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How to Read a 12V AGM Battery Spec Sheet

Oct 21
5 min read

Updated: Oct 22

A 12V AGM battery spec sheet packs a lot into a couple of pages. This guide walks through one real example, the C&D Technologies Pure Lead Plus datasheet for 12V UPS batteries. C&D describes the range as an AGM UPS battery (C&D Pure Lead Plus product page). Every figure below comes from that datasheet unless another source is named. Other makers lay out their sheets differently, so always read the footnotes on the sheet for your own battery.

Start with the basics: voltage and cells

The datasheet's additional data table lists the voltage, the number of cells per unit (6 for each 12V model), terminal location (top or front), terminal type and torque (C&D Pure Lead Plus datasheet, p. 2). Many ratings on the sheet are given per cell, in volts per cell (VPC) or watts per cell. Charging voltages are given per 12V unit (C&D Pure Lead Plus datasheet, pp. 2–3).

Capacity depends on the rate, end voltage and temperature

The technical data table lists three constant-current capacity ratings for each model (C&D Pure Lead Plus datasheet, p. 2):

  • C8, to 1.75 VPC at 25 °C

  • C20, to 1.75 VPC at 25 °C

  • C10, to 1.80 VPC at 20 °C

For the UPS12-545PLP these are listed as 137 (C8), 146 (C20) and 128 (C10). The same battery has three different capacity figures because each is measured under different conditions. When you compare batteries, compare ratings taken at the same discharge time, end voltage and temperature.

Constant-power ratings: watts per cell

The datasheet also gives constant-power ratings in watts per cell for 5 and 15 minutes. A footnote says constant-power ratings are to 1.67 VPC at 77 °F (25 °C), capacity is rated to 1.75 VPC at 77 °F (25 °C), and the ratings "do not include interunit connector voltage drops" (C&D Pure Lead Plus datasheet, p. 2).

The full tables on later pages show watts per cell for each end voltage from 1.60 to 1.75 VPC, at run times from 1 to 60 minutes (5 to 60 minutes at 1.75 VPC). For the UPS12-675PLPF to 1.67 VPC at 77 °F, the table lists 1,100.2 W per cell for 5 minutes and 671.4 W per cell for 15 minutes (C&D Pure Lead Plus datasheet, p. 4).

EnerSys makes the same point in its own manual: a battery is sized for a specific load (amps or kW), run time, temperature and end voltage, so check those parameters with the system or equipment supplier (EnerSys DDmP125-33 LP manual, §5.2, p. 12).

Constant-current tables: amps by end voltage

The constant-current tables show how many amps the battery can supply for a given number of hours to each end voltage. For the UPS12-675PLPF at 77 °F (25 °C), to 1.75 VPC, the table lists 125.6 A for 1 hour and 9.0 A for 20 hours. To a higher end voltage of 1.90 VPC, the 1-hour figure is 103.9 A (C&D Pure Lead Plus datasheet, p. 4). In this table, a higher end voltage means a lower current for the same run time.

Design life is not the warranty

The features list gives two separate figures (C&D Pure Lead Plus datasheet, p. 1):

  • a 12+ year design life at 25 °C (77 °F)

  • a standard warranty of 5 years at 30 °C (86 °F)

They are listed separately and at different temperatures, so don't read one as the other. For how heat affects life, see Heat and UPS Battery Life: What Battery Makers Say.

Charging specifications

From the datasheet's specifications page (C&D Pure Lead Plus datasheet, p. 3):

Specification

What this sheet says

Float charge voltage

13.65 ± 0.15 VDC average per 12V unit

Equalize and cycle service charge voltage

14.40 to 14.80 VDC average per 12V unit at +77 °F (+25 °C)

Recommended maximum charging current limit

C20/5 amperes (20 hr rate)

Charge temperature range, with temperature compensation

−10 °F (−23 °C) to +122 °F (+50 °C)

This datasheet doesn't print a temperature compensation figure. C&D's charging bulletin gives −0.005 V per cell per °C for its VRLA batteries (C&D 41-2128, p. 22). Other makers give different figures for their own products. For example, EnerSys gives ±3 mV per cell per °C around 20 °C for its SBS XL range (EnerSys SBS XL manual, §5.1). Use the figure for your battery.

Temperature ranges

The sheet gives three ranges (C&D Pure Lead Plus datasheet, p. 3):

  • Discharge: −40 °F (−40 °C) to +140 °F (+60 °C)

  • Charge, with temperature compensation: −10 °F (−23 °C) to +122 °F (+50 °C)

  • Nominal operating temperature range: +74 °F (+23 °C) to +80 °F (+27 °C)

Charger ripple

This datasheet recommends AC ripple of 0.5% RMS or 1.5% P-P of the float charge voltage for best results. It gives a maximum allowed voltage of 1.4% RMS (4% P-P) and a maximum allowed current of C/20 (20 hr rate) (C&D Pure Lead Plus datasheet, p. 3). Ripple limits are written differently in other C&D documents: for example, its condensed installation bulletin for the same product family gives a maximum allowable ripple voltage of 0.5% of float voltage and a maximum allowable ripple current of 5 A rms per 100 Ah (C&D 41-6965, p. 4). Check the documents for your exact model.

Storage and self-discharge

The sheet says the batteries can be stored up to 24 months at +77 °F (+25 °C) before a freshening charge is required. Batteries stored warmer than +77 °F (+25 °C) need recharging sooner (C&D Pure Lead Plus datasheet, p. 3). The features list repeats the 2-year storage capability at 25 °C (C&D Pure Lead Plus datasheet, p. 1).

Mechanical and electrical limits

The additional data table also gives maximum discharge current, short-circuit current at 0.1 second, terminal type and initial terminal torque for each model. For the UPS12-545PLP it lists 800 A maximum discharge current, 5,000 A short-circuit current, a 1/4-20 UNC terminal and 110 in-lbs (12.4 N-m) torque (C&D Pure Lead Plus datasheet, pp. 2–3). Dimensions (length, width, height and total height in mm and inches) and weight (lbs and kg) are listed for every model (C&D Pure Lead Plus datasheet, p. 2). Use the torque for your exact model when installing. See Safe Handling and Maintenance for Lead-Acid Batteries.

Certifications and marketing claims

The sheet lists the standards the range complies with (UL1973, UL1778, UL1989, UL924, UL94 V-2, UL94 V-0, BS6290-4 and IEC60896-22) (C&D Pure Lead Plus datasheet, p. 1). On this sheet, the claim about fewer battery replacements carries a footnote that states its assumptions. Read any such footnote before comparing claims between makers.

Matching a replacement battery

Because a battery is sized for a specific load, run time, temperature and end voltage (EnerSys DDmP125-33 LP manual, §5.2, p. 12), compare old and new spec sheets on those same terms, and check the physical and charging data covered above. See When to Replace a UPS Battery, How to Size a UPS and Battery Basics: Voltage, Capacity, and C-Rate.

Need a replacement 12V UPS battery?

We supply replacement UPS and standby batteries and provide service across the Southeast USA. Browse SWU UPS batteries and NPX high-rate batteries, or send us the spec sheet or model of the battery you're replacing.

Request current price and availability: use the request form or email office@luxena.net.

Sources (checked 2026-10-21)

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