Good question 👍 Let’s break it down simply.

You have **3 x 12V batteries in parallel**. The goal is to make sure each battery *shares the load and charging current evenly*.

There are three common wiring methods:

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### 1. **Star (or busbar) method**

* All battery positives go to one common positive busbar.
* All battery negatives go to one common negative busbar.
  ✅ Very good for equal current sharing.
  ✅ Easy to expand and maintain.
  ⚠️ Needs a solid, low-resistance busbar to work best.

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### 2. **Diagonal method** (often used when no busbars are fitted)

* You take the **main positive feed from battery #1**.
* You take the **main negative feed from the opposite end, battery #3**.
  ✅ This balances cable resistance so the middle battery doesn’t get “lazy.”
  ✅ Works better than just connecting both main cables to the same battery.
  ⚠️ A bit trickier to wire neatly if you add more than 3 batteries.

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### 3. **Both cables on one battery** (the “lazy” way – not recommended)

* Positive and negative both taken from the same battery.
  ❌ The first battery ends up doing most of the work.
  ❌ Others may never charge or discharge fully, leading to early failure.

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### So which is better?

* **If you have busbars (or can fit them)** → **Star/busbar method is best.** It ensures each battery “sees” the same connection path, so they all work equally hard.
* **If you don’t have busbars, just cables** → **Diagonal method is the next best choice.** It balances things fairly well.

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👉 Simple rule:

* **Busbars = star connection is best.**
* **No busbars = diagonal is the way to go.**

Would you like me to sketch a simple diagram showing the star vs diagonal connection so you can see the difference at a glance?