Connecting 12V batteries in parallel

[Tom Crowley]

Almost all diesels vehicles have 2 batteries in parallel.  Almost all Motorhomes have 2-4 batteries in parallel.  The trick is to replace them at the same time.  I can give you 50+ more examples if you need them.

Your concept of charging circuits is also in error.  As long as the batteries are equal, than charging them is fine.  There are 100s of thousands of exambles out there.

Good luck,

Tom KT4XN



Sent from Mail for Windows 10

From: Martin
Sent: Sunday, July 7, 2019 01:06 PM
To: Tacos
Subject: Connecting 12V batteries in parallel

Hi All,

A discussion about parallel batteries (12V marine deep cycle) connection for came up.  I wonder if anyone can shed some light on this.

There is a claim that connecting two batteries in parallel will result in a death spiral due to the different state of the cells.  The claim is diodes must be used to isolate the batteries changing and discharging.  I can understand that a parallel battery connection isn't ideal for smart charging circuits.

I am pretty sure I have seen commercial gear that had paralleled battery connections and have used them in the past without problems.  The use case I had in mind was for Field Day - using precharged batteries in parallel.  If capacity is lost due to parallel connection, any estimate?

TNX & 73,

Martin
W6MRR

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