The bluetooth keyboard is the keyboard when I participated in the BBS activities. And today I planned to use it to connect the tablet today, found that it can't use. I opened to check,and found that the inside of the battery had been dead, even the battery interface had been rusted, which cannot be used anymore. This keyboard uses two AAA batteries, because it's also cumbersome to replace the battery, and it is often hard to find when you need.So I wondered whether I can change it to a lithium battery.
When I opened the keyboard, I can't see any screw and finally found that the shell of the keyboard didn't use any screw, which was fixed completely by the card. After it was opened, the keyboard was divided into two halves, half of which are buttons on top, half of which are the control boards and batteries at the bottom. The keyboard and control board are connected with FPC line.
The main chip is AB1108, a bluetooth chip that supports bluetooth 3.0 and is dedicated to bluetooth keyboards. Another chip is T24C64, EEPROM.
Checked the data manual and the input voltage range was 2-4.2 V. The voltage range of T24C64 was 2.7-5.5 V, so it can be powered directly from a lithium battery and did not require LDO.
The process of transformation is relatively simple. It mainly used a lithium battery charging pad and two small lithium batteries, which were removed from other devices in the past and the capacity were more than 100 mAH. Two batteries were used to increase the capacity in parallel and make the keyboard work longer. The panels was TP4056 which is commomly used, but they needed to be replaced the current of 1.2 K to a larger one, to reduce the charging current. The calculation formula for maximum charging current is 1200/ R. The capacity of two batteries in parallel was less than 300mAH, and it is safe to limit the charging current to about 300mA. Therefore, a resistance of 3.3K was used.
The most troublesome was opening hole, because there was no suitable tool. Only the first measure of the approximate position, then used the solder iron to iron a few smaller holes, finally used the electric knife to whittle slowly. The electric knife whittles the plastic very quickly, so that we should notice that the hole can not be cut to too big.
The charging pad was 1-2mm long and needed to be cut with a file, which can be installed very tightly, without fear of shaking and fixing.
The battery is just in the slot.
Lined up the keyboard, aligned the upper and lower parts of the keyboard, pressed the back card button, and installed it. When install, put some anti-shock foam in the battery, so the battery won't shake. Reconnected the phone and the tablet, rematched, and the using was normal, and I no longer have to worry about the battery and running water.
Finally,checked the effect of charging.
Charging completed.
When I opened the keyboard, I can't see any screw and finally found that the shell of the keyboard didn't use any screw, which was fixed completely by the card. After it was opened, the keyboard was divided into two halves, half of which are buttons on top, half of which are the control boards and batteries at the bottom. The keyboard and control board are connected with FPC line.
The main chip is AB1108, a bluetooth chip that supports bluetooth 3.0 and is dedicated to bluetooth keyboards. Another chip is T24C64, EEPROM.
Checked the data manual and the input voltage range was 2-4.2 V. The voltage range of T24C64 was 2.7-5.5 V, so it can be powered directly from a lithium battery and did not require LDO.
The process of transformation is relatively simple. It mainly used a lithium battery charging pad and two small lithium batteries, which were removed from other devices in the past and the capacity were more than 100 mAH. Two batteries were used to increase the capacity in parallel and make the keyboard work longer. The panels was TP4056 which is commomly used, but they needed to be replaced the current of 1.2 K to a larger one, to reduce the charging current. The calculation formula for maximum charging current is 1200/ R. The capacity of two batteries in parallel was less than 300mAH, and it is safe to limit the charging current to about 300mA. Therefore, a resistance of 3.3K was used.
The most troublesome was opening hole, because there was no suitable tool. Only the first measure of the approximate position, then used the solder iron to iron a few smaller holes, finally used the electric knife to whittle slowly. The electric knife whittles the plastic very quickly, so that we should notice that the hole can not be cut to too big.
The charging pad was 1-2mm long and needed to be cut with a file, which can be installed very tightly, without fear of shaking and fixing.
The battery is just in the slot.
Lined up the keyboard, aligned the upper and lower parts of the keyboard, pressed the back card button, and installed it. When install, put some anti-shock foam in the battery, so the battery won't shake. Reconnected the phone and the tablet, rematched, and the using was normal, and I no longer have to worry about the battery and running water.
Finally,checked the effect of charging.
Charging completed.
