C&D Technologies RS-2044 msEndurII Series - Manual (Page 28)

RS02044/1114/CD 28 www.cdtechno.com
10.4 Low Float Voltage and Sulfation
Either because of incorrect charger voltage adjustment, excessive intermittent or static loads paralleling
the charging source, low operating temperature or simply not fully recharged; a battery may not receive
adequate charging voltage. In some cases, the charger may even be turned off, erroneously or by
choice. The net result is a battery left in a partially discharged or undercharged condition. The first
observable signs may be erratic cell voltages. Although not visible to the observer, the plates will
become sulfated.
If you suspect sulfated plates, contact the C&D Technical Services Department 1-800-543-8630 or 215-
619-2700 for assistance. Sulfated batteries are not fully charged batteries thus have not completed the
electrochemical reaction of recharge. Accordingly, they will have reduced capability. If allowed to
remain in a partially charged condition for an extended period of time, sulfated batteries may suffer
irreversible damage, requiring replacement.
10.5 Hydration
A battery that has been severely over-discharged and left in a discharged condition without
immediate recharge is subject to damage known as hydration. This is a phenomenon in which the
electrolyte specific gravity has been reduced to a value so low it permits the lead components to
dissolve into the electrolyte.
The reaction of dissolution forms many compounds and salts, generically referred to as hydrate.
On recharge these compounds react to clog separator pores and form metallic lead. As time passes
thousands of short circuit paths are created in the separators placed between the positive and negative
plates to provide electrical insulation. Very often, the effect of these short circuits goes unnoticed except
for a slight increase in charging current. As the reaction continues, however, short circuits become so
extensive it is almost impossible to keep the cells charged. Finally, the cells experience total failure.
msEndur II batteries are more resistant to hydration than typical wet cells, largely because of the thick
absorbent glass mat separator between the plates. However, in severe cases of hydration, internal
short circuits can form.
10.6 Open Circuit – Late Installations
As soon as a battery is disconnected from a charger, local action (discharge) begins. This is caused by
inherent internal losses within the cell. In the case of msEndur II cells, a self-discharge is expected to
occur at a rate of “up to 3.0 percent” of full charge per month at 77°F (25°C). Therefore, if cells remain,
for whatever reason, on open circuit (with no charge supplied) for prolonged periods of time, the affected
cells may become sulfated and require corrective action in the form of a freshening charge, see Sections
5.2, 7.1 & 7.2.
10.7 Parallel Battery Strings
When strings of batteries of equal voltage are connected in parallel, the overall capacity is equal to the
sum of the capacities of the individual strings. When paralleling valve-regulated batteries is necessary,
the external circuit resistance should be matched for each battery. A wide variation in battery circuit
resistance can result in unbalanced discharge (i.e., excessive discharge currents in some batteries and
less discharge in others). As a consequence, cell failures in one battery string and the subsequent loss
of performance capacities of that string will result in higher loads in the lower resistance interconnections
of some parallel strings that may exceed the ratings of the battery interconnections and/or cables. C&D
recommends paralleling strings to obtain higher capacity, to increase system reliability and with properly
installed disconnects, perform maintenance on one string at a time.