APPENDIX C
1212 & 1212P Manual - Sep 2019
pg. 46
Step 3 — Setting the Empty Voltage
a. Normally a value of 1.7 volts per cell is used as the empty point. This corresponds to a setting of
20.4 V. For some sealed batteries, this may be too low. Consult the battery manufacturer if you
are unsure.
Step 4 — Setting the Discharge Factor
a. Resume driving the vehicle, with a heavy load.
b. Pay attention to the battery voltage, BDI, and time.
c. At some point, you will feel the vehicle become sluggish and notice the battery voltage drop
significantly with basic maneuvers. This is the fully discharged point of the battery. Stop driving.
d. The BDI should have indicated 0% before this point, to prevent the battery pack from wearing
out prematurely.
e. If the BDI does not read 0%, reduce the Discharge Factor parameter proportionately
to the indicated remaining BDI. Use this formula to determine the new setting:
New Discharge Factor = Present Discharge Factor * (1 – BDI%),
with the BDI% being expressed decimally (e.g., 90% = 0.90)
.
Step 5 — Setting the Charge Factor and Start Charge Voltage
How you set the Charge Factor and Start Charge Voltage parameters depends on how you want the
BDI gauge to respond to partial charging. The traditional method is to require a full recharge and
not to reset the BDI gauge until the battery is full. The 1212/1212P can also be programmed to allow
the user to stop the charge in mid-cycle and display a proportional amount of charge, or “partial
charge” reading.
If you want to require a full charge to reset the BDI gauge:
a. Set the Charge Factor to 10.0.
b. Set the Start Charge Voltage equal to the Full Charge Voltage.
With these settings, the BDI will not recalculate until the very end of the charge cycle, and the Reset
Voltage—not the charge time—will trigger the BDI to 100%.
If you want to use the partial charge feature:
c. Based on the Amp Hour rating of the batteries and the charger’s average amp output, initially
calculate and set the Charge Factor using this formula:
Charge Factor = 1.5 * (Battery amp-hrs / Charger amps).
d. Starting with the dead battery from Step 4, plug in the charger. After 10 minutes of charging,
measure the battery voltage with a meter. Set the Start Charge Voltage parameter to this value.
Step 6 — Rerun and Verify
This procedure will give good initial settings for the BDI algorithm. You should test these settings
under various conditions to verify that they provide an acceptable indication of the battery state of
charge. The settings can be fine tuned by repeating the entire procedure.
It is important to note that battery age and driving conditions (hilliness, driving surface, weight of
user) will all affect the accuracy of the BDI measurement.