Universal Power Group UB121000 AGM Deep Cycle Battery

Universal Power Group (UPG) UB121000 AGM battery is large and heavy battery intended for standby and cyclic use in off-the-grid, marine, security, solar, wind, medical and similar applications.

UPG UB121000 belongs to BCI Group 27 and is Absorbent Glass Mat (AGM) Valve Regulated Lead Acid (VRLA) battery of spill proof design that can be mounted in any position, with increased resistance to mechanical shocks and vibrations.

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UPG UB121000 Features and Specifications

UPG UB121000 physical dimensions (L x W x H) are 12.17 x 6.61 x 8.30 (9.16 with terminals) inches (~309 x 168 x 211/233 mm) and is roughly ~0.1 inch (~3 mm) longer than standard Group 27 battery - however, this difference is practically negligible.

UPG UB121000 battery weighs ~64 pounds (~29 kg) and although it comes with carrying handle, one should be very careful when trying to carry it around - use cart or something similar.

Nominal voltage of this battery is 12 volts and nominal, 20h capacity is 100 Ah - nominal capacity is measured at 77°F (25°C) and in real life it depends on the battery temperature:

- at 104°F (40°C), nominal capacity is 102 Ah (102%),

- at 77°F (25°C), nominal capacity is 100 Ah (100%),

- at 32°F (0°C), nominal capacity is 85 Ah (85%),

- at 5°F (-15°C), nominal capacity is 65 Ah (65%).

As one can see, the colder it gets, the less capacity battery has, but it also features smaller self-discharge rate:

- at 104°F (40°C), capacity drops down to 80% in slightly less than two months and down to 60% in ~4.5 months,

- at 86°F (30°C), capacity drops down to 80% in 3 months and down to 60% in 8 months,

- at 68°F (20°C), capacity drops down to 80% in 6 months and down to 60% in 12 months,

- at 41°F (5°C), capacity drops down to 80% in ~18 months.

So, when using the battery, be sure that the battery is at room temperature for optimal performances, and when the battery is stored with no battery maintainer, keep it in the cooler storage area.

UPG UB121000 may be charged with most AGM battery chargers being able to provide enough current, but intelligent AGM battery chargers that monitor battery condition during charging are highly recommended.

When the UPG UB121000 is used in standby/float applications, recommended voltage is 13.6-13.8 volts and for cyclic applications recommended voltage is 14.6-14.8 volts. In order to charge the battery safely, during charging, battery voltage should not exceed 15 volts and the charging current should go above 30 Amps.

Internal resistance of the battery is 5m - it doesn't sound much, but it is relatively large internal resistance for 100Ah battery. But, UPG UB121000 is intended for low current applications and NOT for starting/cranking use.

However, note that UPG UB121000 battery is being discharged faster, it loses some capacity, like all other lead-acid batteries (77°F, 25°C):

- 20 hours discharge, 5.0 Amps current, 100 Ah capacity,

- 10 hours discharge, 9.3 Amps current, 93 Ah capacity,

- 5 hours discharge, 17 Amps current, 85 Ah capacity,

- 1 hour discharge, 60 Amps current, 60 Ah capacity.

This drop of capacity one has to consider when discharging lead-acid batteries in general.

UPG UB121000 Constant Current (Amps) Discharge Characteristics

Following chart shows UPG UB121000 constant current discharge characteristics at 77°F (25°C), with the values given in Amps (A):

Cell End
Voltage (V)
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
1.6 V 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
1.7 V 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
1.75 V 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
1.8 V 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
1.85 V 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

Note: The value for 10 hr current down to 10.80 V is given as an approximation, because official data given by UPG is - wrong.

According to this table, new, fully charged UPG UB121000 battery, at 77°F (25°C) is able to provide ~350 Amps for 5 minutes before the end voltage drops down to 9.6 volts - although it is not designed to be used as starting battery, UPG UB121000 may be used as starting/cranking battery for smaller diesel and especially gas engines.

However, UPG UB121000 performs best when being discharged for hours with low current - typically for deep cycle battery.

UPG UB121000 Constant Power (Watts) Discharge Characteristics

Following chart shows UPG UB121000 constant power discharge characteristics at 77°F (25°C), with the values given in Watts (W):

Cell End
Voltage (V)
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
1.6 V 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
1.7 V 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
1.75 V 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
1.8 V 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
1.85 V 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

Note: Again, the value for 5 hr power down to 10.20 V is given as an approximation, because official data given by UPG is - wrong.

According to this table, new, fully charged UPG UB121000 battery, at 77°F (25°C) is able to provide for example, ~3.7 kW of power for 5 minutes before voltage drops down to 9.6 volts.

Since UPG UB121000 is build for slow discharge applications, that also means that it is able to provide, for example, 250 watts of power for at least 3 hours without the voltage dropping below 11.1 volts.

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UPS UB121000 Cycle Life vs. Depth of Discharge/State of Charge

Despite being deep cycle battery, as the battery is discharged deeply, UPS UB121000 loses its capacity.

When the UPS UB121000 is discharged down to 100% Depth of Discharge (DoD) or down to 0% of State of Charge (SoC), UPS UB121000 nominal capacity drops down to 80% after 180-220 cycles.

In order to prolong the battery's operating life, it should not be discharged down to 100% DoD regularly - keeping the level of discharge down to 50%, number of charging/discharging cycles is more than doubled.

Universal Power Group (UPG) UB121000 AGM battery comes with 1 year warranty, with designed float life of 3-5 years.


Long Story Short: Universal Power Group (UPG) UB121000 AGM battery is deep cycle Group 27 battery with nominal capacity of 100 Ah and nominal voltage of 12 volts.

It can be used in various applications that require relatively strong and reliable battery at acceptable price.

UPG UB121000 battery should not be pushed to hard regarding power output - it is designed for (relatively) low current/deep cycle applications, typically found in off-the-grid systems, standby units, medical/security systems and similar.

It can be also used as the main battery on the boats with gas or diesel engines that don't require large starting currents (for example, less than 300 Amps), but the boat is equipped with the range of marine electronic devices (GPS, chart plotter, fish finder, etc.) that require constant and reliable power. Also, it can be used as trolling motor battery for motors up to 50-60 Amps, but not more since stronger currents would cause large capacity loss.

However, if you need more robust and durable 100 Ah battery, check Group 27 and Group 31 batteries.

For more reviews and recommendations, feel free to check Universal Power Group 12V 100Ah UB121000 Battery Amazon link (link opens in the new window).