Lead-acid battery overcharge protector circuit

With the continuous replacement of lithium batteries, lead-acid batteries are no longer the object of choice for people in the future due to heavy pollution of the environment, but now many electric vehicles and power tools still use lead-acid batteries. There is no doubt that lead-acid batteries As a power battery, it has its advantages in design. The advantage is that the open-circuit power it provides is relatively large (compared to lithium batteries). A 12V battery only needs to be made into a battery, and the lithium battery is used as power The battery may need to be connected in series to form a battery pack. Therefore, for the design of power batteries, lead-acid batteries can be relatively easy to achieve, while lithium batteries need to encounter many problems in the design, later charging, and maintenance. In terms of manufacturing cost, the current power battery is better for the former and higher for the latter. Therefore, it is also very important for us to master some common sense of lead-acid batteries.

The following figure shows a lead-acid battery overcharge protector circuit. It can be used as a medium and small lead-acid battery with a capacity of 2-30Ah to avoid overcharging in the state of floating charge (that is, while supplying power to the load, while receiving trickle charging or solar panel charging).

When overcharge does not occur, the transistor VT does not conduct due to the blocking of the Zener diode VS. When the charging voltage rises to about 14V, VT begins to conduct, it shunts the battery to prevent the evaporation of the electrolyte, which is conducive to heat dissipation. The VT is mounted on a medium-sized heat sink, and the VT can be 2N3055 or NTEI43A. If a lower voltage Zener is used, the circuit can also be used on nickel-cadmium batteries.