Do you mean 2 x 12 volt batteries? If so:
Wire 1st battery's + to load, wire it's - to the + of the 2nd battery.
Wire 2nd battery's - to the other side of the load.
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There are two basic ways to wire multiple batteries together, in "Parallel" or in "Series".
PARALLEL
Wiring two batteries which have the same output voltage in "Parallel", the output voltage of the combination stays the same but the amp/hour capacity of the combination is equal to the sum of their individual amp/hour capacities.
Wiring: Battery 1 Positive to Battery 2 Positive and Battery 1 Negative to Battery 2 Negative is Parallel wiring, retaining the voltage rating of either one of the batteries.
WARNING
It is not a good idea to wire two batteries which have different voltage ratings in parallel because the one with the higher voltage will immediately send current to the other one with the lower voltage to try to make their voltages both the same. The very high current which will flow between the two batteries is likely to make the batteries get very hot. IF THEY ARE CAR BATTERIES THEY COULD EXPLODE!
SERIES
Wiring two batteries which have the same output voltage in "Series" makes their combined output voltage equal to the sum of their individual voltages but the amp/hour capacity of the combination will be no greater than the amp/hour capacity of the smallest battery of the two.
Wiring: Bat 1 Positive to Load, and Bat 1 Negative to Bat 2 Positive, then Bat 2 Negative to the other side of the Load is Series wiring and the total voltage of the combined batteries is the sum of both individual voltage ratings.
So, assuming you want to get 24 volts out of two similar batteries, you could wire two 12 volt batteries in series.
NEVER OPERATE A 12 VOLT ELECTRICAL SYSTEM as in CARS or most BOATS with 24 VOLTS. YOU WILL BURN UP YOUR COMPONENTS AND SOME WIRING.
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Common Flashlights are simple examples of series wiring. Flashlight batteries are usually 1.5 volts whether they are AAA, AA, C or D size. So flashlights with with 1 battery are operating at 1.5 volts, 2 batteries are 3 volts, 3 batteries are 4.5 volts, etc.
That depends on what voltage your batteries are,
wire it in series
Depends on if you want a series or parallel circuit. In a series circuit if you wire six 12 volt batteries together you will end up with 72 volts. Wire the same six 12 volt batteries together in parallel and you will still have 12 volts. In a parallel circuit you just wire all positive posts together and all negative posts together. In a series circuit you would wire positive to negative to increase the voltage with each battery added.
Yes, series the two batteries to produce 12 volts. Tap off of the two end terminals for the 12 volts. Tap off of the series jumper for the 6 volts of one of the batteries. The two 6 volt batteries can not be paralleled in this connection as they will short out.
Wire minus - to positive +. Know that this will increase the voltage but the amps will stay the same. Wire two 12 volt batteries together in series and you have 24 volts. Click the link.
To maintain the 12 volts using four batteries they have to be wired in parallel connections. This means that all of the positive posts are connected together and all of the negative posts are connected together. The total sum of all of the batteries will equal 12 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.
The batteries need to be wired in a series configuration. Wire the negative of the first battery to the positive of the second battery, and the negative of the second to the positive to the third. If the batteries were placed in a straight line they will look like train cars, with all positive ends of the batteries pointing in the same direction. The batteries voltages are now added together for three 12 volt batteries making 36 volts.
Connect three 12 volt batteries in series. You will triple the amperage but the volts will remain at 12. Click the link
You would connect two 12-v batteries in series to get 24 Volts, but if you have four, you can connect two sets of batteries in parallel and then connect the two sets of parallel batteries in series, giving you 24 volts with twice the ampere-hour capacity (four batteries rather than two).
I believe that AA batteries are rated at 1.5 volts each, so if you were to take 6 of them and wire them together in series that would produce a circuit that's pushing 9 volts. But recharge AA batteries are only 1.2 volts per unit so a little lower voltage will be the result. I think most devices will still work on the lower voltage. Also these batteries will never last as long as the regular dry cell.
Two in series, two in parallel The link below has a couple of diagrams.