Do battery voltages stack?

Question

My friend and I were messing around for a little, when he pulled up an article for me on a guy that made a home-made coil gun. Now, this was a table-mounted, low-velocity little toy, and we got the idea to try and make a craft project where we would create a man-portable version of the gun, preferably in the model of a rifle.

We don't have any previous engineering experience given that we're both under sixteen, but we're doing a lot of research on the subject. One simple question that I can't seem to find an answer to is whether or not stacking multiple batteries will increase the overall voltage output of the entire stack. We're looking at this guide here for the time being;

http://www.jeffhove.com/robots/coilgunhowto.html

Given that he's using a AA battery that's 1.5 volts, we've surmised that if we instead used a PP3 battery that ran at 9 volts, we could decrease the recharge rate from 20 seconds to about 6. We figured that if we used two PP3's, and got an increased voltage of 18v's, that perhaps we could lower the recharge rate to 3 seconds. But at the moment, we simply don't know if this is actually possible. Since all PP3's are are six cell batteries stacked into one, we do believe it's possible, but we're not sure how.

I'll be posting more questions about the weapon as time goes on, but for now I'm starting simple.

Answer 1

Yeah but a 9volt (PP3) battery would never last, as it would run out far too quickly. There's a reason the military don't use rail guns (which is what you described) which is because the energy demands are way too high.

Answer 2

OK, simple basic rule:

Series and Parallel connections.

Series connections are the ones in which electricity has only one path, IE, + to - to + to -, etc.  These "stack", or add together.  Two 1.5 volt batteries in series have a potential of 3 volts.

Parallel connections are the ones in which all of the + to one side and all of the - to the other side.  These connections do NOT stack voltage.  Two 1.5 volt batteries in parallel have a potential of 1.5 volts.

Amperes are the opposite.  Two 1 ampere batteries in series have an output capacity of 1 ampere, while two 1 ampere batteries in parallel have an output capacity of 2 amperes.

There's some more to know, but that's the basic rule.  Remember to be careful, and to read up all you can.

Answer 3

You are not charging the battery directly from the battery -- you are charging it through the camera's charging circuit, which will have some sort of step up convertor to get the high voltages (300V) needed.  That circuit is designed for a certain input voltage -- if you exceed that by too much, you are likely to damage the circuit, without decreasing charge time.

You might consider placing batteries in parallel, which will leave the voltage the same, but provide more current should the circuit make use of it.  It really all depends on the specific design of the charging circuit.  

The easiest way to achieve faster recharge would simply to use multiple firing circuits.  It might be possible to just gang all the outputs in parallel, then you only fire the one that is charged.  Then, while that one is recharging, you load the gun again and fire the next camera.  There is some danger that the camera trigger won't like seeing 300 V coming from the other side , in which case you might want to consider diodes to make sure current only goes one way -- to your launcher,

Answer 4

If you are asking if you can put batteries in series to get more voltage the answer is yes.  My TI calculator has 4 1.5 volt batteries running in series to produce 6 volts.

Sounds like you are looking to make a machine gun:-)  Have fun and be safe. You are undoubtedly a smart kid.