How do I charge certain deep cycle 6-volt and 12-volt batteries?

Charging Recommendation for all Deep Cycle Batteries whose part number start with the letter "U" (this includes the following battery part numbers: U1800, U2000; U2200, U2300, U2400, U2500, U3050, U3050HC, UL-16, UL-16HC, U1450, U1850, U1850HC; U8VGC, U8VGCHC, USRM8V19, USRM8V-21, USRM8V-24, USRM8V-27; USRM8V-26, U-BIG-JOE; USRM-16TF, USRM-8D)

Nominal Battery Voltage Charging Current Bulk Charge Voltage (2.4 VPC) Absorption Voltage (2.58 VPC) Absorption Time in Hours Float Voltage (2.2 VPC) Equalization Voltage (2.6 VPC) Equalization Time in Hours
6 Volts (3 cells) C/10 7.35 7.35 +/- .05
2 to 4 6.51 +/- .05 7.65 +/- .05 2
8 Volts (4 cells) C/10 9.8 9.8 +/- .05
2 to 4 8.68 +/- .05 10.20 +/- .05 2
12 Volts (6 cells) C/10 14.7 14.7 +/- .05 2 to 4 13.02 +/- .05 15.30 +/- .05 2
24 Volts (12 cells) C/10 29.4 29.4 +/- .05 2 to 4 26.04 +/- .05 30.60 +/- .05 2
36 Volts (18 cells) C/10 44.1 44.1 +/- .05 2 to 4 39.06 +/- .05 45.90 +/- .05 2
48 Volts (24 cells) C/10 58.8 58.8 +/- .05 2 to 4 52.08 +/- .05 61.20 +/- .05 2

 
Need to determine the volts and amp-hours for your battery? See below
1. C = 20 hour capacity in Amp-hours
2. Float condition is for long term storage (several weeks).
3. Equalize every 4 to 8 weeks and always after a normal charge.
4. Be sure to leave the vent caps on your battery (or batteries) while charging them.

Charging recommendation for the UAGM8D (rated at 250 AH at the 20-hour rate):

Voltage of the Battery System

Charging Current

Bulk Charge Voltage     

Absorption Voltage  

Absorption Time in Hours

Float Voltage   

Equalization Voltage       

Equalization Time in Hours

12

C/10

14.4

14.4

2 to 4

13.2

14.4

2


Notes
1. C = 20 hour capacity in Amp-hours
2. Float condition is for long term storage (several weeks).
3. Equalize every 4 to 8 weeks and always after a normal charge.


Charging recommendations for 6-volt deep cycle batteries. GC2-XHD, GC2-HD, GC2-RD

Nominal Battery Voltage

Charging Current

Bulk Charge Voltage (2.41 VPC)

Absorption Voltage (2.55 VPC)

Absorption Time in Hours

Float Voltage (2.23 VPC)

Equalization Voltage (2.6 VPC)

Equalization Time in Hours

6 Volt (3 cells)

C / 10

7.23

7.65

2 to 4

6.7

7.8

2

8 Volt (4 cells)

C / 10

9.64

10.2

2 to 4

8.92

10.4

2

12 Volt (6 cells)

C / 10

14.46

15.3

2 to 4

13.4

15.6

2

24 Volt (12 cells)

C / 10

28.92

30.6

2 to 4

26.8

31.2

2

36 Volts (18 cells)

C / 10

43.38

45.9

2 to 4

40.2

46.8

2

48 Volts (24 cells)

C / 10

57.84

61.2

2 to 4

53.5

62.4

2



Notes: 1. All charging voltages shown above are for 80 degrees F. For every 10 degrees above 80 F reduce voltage by 0.028 VPC. For every 10 degrees below 80 F increase the voltage by 0.028 VPC.
2. VPC = Voltage Per Cell
3. Charging current; C = The amp hour (Ah) capacity rated at the 20 hour rate.
4. Float condition is for long term storage / (several weeks) inactivity. 5. Equalize every 4 to 8 weeks or when the difference in specific gravity readings vary by 0.020 points or more and always after a normal charge.

Other Charging Notes/Tips/ Definitions: Temperature Compensation: Increase voltage by .028 volts per cell for every 10 degrees below 80 F. Decrease voltage by .028 volts per cell for every 10 degrees above 80F. Typical phases on multi-stage chargers: Bulk: Initial phase where the voltage builds and the most current is provided to the battery. This is typically where the maximum current that the charger is capable of providing is supplied to the battery. i.e. A 10 amp charger will provide at or near 10 amps during this phase. Absorption: The phase where the voltage set point is held constant. Current will decrease gradually during this point as the battery internal resistance comes up. Float:

The maintenance or finishing phase of the charging cycle. Voltage is set at a minimum during this phase (usually 13.0c-13.5v) and current drops significantly. The battery should be nearly complete by the time this phase is reached. An anti sulfation stage may be added where voltage spikes to high levels for very brief time periods for a set amount of time determined by the charger manufacturer, to convert the battery active material back to it's original state. Badly sulfated batteries will not usually respond to this charging regime and will need to be replaced.

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Visitor Comments

  1. Comment #1 (Posted by Scott Sappington )
    what do you mean by long term storage, what should this setting be for a solar system that charges the batteries every day?
  2. Comment #2 (Posted by Andre F Zeehandelaar )
    Please add amp hour rating and equalization voltage. I believe equalization voltage is 31. AH is 225
  3. Comment #3 (Posted by Randy Edwards )
    The damn dropdown covers over the information I searched for. Fix it.
  4. Comment #4 (Posted by Ralph Hiesey )
    Please give a more clear description of exactly how to charge. Here is my guess of what you mean. Is it correct? (Example for 12V nominal battery) "Charge at a C/10 rate OR LESS until the voltage reaches 14.4. (Bulk voltage) Then increase the voltage to 15.5V, no matter what the current, (absorption) and hold this voltage for from 2-4 hours." Is this correct?
  5. Comment #5 (Posted by Morgan Ford )
    Specific instructions for solar charging and temperature compensation would be helpful.
  6. Comment #6 (Posted by Crewzer )
    I'm confused by the different settings for "Bulk" and "Absorption". I'm familiar with multi-stage charger settings for "Absorption", "Float", and "EQ" target voltages, but not with a separate "Bulk" setting. Interstate: Please explain! Thx.

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