Can a 12V 1 Amp Charger Charge a 12V 5 Amp Battery and for How Long?

Yes, a 12V 1 amp charger can charge a 12V 5 amp battery, but it will take longer than if using a charger with a higher current rating.

Charging Time Calculation

To estimate the charging time, you can use the formula:

Charging Time (hours) Battery Capacity (Ah) / Charger Current (A)

Battery Capacity: A 12V 5 amp-hour (Ah) battery has a capacity of 5 Ah.

Charging Current: The charger provides 1 amp (A).

Calculation:

Charging Time 5 Ah / 1 A 5 hours

Important Considerations

Efficiency

The actual charging time may be longer due to inefficiencies in the charging process, typically around 10-20% longer.

Battery State

If the battery is deeply discharged, it may take longer to charge fully.

Charger Type

Ensure the charger is suitable for the type of battery, e.g., lead-acid or lithium-ion, as different battery types have different charging requirements.

In summary, using a 12V 1 amp charger, it will take approximately 5 hours to charge a 12V 5 amp-hour battery under ideal conditions.

Further Considerations

Using a 12V 1 amp charger can still work, but it will take much longer than ideal conditions:

It is only if the voltage in the 1 amp battery is slightly higher. As the voltages equalize, the charging will stop. If the battery charger is made for the same kind of cell chemistry as the battery, it should work, but it will take about 5 times longer to charge. If the battery chemistry is different, it may not work. There is a risk of blowing a fuse on the charger, but most modern chargers are current-limited to prevent this. With a lithium battery and charger, it may not work as well because these have more restrictions on current limits and energy transfer for safety reasons.

Understanding Amps and Amp-Hours

There might be confusion between Amps and Amp-Hours. An Amp is a measure of current, while an Amp-Hour is a measure of total battery capacity. Therefore, your 5 Amp battery is really a 5 Amp-Hour (Ah) battery. If this is the case, your battery may be rated for a maximum of 5 Amp charge current.

No matter the rating, a 12V battery charger will handle the situation without issues. The charger designed for a 12V battery works by automatically adjusting its output voltage so that the battery draws no more than 1A. As the battery charges, the output voltage rises to maintain the 1A output. Once the battery voltage reaches a certain value, the charger drops its output voltage to maintain a very low current charge.

Briefly, you should be fine with a 12V 1 amp charger for a 12V 5 amp-hour battery, provided that the battery can handle a charging current of 1A. A 5Ah battery can easily handle a 1A charging current, and so can a battery rated for a 5A charging current.

Without seeing the charger or the battery, it is impossible to be definitive, but the fundamental principles outlined above are reliable and should guide your decision.