Best Answer

The volts MUST match exactly, the polarity MUST match exactly, and the milliamps MUST be the same or more. The unit will use what it needs, even if to much is being offered. On the other hand, too few milliamps will BURN THE UNIT OUT!

So on top of loosing your equipment, you could loose your life also ... since it is a major fire hazard!

Clearly the voltage is not the same. The phone needs 7V, the charger is at 9V. Mismatching voltage will not work.

Using a power supply with a maximum current rated below what is required will result in 1) the supply voltage dropping, and 2) the device generating additional heat. Such low power requirements do not present a serious hazard, fire or otherwise. However, the higher voltage will likely seriously damage the phone. Had the supply you chose been rated at 7V 400mA, the phone would likely still charge, albeit much more slowly.

2015-07-15 19:43:04
This answer is:
User Avatar

Add your answer:

Earn +5 pts
Q: If a phone needs a 7v 900ma charger can you use a 9v 400ma if the voltage and polarity are the same?
Write your answer...

Related Questions

What is difference between 550 mah and 900 mah in mobile phone charger?

The charger with the 900ma output will charge the battery faster than the charger with a 500ma output. The phone with the 900mah battery will last longer between charges than that of the 500mah battery.

What is the power rating in a Nintendo 3ds?

The power rating is on the bottom of the 3ds, the power rating is 4.6V 4.1W, the power suply input is 4.6V 900mA. the DSI charger will work on a 3DS.

How many amps goes into 900ma?


Is it possible to over use your power supply in the usb outlet?

Yes. A standard USB Plug can provide <at usb2.0> 500mA of power. Some devices if poorly made or malfunctioning could draw too much of that power over a chain of devices and cause the port to shut down. It will not, in most cases, damage the power. The port will detect an overage in power demand and shut itself down. Usb 3.0 allows for at most 900mA of power.

How much mAh capacity does a single AA battery have?

Zinc-carbon AA =400-900 mah Alkaline AA = 1700-3000 mah :: I believe the above answer to be misleading/misguiding, the question is "How much mA does a single AA battery have?" not how many mAh. in mA a single AA batter will have about 3.6mA to 4.0mA it is important to distinguish mA from mAh, if one were to connect a device that required 4.0mA to a power source of 400-900mA this would likely destroy the device. mAh deals more with how long the battery life lasts.

The usb and firewire bus standart and their possible impact on computer of the future?

USB AND FIRE WIRE BUS STANDARDS AND THEIR POSSIBLE IMPACT ON COMPUTERS OF FUTUREUNIVERSAL SERIAL BUS (USB):-A USB flash drive is a data storage device that consists of flash memory with an integrated Universal Serial Bus (USB) interface.· It is hot swappable.· USB version 1.1 provides maximum speeds of up to 1.5 MB/s while the version 2.0 is about 40 times faster.· Most weigh less than 30 g.· Drives of 256 gigabytes (GB) are also available, and storage capacities as large as 2 terabytesInternals of a typical USB flash drive1USB Standard-A plug2USB mass storage controller device3Test points4Flash memory chip5Crystal oscillator6LED7Write-protect switch (Optional)8Space for second flash memory chipUSB STANDARDS:-USB (1.x and 2.0):-USB 1.x provides low speed (up to 1.5 M Bit/s) at distances of 3m, and high speed (12 M Bit/s) at distances of 5m.Version 2.0 supports speeds to 480 M Bit/s at distances of up to 5m.In all cases a maximum of 5 hubs may be supported.USB (1.x and 2.0) provide a base current of 100MA and a maximum current of base X 5 = 500MA for powering of peripherals or battery charging applications.USB 3.0:-USB 3.0 provides speeds up to 5.0 G Bit/s - termed Super Speed in the specifications. USB 3.0 uses new Standard and Micro A and B plugs and receptacles using 9 pins to obtain the full Super Speed performance (5.0 G Bit/s). USB 3.0 increases the base current from 100MA (USB 2.0) to 150MA. The maximum load is 6 x base to 900MA (up from USB 2.0 x 5 = 500MA).USB 0.7 :-· Released in 1994· Voltage - Input2.7 V ~ 5.5 V· Current Limit= 700mA· Operating Temperature= - 40°C ~ 85°COTHER STANDARDS:-· USB 0.8: Released in December 1994.· USB 0.9: Released in April 1995.· USB 0.99: Released in August 1995.FIREWIRE BUS:-FireWire is High Performance Serial Bus, for connecting devices to your personal computer. FireWire provides a single plug-and-socket connection on which up to 63 devices can be attached with data transfer speeds up to 400 Mbps.It is Hot-plug and plug and play capability without disrupting your computer.FIREWIRE STANDARDS:-FIREWIRE 400 (IEEE 1394):-High interface transfer rate: up to 50MB/s.Flexibility: use your IEEE 1394 peripheral on both Mac or Windows platforms.Ease of use: hot-pluggable FireWire technology.Small cables: space-saving thin serial cables.Connect up to 63 devices.Self-powered: directly powered by the bus.The IEEE 1394 interface is specifically aimed at multimedia peripherals such as digital video camcorders, CD-RW drives, DVD drives and hard drivesFIREWIRE 400 (IEEE 1394a):-Brings high-speed connectivity to your desktop computer, quickly and easilyIt added support for asynchronous streaming, quicker bus reconfiguration, packet concatenation, and a power-saving suspend mode.Great for use with multimedia peripheralsFirewire 400 (IEEE 1394a) provides 100, 200 and 400 Mbits/sec transfer at a distance of 4.5 meters between devices.FireWire 800 (IEEE 1394b)· FireWire 800 (IEEE 1394b) increased transfer rate to 800 Mbits/sec and cable distance to 100 meters in 2003. · It also expanded cable options to glass and plastic fiber and Cat 5 Ethernet.· Also included in IEEE 1394b, FireWire 1600 and FireWire 3200 increase transfer rates to 1.6 and 3.2 Gbits/sec respectively.· FireWire 800's connector, referred to as a beta connector, is different from FireWire 400's alpha connectors, making legacy cables incompatible.FireWire S800T (IEEE 1394c):-· High Performance Serial Bus Amendment to enhance the physical layer for higher data rates over CAT5 or better rated UTP cable Scope. · This is a full-use standard whose scope is to amend the IEEE 1394 base standard (IEEE Std 1394-1995 as amended by IEEE Std 1394a-2000 and IEEE Std 1394b-2002) to specify alternate physical layer(s) that provide greater than S100 data rate over CAT5 or better cable.· This physical layer is capable of negotiating with a peer device to select the appropriate next higher protocol layer.Future enhancements (including P1394d)A project named IEEE P1394d was formed by the IEEE on March 9, 2009 to add single mode fiber as an additional transport medium to FireWire. P1394d - IEEE Standard for a High-Performance Serial Bus - Amendment: IEEE 1394 Single-mode Fiber Fiber Physical Medium (PMD) SpecificationOther future iterations of FireWire are expected to increase speed to 6.4 Gbit/s and additional connectors such as the small multimedia interface. IMPACT of USB and FIREWIRE on future Computers:-USB and Firewire represent the newer generations of external serial interfaces being adopted to reduce PC and connection costs and to improve performance.BY :- AWAD ZAFAR

Is it dangerous to charge mobile phone battery with different charger?

Yes it is dangerous as the charger might be charging at a higher voltage than your phones battery charger also the polarity might be different which could cause a fire

Can a 0.9V 400MA solar panel be used to charge 2 AA batteries?

To charge a battery, the charger voltage must be higher than the battery voltage. If a AA battery (or any other) has a normal voltage of 1.2V the charger voltage must be at least 1.2V. The type of voltage supply and its current capability is immaterial. No, the charging voltage have to be larger than the battery voltage, to charge 2 AA batteries, that is 3 volt if connected in series, so a voltage of at least 4 volt is needed

What is the standard voltage of a laptop charger?

the voltage of a laptop charger is in between fifteen to twenty four voltage.

How a bucking voltage acts?

bucking voltage is a voltage which is of opposite polarity to the voltage it acts .

Can you charge a 18v battery with a 12v charger?

NO, voltage of the charger must match the battery voltage.

Is a HA90PE1-00 dell charger the same polarity as a LA65NS0-00 dell charger?

The engineering standard is that the center of the connector is the positive, and the outside is the ground. I can't think of a case I've ever run across that was wired opposite to that.But there could be other differences in the chargers beyond polarity (such as voltage!). So beware.

Can you use a 12V 400mA power adapter instead of a 12V 800mA to run a device that calls for a 12V 800mA?

No. The voltage rating is the same, but the lower current rating on the 400ma power supply might cause the voltage to drop way below 12 volts, and on some devices a lower voltage than it is rated for will cause it damage.

What is mean by polarity?

What is meant by polarity? Answer An electric charge has a polarity of either positive or negative. Also a voltage has a polarity, in that it could be positive or negative, with respect to some other voltage, such as the one at the other end of a battery or electric circuit.

Does an AC voltage have a polarity?

If you use 'polarity' in the sense of electric charge, no, it does not. Voltage is simply another word for potential difference and potential difference doesn't have an electric charge. Potential, on the other hand does, but its charge polarity depends on from where it is being measured. If you use 'polarity' in the sense of direction, then, yes, it does. You can allocate direction to a voltage.

Did the armature voltage reverse its polarity?


Where is the Voltage regulator in a 89 ram-charger?

It's in the computer...

Can you use a 800ma adapter to power a 400ma device?

Yes, as long as the adapter voltage matches the devices requirement voltage. The capacity of the adapter is more that ample to run the device.

Why polarity test is done on single phase transformers?

They don't have a polarity as such because that alternates with the current, but in some designs the windings are coupled, so the manufacturer has to be sure the alternating poles do correspond.AnswerPolarity is one of the characteristics you need to know if you are to parallel two or more single-phase transformers. Polarity describes how the secondary voltage relates to the primary voltage, and may be 'additive' or 'subtractive'. These terms describe whether the secondary voltage is in phase or in antiphase with the primary voltage, and depends on how the two windings have been wound, relative to each other.A polarity test is normally performed from the high-voltage side of the transformer. To perform a polarity test, the primary and secondary windings are connected in series with each other, and a small a.c. voltage is applied to the high-voltage winding. The resulting voltage across both windings is then measured. If this voltage is higher than the applied test voltage, then the transformer is said to have 'additive polarity'; if the voltage across both windings is lower than the applied voltage, then the transformer has 'subtractive polarity'.

Why carbon is not considered as a semiconductor?

The resistance of a semiconductor depends on the amplitude and polarity of the applied voltage. The resistance of carbon doesn't depend on the amplitude or the polarity of the applied voltage.

How do you test for polarity of 3 phase motor using voltage?

There is no such thing a polarity in AC voltage or current. It changes back and forth 60 cycles a second.

What do you mean by Polarity of a transformer?

The 'polarity' of a transformer describes the direction of the secondary voltage with respect to the primary voltage. This depends on the relative directions in which each of the windings have been wound. Polarity is a very important factor when two transformers are to be connected in parallel with each other in much the same way as the polarities of two batteries are.To determine the polarity of a transformer, the high- and low-voltage windings are connected in series, and a small voltage is applied to the high-voltage windings. If the voltage then appearing across both windings is greater than the applied voltage, then we describe the transformer as having 'additive' polarity; if, on the other hand, the resulting voltage is lower than the applied voltage, then we describe the transformer as having 'subtractive' polarity.In North America, with the high-voltage windings on the far side of the transformer from the viewer, if the diagonally-opposite terminals both 'go positive' at the same instant then the transformer is 'additive' polarity; if the directly-opposite terminals 'go positive' at the same instant, the transformer is 'subtractive' polarity.

Can use 14.4 volt charger to charge 18 volt battery?

Charger Output Voltage versus Battery VoltageNO, the output voltage of a charger must be greater than the rated voltage of the battery, usually at least one and a half to two volts difference.

Can you use a 120v dewalt battery charger in Europe with 220v without a voltage converter without damage to the charger or battery?

No, by doubling the input voltage to the charger which is just a transformer you will be doubling the output of the charger. Batteries like to be charged at about a volt and a half above their working voltage.

What is transformer polarity?

The sense, or direction, in which the secondary voltage acts in comparison with the primary voltage. In North American terminology, if, at the instant when terminal H1 (high voltage) goes positive, if terminal X1 (low voltage) also goes positive, then it is a additive-polarity transformer. But if X1 goes negative, then it is a subtractive-polarity transformer.