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Section IV
Constant Current Model
006-0007207 MPC-1250DC Guide
Rev F
31 of 44
03/03/2022
Note that the battery’s output voltage is only an approximate indication of the charge level.
The true charge level of the battery cannot be measured by the MPC‑1250 since the MPC‑1250
cannot differentiate between current delivered to the battery and current delivered to the end‑
use equipment. A third party battery monitor must be used to increase measurement accuracy
of the battery’s state of charge.
Output Vampire Current – Unpowered
When input power is unavailable, the constant current model is designed to draw < 2 uA while
connected to an external 28 V battery. This allows the MPC‑1250 to remain connected to a
battery for extended periods of time while in storage without the concern of discharging the
battery. It is likely the self‑discharge current of the battery will be higher than the MPC‑1250
vampire current.
When input power is available and the MPC‑1250 is not enabled, the vampire current increases
to 250 – 450
µ
A, depending on the output voltage. The MPC‑1250 output should be enabled
periodically to keep the battery charged when input power is available.
Reverse Polarity Protection
The Constant Current model provides reverse polarity protection on the DC output. This prevents
catastrophic damage in the event the output is connected to the battery terminals improperly.
The Constant Current model is the only model that has reverse polarity on the output.
The MPC‑1250 monitors the output voltage, and will not enable the output if it measures lower
than ‑1 V. Once the output voltage is measured higher than ‑1 V, the output will respond to
enable commands from the user. Note that all other features will still be available if reverse
voltage is applied to the output. This includes indication LEDs, serial communications, and the
web page.
The output is protected as low as ‑60 V. Applying a voltage lower than ‑60 V will cause
permanent damage.
Unlike the DC output, the DC input includes reverse polarity protection for all models. The DC input
is protected as low as ‑60 V. Applying a voltage lower than ‑60 V will cause permanent damage.