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Marine Product Guides >

Marine Battery Charger Guides



What type of batteries should I use in my inverter/charger installation?

Xantrex recommend using only high-quality deep cycle batteries in Wet, Gel or AGM (Absorbed Glass Matt) technologies to be used with Xantrex products. Deep-cycle batteries are designed specifically for a deep discharge and a rapid recharge. Wet cell batteries include 6-volt (golf cart) batteries and require some maintenance. Gel cell batteries and AGM batteries are sealed and typically require very little maintenance. Do not use starting batteries for inverter applications.

Battery 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 (available in 2005) 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.

How many batteries do I need?

There are a few factors that need to be considered before you determine the quantity of batteries needed. First, consider the type of battery you intend to use with your application. Next, determine the size of the battery and the number of amp hours you require between charge cycles. Most people have a 400-450 amp-hour battery bank, but this depends on use of your system.

Why do my batteries go dead when i use the inverter/charger in inverter mode?

A Xantrex inverter takes available battery power and converts it to AC power to operate household appliances. In many cases there are additional "hidden loads" that will draw power from the inverter even when they are turned off. Some examples are: TV tubes being kept warm and microwave & VCR clocks. In addition to AC loads, there may also be DC loads that draw power from the same battery bank as the inverter. These loads can include CO detectors, accent lighting, bay lights, and water pumps. Phantom loads may consume over 70 amp hours per day and most banks will be depleted in about three days with the inverter running with no loads on connected.

Battery type comparison chart

Type Pros Cons
Gel Cell
  • Better for rough service environments•Leak proof
  • Can be installed on its side with small drop in performance
  • Less susceptible to low temperatures
  • When charged correctly does not vent much gas
  • Low self discharge rate
  • Higher initial cost than Liquid Cell
  • Electrolyte cannot be replaced
  • Charging tolerances are tighter; cannot be charged over 14.2V without damage
  • Not ideal for use with automotive or unregulated chargers
  • NOTE all lead acid batteries sulphate if left discharged and require maintenance charging
  • Maintenance-free
  • Leak proof when tipped or if case is cracked
  • Used for both deep cycle or starting batteries
  • Can be installed at any angle (except upside down)
  • Shock and vibration resistant
  • Minimal gas release when
    charged properly
  • Low self-discharge rate
  • Can be submerged in water without internal damage (battery terminals will corrode)
  • Many charge cycles when properly charged
  • Better performance for DC loads
  • Highest initial cost of all three types
  • More weight per Ah than wet cells
  • Electrolyte cannot be replaced
  • NOTE all lead acid batteries sulphate if left discharged and require maintenance charging
Liquid Cell - also called Flooded Lead Acid
  • Lowest cost to purchase by amp hour
  • Less sensitive than the other two styles in accepting higher charging voltages and less expensive / less regulated charging methods
  • Good deep cycle performance
  • Can spill corrosive battery acid
  • Must be installed upright
  • Requires regular maintenance
  • More quickly damaged if left discharged
  • NOTE all lead acid batteries sulphate if left discharged and require maintenance charging
  • Not suitable for high vibration environments

What is three stage charging?

Multistage charging ensures batteries receive optimum charging, but with minimal wear and tear, regulating the voltage and current delivered to the batteries in three automatic stages:
  • Bulk: Replaces 70-80% of the battery’s state of charge at the fastest possible rate.
  • Absorption: Replenishes the remaining 20-30% of charge, bringing the battery to a full charge at a slow, safe rate.
  • Float: Voltage is reduced and held constant in order to prevent damage and keep batteries at a full charge.


Docement Downloads:

Xantrex Technology has recently launched a new educational series entitled “Tech Doctor” for marine, commercial and recreational vehicle applications. Designed for dual usage, the series is produced for editorial reproduction and industry education. Written by Xantrex Sales Engineer Don Wilson, who conducts technical training seminars throughout the country, the series covers topics of general interest in an easy-to-understand, Q & A format. Xantrex also encourage its partners to use articles in this series as a tool to educate their customers.

Document Name Last Updated Size
  Back to top
Why is Regualtory Compliance Such a Big Deal? 06/17/2015 91 KB
Inverter Installation:Troubleshooting 101! 5/14/2015  221 KB 
The Mystique of Automatic Generator Start (AGS)! 10/16/2012  221 KB 
Don't Judge An Inverter By Its Package! 03/12/2012  193 KB 
The Power Installation Dilemma  03/12/2012  193 KB 
The Inside Scoop on Battery Chargers 04/05/2011 186 KB
Three Top Tips to Maximize Your Electrical System 07/29/2010 114 KB
Shocking News About Inverter/Charger Installations 05/27/2010 96 KB
How to Select the Right Inverter for Vehicle or Boat? 05/27/2010 87 KB
Sine Wave vs. Modified Sine Wave 05/26/2010 100 KB
Are Your Maximizing Your Power Sources? 6/22/2010 436 KB
Inverters vs. Generators: The Ultimate Grudge Match! 5/28/2011 132 KB



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WarningWARNING: This product can expose you to chemicals including Di-n-hexyl Phthalate (DnHP) which is known to the State of California to cause reproductive harm, and Vinyl Chloride which is known to the State of California to cause cancer. For more information go to P65Warnings.ca.gov. __________________________________________________________________________________________


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