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Old 3rd May 2019, 16:23   #16
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Default Re: Maruti starts fleet testing of Electric Vehicles in India

There is one quote about charging to 80 % and discharge till 0 % than to charge to 100 % and discharge to 20 % in Nissan Leaf report. If you are an EV car manufacture, I wouldn't allow any battery to discharge till 0%. This is for protection of components. When our team designed battery management systems for European OEM, we have charging cut off levels. When only 12% charge is left, we used to log a Diagnostic Trouble code(DTC) but perform no action. When 4% charge was left, we used to open contactors and log a DTC so that car comes to a safe halt. It's not a mobile phone to use till 1%. Anyways, that 4% boundary can be calibrated by OEMs and we used to get the requirements for same from the OEMs.

Regarding age of battery, the battery management system has a battery core software component. It stores the age of battery in non volatile memory since the BMS is flashed and powered with battery modules. The battery core will use this counter and run it's own algorithms to extract the best out of the battery. Also it looks like our team has overlooked the scenario of how the battery core will perform when the whole battery gets replaced. I will have to get more information from my colleagues about ageism of batteries as I didn't work on battery core part of BMS.
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Old 7th May 2019, 11:29   #17
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Default Re: Maruti starts fleet testing of Electric Vehicles in India

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Originally Posted by Ravi Parwan View Post
2. The SoC of a battery is estimated with the "net" current outgo from the battery. The storage is calculated on the last known full charged state of the battery. The net input and outgo of current is stored with the device and on the chip in the battery.

In second scenario, the current outgo from a battery once charged will be stored on the battery chip, but if the battery is left to discharge, not sure if that will be lead to inaccuracy in charge calculations.
.
This was the problem with earlier BMS (battery management systems), but now the accuracy of coulomb counting(current outgo) has increased a lot due to advanced learning and computing incorporated in BMS related to previous SoC and current battery state. Even aging, degradation, temperature etc.
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Old 7th May 2019, 23:55   #18
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Default Re: Maruti starts fleet testing of Electric Vehicles in India

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Originally Posted by rst89 View Post
There is one quote about charging to 80 % and discharge till 0 % than to charge to 100 % and discharge to 20 % in Nissan Leaf report. If you are an EV car manufacture, I wouldn't allow any battery to discharge till 0%. This is for protection of components. When our team designed battery management systems for European OEM, we have charging cut off levels. When only 12% charge is left, we used to log a Diagnostic Trouble code(DTC) but perform no action. When 4% charge was left, we used to open contactors and log a DTC so that car comes to a safe halt. It's not a mobile phone to use till 1%. Anyways, that 4% boundary can be calibrated by OEMs and we used to get the requirements for same from the OEMs.

Regarding age of battery, the battery management system has a battery core software component. It stores the age of battery in non volatile memory since the BMS is flashed and powered with battery modules. The battery core will use this counter and run it's own algorithms to extract the best out of the battery. Also it looks like our team has overlooked the scenario of how the battery core will perform when the whole battery gets replaced. I will have to get more information from my colleagues about ageism of batteries as I didn't work on battery core part of BMS.
I got some more information how BMS acts when battery packs are replaced due to degradation or ageing.

Battery core of a BMS estimates the capacity or input resistance based upon inputs it receives from cells and keeps updating non volatile memory to understand how much it has aged. Suppose a battery pack is changed in BMS, the core algorithm is smart enough to self realise that a pack is new when it sees a significant change in resistance of the pack. Other approach is BMS has information for storing the history of replacement, status of battery when it was installed and date at which it was integrated in car. All this is done at end of line. When a new battery pack is installed, the BMS realises that it is new pack from it's historic data and core algorithm recalibrates itself.
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