Multistage Battery Charging

A typical 12 volt lead-acid battery must be taken to approximately 14.2-14.4 VDC before it is fully charged. (For 24 volt systems double these figures.) If taken to a lesser voltage level, some of the sulfate deposits that form during discharge will remain on the plates. Over time, these deposits will cause a 200 amp-hour battery to act more like a 100 amp-hour battery, and battery life will be considerably shortened. Once fully charged, batteries should be held at a considerably lower voltage to maintain their charge -typically 13.2 to 13.4 volts. Higher voltage levels will "gas" the battery and boil off electrolyte, again shortening battery life.

Most battery charger designs cannot deal with the conflicting voltage requirements of the initial "bulk charge" and subsequent "float" or maintenance stage. These designs can accommodate only one charge voltage, and therefore must use a compromise setting - typically 13.8 volts. The result is a slow incomplete charge, sulfate deposit build-up, excessive gassing and reduced battery life.

The charger available in our inverters automatically cycles batteries through a proper multi-stage sequence to assure a rapid and complete charge without excessive gassing.

Factory battery charger settings on our inverter-charger combinations are optimal for a lead acid (liquid electrolyte) battery bank of 250-300 amp hours in a 60° F environment. If your installation varies from these conditions, you will

Lead Acid Battery Hazard

obtain better performance from your batteries if you adjust the control settings.

The Maximum Charge Rate in amps should be set to 20-25% of the total amp-hour rating of a liquid electrolyte battery bank. For example, a 400 amp-hour bank should be charged at no more than a 80-100 amp rate. Excessive charge rates can damage batteries and create a safety hazard.

The Bulk Charge Voltage of typical liquid electrolyte batteries should be about 14.4 VDC; gel cells like the Deka about 14.1 VDC. There is no one correct voltage for all types of batteries. Incorrect voltages wiil limit battery performance and useful life. Check your battery maker's recommendations.

The Return Amps setting controls how long the batteries will be held at the bulk charge voltage before dropping to the float/maintenance level. A good setting is 2-4% of the amp hour capacity of a liquid electrolyte battery bank. A fixed, "one-size-f its-ail" setting will overcharge a large battery bank (gassing the batteries) and undercharge a small bank (limiting battery performance).

The Float Voltage setting should hold the batteries at a level high enough to maintain a full charge, but not so high as to cause excessive "gassing" which will "boil off" electrolyte. For a 12 volt liquid electrolyte battery at rest, a float voltage of 13.2-13.4 is normally appropriate; gel cells are typically maintained between 13.5 and 13.8. If the batteries are being used whiie in the float stage, slightly higher settings may be required.

Charge voltage guidelines used here are based on ambient temperatures of 60° F. If your batteries are not in a 60° F environment, the guidelines are not valid. Temperature Compensation allows easy single dial re-scale of the voltage settings to compensate for the differences between ambient temperature and the 60° F baseline. Temperature compensation is important for all battery types, but particularly gel cell, valve-regulated types wnich are more sensitive to temperature.

DIY Battery Repair

DIY Battery Repair

You can now recondition your old batteries at home and bring them back to 100 percent of their working condition. This guide will enable you to revive All NiCd batteries regardless of brand and battery volt. It will give you the required information on how to re-energize and revive your NiCd batteries through the RVD process, charging method and charging guidelines.

Get My Free Ebook

Post a comment