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Can I Use a Charger that Provides the Same Voltage but a Different Amperage?

I’d like to know if it is okay to use a different power charger for my netbook. Originally, the charger specs are 19v and 1.58A. This charger is not available anymore and I can only find a 19v and 2.15A. Can I use this as a replacement?

Yes — with a couple of caveats, of course.

If it’s not made specifically for your particular computer, getting the right power supply is important, and involves matching voltage, amperage, and polarity.

Each have different constraints.

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Let’s start with the simplest: voltage.

The voltage output by your charger or power supply must match what is required by your computer or device as closely as possible. In your case, you’ve got this covered: the old charger supplied 19 volts and your replacement is also 19 volts.

It’s important to get the right voltage. Some devices are quite tolerant of voltage variations and will work just fine. Others, not so much. The device may work with voltages that are close, but often at the cost of shortening its lifespan.

If the voltage is significantly off, it can damage your device.

Because there’s no easy way to know which category your device falls into, you should just make sure to get the right voltage from the start.


USB Charger Many people are confused by amperage ratings and what they mean when it comes to power supplies and replacements.

The amperage rating is the maximum amount of power it can supply.

One way to look at it is as if amperage were “taken” (often referred to as “drawn”, as in pulling) by the device being powered. That device will only draw as much amperage as it needs to perform whatever it’s doing. Your computer will use more power, in the form of higher amperage draw, when it’s working hard than when it’s not. (Voltage remains the same regardless.)

Thus, as long as you replace your power supply with one capable of providing as much or more amps than the previous supply, you’ll be fine.

If for some reason your replacement power supply has a lower-than-required maximum amperage rating, you may end up with a burnt out or overheating power supply, and the device itself may not function.

Input Voltage

Input voltage — the power you get from the wall socket into which you plug these devices — is really interesting.

These days, for most power supplies, almost anything works.

If you look closely at many power supplies, you’ll see they’re rated to be plugged in to anything from around 100 volts to 250 volts as input. That they can do that — take just about any input and create a fixed, stable output — amazes the electrical engineer in me.

It also means that most can work worldwide with nothing more than an adapter to account for the physical plug differences – no transformer needed.

Check your power supplies before you travel, of course, but it’s very, very convenient.


This final item catches many people by surprise, especially when replacing simple or small power supplies with generic equivalents.

Most power supplies provide DC (direct current) power via two wires, labeled positive and negative. Polarity refers to which wire is which.

Just because the physical plug into your device matches doesn’t mean that the positive and negative connections are hooked up the right way. In fact, there’s often no real standard.

Particularly when it comes to popular circular power connectors, make sure the expectations match: if the device expects the center connector to be positive and the outer ring to be negative, your power supply’s connector must match. There’s no getting around this. Failure to get it right at best simply doesn’t work, and at worst damages the device. Look carefully for indicators on both the power supply and the device to which you’re connecting it.

The good news here is that there are some standards where the polarity is always the same and always correct. For example, USB is a standard that more and more devices are using to supply power. In that same vein, if you’re replacing a power supply that uses a custom connector used only by one manufacturer, then you won’t have to worry about polarity either.


In short, when replacing an external power supply or charger:

  • Make sure the voltage matches.
  • Make sure the new power supply is rated to provide the same amperage or more.
  • Make sure the connectors match, both in physical form and in polarity.

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62 comments on “Can I Use a Charger that Provides the Same Voltage but a Different Amperage?”

  1. Interesting analogy for volts vs amps. I’d always heard the water hose comparison, voltage is the water pressure, amperage is the amount of water flowing through the hose.

    • Your water analogy is incomplete: voltage is the water pressure, and amperage is the SIZE of the hose. A small hose under a lot of pressure will get you wet; a huge hose, even under low pressure, can wash you away. But none of that has to do with the volts pushed to and amps drawn from a computer, really.

  2. Just be careful with some laptops. I know that with my Dell laptops, if the chip in the charger goes bad (the chip that tells the Dell laptop that this charger is the correct charger for the computer), it will no longer charge the battery, and the laptop will draw less power (or amps – but Amps times Volts gives you Watts – or power) – thus slower laptop. Their reasoning, is so you don’t plug a charger in that isn’t rated for your laptop and damage it, but it forces you to only buy the correct Dell chargers, and when that chip goes, even if the charger is working – you no longer can charge, and you have a slower system (even my USB ports wouldn’t produce the correct power output when the Dell isn’t able to read the charger’s chip.)

  3. You mentioned “most” are DC currents. I think you should caveat that with most “U.S.” I may have missed it, but I didn’t see that mentioned.

    The output of most power supplies and chargers is DC world-wide. The input is typically AC world wide, but with voltages that differ depending on where you are.


  4. Very good explanation. Two other problems arise, though. The TYPE of voltage. While most chargers are DC, some are AC or pulsating DC, which just will NOT work place of the correct one. AC chargers are usually represented by a tilde (~), and pulsating DC chargers are indicated by a solid line over a dotted line, kind of like highway dividers where there’s no passing in one direction.

    The other problem is size of the coaxial connector, and the combinations are nearly endless. There is the I.D. or Inside Diameter, which is what size the pin will fit into, and then there is the O.D. or Outside Diameter, which is the outside ring that plugs into the device to be charged.

    Nothing more frustrating than to spend $10 – $25 on a replacement charger and find that it doesn’t fit at all. And often, none of the adapter fittings work, either.

  5. Dell Laptops have that center pin, I forget what the interface is called, but it makes it likely that other chargers won’t work. I bought a higher amp Dell charger to replace my busted one, and it works great, but I had a Dell parts expert guide me to the right choice

  6. Leo, what are the voltage and amperage ratings of a USB 2.0 port on a PC? I’m looking to purchase a USB recharger that plugs into the wall for use with a MP3 player when traveling without a PC. Do the rules you list in the Summary section apply to a USB wall recharger? (By the way, does the voltage and amperage output for each USB port decrease when you are using more than one USB ports at the same time? And are the power ratings for a USB 3.0 port different from a USB 2.0 port?) Thanks…

    I believe that USB provides 5 volts at 0.5 amps maxium per connection (that’s often whil you’ll find some devices that connec to two USB ports, because they need more than 0.5 amps but less than 1.0). Remember what the article said: the voltage remains constant, and the amperage is dependant on the device’s needs, regardless how many are connected. USB wall chargers have to provide the same voltage (like the article said, it’s fixed), but some are capable of providing higher amperage for those devices that can use it.

  7. “Amperage
    Many people are confused by amperage ratings and what they mean when it comes to power supplies and replacements.
    One easy way to look at it is this:

    Voltage is provided by (or pushed) by the power supply.
    Amperage is taken by (or pulled) by the device being powered.”

    – facepalm –
    Oh Leo, you’re a great IT guy but not so hot at getting electronics across to beginners. I could agree with your definition of Voltage – the ‘push’ on the electrons that tries to make them move and make a current, but not your definition of Current. The load / laptop / whatever does NOT pull – it lets the current through; faster if the resistance is low, slower if it’s high. Current is how fast the electrons (that carry the charge) are moving.
    But I thoroughly agree with your working rules; get the voltage exactly right, and only substitute a higher current power pack where a lower current one used to be.
    And if you use a different size plug you’ll be sorreee…

    I stand by the analogy (or is is a metaphor?). Of course it’s not technically correct, analogies rarely are. But in terms of making the concepts usefully understandable to people who don’t care about Ohm’s law I think it works.

    • I am an electronics guy and am with Leo on this one. Andrew’s comments are more about the internals of a device being run but the question was about the current rating of a charger.
      The device being uses wants to let xx amps through it and wants to take it from the charger. If the charger cannot supply enough of the current that the device wants, if may decide that it doesn’t have enough to run. That is where the pull analogy comes from.

  8. For Mr. Keir. I prefer to think of current as volumn and voltage as pressure. An example being a water pipe with a pressure/voltage of 10psi and a diameter(volumn)/current of 1 inch allows so much water through. Increase the volumn/current to 2 inches and it lets 4 times as much volumn through. aka available wattage. ( I think I got that right) Its been a long time….

  9. Leo, I agree with your analogy re power supplies. However, your statement that voltage is constant is not correct. If you load up a power supply, you will have losses in the wire that connects the supply (wall wart) to the device. Engineers like to refer to this as I^2R (I squared R) losses. The losses increase a the square of the current so a doubling in load will more than quadruple the I^2R losses in the wire. These losses cause a voltage drop in the connecting wire so that the voltage seen at the load drops when the current increases.

    As you said, if you get a supply rated at the same voltage as the one being replaced and with a current rating at least equal to your device’s requirements you will be fine with respect to I^2R because these losses will already be accounted for in the design of the power supply. I just couldn’t resist picking a nit. 🙂


    Yep. And for the audience and use for which this article is targeted that nit is just unnecessary distraction. 🙂 (My degree is actually Electrical Engineering, so I do have a clue about how complex this can get. However my audience isn’t nor should they need to be. Smile)

  10. This is a great and *necessary* question-and-answer. At the risk of seeming politically incorrect, it may be more helpful to female computer users than male. In 2007, my terrific but three-year-old Lenovo laptop was fried after a now defunct, major electronics dealer opened a Kensington “choose-your-AC-tip” package, stuck it into the power supply, and “told me” it was right. The laptop fried within a week, and I resignedly concluded that its age was the problem. Several months later, packing the otherwise new Kensington adapter set to sell, I read the Instructions that came with it. I also noticed that the little baggie that held the color tip I *should* have used was unopened. In short, I settled with the retailer’s insurance carrier on the eve of its bankruptcy. Otherwise, I would have been out not only an excellent machine, but the amount I paid for the tips. I’m making this comment to warn husbands with non-electronic-savvy wives not to allow any “expert” to tamper with equipment on the basis of the (stereotypical) assumption that because an “expert” is male, he knows all about electricity and how it works. (I hope I don’t offend anyone, but I have seen other cases where female computer users just assume that men understand all about electricity.)

  11. Very good article and comments. No mention was made about Lithium Ion batteries and their associated chargers. The little bit of reading I did on the topic scared me away from exploring substitute chargers for Lithium Ion batteries. Was I being too cautious?

    • You have some right to be scared away from replacing a charger that is directly connected to a lithium ion battery other than the correct one but that is usually almost always impossible. Power tool batteries tend to be directly connected to a charger but they are made to only fit the custom charger for it.

      On a computer, the thing that plugs into the wall is not actually the charger for the battery. It is just the power supply to power the charger. The actual charger is a group of circuitry inside the computer.

  12. I’m not sure your answer about current rating is truly “exact”. When you refer to replacing a charger with equal voltage with equal or greater current rating you are “sort of correct’ -BUT — the issue of current is a bit fuzzy. IF you want to run the device off the charger it MUST have a current rating equal #or greater# – however if you want to CHARGE a battery a lower current is permissable! The HIGHER the current rating of the CHARGER the faster the battery will charge.

    • CORRECT!
      I do some support work at our company and frequently have laptops (we use Dell) at my desk for installing software. When a Dell charger was going to be discarded, I grabbed it so that I wouldn’t need to bug people to also bring their charger.
      One day, I happened to be working on a large laptop (it comes with a much higher current charger) and plugged it in to the one on my desk. I was pleasantly surprised to get a warning on the screen warning me that the power supply had a lower current rating than the proper one and that the computer may not charge well while running.
      It ran well but only minimally charged until I turned it off.

  13. Chargers come in many qualities. A 19V charger with lower quality may have 21-22V when no current is drawn. However, a charger intended for brand A with 1.6 Amp will have about 19V at full charge and operation simultaneously. With the battery charged, it will have about 19.5-20.5V output fed to a laptop and the battery will continue charging at a negligible trickle rate. When a more powerful charger with 2.5 Amp rating is used, intended for laptop B, with higher power consumption, its output with the laptop A maybe as high as 20-21V with full current drawn and higher after charging finishes. This will cause a higher charge to a battery, even after it is completely full and shorten its life and may even cause an explosion. The chargers are PWM regulated, and ideally such problems would be avoided, but to keep costs down, regulation is not 100% and compromises against costs are made. Exceptionally good chargers are not common and these cost very high. At home, I use a variable Voltage and current supply to monitor and adjust charging curve against time to match aging characteristics of the battery. Travelling, I use chargers with a display and Voltage adjustment slider to prevent overcharging at high levels for my two laptops.

  14. Your explanation is correct. However would still like to know whether an original charger supplied with a new laptop does charging such that the charging current decreases as the battery attains its full voltage. I have a sony fz series. The ac adapter has an output voltage of 19.5 volts, 3.9 amps. The battery is li ion 11.1 volts, 4800 mAh. I have a regulated series power supply 0 to 30 volts adjustable to 19.5 volts and can supply 0 to 5 amps. Can I use this safely after setting the correct voltage.

    • YES.
      What is generally referred to as a charger is not really the charger. It is a power supply to the computer that powers the charger built into the computer.
      Lithium ion batteries are extremely touchy about how they get charged or discharged with errors leading to fires. That is why you don’t see them for general use like the old NiCad rechargeables or the newer Nickle Metal Hydride. The charger has to know the exact limits of the Li ion battery to charge it well and stay in the safe range. In like manner, the item pulling power from the battery has to have circuits to be sure it stays in the safe range so it does not start a fire.

  15. Thank you! This article provided me with exactly the info I needed (with a bunch of device-specific USB chargers at 5V, choose the one with the highest amperage to charge them universally), from a trustworthy source, in exactly the amount of technical detail needed for someone with only vague memories of highschool physics.

    I’m a bit miffed at google for not ranking this higher in the search results.

  16. Hi there!

    I have an HP dv6 laptop that I’ve had for a little more than 2 years. The original power adapter started giving me a problem in that it wouldn’t always supply power to the laptop (the light next to the port wouldn’t always come on, when I plugged it in). I would try it unplugging and plugging it back it in a couple of times and sometimes it worked, others it didn’t.

    I found a replacement HP adapter online for $30 and bought it but it’s not exactly the same as the original one.

    Original (65 Watts)
    Input: 100-240V ~ 1.7A(1,7A) 50-60Hz
    Output: 18.5V(18,5V) — 3.5A(3,5A)

    Replacement (90 Watts)
    Input: 100-240V ~ 1.5A(1,5A) 50-60Hz
    Output: 19V(19V) — 4.74A(4,74A)

    I read this article and it mentioned that the voltage should be as close as possible. Since the voltage differs by half a volt, am I okay to use it or should I look for one that is exactly the same? Also, would the higher wattage harm my laptop or battery in any way?

    Thank you very much.

  17. @Kay
    Using a slightly higher voltage might have a negative effect on the life of your battery. As Leo says in the article “The device may work with voltages that are close, but often at the cost of shortening the lifespan of the batteries being recharged.” It’s a controversial subject and there are opinions on both sides, but I tend to the better safe than sorry approach.

  18. My tomtom worked fine until I used wrong in car charger.Now it won’t start even after mains charge and resets.The charger is input DC=12v. Output DC=10.5v fuse 5A PositiveCentre pin. Tomtom label 5v DC 2A positive pin.Have I “cooked” the battery or worse?

    I don’t know about the battery, but putting 10.5 volts into a device that expects 5 volts is a Bad Thing and could have damaged the electronics inside.

  19. I am looking for an external battery pack for my laptop. I have seen they all say 19 volts but my laptop charger says 19.5volts=2A. Can i use the battery pack?


    Best I can say is “maybe”. It’ll probably work, but it may shorten the life of your computer’s battery by being off by half a volt.

  20. Hi Leo … I need help I have laptop
    19 V …2.15 A…is required power supply
    now my new adapter is 19 V …1.58 A

    it is ok to use that adapter to my laptop?..

      • And also his new adapter could potentially overheat or even burn out the power supply, if I understood correctly from the article?

  21. Hi Leo,

    Can you please help me with this question. I am about to buy a jumper battery from called jumperpack. It soppoused to have a usb port with 2.1 amps. My question is can I charge my laptop that takes 19.5 volts at 4.6 amps ? providing that I have the right connection or adapter to go from a usb to my laptop charge connector. I am a truck and bus technician and use my laptop in order to do diagnostics so sometimes I am in a road test and all of a sudden it is a longer road test and my battery runs low and sometimes the bus or truck does not a 12 v power supply for my inverter TRIPP 400 watts. so It would be great that I can provide power to my laptop just to finish my job may be 30 minutes to an hour sometimes. would the 5 volts provide enough power to my laptop ?

    Thanks a lot

      • You stated that USB provides 5Vout. You also stated that the power supply output voltage must equal the voltage of the device that you’ll be charging (or at least that’s how I interpreted what your article stated). So, does that mean that the batteries in our USB powered device has a voltage of 5V (i.e. USB voltage input to device = 5V and device battery that needs to be charged =5V)?

  22. can i ask question leo i if the voltage is not same and the current is higher what is the effect?

  23. Leo, thank you, your article presents the required information in a way that is easy for those of us that haven’t had the benefit of technical training to comprehend and apply to our particular situation. I think many of us go through the joy of either upgrading or replacing our PC’s on a regular basis and there is just a lack of consistency in the power adapters on the PC’s on the market so we generally have to face acquiring a new back up adaptor to support travel. A great concise article thanks again.

  24. So my power hungry smartphone’s charger has an output of 5V @ 1.2 amps, I got a power bank for it that has a matching voltage, but the output is 1 amp, or 2.1 amps. Charging from the 1 amp seems to do fine just takes slightly longer to charge. The 2.1 amp just kills the power bank faster with the same charge time as the wall charger that came with the phone.

  25. pls I need help my Xbox 360 AC adaptor burned out by high voltage my question is that if it has affected my Xbox too
    pls reply as soon as possible

  26. hi,
    i have a shaver power adapter from the US that i took to Europe, and plugged it right in….a few mns later…Pfffff (smoke) from the transformer.
    im now back in the US, and the transformer is gone. i.e. when i test is. no juice in the output adapter.
    the original adapter says 4.85v 800mA. i cannot find ANY adapters with the same voltage.
    the nearest i found is 5v 0.8A.
    Will this 0.15v difference fry my shaver or will it work?

  27. read all the article , one doubt.
    As mentioned earlier “Amperage is taken by (or pulled) by the device being powered”
    lot of cases we experience when the ampere in the power supply is more the device regulator or related component get faulty or burned out .
    one example ‘ go for a simple device mention power rating 12 v 1 amp . if we give a supply of 12 v 3 amp device get faulty “

  28. Hi. This is a very helpful article, but I have this scenario:

    My power bank’s rated power input is 5V , 1A. But when I am using a 5V 1A charger, the charger heats up fast. (And smells foul when I am very near it) When I tried using a 0.7 A charger, the heat is moderate, and on a 0.5A charger, the temperature is normal. What should I use then?

    P.S. All chargers mentioned are in good condition. The USB cables used are the same for every chargers tested.

    • You really need to look at the device requirements (in this case your power bank – I guess). It is always possible that you have a “lemon” if your charger heats up fast.

      I am assuming that the “power bank” is the device you’re attempting to charge. I could be wrong.

      It is my understanding that the volts you are trying to input should be the same or less than the device you are charging. While the amps should be the same or they can be slightly higher than the device you are charging.

      I would just state the obvious, use the charger that has a normal temperature as long as it is not damaging the device you are charging. The fact that you’ve charged a device with .5A tells me that the device you’re trying to charge will not blowup and the requirement of that device requires at least .5A. But again, without knowing what your charging exactly it can vary with what device you are actually charging. I would recommend you either look for the fine print or google your device’s input power requirements.

      I hope this helps. Does anyone else have anything to add?

  29. I have an interesting question.

    I have a Nintendo 3ds that requires 4.6 Volts and 900 mA (you might as well say 1 amp). Older Nintendo DS’s required 5 Volts so I was ok cutting the charger cable and making my own USB charger out of it so I can either charge it in the wall or with a portable charger.

    I had a vision about just buying an official Nintendo car adapter charger and then making a new cable that was USB to a cigarette lighter socket as a way to try to still use a portable charger.

    Of course I was excited to do it. My thought was that if the Nintendo car adapter charger steps 12 volts down to 4.6 Volts at 900 mA, then this new cable should step 5 volts down to 4.6 at 900 mA. But it did not work.

    I got to doing a little more research regarding USB ports and cables have different amperage capabilities. For example USB 3.0 does 900mA, while USB 2.0 does something like 500mA.

    Unfortunately the gauge of the USB 2.0 cable is really a high number (meaning that the wires are few and small). I’m thinking I should redo my cable and use a USB 3.0 cable because I think it may be able to handle the Voltage.

    When I took my multimeter and took a reading on the output of the car adapter from a 5V charger, it was reading 4.14V or 3.8V, and the Nintendo 3DS charger light would blink.

    Am I getting this concept wrong? Or is a special cable an impossible vision because the car adapter will only work if it is getting 12V and not 5V?

    I have a USB 3.0 cable, but if it is an exercise in futility then I’m just wasting money on a fantasy.

    If I knew what kind of resistor I can buy to solder in with a wire that would be about my only option.

    Thanks in advance,


  30. Here is something related that I discovered. I have a cordless phone that needed a new set of batteries. I bought batteries with a higher amperage than the originals. They only lasted a few months, and it dawned on me that I made a mistake. Putting in batteries that are of a higher amperage than recommended can shorten battery life because the charger doesn’t supply enough amps to fully charge it.

  31. Old article, however the specs between the old and new charger don’t add up, the new charger if indeed it is 60 Watt would have a maximum amperage of 3 amps not 4.7 amps, whilst this does not necessarily render it unsuitable (Dell often has both 60 W and 90 W chargers available for some models of the same laptop) It may be unsuitable as is the case with other Dell laptops that require a 90 Watt charger. Not certain with Sony. Another issue for some laptops is that although the specs maybe exactly the same Voltage / Amperage it still may not charge the laptop due to specialised circuitry

  32. Excellent article! Any suggestion on how I would determine the polarity that’s required on a device? I have an iClever ic-T01 “laptop” which is no longer made, and I have an appropriate charger that has reversible tips. But there’s no indication on the device what the polarity should be. I contacted iClever, and they don’t even know since they no longer make it. I have a multimeter, but don’t know how I would go about testing it. Thanks!
    P.S. Am I right that guessing the wrong way will be bad, not just ineffective?

    • The wrong way can be bad. You don’t happen to have an old charger, do you? That would be one way. I guess I shouldn’t be surprised that there’s no polarity indication. If you opened it up perhaps you can determine from the internal connections, but not sure you want to go that far. A little research shows that it’s 5 volts? I can’t take responsibility for the results, but … I’d just try it. In my experience 5v rarely does damage if reversed. Again, in my experience, it’s more common that the outer ring be negative, and the center pin be positive, so I’d start with that. But … no guarantees I’m afraid.

      • Thanks much! Yes, on the back it did list the volts/amps: DC 5v 2.0A max. Just not the polarity. I fear it’s likely “dead” anyway, as I read reports from others that leaving it uncharged for a long period resulted in the battery being unable to charge. So, I’ll give it a shot.

  33. Thank you so much for a clear and very helpful article! So if I read correctly, input amperage does not matter as long as output match, right? I found a replacement charger for my laptop that has exaclty the same stats (polarity included), but input amperage goes from 2.5 to 1.5. Am I good to go?
    Thank you for your time.

    • Three things matter: polarity, output voltage (must be the same as the original), output amperage (must be the same or higher than the original). Input voltage should, of course, match and as long as your electrical outlets have enough amperage to power the transformer (that would almost never be a problem), then it’s OK.

  34. There must be a trade-off with using a charger that has a higher amperage rating than the intended device… With my rudimentary understanding of electricity I can only assume the resistor components of the device would produce more heat. Is this correct? If so, the question than becomes how long can a device handle the increased load before overheating and frying resistors and other internal components? How much more can the amperage supplied be from the manufacturer specifications before problems arise?? I’m most interested in how this applies to small handheld electronics like cellphones and charging banks that typically require 5V but amps ranging from 0.5 to 2. Any insights? Thanks!

    • A higher amperage doesn’t produce more heat or supply more current to the machine. It simply has the capability of supplying more current if called upon to do so.

    • Actually a charger with MORE amperage capacity than is needed often tends to run cooler … to oversimplify, it doesn’t have to work as hard as it was designed to.

  35. This is a reverse of that question. I bought a higher amperage battery than the original for my wireless landline phone. It died after a short time and I realized that if you have a battery which requires more amps than the charger can supply, it will only charge up to the number of amps which the charger puts out and wear out the battery quicker. I suppose using a higher amperage charger would work but the phone uses a charging station, not a plug-in charger so now I buy batteries with the original amperage and they last longer.

    • Batteries don’t “require” more amperage, they just charge more slowly (or sometimes not at all) if the power supply can’t provide the ideal amperage. I’m sure that the battery wearing out is unrelated to the under-powered charger.

  36. Great article well written well explained spot on as for the nit pickers my basis is in the telecomunication side of electronics where things can get realy weird if they want to nit pick on that subjet transistor theory will give you a headache to remember lol. But for the target audience and people like me who needed a little memory jog this article is ideal and your analogies are far better than mine the water and hosepipe. well done m8 kudos to you and thank you.

  37. HI leo sir,
    I have a cctv power supply 12Volt 10a for 8 camera in the output 12Volt an 1a per ports,
    when i using its power supply more then 90mtrs. wire it give 12volt but amp. is give down,
    So please suggest me what should i do for resolve or add any small circuit end wire

    • Using heavier gauge cable might work, as thicker wires reduce resistance, or use a longer AC power extension cord.

  38. Thanks for that. I was told by a couple of people that the same ampage was important but seems not the case as long as it is not less. I just can’t undersatand why the machine worked in the shop and when I got it home a couple of hours later it did’t work!!

  39. I have a 12V 700ma specified item I was using a 12V 1000ma power supply for (240V), but it would get incredibly hot to touch. I feared it would melt when on for a long period on hot days. How can this be? Would getting a higher ma rating, far beyond the specified rating be a ‘cooler’ option?
    Thanks for dumbing this down!!

    • All I can say is maybe. Honestly I think just using a different power supply would change things. Some just tend to run hot. If it’s too hot to touch, however, then stop using it.

  40. I’m closing comments on this article since so many people are simply asking questions that are clearly answered by the article.

    Read the article. It’ll tell you what you need to know.

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