Deep Cycle Marine Battery

UPG UB12750 Deep Cycle AGM Group 24 Battery

UPG UB12750 Deep Cycle AGM Group 24 Battery is very popular BCI Group 24 Absorbent Glass Mat (AGM) lead-acid battery. UPG UB12750 battery is designed as general purpose deep cycle battery for applications in off-the-grid applications, in electric cars and vehicles, as trolling motor battery, as UPS battery, for medical applications, as wheelchair battery etc.

UPG UB12750 features good charging and discharging characteristics, low self-discharge rate, acceptable weight and it comes at affordable price, making it one of the more popular batteries in its class.

Published: July 24, 2019.

upg ub12750 45821

UPG UB12750 battery features nominal voltage of 12 volts and nominal capacity of 75 Ah.

It is AGM battery, very resistant to vibrations, can be mounted in any position, practically requires no maintenance (just check for corrosion on the terminals every few months), and it is spill proof.

UPG UB12750 comes in two versions:

- UPG UB12750-45821 with Z post terminals,

- UPG UB12750-45822 with threaded terminals.

Other differences between these two models are practically negligible and can be ignored.

upg ub12750 45822

Note: all further data in this article are given for the UPG UB12750-45821 model, unless otherwise stated.

UPG UB12750-45821 is BCI Group 24 battery and its physical dimensions are (L x W x H) 10.24 x 6.61 x 8.27 (9.13 terminals) inches (260.1 x 167.9 x 210/231.9 mm) and it weighs 49.1 pounds (~22 kg).

UPG UB12750 battery features 8mΩ internal resistance, which somewhat limits maximum discharging current - UPG UB12750 is not good cranking/starting battery, but that is NOT what this battery is designed for.

Shelf life depends on the self-discharge rate and it is rather good - when the new, fully charged battery is stored at 77°F (25°C), its charge level decreases:

- after 3 months: 91% of full charge,

- after 6 months: 82% of full charge,

- after 12 months: 64% of full charge.

So, when the battery is stored at 77°F, be sure to fully recharge it after 6 months, or store it at lower temperatures - refer to the manual for required storage temperatures.

Maximum charging current during bulk charging phase should be 22.5 Amps.

When the battery is used for cycle applications, maximum charging voltage should be limited to 14.5-14.9 volts and for float/standby use, maximum charging voltage should be around 13.6 - 13.8 volts.

Nominal capacity of the UPG UB12750 battery is 75 Ah (measured at 77°F, 25°C) - that is the capacity when the battery is being discharged for 20h. When the battery is being discharged faster, its nominal capacity is decreased:

- 20h, 3.75 Amps: 75 Ah,

- 10h, 6.98 Amps: 69.75 Ah,

- 5h, 12.75 Amps: 63.75 Ah,

- 1h, 45 Amps: 45 Ah.

Usually, battery capacity is measured when the battery voltage drops to 10.50 volts, but when the battery is being discharged faster, electrolyte near the plates is being 'depleted' faster, leading to voltage drop. Thus, when the batteries are discharged faster, they can be discharged below 10.50 volts without adverse effects on the longevity - assuming that the battery is being recharged right after discharging, using smart/intelligent AGM battery charger!

Note: personally, if you want your batteries to last (not just UPG UB12750, but other AGM batteries as well), don't discharge them below 10.50 volts, at least not very often :) It is highly recommended to check the battery's manual for exact figures when the battery arrives. For example, when its open circuit voltage is around 11.50 volts (or slightly higher), residual capacity of UPG UB12750 is 0% - battery is fully discharged. Again, this is the open circuit voltage, not when the battery is under load.

Constant current discharge characteristics are given in the following chart (in Amps, at 77°F/25°C):

Battery End Voltage 5 min 10 min 15 min 30 min 1 hour 2 hours 3 hours 4 hours 5 hours 8 hours 10 hours 20 hours
9.60 volts 259.0 189.0 133.0 81.0 42.0 25.0 18.0 14.0 11.6 8.1 7.4 4.0
10.20 volts  228.0  172.0  119.0  76.3  39.5  23.4  17.5  13.7  11.3  8.0  7.2  3.9
10.50 volts  220.0  164.0  112.0  74.0  38.0  22.8  17.1  13.4  11.2 7.9  7.0  3.8
10.80 volts  211.0  155.0  105.0  72.0  37.0  22.3  16.7  13.2  10.9  7.7  6.9  3.7
11.10 volts  203.0  147.0  98.0  70.0  36.0  21.7  16.1  12.8  10.6  7.5  6.7  3.6

Constant power discharge characteristics are given in the following chart (in watts, at 77°F/25°C):

Battery End Voltage 5 min 10 min 15 min 30 min 1 hour 2 hours 3 hours 4 hours 5 hours 8 hours 10 hours 20 hours
9.60 volts 2750.0 2007.0 1412.0 855.0 486.0 284.0 208.0 162.0 134.0 94.0 85.0 46.0
10.20 volts  2566.0  1911.0  1321.0  847.0  457.0  271.0  203.0  158.0  131.0  92.0  83.0  44.8
10.50 volts  2493.0  1857.0  1270.0  841.0  443.0  264.0  198.0  156.0  130.0  91.0  82.0  44.3
10.80 volts  2461.0  1809.0  1222.0  839.0  430.0  259.0  194.0  153.0  128.0  90.0  81.0  44.0
11.10 volts  2416.0  1749.0  1166.0  833.0  425.0  258.0  192.0  151.0  126.0  89.0  79.0  42.7

Note: these values are average values and they vary from the battery to battery.

Depth of Discharge (DoD) vs Number of Cycles

When used in cycle applications, depth of discharge is very important for the battery operating life (number of cycles).

For example, when the UB12750 battery is being discharged down to 100% DoD (0% SoC, State of Charge), it can withstand ~200 charging/discharging cycles with the nominal capacity loss down to 80%.

Number of cycles dependency is given in the following chart:

DoD 100% 50% 30%
80% Capacity ~200 ~475 ~1180
60% Capacity ~230 ~500 ~1220

As one can see, avoiding deep discharges significantly prolongs the operating life of the battery. But, even when the battery is fully discharged every time, it can be used for ~200 times before the nominal capacity drops down to 80% capacity of the new battery.

UPG UB12750 battery comes with 1-year warranty.

UPG UB12750 Battery as Trolling Motor Battery

newport 23M1000096 1UPG UB12750 battery is capable of providing ~40 Amps for 1 hours, and ~25 hours for 2 hours, after which the battery is almost fully discharged.

Since medium size trolling motors feature maximum currents of around 40 Amps, UPG UB12750 battery is able to power them for ~1h when they are used at the full throttle all the time.

When used for powering smaller electric trolling motors (25 Amps max) or medium size motors at half the power, UPG UB12750 battery is able to provide energy for almost 2 hours.

When used for larger electric trolling motors (max currents in the 50-60 Amps range), UPG UB12750 battery is able to provide energy for 35-45 minutes.

Since it is AGM battery, UPG UB12750 batteries can be easily connected in series and parallel for larger voltages and/or capacities.

UPG UB12750 Battery as UPS Battery

When used as UPS battery, UPG UB12750 is being able to provide plenty of power for short periods of time (5 -15 minutes, for example).

UPG UB12750 battery can easily provide ~2.5 kW for 5 minutes, ~1.9 kW for 10 minutes and 1.3 kW for 15 minutes.

Nonetheless, UB12750 battery is not good as starting/cranking operations, except for starting (perhaps - check the required Amps) the small gas power generators or similar internal combustion engines.

UPG UB12750 Battery for Off-the-Grid Applications

UPG UB12750 battery is often used for smaller off-the-grid applications, where it is being charged during the day with solar panels and/or wind turbines and the battery provides the power during night.

UPG UB12750 can provide ~7 Amps (~80 watts) for the period of 10 hours, after which it must be recharged.

Such power is enough for smaller applications like LED lights, smaller TVs, ventilation, USB chargers ets.

upg ub12750 45821 mUPG UB12750 battery can be used for other purposes as well, like RV house battery, golf cart battery, wheelchair battery (if it fits), medical equipment etc.

UPG UB12750 battery is well balanced, general purpose AGM battery and very popular in its class.

For more reviews and recommendations, feel free to check UPG UB12750 Deep Cycle AGM Group 24 Battery Amazon link (link opens in the new window).

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