Is it possible to draw this in a circuit diagram?

Thread Starter

donayre21

Joined Jul 20, 2017
3
Good Evening everyone,I'm currently confused in a circuit set up for the batteries of a solar cell.I wanted to know how to properly draw it since I have a general idea and want to know if I'm right.The circuit is a series+parallel set up for 6 V batteries.This is not homework it just struck me as odd since I have never seen it before.By the way I'm currently in university and have already take general circuits for physics.I understand a series and parallel set up.



would you draw the first picture as follows:

question.png

Sorry for the bad picture,I don't own a circuit drawing program.The middle of my figure has two batteries each 6 V which add up to 12 v.Any help on this will be great,I'm just genuinely curious on how the first picture should look in a circuit diagram.
 

WBahn

Joined Mar 31, 2012
29,930
What you have is okay, but convention would have it drawn upside down compared to what you have -- normally the negative terminal is down and the positive terminal is up.

If this is predominately a source, it would also be flipped left to right since sources typically go on the left of a schematic and power things to the right. But if it is predominately a load, then would be on the right. For a solar cell set up, they are both and so it's up to you. The idea would be to make things neat and understandable.

EDIT: THANKS absf! As absf points out below, you are shorting your power rails with the connection on the far right. Simply remove it.
 
Last edited:

JoeJester

Joined Apr 26, 2005
4,390
This is not homework it just struck me as odd since I have never seen it before.
You have seen battery packs before. Some AA/AAA batteries are in series some could be in parallel. The application determines the setup.

Your group was "constructed" to supply 12V @ 600 AH. Economics could be the driver.

Some 1 kW Uninterruptible Power Supplies were powered by seven, 12V 22AH batteries, in series.

What would you do if you were asked to supply power to a 6 V 1 W device using AA batteries? The device must work without fail for a period of 24 hours.
 

MrAl

Joined Jun 17, 2014
11,342
Good Evening everyone,I'm currently confused in a circuit set up for the batteries of a solar cell.I wanted to know how to properly draw it since I have a general idea and want to know if I'm right.The circuit is a series+parallel set up for 6 V batteries.This is not homework it just struck me as odd since I have never seen it before.By the way I'm currently in university and have already take general circuits for physics.I understand a series and parallel set up.



would you draw the first picture as follows:

View attachment 131280

Sorry for the bad picture,I don't own a circuit drawing program.The middle of my figure has two batteries each 6 V which add up to 12 v.Any help on this will be great,I'm just genuinely curious on how the first picture should look in a circuit diagram.

Hi,

As others have pointed out, the wire to the right side is shorting out the battery pack, but i just wanted to add a little practical information which is actually sometimes vital when doing this knid of thing in real life.

First, two batteries can be connected in parallel, but they should be of very nearly the same voltage with very little difference. This is because if one is lower than the other, the higher one discharges into the lower one with a series resistance that is only the sum of the two cells internal resistance which itself can be very very low. This is especially important with chemistries like Li-ion. If the two resistances are 0.05 ohms (typical even in smaller cells) then the total is 0.1 ohms, and if one cell is 1v higher than the other then the current flow would be 1/0.1 which is 10 amps. This is especially a big problem if one of the cells is bad.

Second, two batteries can be connected in series but again they should be charge balanced to make sure that they drain in a somewhat consistent manner. If one cell happens to drain down to 0v then the other cell starts to charge it in REVERSE which is very very bad for most cells. In this setup it is a good idea to apply some voltage monitoring to make sure this never happens.
 

Thread Starter

donayre21

Joined Jul 20, 2017
3
THANK YOU SO MUCH EVERYONE!!! All of you are very nice and helpful,thank you for all the help.I have one more question why would you use this set up instead of just using a just series since it will give you a high voltage to store?

Is there a benefit on having higher amperage since series has high voltage but low amp and parallel has low voltage but high amps.
 

WBahn

Joined Mar 31, 2012
29,930
In order to perform a given task, you need so much voltage and so much current. You have to have both.

Many tasks are relatively low voltage and high current. As just one example, electromagnets generally don't need a lot of voltage, but they typically require lots of current.
 

Thread Starter

donayre21

Joined Jul 20, 2017
3
In order to perform a given task, you need so much voltage and so much current. You have to have both.

Many tasks are relatively low voltage and high current. As just one example, electromagnets generally don't need a lot of voltage, but they typically require lots of current.
Thank you for the help!
 

MrAl

Joined Jun 17, 2014
11,342
THANK YOU SO MUCH EVERYONE!!! All of you are very nice and helpful,thank you for all the help.I have one more question why would you use this set up instead of just using a just series since it will give you a high voltage to store?

Is there a benefit on having higher amperage since series has high voltage but low amp and parallel has low voltage but high amps.

Hi,

When you put two batteries in parallel you effectively double the current draw capability if you need that, but if you dont need more current capability then you double the run time of the device being powered.

For example, if you have a device that draws 1 ampere and you have just 1 battery rated for 20 ampere hours, you get roughly 20 hours of run time. If you connect two of the very same batteries in parallel however, you get roughly 40 hours run time.

Since many batteries are also rated for maximum current draw, sometimes you need a higher current capability so connecting them in parallel would help in that application too.

A third possible use is to reduce voltage droop either right away or over time. As the battery (batteries) voltage(s) start to drop, it may be a little too much reduction for a given application. Connecting two in parallel with help with that also to some degree.

So a short list of the things i can think of offhand for a given application are:
1a. Longer run time due to higher base ampere hour capacity
1b. Longer run time due to better P factor for each battery (running at 1/2 current).
2. Higher current capability.
3. Lower voltage droop.
4. Lower battery temperature (in some cases).

Of course there are also some disadvantages.

5
 
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