Universal Power Group UB121000 12V 100Ah Sealed Lead Acid Battery

Universal Power Group UB121000 is very popular deep cycle Absorbent Glass Mat (AGM), Sealed Lead Acid (SLA), deep cycle battery, very often used in standby and cycle applications like solar/wind battery, medical/security battery, UPS battery, but also as trolling motor battery, RV house battery, etc.

Universal Power Group UB121000 offers good performances, strong and reliable construction, spill-proof design, etc. at a rather affordable price.

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Universal Power Group UB121000 Features and Specifications

UPG UB121000 battery features a nominal voltage of 12 volts and a nominal 20h capacity of 100 Ah.

Its physical dimensions are (L x W x H) 12.17 x 6.61 x 8.3 (9.16 with terminals) inches (~30.9 x 16.8 x 21.1/23.3 cm) and it weighs 63.9 pounds (~29 kg).

UPG UB121000 battery belongs to BCI Group Size 27 batteries, although it is somewhat longer than the actual group 27 battery size, and with terminals, it is somewhat taller:

- BCI Group 27 Size: 12.0625 x 6.8125 x 8.875 inches (306 x 173 x 225 mm),

- UPG UB121000 size: 12.17 x 6.61 x 8.3 (9.16 with terminals) inches (309 x 168 x 211/233 mm).

Note: whenever You need to buy a new battery (or batteries), check your battery compartment size and check the actual battery size. Among other details, of course ...

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UPG UB121000 battery comes in two versions, differing only in terminals: UPG #45978 with Z1 terminals and UPG #45973 with M6 terminals. All information in this article is given for the UPG #45978 with Z1 terminals.


UPG UB121000 may be used in standby and deep cycle applications.

When the battery is used in standby applications, its estimated operating life is 3-5 years, which depends on the average battery temperature (cool and dry areas are recommended for longer operating time), but also on the quality of battery charger/maintainer that keeps the battery charged during this period.

In standby/float applications, charging voltage should be in 13.6 - 13.8 volts range, with a maximum charging current of 15 Amps.

When the UPG UB121000 battery is used in deep cycle applications, charging voltage should be in the 14.5 - 14.9 volts range, with the maximum charging current of 30 Amps.

Personally, if you are not in a hurry, charge UPG UB121000 battery even in deep cycle applications with 15 Amps max - this will prolong charging time, but it will also keep the battery cooler.

When charging UPG UB121000 and similar AGM battery, it is highly recommended to use smart/intelligent AGM battery chargers that analyze the battery first and only then charge it according to the battery's condition - temperature compensation included.

When the UPG UB121000 battery is used in deep cycle applications, its operating life is defined as the number of charging/discharging cycles that the battery may endure with the certain capacity loss:

- 100% DoD: ~200 charging/discharging cycles with the capacity loss down to 80% of nominal capacity, ~210 cycles charging/discharging cycles with the capacity loss down to 60% of nominal capacity,

- 50% DoD: ~470 charging/discharging cycles with the capacity loss down to 80% of nominal capacity, ~510 cycles charging/discharging cycles with the capacity loss down to 60% of nominal capacity,

- 30% DoD: ~1180 charging/discharging cycles with the capacity loss down to 80% of nominal capacity, ~1210 cycles charging/discharging cycles with the capacity loss down to 60% of nominal capacity.

For short, in order to prolong the operating life (increase the number of charging/discharging cycles) of your battery, don't discharge it completely.


UPB UB121000 battery features acceptably low self-discharge rate - it can't be compared with some Gel-cell models and certainly not with lithium batteries, but if left unattended for some time, UPB UB121000 battery will not self-discharge in a blink of an eye. On the contrary:

- when the battery is stored at 68°F (20°C), the fully charged battery will keep ~91% of its charge after 3 months, ~83% after 6 months and ~64% after 12 months,

- if the storage temperature is 104°F (40°C), the fully charged battery will keep ~80% of its nominal charge after ~3 weeks,

- if the storage temperature is 86°F (50°C), the fully charged battery will keep ~80% of its nominal charge after 3 months,

- if the storage temperature is 41°F (5°F), the fully charged battery will keep ~80% of its nominal charge after 18 months.

Note: when the battery is stored, it should be recharged when its capacity drops down to 80%. In order to store the battery safely, store it in a cool area and preferably, connect it to a good AGM battery maintainer.

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 UPG UB121000 Discharge Charts

Constant current discharge features for the UPG UB12100 battery are given in the following chart - values are given in Amps, at 77°F/25°C:

Battery End Voltage (V) 5 min 10 min 15 min 30 min 1 hr 2 hr 3 hr 4 hr 5 hr 8 hr 10 hr 20 hr
9.60 V 351.5 256.5 180.5 109.3 57.0 33.3 24.4 19.0 15.7 11.0 10.0 5.4
10.20 V 309.7 233.7 161.5 103.6 53.6 31.7 23.8 18.5 15.4 10.8 9.7 5.3
10.50 V 298.3 222.3 152.0 100.7 52.3 31.0 23.2 18.2 15.2 10.7 9.5 5.2
10.80 V 286.9 210.9 142.5 97.9 50.4 30.2 22.6 18.0 14.8 10.5 9.3 5.1
11.10 V 275.5 199.5 133.0 95.0 48.5 29.5 21.9 17.4 14.4 10.2 9.0 4.9

Nominal 20h capacity of the UPG UB121000 is 100 Ah, but as the discharge current is increased, the actual capacity is decreased - the actual capacity of UPG UB121000 is given in the following list (official manufacturer data, and our recommendation):

- 20h, 5 Amps: 100 Ah; 5 Amps, 100 Ah,

- 10h, 9.3 Amps: 93 Ah; 9.3 Amps, 93 Ah,

- 5h, 17 Amps: 85 Ah; 15.2 Amps, 76 Ah,

- 1h, 60 Amps: 60 Ah, 53.6 Amps, 53.6 Ah.

Note: as the battery is being discharged faster, lower end-voltage is acceptable (electrolyte mixing in AGM batteries is somewhat different/slower than in flooded/wet cell batteries), although personally, I would never discharge AGM below 10.5 volts - better safe than sorry.

Constant power discharge features for the UPG UB121000 battery are given in the following chart - values are given in watts, at 77°F/25°C:

Battery End Voltage (V) 5 min 10 min 15 min 30 min 1 hr 2 hr 3 hr 4 hr 5 hr 8 hr 10 hr 20 hr
9.60 V 3732.6 2818.7 1917.1 1160.0 660.3 384.8 283.1 220.4 181.5 128.3 115.9 62.4
10.20 V 3438.1 2594.5 1792.7 1149.5 620.4 367.7 275.5 214.7 178 125.4 113.1 60.8
10.50 V 3383.0 2521.3 1723.3 1141.9 600.4 359.1 268.9 210.9 175.8 124.5 111.2 60.0
10.80 V 3339.3 2454.8 1658.7 1139.1 584.3 351.5 263.2 207.1 172.9 121.6 110.2 59.8
11.10 V 3278.5 2374.1 1582.7 1130.5 576.7 350.6 260.3 206.2 172.0 120.7 107.4 58.0

As one can see, UPG UB121000 is able to provide 3732 watts for 5 minutes when being discharged down to 9.6 volts.

As one can see from these charts, UPG UB121000 is not the best starting/cranking battery, despite its size. On the contrary, there are much smaller batteries that can crank much larger gas/diesel engines.

However, UPG UB121000 features ~5 m internal resistance and can be safely used for cranking smallish engines NOT requiring more than 250-300 cranking Amps - typically found at power generators, smaller boats, and similar.

But, cranking/starting is not what is UPG UB121000 designed for.

UPG UB121000 As The Off-The-Grid Battery

UPG UB121000 may be used as an excellent and affordable off-the-grid battery.

With its 12V voltage and 100Ah capacity, it is able to provide ~100 watts for 10 hours, without voltage dropping below 11.1 volts - and this is excellent for the battery durability.

Also, when the battery is being recharged using solar panels and wind turbines with a maximum charging current of ~15 Amps, it can be recharged in less than 8 hours, without additional stresses on the battery.

Note: 30 Amps is the maximum initial charging current recommended by the manufacturer for deep cycle applications. Keep it lower, and the battery will last longer ...

UPG UB121000 As The Electric Trolling Motor Battery

upg ub121000 mUPG UB121000 is an excellent and very popular electric trolling motor battery - there are similar group 27 batteries that may store more energy, that can power electric trolling motors for a longer time, etc.

But, UPG UB121000 can do all that at a rather affordable price and since it was and still is used by many users, the battery is tested in real-life situations by countless users and it has shown to be very reliable when used and charged properly.

And when not used/charged properly, it may lose capacity and ability to recover when discharged down to 100% DoD, but short-circuit cells are very rare - which is very important when you are trolling away from the shore.

When 50 Amps trolling motors are used at full throttle, UPG UB121000 may power them for at least 1 hour and when the current is lowered down to 25 Amps, then:

- according to the constant current discharge charts, UPG UB121000 may provide 25 Amps for almost 3 hours,

- according to the constant current discharge graph, UPG UB121000 may provide 25 Amps for 3 hours down to 1.8 volts per cell (10.8 volts battery end voltage).

Note: data are taken from the official UPG UB121000 manual. Since UPG doesn't provide official Reserve Capacity (RC) value for UPG UB121000, it is safe to assume that the RC for UPG UB121000 is slightly less than 180 minutes, probably around 165-170 minutes (180+ minutes according to the discharge graphs, but always play safe and assume lesser values).


Long Story Short: UPG UB121000 battery is well balanced deep cycle AGM battery, suitable for various both standby and deep cycle applications.

It can be even used for starting/cranking of smaller gas/diesel engines (250-300 Amps max.) found in power generators, smaller boats, and similar, but that is not what this battery is designed for.

As a trolling motor battery, solar/wind battery, in security/medical systems and similar, UPG UB121000 is excellent and affordable choice.

And if larger battery packs are required, it can be easily connected in series/parallel for achieving larger voltages/capacities.

If UPG UB121000 fits your needs (and your battery compartment), consider it as your next deep cycle AGM group 27 battery.

For more reviews and recommendations, feel free to check Universal Power Group UB121000 Deep Cycle AGM Battery Amazon link (link opens in the new window).