be able to put out 3.0V (or even 3.6V, though the label says otherwise). You should be able to use it safely if you use a 3.0V regulator, preferrably one that can handle decent (>500mA) loading.


Wow man thanks for the info! that's all new to me i must remeber that :) I'm actually really interested in computer electronics ( A bit obvious since im taking a course in it soon lol ) I've always been one of them people to take stuff apart just to see how it works and put it back togehter lol I must look into getting a regulator soon, have you guys got any other necessary info?.
Thanks for the replys :D!