But I have been using them for a while and these are the best cutoffs I’ve found
so that’s 2.875V & 2.75V per cell or 46V & 44V for a 16S string
The battery will go and go and go and have very little noticeable sag at all until it just starts puttering out very, very fast. It’s nothing like the gradually increasing aggressive sag of a 4.2V chemistry li-ion cell. By the time you feel sluggishness, it’s nigh empty.
I’ve also accidentally overcharged a 12S one braking down a hill to 51V (4.25V/cell on 3.65V cells) and that battery still performs excellent even today. (I just let the ESC idle for like 15 minutes until it was down to 44V)
I did ask @mooch, but he said that it varies awfully a lot depending on the cells and manufacturer, and was just curious of your specific long term use experience.
VESC_TOOL explains that “Battery Voltage Cutoff End: The input voltage below which current draw is not allowed anymore. There is still full braking current available as braking only charges the battery.”
Does it mean it will have 0 output current when input voltage is below this value?
There will still be a tiny, nearly irrelevant bit of input current drawn to idle the ESC. (in the milliamps range) No current will be sent to the motors for torque production though.
Have you ever come across this situation: when voltage is lower than battery voltage cutoff end vlaue, the motor still rotates. Only when voltage is lower than “minimum input voltage value”, then motor stops?
What do these three parameters work to each (battery voltage cutoff start/end, minimum input voltage)?
it’s 5.2 firmware, switching power supply, battery voltage cutoff start 28V/end 26V, when voltage is lower than 26V, motor still rotates. do you see any problem? thanks!
Don’t worry about the 3.2V/3.3V/whatever “nominal” voltages that are used on different web sites. Many sites get it wrong and different cells from different manufacturers can have different nominal voltages even if they are in the same chemistry family.
The nominal voltages have no practical purpose that we need to account for. All that voltage does is help to identify the chemistry and give you a rough idea where the cell spends a lot of its time if discharged very slowly. If you want to know what it is anyway then check the cell’s wrap or the datasheet for the cells you are considering buying.
If the cell is wrapped by anyone other than the cell’s manufacturer then the nominal voltage can be wrong though. But since this voltage is really nothing we need to be concerned about I guess this doesn’t matter.
The important voltage specs are the charge voltage and the low (discharge) cutoff voltage. You can check the datasheets for this too as some LiFePO4 cells have a 3.60V charge voltage spec and others use a different number. Some datasheets say to stop at 2.5V, some say higher or lower.
Oh the 3.2 is nominal…
Arrrgh
Gosh I got bamboozled lmao
Thanks for the clarification!!
I couldn’t understand why the charge voltage would be different than the max charge cutoff
Whoopsydaisy
That is too high for some LFP (LiFePO4) cells. We need to be careful about generalizing and saying all cells for a particular chemistry share the same voltage specs.
The popular A123 and Lithium Werks LFP cells have a 3.60V charge voltage spec. I’d be surprised if they were the only ones.
do you see any problem? thanks!
