The battery voltage or internal resistance of different brands may be different, and the composition of chemical substances may also be different. The same type of specifications but different brands of battery mixing is less harmful, just because the internal resistance of different brands is different, although it will also reduce battery efficiency, but it is not very large.
The old and new batteries can’t be mixed. The internal resistance of the old battery is large. After mixing, the new battery will be wasted. Because the old and new batteries are connected in series, the discharge current is equal in the work and the amount of electricity discharged is also equal. Old batteries have low available capacity. Therefore, the old battery will be discharged first. Then there are two situations with the appliance.
- Electrical appliances do not work. Then the new battery has the remaining capacity but it can’t be used, so the new battery is wasted.
- The appliance can continue to work, the old battery is over-discharged, which may lead to leakage or even explosion.
The rechargeable battery should use the same brand and use the battery that is charged together. The life will be longer.
If the old and new batteries are used in series, then in the state of charge, the charging voltage at both ends of the old battery will be higher than the charging voltage at both ends of the new battery, resulting in the new battery not being fully charged, and the old battery is already too high.
On the contrary, if the old and new batteries are used in series, in the discharged state, since the capacity of the new battery is larger than that of the old battery, the old battery is excessively discharged, and even the old battery is reversed, and the battery bulges causes side effects. Do not mix rechargeable batteries of different brands.