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.
Without knowing the maximum output current it was designed to produce it isn't possible to say exactly how much voltage a charger produces. Also, was it intended to give a slow or a fast charge? In general all that can be said is that the output voltage of a battery charger must always be slightly higher than the nominal voltage of the battery it was designed to charge. This is for the simple reason that it won't be able to put any charge into the battery unless the charger's "on-load" voltage is higher than the battery's voltage. For the same reason, a charger which can deliver a high output current (amps) will need a higher "on-load" output voltage than a charger which can only deliver a low current. Also, when it is switched on but is not connected to a battery, the output voltage of any charger will always be higher than when it is doing its job of charging a battery. That voltage is called the "no-load" voltage. Assuming the battery being charged is a standard low-voltage type, of less than, say, 24 volts DC, it is quite safe, using a standard electrician's voltmeter, to measure the load and no-load voltages of the charger as described above.
Milwaukee manufactured many battery operated types of equipment. Without knowing what type of equipment you refer to, an answer can not be given. Try looking on the nameplate of the charger. It should state an output voltage in DC volts.
Provided the charging system on the mower engine is operational, a small amount of charging voltage will be supplied to the battery during use.
You cannot charge a battery without a battery charger or having it charged by the alternator in your vehicle while it is running.
There is no safe way to charge ANY battery without a charger rated for that particular battery. You could easily destroy the battery if you try.
TAKE CARE with a trickle charger as a battery of that type and size will most often be over loaded by a constant charge rate of 2AMPS which is most trickle types. A "Float Mode" charger such as the Schumacher Battery Companion has a max charge rate of 1.5Amps and a peak charge voltage of about 16vdc which prevents heat build up and the high voltage is good for the battery internals without cooking your battery. You can charge the battery from a dead state with one of these and if you forget about it the charger cycles off when the voltage peaks so you don't boil your battery. The relationship between charge amps vs volts and the health of your battery internals is huge which I have not gone into here.
There is no safe way to charge a phone without a charger made specifically for that phone/battery
Hook it to a battery charger.
No
U cant
Most often, yes. But... it would have to be in contact with the battery charger. There is no way I know of to charge a camera battery without it being in contact with either the camera or the charger.
My lifan CT110cc can run without a battery. It has an internal charger built in.