# Q & A: Which Battery is Better: C or D?

Q:
If you look at a C battery and a D battery they are both listed as 1.5 volts. What is the difference between them (besides size)? Also, when you put two batteries together (say to run a flashlight) what is the combined voltage?
- Cameron
fairfax, va
A:
You're right, C and D batteries both are 1.5 volts. Actually, AA and AAA are also 1.5 volts. That makes you wonder what the difference is. If they're the same voltage, why not just use all AAA batteries and make things lighter and smaller. But there is a big difference between them all.

In an electrical circuit or device, there are 2 really important things. One of them is voltage. The other is current. The classical way you hear them talked about is by comparing them to a pipe with water in it. The voltage is like the water pressure which pushes things down the pipe. And current is like the amount of water flowing down the pipe. Some electronics need lots more current but don't need more voltage.

That's where the batteries come in. The D cell batteries can give more current than the C batteries. If you needs lots of current and try to get it from a tiny battery, it won't work as well.

As for adding them together, you'll notice that in most electronics, you put them in so that the positive end of one touched the negative of the other. That adds the voltages of the batteries. This is called adding them "in series". So if you have 2 D batteries in series, you have 3 volts.

(published on 10/22/2007)

## Follow-Up #1: Batteries in series vs. parallel

Q:
What if a device takes multiple batteries, but not in the congifuration where the negative side of the battery touches the positive side? Do you still calculate the voltage by adding up the voltages, or are they seperate entities?
- John (age 17)
Staten Island, NY, USA
A:
If the batteries are in series the total voltage is the sum.   If two equal batteries are connected in parallel the voltage will be the same as a single one.   You have to be very careful though.  If you connect a 5 Volt battery in parallel with a 1.5 Volt battery, they will get into an argument about which voltage to be at.  The likely outcome is undetermined.  Do not try this at home!

LeeH

(published on 05/11/2008)

## Follow-Up #2: battery for low-current circuit

Q:
If a low current circuit calls for say 12 volts, will there be a problem if I hook the circuit up to a big honking car battery? Will it damage components or will the circuit only trickle through the current it needs even if a lot more is available?
- John (age 50)
Seattle,WA
A:

Most circuits are just fine with a big battery at the right voltage. The resistance of the circuit automatically limits the current when the right voltage is applied.

Occasionally there's a slightly different situation. Some of those cheap plug-in DC supplies that come with electronic devices are designed to put out the right voltage only when hooked to a device that drains the right current. If the drain is too low, the voltage drifts up some. Batteries aren't like that, however. Their maximum voltage is just a little above the rated voltage, well within the tolerable range for the circuit.

Mike W.

posted without vetting until Lee returns from the Serengeti

(published on 10/28/2014)