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Batteries in parallel circuit question

Batteries in parallel circuit question

Batteries in parallel circuit question

(OP)
Hello,

I use 4 12V-7.2AH batteries in parallel connected to a seismograph and a modem which are in parallel too. Based on this configuration, isn't the voltages of the individual batteries supposed to remain the same as each other?

What I'm finding is that when I charge / use them (they are used as a pack), the battery furthest from the load / charger has the lowest voltage level after use / charge and the voltage increases as you move along the batteries to the load.

So if they were in parallel,

Battery 1 , Battery 2, Battery 3, Battery 4

Batteries 3 and 4 would have the lowest voltages.

Is this normal or does this mean that some batteries are wearing out / getting old.

RE: Batteries in parallel circuit question

Voltage drop on the leads maybe

RE: Batteries in parallel circuit question

Yep. That's the reason. The charger's current is being gobbled up by the front batteries leaving the rear ones slightly deficient all because of the lead resistance.

What wire gauge are you using?

What are the actual voltage differences like?

How much current does your seismograph use?

What kind of charger do you have? If the charger has a high output this will exacerbate the situation.

You can either change the wire size to a larger gauge or re-configure to a star pattern where all the wires come together at a terminal block and then hook to there with your load/charger.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Batteries in parallel circuit question

I suggest you connect the load and the charger catty corner, so one set of connections connections (say the positive) is made on battery #1 and the other set of connections (say the negative) is made on battery #4. This should reduce the voltage spreaad you are seeing.
-JFPE

RE: Batteries in parallel circuit question

And use larger wire!!

Bill
--------------------
"Why not the best?"
Jimmy Carter

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