Battery Drain with Bluetooth modules

Hello, I am wondering, say you don't want to recharge your battery that is powering your bluetoothmodule for a +6months, is the technology there yet? With that I mean both in the battery department and bluetooth models that drain less. To be precise, the BT-module won't be receiving any data from the master, it's only to be visible to the master(lowest energy using mode, sleep or w/e its called). Also is it possible to charge a uC battery through your computer through the usb port?

Also, I'm checking this site out
**broken link removed**
But there isn't any info on where I can purchase the csr1000 chip.

Hello!

What you say is way too imprecise to be answered.
Basically a signal transmission costs you energy. Part of this energy is proportional
to the bitrate, and there is also a part of this energy which is used to power various
elements of your bluetooth module. Beside this, will your bluetooth connection be on
for 6 months without interruption? Or will it be used to transfer data to a PC once in
a while? (in which case you can just shut down the module when unused).
Now for your question:
- Check the specs of the module (consumption in mA);
- Calculate how many mAh you need for 6 months
- Choose a battery (don't forget to take the natural discharge into account).

Example: to power a bluetooth module that uses, say, 40 mA for 6 months,
you will need basically 1 Ah per day, or about 200 Ah for 6 months.
200 Ah is a battery for a truck, and its weight is about 50 kg.

Now it's perfectly possible to charge a Li-ion battery (for example) through
USB. But be aware that USB can deliver 100 mA only, (or 500 if you ask
the controller gently, ther is a protocol for that). So a 1000 mAh battery
(which is 1 day of bluetooth use, see above), will need at least 2 hours
to be fully charged.

Dora.

I see, have I understood this correct, the specification in the data sheets on the various modules, when it says 40mA, it means 40mA per hour? And then for 1 day, it's 40mA*24= 1 Ah(960mAh). Also, I am wondering whenever I am looking at batteries online, they are in volt. How do you translate that into A?
The bluetooth module that I was going to experiment with will only be in standby mode or how it's called, it should only be visible to its master(either pc or mobile phone) and no data will be transferred between them.

Thanks.

Bluetooth in visible mode still eats a lot of juice. 40mA is possible.
it's 40mAh if the current is 40mA for an hour. Batteries should include both voltage and mAh (Ah) rating. Check out ni-mh or li-ion/poly accumulators as they usually have this data.

Hello!

Let's go back to the basics.
- mA (or mor generally A for Amperes) is a unit for intensity. Intensity is
basically the number of electrons crossing the section of a wire during 1
second, and this is by reference to 1 Coulomb (C). 1 Coulomb is the quantity
of electricity of 1,6 x 10^19 electrons.
So 1 A means that 16,000,000,000,000,000,000 electrons will cross a given
section of the wire every second. Now Coulomb (C) is the unit for quantity
of electricity, which is basically the number of electrons. And if you multiply
Amperes by hours, you get the capacity of the battery. It is expressed in
Ah, and 1 Ah is 3600 coulombs or 5.76 x 10^22 electrons.

What it means is that a battery of 1 Ah can deliver a current of 1 A for 1 hour.
Or 2 A for half an hour. Hint: you multiply the current you need by the time
you want it and it gives you the size of the battery. Exactly like water: if you
need 5 liters of water per day to survive and if you plan to cross a desert for
a week, then you'll need 35 liters.

Second thing, the voltage of a battery has nothing to do with its capacity.
You cannot convert volts into amperes or Ah, neither can you convert volts
into square meters or into seconds or into kilograms.

You may have noticed that there are A, AA, AAA batteries. All of them have
the same voltage, around 1.5V for alkaline, about 1.2V for NiMH, etc.
The difference is the capacity. The bigger the battery, the more electricity
you can store.

Now as MirekCz said, even being only visible means that it may use quite
a lot of current. It depends whether it is a class 1 or 2, but the order of
magnitude is 10 mA (order of magnitude shall mean that the current
is a 2 figures number, it can be 20, it can be 30 or more, but I guess it will
not be 100).

Dora.