Blue Sea Systems P12 user manual Absorption Parameters and Timers

Absorption Parameters and Timers	P12
	7521 AND 7522 BATTERY CHARGERS

CAUTION

The default Absorption Timer values are set to satisfy a majority of the battery configurations that exist. Unwarranted changes to Absorption timers could result in damage to the batteries and reduced battery life. To optimize Absorption Timer based on specific configurations please contact your

battery manufacturer for setting guidelines for your specific battery.

The Absorption stage is the charging stage in which a battery “fills” to max capacity. Absorption timers help define the amount of time a battery bank will remain in the Absorption stage. Having a correct Absorption time is vital for optimum charging of a battery bank. Under Absorption can lead to a battery being consistently under-charged causing sulfate buildup. Over Absorption can dry out the electrolytes in a battery. Both of these conditions can lead to reduced battery life.

There are three user selectable parameters that help define when a connected battery bank will be moved from Absorption to either Pre-Float, or Float.

End Absorption Amps

The maximum amount of current that a battery bank can receive while in Absorption and still change to Float. If a load is active and drawing more than the designated End Absorption Amps, the battery bank will not leave Absorption until the maximum Absorption time is met. For a battery bank to move from Absorption to Float before the maximum Absorption time is met, the minimum Absorption time must be met, and the amperage output must be less than or equal to the designated End Absorb Amps.

Recommended End Absorption Amps

End Absorb Amps will vary based on your specific system. To set the correct End Absorb Amps it is recommended that you monitor the amperage entering your battery banks near the end of the absorption cycle. Constant loads will affect this number, and should be incorporated into End Absorb Amps if present. However, in a typical system (without constant loads) it is recommended that the End Absorb Amps be 1% of your battery banks amp-hour capacity (see Table F).

Table F: Approximate End Absorb Amps

(1% of Ah Capacity)

	Flooded			AGM			Gel		TPPL
Group	Ah	1% End	Ah		1% End	Ah	1% End	Ah		1% End
Size		Amps			Amps		Amps			Amps
24	75	0.8	79		0.8	73	0.7	76		0.8
27	90	0.9	92		0.9	86	0.9	91		0.9
31	105	1.1	105		1.1	97	1.0	102		1.0
4D	150	1.5	198		2.0	183	1.8	185		1.9
8D	200	2.0	245		2.5	225	2.3	228		2.3

Minimum Absorption Time: 1 hour default

The minimum amount of time a battery bank will be in Absorption. The battery charger will not move a battery from Absorb to Float unless the Minimum Absorption Time is met.

Maximum Absorption Time: 4 hour default

The maximum amount of time a battery bank can remain in Absorption. While still maintaining its Absorption voltage, if a battery has been in Absorption for the maximum designated time it will move into Float even if End Absorb Amps is elevated. This is commonly caused when active loads are present.

Recommended Absorption Time

Minimum and Maximum Absorb Times can vary from installation to installation. It is recommended that Minimum and Maximum Absorption Times be based on the time it takes a battery bank to reach End Absorb Amps. Read and understand the End Absorb Amps section above and set according to your system. After an accurate End Absorb Amperage is set, monitor the minimum and maximum time it takes for each battery bank to reach their End Absorb Amps. The Minimum Absorb Time should be based on the minimum time it takes a particular battery bank to reach End Absorb Amps. The Maximum Absorb Time should be an hour more than it takes a deeply discharged battery bank to reach End Absorb Amps. It is recommended to monitor charging while the battery banks are in different states of discharge to get the most accurate Minimum and Maximum Absorb Times.

Absorption Timer Counter

The P12 battery charger uses a counter to determine the amount of time a battery bank should remain in Absorb relative to the Maximum Absorb Time. The Absorb timers counter can be seen in the System Status Screen and also referenced on page 19.

Available Timer Modes

When in Float or Standby, the timer will pause.

When in Pre-Float mode the timer for that channel will pause.

When in Bulk mode the remaining time will increase.

When in Absorption mode, the remaining time will decrease.

Once a battery bank’s Absorb timer is reduced to zero, then its output will be changed to Pre-Float. There are other factors in a battery bank leaving the Absorption stage prior to the Absorb timer running out. Once all battery banks leave Absorption, all outputs will enter the Float stage.

14Specifications are subject to change. See bluesea.com/P12 for current information.