# Battery question

Discussion in 'General Electronics Discussion' started by ratstar, Oct 17, 2020 at 3:11 AM.

1. ### ratstar

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Aug 20, 2018
Say you have 2 batteries.
Can u conduct from the + of one battery to the - of the other?

If you cant, and they have to be from the same battery, why not?

138
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Aug 20, 2018
3. ### dave9

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Mar 5, 2017
Connecting two batteries, or I should write cells, in series like this is done all the time.

The negative of one must only contact the positive of the next in series. There are exceptions, mostly dodgy designs, or of course a lead going to a battery monitoring circuit, but mostly it means that the negative poles of both can't be connected directly to the powered device ground.

The other issue is what happens as voltage drops. If the batteries are not very close in capacity, the capacity of the weaker battery will determine end of useful life, and if one discharges to too low a voltage it could be damaging, and if damage could result in a dangerous situation (or just for practical purposes of not ruining the battery) then a battery monitoring system with a low voltage cutoff should be used. In other words unless it is an emergency situation, it's best to always use batteries of the same capacity in series.

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4. ### ratstar

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Aug 20, 2018
Thanx dave9, but I meant making a circuit from 1 pole of one, to 1 pole of the other, and that doesnt work.

But yes indeed, you can put them in series, as long as they are a full circuit including them both.

Last edited: Oct 17, 2020 at 10:41 PM
5. ### Alec_t

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Jul 7, 2015
That isn't a circuit. A circuit requires a complete go-and-return 'circular tour' for current to take.

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6. ### ratstar

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Aug 20, 2018
The amazing thing here is that if you have 2 batteries in a circuit, Is I think they can actually conduct on top of each other and return only to their own negatives each.

Isolation, be it capacitor, battery or transformer, I think they all exhibit a similar property.

But is there a pneumatic equivilent - or does air just go everywhere...

7. ### Harald KappModeratorModerator

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Nov 17, 2011
Hard to understand what you mean without a schematic diagram.
What "property" are you talking about?
A capacitor or a transformer may be used to isolate circuits from each other. However, both can, obviously, transfer energy between the isolated circuits.
A battery by itself is not an isolating device, but it can supply energy. And it can be used in isolated or non-isolated circuits.
Air is a gas and follows the laws of physics. It doesn't just go anywhere, it will try to minimize the energy within the gas. This means that it will flow from regions of high pressure to regions of low pressure, wherever these are and by whichever means are available (tubes, hoses, convection etc.)

8. ### ratstar

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Aug 20, 2018
I tried out an experiment and I found that the 2 batteries pass through each other with a dull response in the centre where they are overlapping.

Last edited: Oct 19, 2020 at 11:56 AM
9. ### Harald KappModeratorModerator

10,336
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Nov 17, 2011
I'm sorry, neither your description nor your diagram make any sense to me. How would
?
What is the "attraction" you mention in your diagram? Electrostatic attraction, magnetic atttraction?
The labels "battery 1" and "battery 2" in your diagram do not match where I'd expect to see batteries according to the "+" and "-" labels. I recommend you learn how to draw a good schematic diagram. It will help you get organized and will help us understand what you mean.

10. ### ratstar

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Aug 20, 2018
I mean no attraction as in the battery + of one battery isnt attracted to the - of the other battery, like we were saying.

Theres 9v on all lines except the centre, where the battery power seems to be passing through itself, subtracting - and cancelling out.

Phase cancellation - if you will.

11. ### Harald KappModeratorModerator

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Nov 17, 2011
I won't. There is no phase in DC. This is really incomprehensible without a well arranged schematic circuit diagram.

12. ### ratstar

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Aug 20, 2018
If you have the batteries backward to each other, it looks like I did the drawing wrong, and its not 9v up the sides, when its inverted I think the batteries are actually going in series with each other, because im getting a louder response with them both connected.

It actually conducts through the battery itself it seems.

13. ### Harald KappModeratorModerator

10,336
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Nov 17, 2011
Placing 2 × 9 V batteries in series results in a configuration which can be interpreted in different ways, whichever suits the needs of the circuit designer best:

If you place the batteries with like poles facing each other, you have these possibilities:

In this configuration you may as well connect the "+" poles (arrangement 3) or the "-" poles (arrangement 4) which puts the batteries in parallel. If you were to connect a load between the two "+" poles of arrangement 4, no current will flow as both connections are at the same potential and the voltage difference between them is 0 V. The same is true for arrangement 5 with polarities reversed.

Do you see why a clear schematic diagram is truly helpful to gain understanding?

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14. ### ratstar

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Aug 20, 2018
Thanks for the info, sorry if my drawings are so hopeless, I've got a ghost in my mouse which makes them messier than they should be. But I definitely learnt something. I learn something new every day.