Riassunto analitico
During the internship, I designed and developed a board to test some types of batteries, especially the Lithium-Ion (Li-Ion) ones, and those with have a nominal voltage between 3.7 V and 24 V. Specifically, I designed this board mainly for the Accu and Jauch Li-Ion 3.7 V batteries, but this board is also able to test other batteries with different nominal voltages, up to 24 V.
The purpose of the board is to identify any defective batteries. To do that, the board performs a test to one or more battery pack (up to 5), which are connected to the board through an appropriate connector on the board by the tester.
After that, the tester must configure the test according to his needs, by inserting some parameters through via the switches and the display, these parameters includes: the nominal voltage and nominal capacity of the battery pack, the discharge current and the percentage of the battery pack at both half and the end of the test, but the most important are the pre-charge and the fast-charge currents.
Then, the test of the connected battery packs will start according to a specific Fine State Machine (FSM) and there will be monitored some parameters, including: the voltage and the current of the battery packs being tested. If any error occurs, the corresponding type of error will be reported in a few ways: on display, by lighting up a red LED and also a buzzer will beep.
There are five fans, one for each battery pack, in such a way that they can cool each battery pack in case they overheat during the test. All the parameters entered by the tester are stored in a EEPROM memory, so that the tester doesn’t have to reinsert them in case he need to test identical batteries.
As regards the technical part, the main block of the board is obviously the “battery pack block”, which includes some fundamental sub-blocks, that are: charge, discharge and monitor circuits of all connected battery packs. The “charge circuit” is composed essentially of a particular DC-DC converter suitable for the recharge of Li-Ion batteries. The “discharge circuit”, is instead more articulated and complicated, indeed it is composed of various components including: a low-pass RC filter, a Darlington transistor bjt, a non-inverting operational amplifier. To design correctly it, I had to do some test through a simulation software.
I started to design the board starting from the requirements imposed by the company, and then I started to choose the main components, and then I’ve done the complete schematic diagram of the board, during which I tested both the Accu and Jauch batteries, doing some charge and discharge cycles. Then, I started with the realization of the firmware, doing some tests on an older board and doing the FSM of the firmware. Unfortunately, due to the limited time of the internship, I couldn’t finish the firmware.
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Abstract
During the internship, I designed and developed a board to test some types of batteries, especially the Lithium-Ion (Li-Ion) ones, and those with have a nominal voltage between 3.7 V and 24 V. Specifically, I designed this board mainly for the Accu and Jauch Li-Ion 3.7 V batteries, but this board is also able to test other batteries with different nominal voltages, up to 24 V.
The purpose of the board is to identify any defective batteries. To do that, the board performs a test to one or more battery pack (up to 5), which are connected to the board through an appropriate connector on the board by the tester.
After that, the tester must configure the test according to his needs, by inserting some parameters through via the switches and the display, these parameters includes: the nominal voltage and nominal capacity of the battery pack, the discharge current and the percentage of the battery pack at both half and the end of the test, but the most important are the pre-charge and the fast-charge currents.
Then, the test of the connected battery packs will start according to a specific Fine State Machine (FSM) and there will be monitored some parameters, including: the voltage and the current of the battery packs being tested. If any error occurs, the corresponding type of error will be reported in a few ways: on display, by lighting up a red LED and also a buzzer will beep.
There are five fans, one for each battery pack, in such a way that they can cool each battery pack in case they overheat during the test. All the parameters entered by the tester are stored in a EEPROM memory, so that the tester doesn’t have to reinsert them in case he need to test identical batteries.
As regards the technical part, the main block of the board is obviously the “battery pack block”, which includes some fundamental sub-blocks, that are: charge, discharge and monitor circuits of all connected battery packs. The “charge circuit” is composed essentially of a particular DC-DC converter suitable for the recharge of Li-Ion batteries. The “discharge circuit”, is instead more articulated and complicated, indeed it is composed of various components including: a low-pass RC filter, a Darlington transistor bjt, a non-inverting operational amplifier. To design correctly it, I had to do some test through a simulation software.
I started to design the board starting from the requirements imposed by the company, and then I started to choose the main components, and then I’ve done the complete schematic diagram of the board, during which I tested both the Accu and Jauch batteries, doing some charge and discharge cycles. Then, I started with the realization of the firmware, doing some tests on an older board and doing the FSM of the firmware. Unfortunately, due to the limited time of the internship, I couldn’t finish the firmware.
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