These settings have been extensively tested by SOK Battery to ensure the proper function of both the battery and the shunts. Deviating from these settings may lead to inaccurate measurements.
Settings For Victron SmartShunt & BMV-712:
The settings only – these are explained more in depth below to better explain if these need fine tuning.
- Battery Capacity: Varies depending on system. See below
- Charged Voltage: 13.8 (12v systems) / 27.6 (24v systems) / 55.2 (48v systems)
- Discharge Floor: 10%*
- Tail Current: 2.00%
- Charged Detection Time: 3m
- Peukert Exponent: 1.05
- Charge Efficiency Factor: 98%
- Current Threshold: 0.10a
- Time-to-go averaging Period: 3m
- Battery Starts Synchronized: Disabled
- State of Charge: 30% (If connecting to new batteries only!)
Settings for Victron Lynx Shunt:
- Battery Capacity: Varies depending on system. See below
- Charged Voltage: 13.8 (12v systems) / 27.6 (24v systems) / 55.2 (48v systems)
- Discharge Floor: 10%*
- Tail Current: 2.00%
- Charged Detection Time: 3m
- Peukert Exponent: 1.05
- Charge Efficiency Factor: 98%
- Current Threshold: 0.10a
- Time-to-go averaging Period: 3m
NOTE: The lynx shunt will initially show “–” on the Cerbo-GX for state of charge. If you ever see this “–” reading, simply charge the battery until the cycle has completed. At this point the %SOC will synchronize to 100% and be accurate from then on. If you have been using the Lynx Shunt and loose power to the system (such as the situation where the batteries shut down), then the SOC% will be lost – only to be regained when the batteries reach 100% again.
Explained:
Battery Capacity:
This is calculated by adding up the amp-hour (Ah) rating of all PARALLEL strings. For example 2x 100ah batteries in parallel would be 200ah. Series batteries add voltage together; amp-hour capacities do not add together in series.
Charged Voltage:
This is DIFFERENT than the absorption / charging voltage! It is the voltage at which the shunt considers the battery close enough to fully charged to start detecting a current drop (the current drop indicating a true full charge).
Victron’s recommendation is setting charged voltage .2v below absorption voltage – while perfect for most lead-acid batteries with a long absorption period, it’s not perfect for the SOK Lithium batteries.
The problem is, in order for the shunt to synchronize to 100%, the batteries must be above this voltage, and while above this voltage, the current must drop below the tail current threshold. If this voltage is set too high, then it will never start monitoring for the current to drop meaning it never catches the condition that means the batteries have truly reached 100% state of charge.
Discharge Floor:
This is for you to adjust. Let’s say you setting this at 10%; when you get to 10%, the Smartshunt will indicate 10% remaining and 0 minutes until empty on the “time to go” reading. If you choose to know how long until you have fully discharge your battery instead, then set this to 0%. If you want to be more conservative on your time remaining, then set this to 20% or higher.
Tail Current:
After the previously mentioned “charged voltage” has been reached, this is how much the current must taper down to trigger a synchronization. Our testing has proven the default value from Victron is sufficient for proper detection.
Charged Detection Time:
Also working in conjunction with “charged voltage” and “tail current”, once the tail current has reached the appropriate set-point, it waits this amount of time to make sure the current drop isn’t just momentary and that it is truly occurring because the battery is full.
Peukert Exponent & Charge Efficiency Factor:
These are fixed values driven by characteristics of the battery itself. No tweaking or adjusting needed here.
Current Threshold:
The minimum amount of current the shunt can detect. This does not pertain to the battery itself.
Time to go averaging period:
How often the time-to-go readout is recalculated and update. This also has no effect on the battery itself.
Battery Starts Synchronized:
This only applies to the SmartShunt and BMV-712. If this setting is enabled, then every time the shunt looses power, it will set the SOC% to 100% at power up, instead of saving where it was previously at. This could cause confusion if turned on. Let’s say you are draining your batteries and reached 0% remaining and the BMS cuts off. When you start recharging, the shunt will show 100% immediately, since the shunt lost power and changed the SOC% to 100%. Obviously a totally empty battery just put on the charger wouldn’t be at 100%!
State of Charge:
This is a manual override to set the SOC%. If you just got your batteries, then they ship from the factory at approximately 30% charge, per DOT regulations. You could then manually set 30% so your shunt is close to accurate on the first charge. Similarly, if the batteries shut down on over-discharge, and the shunt lost it’s place, then you could also set this to 0% so you could have an idea of how much the batteries have charged.