[Megatron451]

So I haven't seen one yet, so I'll start it and probably someone has already done it. So I've got a nominal battery pack that is 364.8V, a calculated Charge voltage cut-off of 403.2V, and a calculated discharging cut-off of 316.8V. So what should my fuel gauge full and empty voltages be? I was thinking of removing 10% from the discharge, so something like full would be 365ish volts to 347V? Doesn't seem like very much, what do you guys use for full and empty? I know we don't want to go from 100% to 0%, but something in-between.

For sake of argument, my batteries are basically the LG 60.8V, 6 in series that EV west sells here Lithium Ion Battery - 60.8V, 2.6kWh, EV West - Electric Vehicle Parts, Components, EVSE Charging Stations, Electric Car Conversion Kits


Thanks for the feedback and info.

 

[Zieg]

Knowing the type of cells would help a lot. The chemistry matters for this.

 

[Megatron451]

Knowing the type of cells would help a lot. The chemistry matters for this.

Sorry about that, I have now updated my post

 

[remy_martian]

You have to count coulombs - voltage readings won't work very well.

 

[Ken S]

You could setup a low voltage warning indicator, or a low voltage cutoff, but it's difficult to measure state-of-charge directly, especially while the battery is discharging. Coulomb-counting is part of the job of the BMS.

Speedhut sells state-of-charge gauges that read from the CAN bus output of the BMS.
Gauge Applications - Freedom CAN-Bus for EV - EV Gauges for Orion, Zero EV & Thunderstruck - EV Battery Level - SPEEDHUT® Custom Gauges

Some suppliers can customize gauges. I have an SOC gauge that reads a 0-5V analog signal from the BMS.

 

[remy_martian]

Anyone know if those CAN messages for those gorgeous Speedhut guages are documented anywhere?

May be useful to those brewing their own BMS...