Battery power failure protection circuit example

Many people have asked me about the protection of low battery voltage . Today I designed a battery power shortage protection circuit for everyone . The manual switch is a hiccup protection with an interval of about 30 seconds. Once the fixed switch trips, it will be permanently protected. You can wait for a while after turning it off and then restart it. The battery voltage drops to 9.6v and the protection is activated, and the LED indicator light is on.

The picture only shows the power failure protection part and does not involve other circuits. If you can't see the picture clearly, you can enlarge it.

annotation:

The voltage of this 9.6v protection action is the voltage of transient drop when large current is applied , not the average voltage when the battery is exhausted. If this circuit is installed and a small battery is used to drive a large machine, the machine will be protected after a few times, because the small battery cannot supply a very large current, and the voltage transient drop is normal. The sampling voltage can be changed to a 9.1v voltage regulator tube, and amateurs can string several P/N junctions to adjust it. If you think the circuit is complicated, the following figure is a simpler circuit diagram.

The black picture saves two parts compared to the white picture, and replaces a larger capacitor , but there is still a difference in performance. This picture is relatively simple.

Design this circuit with the following required functions:

Base Voltage Required: Battery voltage drop count

Sampling amplifier required: difficult to design direct push relay

Power output required: Transistor direct output can be designed, but cannot handle slightly larger currents

Small power relays are required: machines below 300w can directly control the entire power supply

LED indicator light is required: it can prevent the machine from being mistaken for a malfunction

Locking circuit is necessary: ​​the release of the locking relay after power failure can avoid inverter burning failure caused by continuous malfunction

There are 12 components in total plus a relay. It is impossible to simplify any more components. If one component is missing, a function will be lost. Moreover, the reliable operation of this circuit also borrows components outside the "diagram".

Actual functionality:

The LED power-off indicator light will illuminate and indicate that the battery is low on power and the machine cannot be started.

Locking circuit, when the battery voltage is lower than the set value, the locking circuit works, and the relay is no longer attracted. The existence of the locking circuit implements the "perfect power failure protection function".
The sampling point of low power should be higher, perhaps 10.5v is very suitable, and 9.6v of high power may be too high, because the sampling circuit takes the transient value, which is the voltage of transient drop when the current is large, not the average voltage when the battery is exhausted. The sampling voltage can be changed by replacing the 9.1v voltage regulator tube, and amateurs can string several P/N junctions to adjust it.