Connecting Battery Tender to Ram 3500 diesel batteries?

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THBailey

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Picked up a Battery Tender 4.5 amp today for my diesel 3500. As the batteries are in parallel probably doesn't make a difference but should the charger go to the drivers side, passenger side, or the positive on one and negative on the other? Thanks so much.

And if anyone might be interested, I found the unit at Costco in Folsom, Ca for $46.99, which is a pretty good price compared to Amazon or Walmart.
 
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crash68

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Doesn't matter which battery it's connected to, they're wired in parallel to each other. Pick the side that's easier to get to.
 

Arth

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Picked up a Battery Tender 4.5 amp today for my diesel 3500. As the batteries are in parallel probably doesn't make a difference but should the charger go to the drivers side, passenger side, or the positive on one and negative on the other? Thanks so much.

And if anyone might be interested, I found the unit at Costco in Folsom, Ca for $46.99, which is a pretty good price compared to Amazon or Walmart.

Since I am a weirdo I bought a dual battery charger and use that. Even though they are in parallel and should charge one or the other I haven't experienced any issues using a dual charger.

That being said for whatever reason my passenger side battery wants more juice than the driver side whenever I hook it up.
 

crash68

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Even though they are in parallel and should charge one or the other I haven't experienced any issues using a dual charger.

That being said for whatever reason my passenger side battery wants more juice than the driver side whenever I hook it up.
That's a physical impossibility unless you disconnect the batteries from each other. Your probably seeing the difference in calibration between the two charger outputs or it's power supply potential issue being both outputs are connected together.
 

BossHogg

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Picked up a Battery Tender 4.5 amp today for my diesel 3500. As the batteries are in parallel probably doesn't make a difference but should the charger go to the drivers side, passenger side, or the positive on one and negative on the other? Thanks so much.

And if anyone might be interested, I found the unit at Costco in Folsom, Ca for $46.99, which is a pretty good price compared to Amazon or Walmart.
I have a collection of the Costco 4.5 tenders, can't beat the price but I do remember when they were only $30 a copy (4 amps) just 2 short years ago.

On my 3500 Cummins, I wired the battery tender onto the passenger-side battery, less wiring on the passenger side. Also, wire the charger so it is on the load side of the BMS sensor, this will match the driver's side battery and the ECM does collect the amount of charge current that flows into the batteries.

If you were to wire some sort of aftermarket high current load, like a snow plow, you would want to wire to the positive on one battery and the negative on the other battery. This corrects for voltage drop. I think the rule is for loads exceeding 10 amps. Battery Tender has a nice FAQ that discusses the various ways to connect to parallel batteries.
 
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BossHogg

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Since I am a weirdo I bought a dual battery charger and use that. Even though they are in parallel and should charge one or the other I haven't experienced any issues using a dual charger.

That being said for whatever reason my passenger side battery wants more juice than the driver side whenever I hook it up.
Like crash68 said, impossible.

If you have a dual battery charger and connect one port of the charger to each battery in the truck that is wired in parallel, you are likely defeating the purpose. It is most likely the charger is seeing itself thus thinking the battery is at potential thus not causing anything more than a float state. The actual behavior of the chargers is brand based.

When batteries are wired in parallel there is no "one or the other", it is both or none.

You are likely connecting the passenger-side battery to the charger first and that is why you see the initial current in-rush until the driver's side is connected. Then the passenger side charger sees the driver's side charger and charging on both chargers turns into float since the battery charger thinks the battery it is connected is at potential.
 
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