Homemade simple battery discharge meter circuit diagram

Using the brushed controller of an electric vehicle (48V×8A≈400W), I made a homemade battery discharge meter, as shown in Figure 1. When the battery voltage drops to 42V, the brush controller will no longer output and will sound an alarm. 48V electronic horn for electric vehicles. The time measurement system directly uses electronic clocks on the market to measure time. After the electronic clock is powered on, it starts timing from "0.00". When the speaker sounds an alarm, the time displayed by the electronic clock is the battery discharge time. Multiplying this time by the discharge current is the actual capacity of the battery group.

In actual use, a red clip is welded to the positive end of the discharge meter to connect to the positive pole of the battery pack, and a black clip is welded to the negative end to connect to the negative pole of the battery pack. At this time, the electronic clock starts timing, and at the same time a loud alarm sounds from the speaker. Press it quickly. ANI (button switch without self-locking), the horn will no longer sound, and the ammeter should have a discharge current indication. When the voltage of the battery pack drops to 42V, the controller will stop output, relay K loses power, normally open contacts K1 and K2 are disconnected and will no longer continue to discharge, normally closed contacts K1 and K3 are closed, and a loud sound is emitted from the speaker. The alarm sounds to indicate that discharge is complete. At this time, write down the time displayed by the electronic clock. This time is the discharge time of the battery pack. Then multiply this time by the discharge current to estimate the actual capacity of the battery pack. This method is convenient and practical, and interested colleagues may wish to give it a try.