Chronic Battery Undercharge: A Hidden Threat in Winter

The battery's performance directly determines whether the engine will start, especially in winter. If the actual capacity is reduced or the starting current is insufficient, the starting process becomes noticeably more difficult, and sometimes impossible. It is noteworthy that even owners of cars with a newly installed battery face such difficulties. In most cases, the reason is not a defect, but a constant undercharge, which gradually worsens the key characteristics of the battery.

Why There Are Almost No Problems in Summer

In warm weather, the battery rarely causes trouble. At temperatures close to room temperature, its parameters are close to nominal values. The engine turns over more easily because the engine oil retains low viscosity. All this creates favorable conditions for starting and quickly recharging the battery from the generator.

With the onset of frost, the picture changes radically. Starting the engine requires significantly more energy, while the battery itself begins to lose efficiency due to the cold. Thus, at a temperature of −20 °C, even a fully functional new battery is capable of delivering only about 35% of the stated characteristics. As it wears out, the real capacity and starting current decrease even more.

Chronic Undercharge as a Key Problem

Regular undercharge creates an additional load on the battery. It occurs when the car is operated in short trips, when the battery does not have time to recover the spent capacity. In summer, this rarely happens: the generator replenishes the charge quickly enough. In winter, the situation is fundamentally different. At −20 °C, a standard battery accepts a charge approximately 20 times slower. Only as the underhood space warms up does the charging efficiency gradually increase.

If the car is regularly used for trips lasting up to 30 minutes, the risk of chronic undercharge becomes very high. This condition triggers the sulfation of lead plates, which leads to a decrease in capacity, a decrease in starting current, and a deterioration in other battery parameters.

How Much Time is Needed for a Full Charge in Winter

Measurements taken at a temperature of −20 °C show that to compensate for the energy spent on one engine start, the battery requires about 20 minutes of idling. During this time, the battery begins to warm up and better receive charge from the generator. The exception is cars in which the battery is located in the trunk: the temperature there rises much more slowly, so the charging process is delayed.

However, returning the energy spent on starting does not mean a full charge. If the battery is already in a state of undercharge, it also needs to be compensated. Measurements show that at −20 °C, this requires approximately two hours of driving in urban mode. During this period, the battery fully warms up and is able to restore capacity to the maximum level. In more severe frosts, the required time increases, and in milder weather, on the contrary, it decreases.

Long-Term Consequences of Short Trips

In modern conditions, many drivers operate a car mainly over short distances and rarely go on long trips. In the short term, this does not cause serious problems, but over time the battery begins to wear out noticeably faster. In addition, concomitant negative effects may appear. For example, in some engines with direct fuel injection, gasoline accumulates in the engine oil during winter short trips. It worsens the properties of the lubricant and completely evaporates only with sufficiently long driving.

What to Do for a Car Owner

You can ignore the problem, but then you should be prepared for a reduction in battery life and difficulties starting the engine in severe frost. An alternative to regular long trips is to independently recharge the battery with a small current using an external device. It is enough to perform this procedure once a month in winter to minimize the negative impact of short trips and maintain battery characteristics at an acceptable level.