4.5-volt MN1203 Flat Lantern Battery
4.5-volt MN1203 battery is a non-rechargeable flat battery commonly used in toys and lanterns and other flashlights, mostly in Europe, but other parts of the world as well.
4.5-volt MN1203 battery is available in zinc-carbon and alkaline chemistry, having different features and specifications.
Published: March 11, 2023. 
4.5-volt MN1203 Lantern Battery Features and Specifications
4.5-volt MN1203 battery is a flat battery featuring physical dimensions of (H x L x W) 67 x 62 x 22 mm (2.64 x 2.44 x 0.87 inches) and a pair of battery terminals on top of the battery.
Internally, a 4.5-volt MN1203 battery consists of three B-cell batteries connected in series.
Note: B-cell is cylindrical (DxH) 21.5 x 60 mm battery featuring carbon-zinc (R12) or alkaline (LR12) chemistry and is mostly labeled as U10, 336, R12, LR12, etc.
4.5-volt MN1203 battery terminals are of a different length, with a positive battery terminal/strip being shorter.
4.5-volt MN1203 battery feature several labels, including 3LR12, 2R12, G3LR12, 1289/AD28, 210, GP312S, 3336, etc.
Carbon-Zinc 4.5-volt MN1203 battery features a nominal capacity of 1000-1700 mAh, although capacity depends on the battery age, drain current, temperature, and similar.
Most common Carbon-Zinc 4.5-volt MN1203 battery label is the "3R12" battery, after Zinc-Carbon B-Cell "R12" label.
Carbon-Zinc 4.5-volt MN1203 batteries are cheap, reliable, and can provide relatively strong currents, but their shelf-life is relatively short and their capacity is smaller than the capacity of the alkaline 4.5-volt MN1203 batteries.
Alkaline 4.5-volt MN1203 batteries do cost more than Zinc-Carbon batteries, but their capacity range from 2000 mAh (high-drain applications) to 6100 mAh (low-drain applications). But, actual capacity also varies depending on the battery age, temperature, current drain, and similar.
Note: Practically all battery manufacturers offer alkaline 3LR12 batteries, with only a few also offering Zinc-Carbon 3R12 batteries.
Both Zinc-Carbon and alkaline 4.5-volt MN1203 batteries are non-rechargeable batteries and after being fully discharged, they should be recycled properly.
Rechargeable 4.5-volt MN1203 Batteries
Rechargeable 4.5-volt MN1203 batteries are rare, but thanks to the 4.5-volt MN1203 battery adapters, three AA batteries may be used instead of one 4.5-volt MN1203 battery, rechargeable chemistries included.
Rechargeable AA batteries are NiCd and NiMH batteries with NiMH batteries having a no-memory effect, very low-self discharge rate, support a large number of charging/discharging cycles, etc.
The single AA NiMH battery features capacity in the 1500-2200 mAh range and a nominal voltage of 1.2 volts.
Hence, a rechargeable 4.5-volt MN1203 battery based on three such 1.2V AA batteries, has a nominal voltage of 3.6 volts.
Due to the voltage difference of ~0.9 volts between the Carbon-Zinc/Alkaline 4.5-volt MN1203 battery and three NiMH 1.2V batteries connected in series, some devices may not operate properly.
Long Story Short: If You are looking for a new 4.5-volt MN1203 battery, go for the alkaline 3RL12 battery from reputable sellers.
Such batteries have a good capacity, they tolerate strong currents rather well, and have a good shelf life.
Carbon-Zinc 3R12 batteries are cheap, but their shelf life is too short and the capacity is too low when compared with alkaline 3LR12 batteries. IMHO of course ...
