state of charge (soc)/ battery load value

[dougs_huntingcart]

Installed a scottyb meter to provide a numeric value to my state of charge. I think its a great accessory, however with some knowledge comes more questions.... I need to now better understand how that value correlates to my batteries...

At full charge (post 12 hrs) the soc is 50.8 .

While travelling at full throttle (FT) :
flat road 47.3~46.9
moderate grade 45.4~45.0
significant grade 44.5~43.9

At rest (post test) 49.4 with slow climb back to 50.7.

Is it accurate to state that my soc is always indicated by the "at rest" value and the load value (at whatever load is indicated at a specific interval) is simply just that, a load value, however can be indicative of battery life?

When grading the life of my battery, I should be conscious of the soc post 12hrs, and the amount of time that the packs stay charged, right?

The load value is important, however the soc value (at rest) is the value that I should always use to indicate a need for recharge, right?

Thanks in advance.
Doug

[JohnnieB]

The are three separate battery voltages to contend with and they each provide useful information, but you have to know which of the three the meter is measuring at the time.

1. On-Charge voltage: Battery voltage while a charging current is passing through them. The charger more or less takes care of it automatically, but useful when troubleshooting battery and/or charger problems.

2. Under-Load Voltage: Battery voltage while a discharging current is flowing through the batteries. The battery voltage is inversely proportional to the amps being drawn from it. The more amps drawn, the lower the voltage.
During normal operation, try to stay above 1.75VPC (Volts per Cell), which is 42.0V for a 48V battery pack.
Never load the battery pack down to 1.50VPC or lower, which is 36.0V for a 48V battery pack. (Irreversible battery damage starts occurring at 1.5VPC)

3. At-Rest Voltage: Immediately after charging, the battery voltage is artificially high and immediately after discharging the battery voltage is artificially low. To get a reasonable accurate estimate of the battery's SoC (State of Charge) the battery has to rest for a period of time for the On-Charge voltage or Under-Load voltage to become the At-Rest voltage.
It takes about 12 hour for the On-Charge voltage to reach the At-Rest voltage and about an hour for the Under-Load voltage to reach the At-Rest voltage.

Most of the recovery from Under-Load occurs in the first few minutes, so checking the pack voltage about 5-10 minutes after stopping cart is usually sufficient for estimating SoC for determining when it is time to head towards the charger when you are out and about.

------------
Battery lifespan is determined by average SoC maintained. See Chart.

The batteries should be charged after each use. If you make numerous short trips during the day, charge each night.

[dougs_huntingcart]

Originally Posted by JohnnieB

The are three separate battery voltages to contend with and they each provide useful information, but you have to know which of the three the meter is measuring at the time.

1. On-Charge voltage: Battery voltage while a charging current is passing through them. The charger more or less takes care of it automatically, but useful when troubleshooting battery and/or charger problems.

2. Under-Load Voltage: Battery voltage while a discharging current is flowing through the batteries. The battery voltage is inversely proportional to the amps being drawn from it. The more amps drawn, the lower the voltage.
During normal operation, try to stay above 1.75VPC (Volts per Cell), which is 42.0V for a 48V battery pack.
Never load the battery pack down to 1.50VPC or lower, which is 36.0V for a 48V battery pack. (Irreversible battery damage starts occurring at 1.5VPC)

3. At-Rest Voltage: Immediately after charging, the battery voltage is artificially high and immediately after discharging the battery voltage is artificially low. To get a reasonable accurate estimate of the battery's SoC (State of Charge) the battery has to rest for a period of time for the On-Charge voltage or Under-Load voltage to become the At-Rest voltage.
It takes about 12 hour for the On-Charge voltage to reach the At-Rest voltage and about an hour for the Under-Load voltage to reach the At-Rest voltage.

Most of the recovery from Under-Load occurs in the first few minutes, so check the pack voltage about 5-10 minutes after stopping cart is usually sufficient for estimating SoC for determining when it is time to head towards the charger when you are out and about.

------------
Battery lifespan is determined by average SoC maintained. See Chart.

The batteries should be charged after each use. If you make numerous short trips during the day, charge each night.

Thank you very much. Great to have this information in one place.