Iota Technical Paper - Charging Lead Acid Batteries for Long Life

BATTERY VOLTAGE:
12V
BULK
STAGE
ABSORPTION
STAGE
FLOAT
STAGE
14.8V
14.2V
13.6V
48V24V
29.6V
28.4V
27.2V
59.2V
56.8V
54.4V
The two leading causes of
battery failures, sulfation
and excessive gassing, can
be prevented.
Sulfation and excessive gas-
sing are the results of under-
charging and overcharging,
respectively.
Maintain proper full charge
in ooded lead acid bat-
teries with an automated,
multi-stage smart charger
recommended by the battery
manufacturer.
Check the water level of your
unsealed batteries regularly.
From the IOTA Power Products Technical Library
Stage 1 Bulk: Also called the boost stage, this is a period of constant current and
increased voltage that provides most of the charge. Charging voltage runs up to
the full-rated output of the battery charger for faster charging. If a battery is
left at this charge stage it will overcharge.
Stage 2 Absorption: Also called the soak stage or topping stage, the charging
voltage drops during this stage and is then held for a controlled period so the
electrolyte solution has the opportunity to absorb the charge fully and complete-
ly. If a battery is left at this charge stage it will overcharge.
Stage 3 Float: A lower voltage “trickle” charge is delivered to maintain the bat-
tery’s full charge while not overcharging. In the oat stage, the battery is at full
charge and ready for discharge with normal operation for motor-start cranking
or for running lights, appliances, and electric motors. If a battery is left at this
charge it will undercharge as it slowly self-discharges.
The Fourth Phase: Equalization: The fourth phase is called the equalization
phase. Since the battery will gradually self-discharge if left in the oat stage,
multi-stage charging will boost the charge voltage should the voltage drop below
a certain level. Additionally, if left in an extended oat state, the battery faces
the threat of acid sulfate stratication. Stratication occurs when electrolytes
concentrate at the bottom of the battery, reducing performance. A smart charge
controller, such as IOTA’s IQ4 Smart Charger, monitors if the battery has remained
in the oat stage for a specied length of time or if the battery voltage drops
below a minimum level. The smart charge technology then enters the equalization
phase of automatically initiating a new round of charging through the multi-stage
cycle, correcting the undercharge condition and stimulating the mixing of the
electrolyte solution. Specically, the equalization phase of the IQ4 Smart Charger
automatically repeats the charge cycle every seven days or when the battery
voltage drops below a determined voltage level (see Table A for oat voltages
by battery size). By automatically re-initiating the multi-stage cycle, a balance is
achieved between overcharging and undercharging, and stratication is pre-
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vented.
Four-Phase Smart Chargers Help Prevent Sulfation and
Excessive Gassing
Multi-stage, smart charging technology automatically controls the
balance between undercharging and overcharging, and signicantly
reduces the negative impact of these conditions.
The smart charge technology brings the battery to a full charge safely,
effectively and automatically, and then maintains the full charge to
avoid sulfation of the battery plates caused by undercharging.
Multi-stage charging also helps prevent excessive gassing caused by
overcharging by controlling the duration and amount of charge permit-
ted when charge voltage is highest in the bulk and absorption stages.
For example, IOTA’s IQ4 Smart Charge Technology prevents overcharg-
ing by allowing the IOTA battery charger to deliver a charge in the
bulk stage until the battery voltage achieves the high value or, if the
high value is not achieved, terminates the bulk charge and transitions to
absorption after 240 minutes. The second stage, absorption, is prone to
overcharging if left unchecked. The IQ4 limits the absorption stage to
eight hours, preventing overcharging, and initiates the oat stage.
Table A: Typical charging voltages using
IOTA IQ4 Smart Charging Technology.
What Battery Owners
Need to Know...
3
An example of an IOTA DLS charger utilizing an
external IQ4 smart charge controller option.