Yes, if you put them in series.
Connect three 12 volt batteries in series and you will have 36 volts but will only have the amperage of one of the batteries.
That is Impossible. You can however make two 6 volt batteries into a 12 volt system by wiring the two 6 volts batteries in Series. You will then have an output voltage of 12 volts but the amperes will only be what one of the batteries have, In other words the volts will double but the amps will stay the same as if you only had 1 battery connected.
Connect three 12 volt batteries in series. You will triple the amperage but the volts will remain at 12. Click the link
You only need 2 12 volt batteries to get 24 volts. Join the negative post on one battery to the positive post on the other battery with a cable then connect the remaining positive and negative posts to the vehicle that has a 24 volt system.
Add two 1 volt batteries in series with it.
Two 24 volt batteries in parallel will give you 24 volts. The only other way is two 12 volt batteries in series.
Paralleling four sets of 6 volt batteries will still give you 6 volts. Two 6 volt batteries in series will give you 12 volts. Parallel these series sets will give you longer endurance at 12 volts. There is no way you will ever get 48 volts out of four 6 volt batteries.
You can only do that with a transformer. Or you can wire three 9 volt batteries in series to get 27 volts.
You do not need three 12 volt batteries to get 24 volts, all you need is two batteries. So I assume by using three batteries you want to increase the amperage. Wire two of the batteries in series and then wire the third battery to the second battery in parallel and you will have 24 bolts. Or you can just wire two 12 V batteries in series to get 24 V.
Yes, if you connect the two batteries in series. You will then have 16 volts, but the current will stay the same as if you only had one battery connected.
Don't know what your intentions are but the 6 - 6 volt batteries would probably deliver more amps. ======================================= -- If the batteries are connected in series, six 6's are exactly equivalent to three 12's. -- If they're operated in parallel, then the terminal voltage of six 6-volt batteries is still just 6 volts. There's no way to connect 12-volt batteries and make them look like 6-volt units in parallel. It's really important to find out exactly how the original 6-volt batteries are connected in the device. 1). They may be all in parallel, giving an output of 6 volts. 2). They may be all in series, giving an output of 36 volts. 3). They may be connected in three parallel branches of two series units each, for an output of 12 volts. 4). They may be connected in two parallel branches of three series units each, for an output of 18 volts. If you know what you're doing, you can replace them with 12-volt units in cases 2). and 3)., but not in cases 1). or 4).