How much higher voltage is desirable while charging a battery? What limits the upper voltage level of the source?
The voltage of the charger has to be high enough to push a useful level of current through the battery's internal resistance. In practice that means a few volts higher than the battery normal output voltage. Thus for a 12V car battery the charger must put at least 14 volts or thereabouts across the battery. If it put too much more in, the excess energy not going into the chemical storage would end up as heat.If you put an 800 volt source across a 12V battery, and assuming the 800 v source had moderate current output capability, the source would pump enough energy into the battery to seriously overheat it and the battery fluid would boil from heating due to resistance heating. There is no such thing as a 'flash' charging capability for a lead acid car battery. 'Fast' charge generally heats up a battery and does bad things reducing its life.So a charger must be matched somewhat to the battery voltage, a little over but not too much over. This generally applies to all types of batteries, NiCd, NiMH, Lithium, lead acid. Lithium cells will greedily absorb lots of charge but also get hot, and that can lead to bad things. So Li chargers have special designs to guide charging but not let it run away.Added: you can use a 100V source to charge a lower voltage battery. You do it by what's called 'trickle' charging. This is charging through a higher value resistor that limits the current to a tiny amount. It takes quite a while to get any useful charge into the battery this way. if you dissipated for instance 89 volts at 1 amp in the series limiting resistor, to put 11 volts across the battery, that resistor would have to handle 89 watts of heat. So this is not a very practical way to charge any battery. But it is possible to do it.Added: I've recently discovered that overcharging sealed lead-acid batteries produces bad results. What it does is liberate hydrogen and the electrolyte then decreases until the plates can go dry.
Car Battery Too high voltage?
Um, while driving my car, i was watchin the voltage gauge and it goes crazy between 13 and 16 volts and after a while my speedometer hud turns off.. Then bak on after about 2 seconds.. When im standing still and not moving, the voltage reads over 14 volts at about 15 until i start moving and then it goes up and down until the car speedomter hud resets again and it does repeatedly.. What is the problem? I have a 2001 Ford Focus Zx3.. I knw the car battery is suppost to be steady at about 13.5 or so.. but this is going to 16 and beyond at some points and the car keeps reseting when it gets that high.. And, my battery light is on.. Could it be a bad alternator?
My car battery voltage shows 14.4v after starting, but after either idling or driving normally for about 20 seconds it drops to 12.5v. Do I have a bad alternator?
Alternators, or generators as some nitwits decided to call them for new and improved computer controlled vehicles, but that's another story, anyways charging voltages are directly related to temperature. Starting with a cold engine and surrounding areas, the voltage is higher, as it warms up the voltage goes lower to protect the battery. Start with a hot engine and you'll see a lower voltage. I prefer ammeter due to it actually shows what the charging system is doing at any given moment.
Can I use a slightly different Voltage/Amperage rating for my laptop's AC adapter?
The following three conditions should be met before you buy a new ac adapter 1) Output Voltage is within +/- 5% of your old charger's output. For example, if your old charger provides 19V, then you can use a charger that provides 18.5V or 19.95V. 2) Output Current is the same or higher than that of your old charger. For example, if your original adapter provides 4.74 Amps, then you can use a charger that provides 4.74 Amps or higher. 3) Connector tip must fit securely into your laptop. So the 18.5V@4.9A is OK with your laptop,and you can get it on www.chargerbuy.com
What happens if you use the wrong wattage charger to charge your laptop?
Thanks for the A2A.If the pinout and the voltage are not correct then hopefully it just won’t fit and no harm done, if the pinout is reversed or the voltage is way too high then you could let the magic smoke out of some of the components and the laptop could get damaged and not work any longer.If you are using a significantly higher wattage but other wise correct charger, the laptop may charge while running a bit faster, but in all likely hood you would not see any real change, other than the charger running a bit cooler than the original.If the new charger is a significantly lower wattage unit, then the laptop may take longer or may not charge or even discharge the battery when the laptop is on. The battery should still charge albeit slower than normal when the laptop is off. It will likely run pretty warm/hot when the laptop is on, since it could be running flat out in this condition.Those are the extremes, if the wattage is not that different, then you may not see any real difference, in many cases a 10 or even 20 watt difference doesn’t translate to a major change in available current, most laptops seem to use around 19 volts DC for power, and that would mean a half amp difference at 10 watts and a full amp difference at 20 watts.Personally I tend to buy a little larger charger when/if the original fails, especially if I notice that it tends to run really warm/hot. I had a string of 12v 5 amp adapters that ran pretty hot fail on some old-school linksys NAS devices, I replaced them with 12v 6 or 7 amp units, and I immediately noticed that they units ran much cooler than the originals, which I am hoping will result in these units lasting longer than the originals which did run for many years before finally giving up the ghost (all the units suffered filter capacitor failures), I guess I could have repaired them, but then they would have looked pretty ugly after they would have been put back together after using a saw to cut the cases open…To recap, if the wattage is pretty close or higher, then it should be no real issue, if the replacement is significantly smaller, then it could still work (if it provides enough power for the laptop and battery), it will likely run hotter than the original, and as a result of the extra heat from overwork, it may have a shorter life.I hope that you found this info to be helpful.