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Ignition installation
Wire to the 12 V power

To protect the battery, the BMS must be powered whenever there is any current in or out of the pack.

If there is any current in or out of the pack, yet the BMS is off, your pack IS NOT PROTECTED!

If there can be any drain on the battery when the ignition is off, then the BMS has to be powered at all times, and the BMS has to be able to shut off that load as well.

A load that is permanently connected to the battery pack will damage your pack, even if it has a low voltage cutoff. That is because the lowest capacity cell can be overdischarged before the pack voltage is low enough to trip the low voltage cut-off.

Therefore, the BMS MUST be able to shut down all the loads draining the battery; a load with a low-voltage cut-off may be of no help.

In a properly designed EV with a Li-Ion pack, there is no load on the pack whenever the ignition is off (and the vehicle is not plugged into the AC power).

In that case, the BMS is powered by the ignition 12 V.

These instructions assume that:

User supplied required parts:

Here are some suggestions for proper tools.

Connect the ignition power to the BMS master:

  • Find a +12 V line that is fused and switched by the ignition switch and wire it to the BMS master, control connector, pin 23 ("IGN")
  • Find a ground line (a.k.a: "12 V common", or "12 V return", or" 12 V negative") and wire it to the BMS master, control connector, pin 24 ("GND" symbol)

Note that this schematic shows a 12 V auxiliary battery (Lead Acid); whenever the EV is plugged to the AC power, a charger (simple, inexpensive and widely available) charges the 12 V battery.
Be sure to install an AC fuse at the AC power inlet.

BMS master, connection point highlighted
Connection location.
Ignition power to a Lithiumate Lite master


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Page published on: Jul 19 2013.      Installation manual