Duracell® Power Inverters: Frequently Asked Questions (FAQ)

Please choose from the topics below to view answers to common Power Inverter questions.
All Power Inverters

General Questions Technical Questions
What is an Inverter/Charger?
Many systems incorporate an inverter/charger, which is a combination of an inverter, battery charger and transfer switch in one. The inverter portion converts DC power from an energy source into AC Power. The battery charger processes incoming AC power into DC power and recharges batteries using a multi-stage process, which helps assure maximum battery life. Some models are also able to automate supplementary power production with automatic generator start and stop capabilities.
Back To Top ↑
Battery Technology and Maintenance 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 quickly, which is important in inverter applications
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 in one bank (group of batteries used together for a single application) 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 Duracell Power line of battery chargers for a battery charger which can charge different types of lead acid batteries at once.
  • 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.
Back To Top ↑
What's the difference between "deep cycle" and "starter" batteries?
Deep cycle 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 the batteries are properly charged, you won't get the rated capacity back out of the batteries. Remember: 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.
Back To Top ↑
How big a battery is needed?
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.
Back To Top ↑
What battery type do I need: Gell Cell, Absorbed Glass Mat (AGM), or Liquid Cell (Flooded Lead Acid)?
Battery-Biz recommends using only high-quality deep cycle batteries in Gel, AGM (Absorbed Glass Matt) or Liquid technologies to be used with Duracell Power 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.

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. Following is a comparison chart displaying some of the pros and cons of each battery type:

Battery 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 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


AGM (Absorbed Glass Mat)
  • 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 (terminals will corrode)
  • Withstands many charge cycles when properly charged
  • Better performance for DC loads
  • Highest initial cost of all three battery types
  • More weight per Ah than wet cells
  • Electrolyte can not be replaced
Liquid Cell (Flood Leaded Acid / FLA)
  • 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
  • Not suitable for high vibration environments
NOTE: All lead acid batteries sulphate if left discharged and require maintenance charging.
Back To Top ↑
How many batteries do I need?
There are a few factors that need to be considered before you determine the quantity of batteries (also referred to as a "battery bank") 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.

Determine the size of your battery bank
  1. Convert AC amps to Watts: AC amps x 120 Volts = Watts
  2. Convert Watts to Actual DC amps: (Watts / 12) x 1.1 = actual DC amps
  3. Calculate Amp hours consumed between charge cycles: run-time of appliance (hours) x actual DC amps = amp hours consumed
  4. Determine number of batteries required*: (Total amp hours consumed x 2) / amp hour rating of battery = Number of batteries required
    *Since deep cycle batteries should only be discharged to 50% total capacity, the total amp hours consumed between charge cycles should be multiplied by 2.

    • Amp hours consumed between charge cycles = 126
    • Amp hour rating of battery = 90 (Group 27) (126 x 2) / 90 = 2.8 (Round up to the nearest whole number.)
    • Therefore, the minimum number of batteries required is three with the above values.

    Typical Battery Amp Hour Rating
    Battery Size (BCI Group)* Amp Hour Rating
    Group 27 90
    Group 31 105
    4D 160
    8D 220
    6V Golf Cart 225
    *Note: BCI Group typically refers to the dimensions and configuration of your battery. This group number can usually be found on the top label of your battery, along with battery type and cranking amperage.
Back To Top ↑
How do I determine which size power inverter I need?
Choosing the right size of inverter depends on the power requirements of the appliances you expect to operate at any given time. You should consider both the continuous and surge power rating of your appliance. The continuous rating must be high enough to handle all the loads that may run at the same time. The inverter must also be capable of handling the starting surge of all loads that may start at the same time. Loads typically take many times their continuous rating to start.

Choosing the right inverter
When sizing your inverter, calculate the total wattage required at any one time and choose the inverter with a slightly higher power output. (Start up surge should be considered for compressive loads.)

Determine the total wattage(s) of the device(s) you wish to operate using the inverter
When sizing your inverter, calculate the total wattage required at any one time and choose the inverter with a slightly higher power output. (Start up surge should be considered for compressive loads.) The worksheet below will help you determine the invert and battery bank required to operate your specific loads:

Load (sample) Qty. Wattage
Conversion to
DC Amps
DC Amps
Run Time
(hours - h)
Amp Hours
Consumed Between
Charge Cycles
      w / 12 c x 1.1   a x h
19" TV 1 100 8.3 9.1 4.0 36.4
Coffee Maker 1 1000 83.3 91.7 0.5 45.9
Microwave 1 1200 100.0 110 0.17 18.7
Hair Dryer 1 1600 133.3 146.7 0.17 24.9
  Total Ah 125.9

Back To Top ↑
Do I need to install my inverter near my batteries?
Ideally an inverter should be installed within 10 feet of the battery bank. If you increase this distance, you will need to use larger DC cables to compensate for a drop in voltage and DC ripple.
Back To Top ↑
Can I install my inverter/charger in a gasoline engine compartment?
All Duracell® Inverter/Chargers are not ignition protected and therefore should not be installed in a gasoline engine compartment. They are approved for installation in a diesel engine compartment.
Back To Top ↑
What type of environmental conditions must I consider when installing an inverter/charger?
All Duracell® Inverter/Chargers must be installed in a dry, well-ventilated compartment. While most units are designed to withstand corrosion from the salty air, they are not splash proof. The units also require a fresh air supply to operate properly.
Back To Top ↑
How long can I operate my inverter?
The length of time you can operate an inverter depends on the amp-hour capacity of your battery bank.
Back To Top ↑
Can I use my computer with an inverter?
Both sine-wave and modified sine-wave inverter output will operate a computer, including a laptop. However, some monitors and laser printers can only be powered by true sine wave output. (Click here to learn about modified sine waves vs. true sine waves)
Back To Top ↑
Is it possible to run an air conditioner on an inverter?
Yes, it is possible to operate a small air conditioner in the 5000-9000 BTU range using a higher-powered inverter and battery bank with the right capacity for power. Select an inverter and battery combination that takes into account the startup surge required by the air conditioner.
Back To Top ↑
Should I leave my inverter ON or OFF when shorepower (land-based power source connection to power a boat) is available?
When shorepower is available, you may leave your inverter ON or OFF. There are advantages and disadvantages to both methods. If the inverter is left ON, you have immediate backup AC power if you lose shorepower. You may not be aware shorepower is lost until your batteries are fully discharged. If you choose to leave your inverter OFF you have the advantage of knowing when you have lost shorepower. This, however, is at the expense of losing automatic backup power capabilities.
Back To Top ↑
What is automatic AC transfer switching?
All Duracell® Inverter/Chargers incorporate an automatic transfer switch. This switch senses when outside AC Power is present and transfers the load from the inverter to the source of incoming power (shore or generator). The unit also automatically switches from invert mode to charge mode.
Back To Top ↑
Can I install the inverter without a fuse?
No. A fuse (or circuit breaker, depending on the location and nature of the application) is an integral part of the safe installation of many Duracell Power products. If your installation does not meet the recommendations and specifications in the user guide, it is possible that an unsafe condition may be created, which could result in a fire. Your insurance company may not be obliged to cover damages in this case.

Please follow the installation guidelines in the manual for optimal performance and safety of your Duracell® power conversion product.
Back To Top ↑
Why do my batteries go dead when I use the inverter/charger in "invert" mode?
A Duracell® 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.
Back To Top ↑
Why is the Continuous Output Power listed in the specification sheet lower than the model number of my Inverter?
The power ratings tell you the combined wattage of devices you can connect to the inverter. Each device connected does not always run at the max rated power all the time and the combined continuous output stays below the "continuous" power out capability. If the devices happen to suddenly all need their maximum power for a few seconds then the surge can be handled since it will be below the "surge" capacity. For example a 90W laptop adapter never really pulls 90W. If you suddenly connected a dead battery, run the DVD player, start a processor heavy program and pull power from all the USB ports then the adapter may surge to 90W and then will fall back as the battery needs less and less power.
Back To Top ↑
Using a polarity tester with an inverter: When I check the 115 volt output of a Xantrex inverter with a three light polarity tester, all three lights come on. There is no fault description for the tester covering this. My ground fault outlets do not trip. Is there a problem?
No. What you are seeing is normal if you are testing the output of a Modified Sine Wave (MSW) inverter. The device you're using is for use with household utility power; the internal wiring of the inverter causes this symptom.
Back To Top ↑
Voltage measurement issues (AC output): I've installed the modified sine wave inverter and it's working okay. However, the output voltage doesn't seem right. There is 124 vac between the hot and neutral pins but the safety ground is not at 0 volts with respect to the neutral pin. Instead, the safety ground appears to float about halfway between the neutral and hot pin voltage. Please explain what's going on!
This FAQ applies to Duracell® inverters, including the inverters integral to Powerpacks.

Your inverter is designed to have loads plugged directly into it and not be permanently connected to an AC distribution system. The fact that the inverter is not a permanent installation means the US NEC (United States National Electrical Code) doesn't apply, and the NEC is the main place where the requirement resides for single-phase 120Vac or 240Vac systems to have neutral bonded to earth. The US standard for inverters of this sort, UL458, does not have a requirement for a bonded neutral on the output of inverters.

Regarding the voltage that the you are measuring, the ground does not float halfway, rather the neutral is not at 0 volts. The grounding is correct, in that loads plugged in will have their chassis held at the same ground potential as the chassis of the inverter, but the neutral has approximately 60V on it instead of the usual 0V. The impact of that is minimal, since wiring and equipment connected to the neutral side of the circuit are required by safety standards to be treated as if they were at 120Vac. This is because there are many receptacles that are wired backwards or 2-prong plugs that are not polarized. As a result the 60V neutral is not accessible to the user, and any shock hazard presented is mitigated by lack of access.

The main safety agencies, CSA, UL, and ETL, have all approved inverters with this half-voltage on the neutral scheme, and the manuals contain warnings not to AC hardwire any of these inverters.
Back To Top ↑
Modified Sine Wave (MSW) and True Sine Wave (TSW), compared
There are basically two types of inverters on the market today: modified sine wave (MSW) and true sine wave (TSW). The differences between these two types of inverters are subtle but significant in the way they operate certain types of loads.

Modified Sine Wave
A modified sine wave inverter can adequately power most household appliances and power tools. It is more economical, but may present certain compromises with some loads such as microwave ovens, laser printers, clocks and cordless tool chargers.

True Sine Wave
A sine wave inverter is designed to replicate and even improve the quality of electricity supplied by utility companies. To operate higher-end electronic equipment, a sine wave inverter is recommended.
Back To Top ↑
What are the practical differences between modified sine wave (MSW) and true sine wave (TSW) output?
Most AC products run fine on MSW inverters. TSW inverters are about two to three times as expensive per watt due to having more sophisticated design and manufacturing requirements, and more expensive components. As a result, most people prefer to use MSW inverters if their applications allow it. Battery-Biz Inc. does not guarantee that your AC application will work with an MSW inverter, and we advise our customers to check with the manufacturer of your AC device as to whether or not it will run with a DuracellPower MSW inverter or whether you should purchase a DuracellPower TSW product for your application.
Back To Top ↑
What type of inverter - MSW or TSW - should I use?
In general, any device that senses either voltage peaks or zero crossings could have problems when running from MSW. Devices such as these should be run from TSW inverters. Ham radio and CB radio operators may notice RF noise from MSW inverters; in that case do not run the radio and the inverter at the same time. Electronics that modulate RF (radio frequency) signals on the AC line will not work and may be damaged. You may notice hum or buzz in the audio of TV’s, radios and satellite systems used with MSW inverters. Audiophiles or professionals using sophisticated audio, remote measurement, surveillance or telemetry equipment should use TSW.

Examples of problem devices are motor speed controllers employing triacs, and some small battery rechargers that do not incorporate a transformer between the utility power and the load. To help you visualize this, if there isn’t a ‘wall wart’ between the battery charger (or the battery in the device) and the AC plug, don’t use MSW.

Please note two other common problem loads: electric shavers and emergency flashlights. Both of these items have batteries in them but connect directly into the wall to charge, without an external transformer. Don’t use items like these with an MSW inverter. If you do use an MSW inverter with a transformer-less charger, your product will likely be damaged. Garage door openers, laser printers and large strobes used in photography have all been reported as trouble loads for MSW inverters; they either don’t work at all or stop working entirely, so don’t take a chance – use TSW.

As a general rule, products operating through an AC adapter will work fine from an MSW inverter. These include laptops and cell phone chargers, video games, camcorder and digital camera chargers. Televisions generally work well; some VCR’s with inexpensive power supplies run poorly. Consider switching to another brand of VCR in that case. A potential solution for RV’ers or off-grid cottagers is to purchase a small TSW inverter to run TV, VCR and audio equipment, and a larger MSW inverter  for the coffee maker, hair dryer and microwave.

Duracell Power customers frequently ask us about the use of inverters for medical equipment. Unless specifically noted in the regulatory approvals for the product, assume that no Duracell Power inverter has regulatory approval for use with medical devices or life support equipment. If you use a Duracell Power inverter with a medical device, it’s at your own risk; this is also stated in the warranty for the products.
Back To Top ↑
What do you mean when you say a Duracell Power inverter produces modified sine wave output?
The AC output waveform for many Duracell Power inverters is called a quasi-sine wave or a modified sine wave (MSW). It is a stepped waveform that is designed to have characteristics similar to the sine wave shape of utility power. A waveform of this type is suitable for most AC loads, including linear and switching power supplies used in electronic equipment, transformers, and motors. The modified sine wave produced by the inverter is designed to have RMS (root mean square) voltage of 115 volts, the same as standard household power.
Back To Top ↑
Can I turn an MSW inverter into a TSW inverter?
If you have an MSW inverter and suspect you need a TSW inverter, please note there is no "filter" or "retrofit" you can apply to the output of an MSW inverter to "clean up the output" or "turn it into TSW".
Back To Top ↑