C&D Technologies RS-1476 Standby Battery Vented Cell User Manual

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1.6 Connection voltage drop

The importance of the integrity of inter-cell, inter-aisle and inter-row connections

has been stated. Loose, dirty, or oxidized connections have higher than normal

resistance and increased voltage drop resulting in less reserve time.
Typically, the designed voltage drop between cells should be 30 millivolts or less.

Voltage drop between rows for standard (inter-tier/inter-step) cables is typically

less than 100 millivolts.

1.7 Measuring connection resistance

Reference Information

IEEE-450 provides a comprehensive description of how to measure connection resistance. Details may be

found in the Annex F of IEEE-450.

A preferred method of measuring connection resistance uses a sensitive digital micro-ohm meter. See Figure 4.1.7.
To measure connection resistance with a digital, low-resistance ohmmeter, proceed as follows:
• Be sure all connections are clean and torqued to the values specified in Table 3, Section 1.4.7 for re-torque.
• With the battery on float charge or open circuit, take measurements post to post. (Positive post of one cell to the

negative post of the next cell.)

• Starting at one end of the string, work toward the other end, recording micro-ohm resistance’s and noting

connections with unacceptable resistance’s or resistance values that exceed the average by 20 percent.

NEVER

USE THE DLRO TO TAKE A READING ACROSS A CELL OR THE TERMINALS OF THE BATTERY. THIS

COULD SERIOUSLY DAMAGE THE INSTRUMENT.

• Recheck connections that exhibit unacceptable resistance.

Clean and re-torque to the original (initial) torque

value, when required.

Note: Whenever a connection must be disassembled and reworked be certain to re-torque the connection

to the original (initial) installation torque value.

Compare resistance readings with the original installation readings and records taken when the battery was first

installed. Connections that still exhibit unacceptable resistance after cleaning and re-torquing may indicate the presence

of improperly sized or damaged cables or inter-cell connectors. Contact your C&D representative for assistance.

1.8 Electrolyte containment

Although it is unlikely that a properly maintained battery will exhibit a container failure and electrolyte leakage,

electrolyte containment systems are required by the Uniform Fire Code — Article 64. These systems are available from

C&D. Consult your C&D representative or C&D directly for assistance in specifying and ordering one of these systems.

FIGURE 4.1.7 Measuring connection

resistance with DLRO

PART 4

REFERENCE INFORMATION, TROUBLE SHOOTING & EXTENDED MAINTENANCE (CONTINUED)

RS1476/0215/CD

www.cdtechno.com

CAUTION

Checking voltage drop with conventional voltmeters requires that

measurements be taken while the battery is discharging at its rated

discharge current. The resistance may be calculated using Ohm’s

law. Note that cycling will shorten the life of the battery, (refer to

“Float versus Cycle Life” in Section 4). For this reason, the use

of digital, low-resistance ohmmeters is recommended. This type

of equipment allows the measurement of connection resistance

without discharging or cycling the battery.