Battery charger for AA batteries

batteriesbattery-chargingnimh

I am looking for a battery charger for AA batteries, without taking out the batteries from the board.

The board which is powered by AA batteries is : http://www.tagsense.com/images/stories/products/activetags/ZT-500-datasheet-short-form.pdf

I dont have any idea if I can charge the batteries just by employing the Vcc and Gnd pins I have on the board.

When the batteries are plugged into the board the total voltage at Vcc and Gnd pins is : 3V.

Could any one suggest for a battery charger which can charge the batteries without removing them from the board ..?? I am ready to build the circuit and if I can find already available charger it will be good.

Thanks,

Best Answer

From TagSense’s datasheet (and Matt’s comment), we can see it was designed for CR123 - non rechargeable battery. enter image description here

Also it can be seen the device can operate at 2.2V . Regarding daily average consumption: If 4 Batteries of 1550mAh operate the device for 12 months, this means 517mAh/month, or just 17mAh/day. So it appears to me that any good AA NiMh would work. I have several Eneloop NiMh (1800mAh) and they are great, providing 1.30V when fully charged and around 1.20V along most of its discharging cycle, so 2.2V minimum voltage is fulfilled.

I would try 2 AA Eneloop NiMh batteries. Brand-new and freshly charged, they would last about 3 months. If transmitting power and range would be OK for you, as TagSense will operate at lower voltages, then you could use a SMALL Solar Cell panel as energy source, as one with 

100mA < capacity < 200mA and 5V~12V rated,

powering a low quiescent current voltage regulator adjusted to 2.60V to charge 2xAA NiMh in series. If solar cell is small, you wouldn’t need to worry about current limiting, otherwise is recommended to include a simple current limiting circuit.

A suggestion of series regulator for this charging is based in the TL431 found everywhere, adapted from Texas’ TL431 datasheet, and paralleling common resistor values (5% series) to obtain desired voltage divider. When not charging the resistor divider drains only 100uA or 3mAh/day, so it is negligible for the charging currents. It is mostly a starting point, as other charging methods and charging figures would influence the circuit selection.

enter image description here

Let us know which path you followed, ok?

Related Topic