What would happen if you, say, used D batteries instead of AA batteries in something? Would the device only pull out the current necessary to run the device, or would the batteries provide more?
And, for a bonus, what if, instead of D batteries, you had an AC adapter that was rated for a higher amperage than the AA batteries?
The device would only pull out the current necessary.
Batteries - no problem.
Higher current AC adapter - could destroy your device.
Why?
Cheap AC adapters (just a simple transformer / rectifier + capacitor filter) are rated such that their voltage is specified at at their rated current. In other words, a 12v / 5A adapter will be supplying 12v at 5A, but may be putting out much more voltage at a lower current. This is especially noticeable with cheeseball Radio Shack adapters. I actually smoked a device years ago this way. Newer adapters are usually “switching” regulators, and don’t have this problem. So, measure the unloaded voltage before you try using a substitute adapter.
A larger size of the same voltage means it will just last longer.
It does not matter how large the battery or how many cells as long as the output voltage is the same. The device will only use the needed current. The batteries will last longer if they are bigger as they have more total capacity. I frequently solder cells together to give me longer life in test devices and formerly digital cameras that were so hard on batteries.
You cannot destroy a device with an AC adapter if the voltage is correct-NO MATTER HOW MANY AMPS the adapter supplies. The key is in your statement about cheap AC adapters. They may not supply pure DC at the proper stated voltage. I had one from China for example that I tried to use on a laptop. It seemed OK until I went to use the modem. There was too much interference from the power supply to secure a connection. I decided it was bad to use on the laptop in general and found an OEM product that works fine.
Gee, I think I said that.
The Voltage rating on these cheap adapter IS correct - but only at the specified amperage draw. In other words, they are poorly regulated.
As for batteries that are “too strong,” a device using a switching regulator or voltage pump *might *be adversely affected, depending on the design. Most current designs use a FET to pulse current through a transformer, and one of the factors affecting the peak and RMS current through the FET might be the internal resistance of the battery. All else being equal, a larger battery will have lower internal resistance, which might translate into higher peak and RMS current through the FET, thereby decreasing the life of this component.
Of course, whether or not the peak and RMS current through the FET is affected by the internal resistance of the battery is completely dependent on the design.
Gee, Al Bundy, I think beowulf said that, too. Correctly so, too. I didn’t think of that in my first answer but should have, and regret the oversight.
We might say “You cannot destroy a device with an AC adapter if the voltage is correct - NO MATTER WHAT THE PHASE OF THE MOON.” These things are true as far as they go. As beowulf explained, you can destroy a device with an AC adapter if the voltage is NOT correct.
This is slightly off topic, but I have had batteries that did produce too much voltage and most of the electronics I tried them in wouldn’t work.
There are rechargeables made from nickel and zinc. When fully charged they put out a little over 1.6v. Fresh alkalines come close to that so you wouldn’t think it was a problem. But when I put them in a wireless mouse or keyboard, they wouldn’t work. I think I also tried them in a couple other devices like a wireless thermometer. The only thing they do seem to work in that is electronic is a trail camera i use to photograph the wild life.
edit - I’m sure they’d be fine for digital cameras or other devices that are designed to be a bit more tolerant of input voltages. I think they’re great batteries so I don’t want to bad mouth them.
Interesting. Would a voltage meter thus be able to detect these bad adapters?
Also, I’ll point out that the device in question has a broken adapter port, and that adapter was actually a higher voltage than the sum total of the batteries. This implies that it has a bit of a voltage tolerance, no?
Also, I used a lower voltage adapter with one of my keyboards when the adapter port broke. Various keys have stopped working over time. Then again, it has been (accidentally) dropped a few times, so it could be that instead.