Odyssey AGM Battery Charging

by John Wilson, January 17, 2013

Odyssey is a manufacturer of AGM (absorbed glass mat) lead acid batteries designed for deep discharge and many cycles. In order to achieve the rated 400 deep discharges up to 80% of rated capacity the charging rate must be 40% of the 10 hour rating for Nominal Capacity. Thus for a PC1800-FT battery, rated at 190 aH (10 Hr Rate - Ah, Nominal Capacity), the required charging rate is 76. As the table below shows, for smaller batteries like the PC835 with a 10 Hr rating of 13, the charging amps should be 5.6 (40% of 13).

At the same time the Odyssey manual also has a table that shows the PC1800-FT requiring a 20 amp charger, from fully discharged state, taking 17 hours to charge fully. Charging the PC1800-FT at 10 amps is not recommended in the table shown in the Owners Manual on page 7.

From this, it would appear that the PC 1800-FT requires a high level of amps in order to charge properly. Thus in a configuration where smaller solar panels are used to charge this particular battery, as many amps as possible are required to get the charging rate up to 20 amps or higher in order to meet the requirements for 400 cycles.

Source: Odyssey Owners Manual PDF file

In order to achieve the full design cycle life of ODYSSEY batteries in cyclic applications the charge current must be

a minimum of 40% of the batterys 10-hour rating (column 8 of the chart on page 5). Thus the minimum charge

current for a PC925 battery in a cycling application is 10.8 amps (40% of 27Ah). Please refer to Figure 6 of the

ODYSSEY application manual for a detailed discussion of the recommended charge profile for ODYSSEY batteries

in cycling applications. The manual may be downloaded from www.odysseybattery.com.