Connecting Batteries in Parallel - Is It Possible?

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    Battery Parallel
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Discussion Overview

The discussion revolves around the feasibility and implications of connecting batteries in parallel, particularly when they have different capacities or voltages. Participants explore theoretical and practical considerations, including safety concerns and methods to manage current flow.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants assert that connecting batteries of different capacities or voltages in parallel is possible but may not be practical or safe.
  • One participant suggests using small value resistors to limit current, while another questions the effectiveness of this approach and emphasizes that resistors drop voltage, not current.
  • Concerns are raised about the dangers of charging a battery not designed to be charged, particularly when different voltages are involved.
  • Diodes are proposed as a solution to prevent higher voltage batteries from charging lower voltage ones, although some participants note that this may introduce additional voltage drop and losses.
  • Another participant shares a practical example involving a shottky battery isolator used in electric drive trucks, highlighting its role in preventing batteries from charging or discharging each other.

Areas of Agreement / Disagreement

Participants generally agree that while it is technically possible to connect batteries in parallel with different characteristics, it is fraught with risks and complications. There is no consensus on the best methods to mitigate these risks or the practicality of such connections.

Contextual Notes

Participants express varying assumptions about the safety and functionality of connecting batteries with different specifications. The discussion highlights the need for careful consideration of application and potential hazards, but does not resolve the complexities involved.

s_m
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i know its not possible but isn't there any way in which two batteries of different capacities or voltages be connected in parallel ?
Is there any way to limit the current in that case
by using small value resistance to drop the current?
or by adding a convertor from high to low current value or a control device?
please let me know about it .
 
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Welcome to PF;
s_m said:
i know its not possible but isn't there any way in which two batteries of different capacities or voltages be connected in parallel ?
Of course - just connect up the wires. (What do you mean "I know it isn't possible..."?

Is there any way to limit the current in that case
by using small value resistance to drop the current?
or by adding a convertor from high to low current value or a control device?
please let me know about it .
You can treat the batteries exactly the same as you would a single battery.
You aught to be able to see what happens in a mesh analysis.

Note, however, that resistors are said to "drop voltage", not current.
Perhaps you are concerned about the current flow between the unequal batteries?
 
Hello SM ... Well agreed it is possible , but never practical to parallel batteries of different voltage, or really different types. This can actually be dangerious - if you effectivly start charign a battery that is not meant to be charged.

The simple way is to use a diode on the output of each, that will prevent the higher voltage of one battery from charging the other. But if the battery voltages are low - you may not want the added voltage drop of a diode, or the losses.

Beyond that it really will depend on the application.
 
@Windadct
Absolutely.
Parallelling up batteries, willy-nilly, that are of different ages, conditions, types, capacities and states of charge can damage you or both batteries.
 
There is a type of battery isolator known as a shottky battery isolator, which is just basically uses diodes to prevent the batteries from charging / discharging one another. I work on komatsu 930-E electric drive trucks, they are used there. The battery bank is a set of four 12 volt batteries. Two in series in parallel with two more. They run through the battery isolator to prevent one set from charging the others in case one set loses its charge.

but you shouldn't ever connect batteries of different capacities/voltages it is just used as a safe guard.
 

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