battery configuration

[tuckertrucker]

i dont think ive got this in the right place but oh well.

this is probably a really dumb quesiton. But is it possible to link two batteries in series, whilst linking them in parallel? If not, please explain why it wont work.

I have two 12v batteries in series to provide 24v. But I can still draw 12v from the batteries individually with no issues. So why can't I draw 12v from each individual battery and then place the two +ve's and -ve's together to form a parallel connection? To me this does make sense because even with the 24v series configuration, 12v can still be drawn from each individual battery.

[Checkerhead]

If you connect the same pair of batteries in series AND in parallel, you will end up a positive terminal to a neg terminal and to earth. This will become a welding process as soon as the last connection is made.

At least that's the way the wires run in my head. Maybe draw it?

[Smurf]

You will end up connecting the +ive terminal of one battery to both a +ive and a -ive terminal on the second battery.
I guess it is Guy Fawkes coming up. But it won't end well.
You can only end up with one voltage outcome in one wiring sequence

[Crash bandicoot]

Im no auto sparky, sure we have one around here some where that will chip in.



Series... add the voltages together for each additional battery. 12volt +12volt =24 Volt
because there is only one path the current can take in this circut the current is still limited to the maximum output of the individual batteries. hence most 24 volt systems are lower amp draw then 12 volt systems. Starter motor's are good example.

Parallel.... voltage remains the same (12 volt) regardless of how many batteries, current has a seperate path from each battery so voltage remains the same but for every addition battery added the potential amp draw increases (as just mentioned) there is an individual path for the current from each battery.

so if you hooked two batteries that were in series into parallel at the same time you will get a dead short as in a series circut one of the negative battery posts is hooked to the other batteries positive post causing an explosion of acid in everyones face.

[tuckertrucker]

right, i never actually realised that one batteries positive would connect to both the terminals of the other battery. good lesson to learn before putting it in practise....

[RRS]

The answer is yes, but you need a series parallel switch.

[ChurchurDan]

A series parallel switch is used for 24v starting in a 12v vehicle like an 80 series cruiser and is not without its issues.
What are you trying to do? run 12v stuff on a 24v truck, if so there are better ways to do it.

[tuckertrucker]

yeah I was trying to wire up a 12v compressor in the engine bay. Hoping I could run leads of the batteries directly to it (fused of course) so that I could get 12v, and drain each battery equally.

Would it be possible if there was a high capacity diode inline with all the parallel connections? I'm getting a reducer now for it but still curious.

[mudlva]

Mate your idea will end up going bang.
Buy a suitable sized transformer and do it properly.

Short cuts only fail when being used

[tuckertrucker]

Yeah I agree. I wasn't really trying to short cut, just wondering if it was doable. Obviously not haha. Im not one to risk dangerous shit like that, thats why I ask around first.

Ima head to jaycar and see if I can get a decent voltage reducer either dedicated to the compressor or one large enough to run a sepurate 12v acc. In the future I'm looking at permanently installing a aux battery and this will the power all the 12v stuff and other acc.

[mudlva]

Imho a seperate battery and suitable power suplly would be a the best set up

Give these guys a call
http://www.capitalcivic.co.nz
They supply the trade so will have several options at a guess

[tuckertrucker]

Imho a seperate battery and suitable power suplly would be a the best set up

Give these guys a call
http://www.capitalcivic.co.nz
They supply the trade so will have several options at a guess

will do cheers mate

[ChurchurDan]

You can also get a charge equaliser that connects to both batteries and will keep the charge rate even between them allowing you to run 12v accessories off of one battery. This is a better solution to a reducer if you want higher current toys such as a compressor but they are expensive.
An extra battery with a dc-dc charger is the best setup as you are not risking flattening the starting batteries.