| Electronics > Projects, Designs, and Technical Stuff |
| Intelligent BMS (Battery Management System) |
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| JohnnyBerg:
The boards arrived today, at first sight they look ok. |
| ealex:
it looks interesting how are you shifting the cell voltage to the MCU's adc ? will you publish a schematic ? |
| JohnnyBerg:
There you go ;) What this circuit does: 1. It ignores the first 2.5V of a cell as not being of interest. 2. It converts the cell voltage between 2.5 and 4.5 Volt to a current. 3. The current is then converted to a voltage, with 1.5 times amplification, giving a range of 0 to 3 Volt to the MCU. Total current draw from a cell is < 50 uA U6 = Output to MCU B6 = Positive of cell 6 B5 = Positive of cell 5 = negative of cell 6 |
| ealex:
nice - never thought of that. i've tried with resistor dividers, but the errors stack up quickly -> i've decided to go with the BQ chips. |
| JohnnyBerg:
--- Quote from: ealex on November 22, 2019, 08:58:01 pm ---nice - never thought of that. i've tried with resistor dividers, but the errors stack up quickly -> i've decided to go with the BQ chips. --- End quote --- Yaeh .. resistor dividers are a absolute no go. Not also do errors accumulate, resolution is lost also. This circuit i.c.m. with a 12 bit ADC gives a resolution in the order of 500uV. And because the voltage does not change quickly, the MCU can do noise cancellation with a moving average. |
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