Well I submitted this post just now, but it messed up my text picture so I'll do it all in words. If I have four 12v car batteries what will the voltage be if I hook all of the positive terminals together and all of the negative terminals together? What if I hook it like positive to negative and then postitive to negative like in a series? What if I use car alternators? What changes are there other than in voltage?

-- Evan Sangaline (navarchy@yahoo.com), September 09, 2001

Answers

As far as I know positive to negative results in a spark or worse!!!

-- rick K (rick_122@hotmail.com), September 09, 2001.

Answers: 1) Connected in parallel = 12 volts, 2) Connected in series, pos to neg, would yield 48 volts, 3) do not understand question, 4) amperage changes.

-- Joe (CactusJoe001@AOL.com), September 09, 2001.

Ok, this one I had explained to me by my grandfather who has diesel trucks and a mechanical engineer background. By connecting the positive to positive to positive to positive- the voltage of 4 12 v car batteries will be 4 X 12 so 48 volts DC current. This is if all the batteries are peak charge- the voltage will drop as the batteries discharge. By connecting the batteries in series like this: battery A has ground connected to common ground (the vechicles frame or engine block if used in a auto, or connected to the alternator case if used in a windmill or something. battery A positive is connected to battery B negative. Battery B positive connected to battery C negative. Battery c positive connected to battery D negative. Battery D positive connected to powered items (starter and lights in an auto, hot wire from alternator which is then fed to regulating decice then to the battery D pos in a windmill or such). The final out put is 12 volts from these seriesed batteries. The plus side of series is that the batteries take 4 times longer to discharge BUT all the batteries must be of equal amperage size and condition with condition being the number one consideration... one poor battery in the series will quickly drain the whole system (it is only as strong as its weakest link). So new batteries are almost a necessary. Something else to consider: even equaling 120 v DC cannot be easily changed into 120 v AC. 6v, 12v and 24v DC are the common used DC currents- 24v is often found in RV and semi truck applications, 12v is the most common auto voltage, 6v was used in voltswagons (older ones) and older pre 50s american autos. Many of these vehicles have been upgraded to 12 v systems since their manufacture. 12 and 24 v DC to AC inverters are available, but are expensive. Contact me at Vantravlrs@AOL.com- im on my wifes screen name right now.

-- Kevin in NC (vettsvet@AOL.com), September 09, 2001.

If you hook all the car batteries positive to postive then you keep the 12v, but your total current is addative. This is a parallel system. Keep in mind charging parallel systems is a bit harder since not every battery will charge at the same rate.

If you connect neg to postivie to create a "Serial" chain, then your voltage will be 48 and your current the capactity of the smallest battery.

-- Gary (gws@redbird.net), September 09, 2001.

Batteries connected in series Positive to neg to positive to neg. etc. the voltage will be additive, 12+12+12+12=48 Volts DC, the amperage capability will remain the same. Batteries connected in paralell, positive to positive, negative to negative, the voltage will remain the same but the amperage capability will be additive, so you can store a lot more amp/hours of power. If you are doing this for an electrical storage device I believe you would be better off to connect them in paralell because I think it would be more economical, 12 volt lights and appliances are available many places, you can charge the whole bank from one heavy duty auto alternator driven by wind, water, etc. You could also connect them in series/paralell for 24 volts. Converting the voltage to AC is expensive and not very efficient. Also no matter which way you do it the batteries should be isolated from each other so that a bad one will not pull the others down, this is probably the most important thing to do from a long term cost standpoint.

-- Herb. Smith (herbmsmith@aol.com), September 09, 2001.

Question 3. " What if I use car alternators? ".

The same rules regarding serial and parallel connection apply however you would need to be a bit careful about how the field connections are managed so that each alternator produces the same output, maybe less of a problem if you have latest model alternators with internal voltage regulation etc.

If you just want 12volts and a lot of amps it might be better to go to a truck wrecker and try to find a higher output alternator, if it is more volts you want, like 48volts for example, again try to find a 48volt alternator. I suspect that multiple alternators will loose you a lot of mechanical energy.

If you seek higher volts and not necessarily so many amps then in theory a transformer is what you need but unfortunately common alternators are multi-phase devices so you would need a multi phase alternator which is something I know nothing about except that there is one lying under my workshop bench.

May I suggest that you go to an auto electrician and find someone who is at least as old as I am. You will recognise him as thee guy with the spectacles and grey hair. Ask him if there is any way of altering the output of an alternator to do what you want.

-- john hill (john@cnd.co.nz), September 09, 2001.

What exactly are you trying to accomplish? Is this power for a cabin, car, some device?

-- Yup (Yup@nospam.com), September 09, 2001.

I agree with Gary and Joe, If you conect them all positive to negative this would be series and the voltage would be 48 volts. Positive to positive, and negative to negative would be 12 volts with more amperage.

-- r.h. in okla. (rhays@sstelco.com), September 10, 2001.

Kevin in NC, you misunderstood your Grandpa. You have your series and your parallels mixed up.

-- Anybody (123@abc.com), September 10, 2001.

Yes, Kevin's answer was great. Only problem, he was totally backwards in what he said. Just do the opposite of Kevin's answer. Evan, it occurs to me that if you must ask a question about very basic electrical concepts such as this one, maybe you aren't the man to be stringing batteries together.

The available amperage from a set of four fully charged car batteries is almost infinite in a direct short circuit. You could easily be killed. At the very least, I'd read some good books written by professionals and avoid asking questions about serious matters on internet forums.

-- Jim (catchthesun@yahoo.com), September 10, 2001.

Jim is quite right to sound a note of caution.

You dont need much current at all to be lethal but you do need a minimum voltage which I understand is quite low, maybe as low as 32volts. That is enough voltage to cause a current through your body and just a few milliamps from one hand to the other (which goes through your chest) has the potential to interfere with the tiny electrical signals that control your heart.

-- john hill (john@cnd.co.nz), September 10, 2001.