Xantrex Technology SW Series Technical Information, Page 100, Sealed Lead Acid Batteries

TECHNICAL INFORMATION

Type 8D batteries are available with either cranking or deep cycle construction. The deep cycle versions are 12-volt batteries rated at 200 amp hours or so. Since they are most commonly used to start truck engines, you should make sure you purchase the deep cycle version.

SEALED LEAD ACID BATTERIES

CAUTION: if using gelled batteries, the battery charger must be set to the appropriate settings or battery damage will occur.

Another type of deep cycle battery construction is the sealed "valve regulated" lead acid battery. They are a rechargeable battery which recombines suppressed gases, thus eliminating the need to add water. Since they are tightly sealed, these batteries will not leak and can be installed in certain applications where ’liquid type’ batteries could not be installed.

While there are many manufacturers of quality non-sealed batteries, there are only a few manufacturers of suitable sealed batteries. Don’t confuse sealed batteries with “maintenance free” batteries - the later is typically a standard liquid electrolyte type battery without caps for adding water - when the electrolyte gets low you replace the battery.

The advantages of true “deep cycle” sealed batteries are no maintenance (does not require acid checks or periodic watering), long life (800 cycles claimed) and low self-discharge. The disadvantage is high initial cost and because water cannot be added, they are less tolerant of overcharging.

Two methods are used to seal batteries by a process of immobilizing the electrolyte, which in turn eliminates free-flowing acid. Both these methods can be used in inverter applications.

Gel Cell: Silica gel is added to the electrolyte, causing it to 'set' in gelatin form.

Absorbed Glass Mat (AGM): Highly absorbent glass mat separators are used between each plate to retain the liquid electrolyte.

Even with all the advantages of sealed batteries, there is still a place for the standard flooded deep cycle battery. Sealed batteries will cost 2 to 2.5 times as much as “liquid” or flooded batteries. In many installations, where the batteries are set in an area where you don't have to worry about fumes or leakage, a standard or industrial deep cycle is a better economic choice.

NICAD AND NICKEL IRON (NIFE) BATTERY

Trace™ inverters and battery chargers are optimized for use with lead acid batteries that have a nominal voltage of 2.0 volts per cell. NiCad/NiFe batteries (also called alkaline batteries) have a nominal cell voltage of 1.2 volts per cell. The nominal voltage of a NiCad/NiFe battery bank can be made the same as a lead acid bank by juggling the number of cells (10 cells for 12 volts, 20 cells for 24 volts and 40 cells for 48 volt systems). However, the NiCad/NiFe battery bank must be charged to a higher voltage to fully recharge and will drop to a lower voltage during discharging compared to a similarly sized lead acid type battery. This makes the job for the inverter/charger much more difficult.

The easiest way to use NiCad/NiFe batteries with a 24 volt inverter is to use nineteen NiCad/NiFe cells in the battery bank instead of the usual twenty. This will reduce the battery bank charging voltage requirements to about the same level as a lead-acid bank; so more standard charger settings can be used. The problem with this approach is that the battery voltage will drop as low as 18 volts to fully discharge the battery.

A second option on 12-, 24- and 48-volt systems is to adjust the SET BULK VOLTS DC to its maximum setting. This will provide a complete charge although it may require a longer charging period to completely recharge the battery compared to using a higher charge voltage (or lesser number of cells) were used. The ABSORPTION TIME setting may be set shorter than with lead acid batteries since NiCad/NiFe batteries do not require an absorption stage. If the battery storage requirements are large, industrial grade 2 volt batteries are often more suitable.

Note: In alternative energy applications (solar, wind, hydro) all DC charge controllers must be set to a level below the inverter HIGH BATTERY CUT OUT setting or the inverter may shut off unexpectedly.

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 2001 Xantrex Technology, Inc.	Telephone: 360/435-8826	SW Series Inverter/Charger
5916 - 195th Street N. E.	Fax: 360/435-2229	Part No. 2031-5
Arlington, WA 98223	www.traceengineering.com	Rev. C: February 2001