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Batteries - Technology and maintenance overview

Battery Overview:

A battery is a device that stores energy while it is being charged and releases energy while it is being discharged. There are a lot of different battery technologies, but lead acid batteries, which consist of plates of lead dioxide and spongy lead, immersed in a sulphuric acid solution contained in a durable housing, are most appropriate for use with inverters and mobile power solutions.

Lead acid battery technology has come a long way since 1859, the year it was invented. You no longer have to check the state of charge with a hygrometer, or top the batteries up with distilled water. Batteries are now safer, more reliable and in some cases, virtually maintenance free. Lead acid batteries are recommended for use with inverters because:

? They are low cost, widely available and easy to manufacture
? They are durable and dependable when properly used and stored
? The self discharge rate is lower than that of other battery technologies
? There's no memory effect
? They can produce a lot of current very fast, which is important in inverter applications.

Deep Cycle Verses Starter Batteries:

Lead acid batteries are suitable for applications requiring a big, sudden discharge of current (what you need to start the engine on a boat, or in a car or RV) or a slow, steady discharge of current (to run your scooter, or watch a TV). These two classes of application generally require different battery technology, but they share some chararacteristics. Lead acid batteries of similar amp hour capacity will require about the same length of time to recharge, and all lead acid batteries are damaged by heat, and by storage in a discharged state.

The technology for starter batteries is simple. Many thin plates of lead in the electrolyte give lots of surface area, thus lots of potential current. This is the kick you need to get your car to start on a frosty morning.

Thick plates make batteries better suited to deep cycling ? the type of battery that works best with an inverter. Thick plates aren't the best for short high current use. If you have a quality deep cycle battery, you can discharge and recharge it more than 1500 times. A starting battery can be discharged perhaps 30 times before it will no longer accept a charge.

Because of the differences in the way the lead plates inside the battery are placed, the battery charging requirements are slightly different for the two styles of battery. Batteries that are not charged in accordance with manufacturer's instructions can over gas (referred to as ?boiling?) if overcharged, or sulfate if undercharged. Improper charging reduces the battery capacity and life cycle; that's why it's important to use the right charging technology to protect your investment in your batteries.

Unless they are properly charged, you won't get the rated capacity back out of the batteries. There's no free lunch: You can't take energy out that you haven't put in. Further, you?ll shorten the life cycle of any battery if it's not properly charged. This is because the sulfur crystals which are deposited on the active material of the plate during discharge (while you are running your inverter or DC load) will not be forced back into solution during the charge cycle. Over time, these crystals become harder and thicker, reducing the access of the electrolyte to the plate and ultimately reducing the battery's capacity.

How big a battery is needed?

Check the FAQ http://www.xantrex.com/support/howlong.asp for the Xantrex Technology Inc. battery calculating tool. You will need to know the wattage of the product or products you wish to run in order to use this tool.

Batteries last longest if you only discharge to 50% of capacity and then recharge as soon as possible after the discharge. If you want to run a 1 amp light for 50 hours between charging, you would need a battery which will deliver about 100 amp-hours. Although you can discharge a battery much further than this, you will begin to decrease the battery's cycle life. A good deep cycle battery might deliver 1,500 (or more) discharges to the 50% level. By increasing the discharge to 95% you can reduce cycles to a hundred or so. So don't undersize your battery bank, or you will be buying batteries much more often than necessary.


Gel Cell, Absorbed Glass Mat (AGM) or Liquid Cell (Flooded Lead Acid) Batteries?

Which type of battery you buy depends on your application, your charging system, your budget, your willingness to trade convenience for cost, and weight considerations. Some advice applies to all types of batteries. The following advice is not meant to supersede specific product instructions or cautions supplied by the battery manufacturer.

? Unless your battery charger can be programmed to output the appropriate charging cycle for different battery types, use only one battery chemistry - Liquid (also called Flooded), Gel, or AGM. Different battery types on one bank may result in undercharging or overcharging, and reduce the battery life. This may require you to replace all of the batteries in your system at once.

? Check the Xantrex Charger (XC) line of battery chargers for a battery charger which can charge different types of lead acid batteries at once. The Truecharge series works well with up to three banks of one battery type.

? Never mix old batteries with new ones in the same bank. While it seems like this would increase your overall capacity, old batteries tend to reduce the new ones to their deteriorated level.

? Regulate charge voltages based on battery temperature and acceptance (manually or with sensing) to maximize battery life and reduce charge time.

? Ensure that your charging system is capable of delivering sufficient amperage to charge battery banks efficiently. A rule of thumb is that for every amp of alternator you can have 4 to 5 amp hours of battery capacity. For example, a 100 amp alternator can support 400 to 500 amp hours of battery capacity.

? Keep batteries clean, cool and dry.

? Check terminal connectors regularly and clean in accordance with the manufacturer's instructions to avoid loss of conductivity.

? Add distilled water to flooded lead acid batteries when needed. It is important to adequately submerse the plates in solution, and also not to overfill which will cause loss of electrolyte when charging due to the volume expansion of electrolyte due to gas bubbles generated within the acid electrolyte. Most flooded batteries have a piece of plastic sticking down from the vent cap/filler opening inside the cell a certain height above the plates, which provides a visual depth indication when to stop filling with distilled water. Using a flashlight, watch for the acid solution's meniscus forming when the liquid level hits this level. Don't overfill much past this point.
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