# Using one or two batteries

Discussion in 'The Projects Forum' started by PierreK, Apr 28, 2009.

1. ### PierreK Thread Starter New Member

Apr 28, 2009
8
0
Hi everyone. I made a design that I think will allow a load to be connected to either 12V or 24V depending on the number of battery's that you connect.
I plan on using this in a device that I am building that will operate on a farm and depending depending on the availability of fully charged battery's It may be connected to either one or two 12V battery's. If I use the circuit in the image attached will this work.
If they connect Only B1 12V will be supplied to the Load and if they connect both B1 and B2 24V will be supplied to the load.
Or will this Design cause damage to the battery in B2.

File size:
3.5 KB
Views:
29
2. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
As drawn it will work fine. Be sure the diode can meet the current requirements, and I'm assuming you will remove B2. Actually, put another diode across the other battery and the circuit is symetrical, you can remove either battery at whim.

There is one minor drawback, if you are running off one battery the diode drop will show, figure just over a volt if it is 1-5A. With both batteries in the circuit it will be as if the diodes don't exist.

3. ### RolfRomeo Member

Apr 27, 2009
17
0
As far as I can tell, you're circuit will perform as intended.

Might I ask what the load is? Remember that doubling the voltage will also double the current through a resistor, so your batteries will discharge twice as fast.

edit: and there you go

4. ### PierreK Thread Starter New Member

Apr 28, 2009
8
0
Thank you all very mush for the information. To answer the question about the load. It is a air flow relay. according to the usage diagram it can operate between 10V and 30V and is intended to be connected to between one or two 12V battery's. I was thinking about my solution again last night and came to the conclusion that by having the two battery's and the load in series or disconnecting the one battery and then just short circuiting the two terminal connections of the second battery will result in the desired effect. Since this decision of one or two batteries is made when the device is connected it should work fine. and then I do not have to worry about the voltage drop caused by the diode when only one battery is presented.

Thank you again for the information on this question.