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UM1M820BNA User Instructions
Issue AH, March 4, 2013 Spec No. 1M820BNA (Model M820B)
Spec No. 1M820DNA (Model M820D)
12 Chapter 1. Introduction
This document is property of Emerson Network Power, Energy Systems, North America, Inc. and contains confidential and proprietary information owned by Emerson Network Power, Energy
Systems, North America, Inc. Any copying, use, or disclosure of it without the written permission of Emerson Network Power, Energy Systems, North America, Inc. is strictly prohibited.
Figure 6
Charge Voltage
Equalize Charge: The battery will be recharged at equalize voltage. This is the voltage set in the initial
phase of battery recharge. See Figure 6.
As the voltage limit is reached, the charge current is gradually reduced – effect known as current tail.
When the current tail falls below a set of threshold levels, additional equalize charge time is added.
The equalize charge current tail threshold is settable from 0.01 to 0.05. Default setting is 0.02 (2A per
100Ah). The additional equalize charge time is settable from 0 hours to 7 hours (settable in minutes from
0 to 720), default setting is 4 hours. The duration of the equalize charge is determined as the time from the
start of the recharge to the end of the additional time. (Maximum charge time, determined from the time
charge starts, is settable in the range of 5-24h.)
The end of recharge is determined by a three (3) step approach:
Step1 - calculated battery capacity exceeds 90%. Calculation is performed by measurement of battery
current and time, in Ah.
Step 2 - charge current tail threshold is reached.
Step 3 - additional charge time is added.
Float Charge: Default float voltage is 54.0V at 20°C with a temperature compensation of -72mV per °C.
If battery temperature exceeds 38°C, the charge voltage is reduced to 51V to reduce gassing and prevent
thermal runaway. The same is applicable as well for equalizing charge.
Equalizing Charge: As the cyclic use does not ensure complete battery recharge after every cycle, an
equalizing charge cycle is added. The equalizing cycle will occur up to four times a month, settable for
every 7 to 60 days intervals. Start date and time is settable. Equalizing charge time is 20 hours
independent of discharge time setting. Equalizing charge is performed at equalize voltage until end of
additional equalize time and thereafter at float voltage for the remaining time. Also see Figure 6.
Equalize charge independently settable 0-720 min (already set in equalize charge).