General EV Discussion

[MikeG]

Have you joined the 0% SoC club?

LOL 2% is my best - I've heard that the BYD's have a about 10km range after hitting 0% but I'm not keen to test that

That's not good for the battery - advice is to try to keep SOH above 20%.

Depends on the battery chemistry to a certain extent, and whether 20% in the EV is actually 20% of battery charge - cars tend to have some lee-way with charge below indicated 0%.

 

[Quickstatus]

LOL 2% is my best

The battery shutdown in a Tesla occurs theoretically at -3.5% but that is highly dependant on battery reading calibrations.

Depends on the battery chemistry to a certain extent

It appears from my research that it is independent of Li ion battery chemistry
Tesla have a -3.5% Hidden below displayed 0%

 

[anat0l]

LOL 2% is my best - I've heard that the BYD's have a about 10km range after hitting 0% but I'm not keen to test that

#iykyk

 

[MikeG]

Unlike NMC, dropping LFP to 0% poses no safety risk and causes minimal cycle degradation. However, LFP voltage drops very flat at low states of charge, which can make it hard for your car or system to accurately calculate your remaining range.

 

[Flyerwin]

 

[Quickstatus]

However, LFP voltage drops very flat at low states of charge, which can make it hard for your car or system to accurately calculate your remaining range.

No, at low SoC it is actually accurate as it is at high SoC - because there is a larger change in voltage relative to SoC.
The middle parts is relatively flat which can introduce some inaccuracies in energy estimations- red bottom curve. For example in the graph 40% cold be 60%. That is why LFP require periodic charging to 100% so the car understands how much charge went in to the battery by direct measurement when it hits 100% which is the max voltage.

 

[moa999]

There is another issue in most EVs with keeping a battery at low charge and that is many EVs topup the starter/accessory battery from the main battery. And in many cars that's on old school lead acid battery.

And this is turned off below a certain number.
No issue on a long trip, but will likely kill the secondary battery if you keep the car at low state of charge for weeks.

 

[Quickstatus]

And this is turned off below a certain number.

The low power consumption mode activates when the BMS detects a Main battery voltage corresponding to 0% in most cases -at least that is what happens in a Tesla. That assumes of course that the displayed % is accurate (as it is always an estimate).

If the LV battery goes flat, the car cannot be woken up or doors unlocked in the usual way.

Interestingly a 9V square battery from Bunnings can wake up a Tesla from an extremely low voltage situation. But who ever keeps a 9V battery handy?