Does your Honda Accord struggle to start? Do you end up replacing your battery every year or two, when it should last for 5 years or more? Do you use your jumper cables more often than you would like? Do your headlights dim when you turn on the A/C or lower your windows?

I faced all of these issues. This post describes what finally fixed the problems for me, and it was so easy!

So what’s the solution? Upgrade the battery!

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Background on the Underpowered Original Honda Accord Battery

The original battery that is installed in the 4-cylinder Honda Accord is a 51R battery which has a capacity of 500 CCA (cold-cranking amperes). This is horribly underpowered for this vehicle.

The 6-cylinder Honda Accords use a larger battery, and it is a simple upgrade to put that larger battery into a 4-cylinder Honda. I replaced the 51R battery in my 2004 Honda Accord with a 24F battery which has the same voltage but has 750 CCA. (Note: this upgrade can also be done to the 35 battery which has around 640 CCA).

By increasing the CCA’s by an additional 50%, you eliminate a lot of the problems that you face with the underpowered 51R battery that the Accord originally calls for!

What Problems Does Upgrading the Battery Fix?

The following is a list of problems that upgrading the battery will help with:

  • Car won’t start (or barely starts) in the winter.
  • Frequently need to get a jump-start.
  • Frequently need to replace the battery.
  • Thinking you may need to replace your alternator.
  • Thinking you may need to replace your starter.
  • The headlights dim when you put a load on the battery such as lowering the windows or turning on the A/C or heater fan.

I did this upgrade, and if you have a 4-cylinder Honda Accord with a 51R battery, I HIGHLY RECOMMEND that you perform the upgrade as well, there is no downside! The car starts right up and the lights no longer dim when turning on the fan.

Tools and Supplies Needed/Used:

How to Upgrade from 51R to 24F Larger Battery – Honda Accord

The first step is to remove the battery connectors from the battery. Start with the negative (sometimes black or green) connector. Use a 10mm wrench. Push the connector out of the way so that it is not bumping against the negative terminal while you are disconnecting the positive.

Next use a 10mm wrench to disconnect the positive terminal connector.

Remove the battery.

The new, bigger battery won’t fit into the small tray, so remove it.

Get a new tray that will hold the larger battery. If you want it to look stock, get the Genuine Honda Battery Box (31521-T2G-A00), which is the battery box from the 6-Cylinder Honda Accord. Also get the correct hold-down cross-bar (31512-T2G-A00). There is also a battery cover that acts as a shroud around the battery (31531-T2G-A00). I don’t think it is necessary, but to make things look stock, you should get that too. Here are the part numbers for each of these Genuine Honda components:

If you want everything to fit nicely, go with the Honda OEM battery tray. However, if you don’t care about the look so much, go with a generic battery tray, which is what I did because it was less expense. Here is the battery tray I settled on:

This tray is about 1/2″ too big in the lengthwise direction and about 1/4″ extra in the width.

It is also recommended when you upgrade to the larger battery, that you replace the grounding strap with the beefier one from the 6-cyl Accord as well. This will give more stable current and fewer problems with current draw, like dimming headlights, and etc…

Use a 10mm wrench or socket to remove the grounding strap from the frame of the car.

On mine, the frame was painted where the grounding strap attaches, which can’t be good for the connection. I used a bit of sandpaper to remove the paint.

Sanding away the paint will give you a better connection and more stable power.

Replace the existing grounding strap with the larger diameter OEM grounding strap (32600-SDB-A00). It looks really short, but it is the right length when you get it installed!

Use the 10mm bolt to attach the new grounding strap where the old one was. It is pretty stiff at first, so go ahead and bend it to the approximate correct position so that the connector will be in the right orientation to attach to the battery terminal post.

With the new battery tray and grounding strap installed, you are ready to put in the new battery.

Whether new or old, it is a good idea to roughen the surface a bit for good contact. Use a terminal brush to score/clean the terminals.

Do the same for the inside of the connectors.

Use a 10mm wrench to attached the battery connectors to the terminals. First put down some anti-corrosion felt washers. Then connect the positive terminal connector first, make sure it is snug for a good connection.

Then attach the negative battery terminal connector (grounding strap).

Finally, put the hold-down crossbar in place and tighten up the nuts to hold the battery down.

That’s it for the battery upgrade, I think you’ll be very pleased with the results.

How to Reset the Radio Code – Honda

After changing out the battery for the larger one, you may need to re-enable the radio by entering the radio code. If this is you, locate the radio code for your stock radio.

The radio code is either found in the owner’s manual (often in a small plastic envelope from the dealer), or it can be found on the side of the open glove-box. There is a sticker on the side that can be seen from the driver’s seat.

The radio code consists of 5 numbers. Use the numbers 1 to 6 on the radio to enter the code to re-enable the radio.

Tools and Supplies Needed/Used in this Article: