The Old and New Diesel Generator Set Batteries Cannot be Mixed Use

The battery is an essential component of the starting system of diesel generator sets, with a service life of generally about 3 years. After a certain period of use, the battery will experience varying degrees of wear and tear, and its internal resistance will gradually increase with use, while the electromotive force will gradually decrease. Dingbo Power has found that some users, in order to save maintenance costs, replace batteries with higher losses with new batteries of the same model. This has led to the situation of mixing old and new batteries in series. Dingbo Power does not recommend users to do so because it greatly affects the service life of batteries and also poses a considerable risk.

Different batteries have different internal resistances and potentials due to the different electrolytes inside. When using them in combination, if they are connected in series, it may cause batteries with low internal resistance and potential to discharge excessively, deplete their inventory in one go, and generate internal current exceeding the allowable value, leading to rapid aging and scrapping. At this point, the new batteries in the battery pack will also be dragged down, causing a chain reaction. If connected in parallel, it will generate internal circulation in the battery pack, which may weaken the external output and cause the battery to heat up or even explode. Even for emergency use, do not mix batteries with different internal electrolytes.

New batteries have higher terminal voltage and lower internal resistance due to the presence of more chemical reactants, while old batteries have lower terminal voltage and higher internal resistance. Generally, the internal resistance of a 12V new battery is 0.015-0.018 ohms, while the internal resistance of an old battery is mostly above 0.085 ohms.

If the old and new batteries are used in series, the charging voltage at both ends of the old battery will be higher than that at both ends of the new battery in the charging state, resulting in the new battery not being fully charged while the old battery is already too high. In the discharging state, due to the larger capacity of the new battery than the old battery, the old battery will be over discharged, and even cause the old battery to reverse polarity and swell, causing side effects. It will consume the electrical energy of the new battery, and also cause unstable voltage inside the appliance, as well as the danger of overuse of old batteries.

Mixing old and new batteries, whether used in series or parallel, has many drawbacks. Therefore, Dingbo Power does not recommend users to mix old and new batteries. If you want to extend the service life of the battery, you should correctly and timely maintain the battery in daily use to ensure its service life and normal operation.

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