Battery Average Voltage when low SOC

[twiersum]

My car's range dropped a lot over the last year. I was curious so I drove my car down to below 25 mile range and noticed my brick voltages are still 3.7v? What is the lowest anyone has seen?

If I recall from my battery rebuild a few years back that the car didn't wake up until around 3v. Just wondering how low the system will go before emergency shut down.

 

[twiersum]

For posterity sake...my model S reads 323v (3.36v per) with 9 miles to go. That would lead me to speculate that 0 miles is 3.30v and they are known to go another 20ish miles before shutdown which would maybe be 3.20v.

 

[hcsharp]

I'm pretty sure it's about 3.55 for the original Roadster cells. I used to know exactly but can't find it right now.

 

[Retiredeh]

For posterity sake...my model S reads 323v (3.36v per) with 9 miles to go. That would lead me to speculate that 0 miles is 3.30v and they are known to go another 20ish miles before shutdown which would maybe be 3.20v.

Not sure if this is of help or relevant but according to the Roadster Service Technical Training manual 0% SOC is 3.0 volts which seems excessive and dangerous. As I recall from an EV conversion project I was involved in during the early days of applying Li-Ion, the safe design limit is traditionally to never fall below 3.2 Volts but that was for LiFePO4 so something tells me it depends on chemistry. This seems to imply the Li Cobalt in the roadster is safe to 3.0 volts??

I suggest you call Gruber to confirm how low you can go in the real world and how low you can go before things are unrecoverable.

 

[twiersum]

Good find. That correlates with what I found in recovering the pack....the system woke up at 3.0 volts. However, the curve doesn't look like many capacity tests I've seen where there is still significant capacity from 3.7v down to 3.2v.

 

[twiersum]

Peter at Gruber mentioned his docs state 3.36v is equal to a 1% SOC which would mean it is probably 3.3v to 0% and 3.2v shutoff...same as Model S.

I am going to run mine down to below 3 4v and reset my soc parameter and I suspect my range will increase. We'll see.

 

[Retiredeh]

Peter at Gruber mentioned his docs state 3.36v is equal to a 1% SOC which would mean it is probably 3.3v to 0% and 3.2v shutoff...same as Model S.

I am going to run mine down to below 3 4v and reset my soc parameter and I suspect my range will increase. We'll see.

I suspect we can learn a lot from your experience. How did things go? Does this help balance the pack as well?