Datsun Z-Series (240Z, 260Z, 280Z) Battery Replacement Guide

The Datsun S30 requires a Group 24 battery.

Battery replacement is one of a handful of critical maintenance tasks you should know as a Datsun S30 owner. Whether you need a routine battery replacement, or perhaps you are starting with a 240Z, 260Z, or 280Z that needs a new battery entirely, replacing your Z-car’s battery is a straightforward process. With some basic repair skills, you can follow the process detailed below to replace your battery and make sure your L-series engine cranks to life every time. This guide will detail the battery size you need to purchase and the steps involved in battery replacement, along with some helpful tips and advice on making sure you get the longest possible life out of your new battery.

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In terms of maintenance intervals, it is best to replace your battery approximately once every 3 years as that is generally when battery performance starts to decline. Typically, most batteries will completely fail by the 5-7 year mark. The best time to assess the state of your battery is just after the engine has been started, as after this time, the battery will generally run on charge from the alternator (so this does not indicate the battery‘s performance, but rather your alternator’s reliability). Just after the engine starts, check to see how bright the headlights shine: If you feel that they are dimmer than you remember them being, rev the engine. If the lights dim after revving the engine, your battery is experiencing (normal) decline in performance and you should begin to consider a battery replacement.

So, if you’ve determined you need a new battery, the next question is: what exact battery should you purchase?

Best Battery for a Datsun S30

In terms of battery specifications, you will need a standard 12-volt top-post battery. The most important thing to keep in mind when purchasing a new battery for a Datsun 240Z, 260Z, or 280Z, is that it needs to be a Group 24 sized battery. The S30 engine bay features a unique battery frame which holds down the battery, and it doesn’t offer a lot of versatility in terms of the battery size that can be used. If the battery you install doesn’t fit nearly perfectly, you won’t get a good clamp down on the battery which is important for safety reasons.

Be on the lookout for a battery that features a left-side positive terminal, meaning your positive terminal will sit under the fender inspection lid door. This is a nice safety precaution many recommend, as it can prevent sparking if you happen to hit the inner battery terminal while wrenching in the engine bay.


How to Replace your S30’s Battery

While replacing your battery, make sure to clean any corrosion from the terminals.

The actual process of replacing the S30 battery is a quick and simple process which can be done with tools you likely already have in your garage.

  1. Disconnect the negative terminal first, usually marked on both the battery and the battery terminal with a “-” sign or black color. You don’t need to remove the battery terminal bolts all the way out, just enough that you can wiggle the battery terminal free of the battery post.
  2. Then, remove the positive terminal, usually marked with a “+” sign or red color.
  3. Move your battery terminals to the side, just out of the way of the battery for now.
  4. Remove the battery frame hold-down screws and remove the battery itself.
  5. Inspect the battery terminals for any corrosion. Corrosion will appear as a crusty, fuzzy-looking blue/white substance and is generally very easy to spot. Corrosion can actually interrupt the flow of power from the battery through the cables, so now is a good time to clean it off.
    • Sprinkle a bit of baking soda on the terminal and pour a couple spoonfuls of water over top.
    • The baking soda will react by bubbling up for a few moments.
    • Once the bubbling has subsided, use a battery post/terminal cleaner to scrape off the corrosion.
    • Rinse with water and let dry.
  6. Spray your terminals with battery terminal protector, especially if you had to clean off any corrosion.
  7. Install your new battery and tighten the hold-down frame.
  8. Re-connect the positive terminal first, ensuring you have tightened the terminal to the post so it won’t wiggle loose.
  9. Re-connect the negative terminal.
  10. Start your vehicle, hopefully to the sound of a strong crank and prompt start-up!


Battery Care and Maintenance

As you are likely aware, battery replacements are an expensive aspect of vehicle maintenance, even on a vintage car like the S30 Z-series. There are a few things you can do to make sure you get the longest-life out of your battery so you won’t find yourself purchasing a new battery early.

  • Regularly inspect your battery terminals and posts for corrosion. You can clean both your battery posts and terminals at the same time with the same process described above: sprinkle some baking soda on the affected area and pour water over-top. Wait for the bubbling to subside, and then clean the posts and terminals with an appropriate cleaner tool. Rinse with water and wait to dry.
  • Make sure you apply battery terminal protector to your terminals.
  • A classic car such as the 240Z/260Z/280Z may sit unused for long periods of time between being driven, so battery discharge can happen during this downtime. You can certainly jumpstart your Z-car using another vehicle or a portable jump starter such as this one, but in my experience, nothing beats a slow battery tender which will prevent battery discharge while your Z-car sits unused. I use the a Battery Tender and leave it running every time I park my 240Z. Battery Tender claims you can leave the device unplugged forever, and my experience has actually backed up that claim.


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