Q. Can I charge an AGM battery with a Manual charger?
A. You can charge an AGM Battery with a manual charger with a caveat. In most cases the user will have to monitor the battery voltage while it is on charge. The amount of monitoring required will depend on the charger. One item to be aware of is the number of charge settings the charger has, the larger the number the more likely monitoring will be a minimum. Let’s look at an Associated Equipment 6001A charger as an example:
Here is a chart of the output ratings on the 6001A charger that would be useful for charging an AGM battery. With little monitoring.
From this chart we can see if we charge on the 6HI-3 setting almost no monitoring would be required since the max voltage is just a little above the float voltage for an AGM battery (13.6V). The trade off is that it can take a long time to fully charge a battery. Placed the 6001A on a moderate AGM battery that we fully discharged with the RC rating (25A).
If we want to fully charge the battery you need to return 103% of what was taken out. In this example it took 19:21 to return that amount if we only returned 100% it took 14:51, for 80% the time is 7:51, and for 65% the amount needed to test the battery or start a car the time would be 5:16. Point: to finish a battery to return the last 23% takes the bulk of the charge time in this case 11:31 out of 19:21, or takes 59.5% of the time to return the last 23%.
If we would like to charge faster and can at least lightly monitor the battery the 6HI-S setting would be a good choice since the maximum voltage on this setting is right around the maximum voltage for an AGM battery (15.0V, the ideal charge voltage might be a little lower). If we use the same battery but this time set the 6001A to the 6HI-S setting this is what we see.
Following the same logic, it took 5:57 to return 103% (Battery Voltage of 15.07V), for 100% returned (Battery Voltage of 14.92V) it took 4:37, for 80% (Battery Voltage of 13.70V) it took 2:15, and for 65% (Battery Voltage of 13.35V) it takes 1:15.