07 Accord I4 Battery Upgrade: 51R to 35

[The Critic]

After reading @carviewsonic’s thread and receiving some encouragement from @bbhero, I decided to upgrade the battery in my wife’s Accord from a 51R to a 35.

I ordered the battery tray, battery cover, larger ground cable, new tie-down, both J-Hooks and both nuts from Honda for $128.43.

For the battery, I used a Kirkland 35 AGM, which was $179.99.

Everything fits securely, but it is tight. I think the V6’s wiring harness and air box are slightly different in this area.

 

[michaelluscher]

More CCA

 

[JeffKeryk]

I wish there was room for the larger battery in the 2006 and 2007 TSXs I service. I replaced 1 51R 2 weeks ago and the one in our car, a 2018 date, is not long for the world. The smaller TSX vs Accord makes the upgrade inpossible.

 

[michaelluscher]

Could a 24F be squeezed in for even more CCA?

 

[JHZR2]

For $128 in a mild climate I’m not sure it is worth it, but it’s a good upgrade!

 

[CharBaby]

Nice upgrade Sir.
I always attempt to upgrade if/when needed. If a larger battery will fit, I'm putting it in! Especially from a Group 51R to larger(Group 35 or 24F). I don't alway upgrade to a Group 24F but I always entertain the thought.
However if a vehicle already had a large size, NO need to upgrade.


When my daughter had her 2015 Civic, it had a 51R and to put in a Group 35 would have been extremely tight. When her OE battery died she went ahead and had the "guys" put in another 51R(AAP free install) and she was living in another PA at that time.

IDK what battery size her new 2022 Civic has but it looks small as well. I'll do some searching about upgrading to a larger battery when the OE finally dies now that she has moved back to ROC.

 

[Sayjac]

I considered the move to the 35 (with OEM retrofit parts) from 51R on a 2.4L Accord, but in the end decided against it. Got 6&1/2 years out of the OE Honda battery which I thought was very respectable. Replaced with a Sam's Duracell (3 year full) by East Penn. No assurance I'll get the same, but I use maintainer occasionally as part of battery maintenance. If I get ~5 year 'range', I'd be happy.

The 3.0L V6 comes with group 35, currently using a WM ValuePower about 3.5 years. It's getting weak, tested 12.1 volts resting cold the other day, still started. Put on Noco 2amp and brought it back up, but considering another WM VP soon. Gone up from ~$50 to ~$60. If I got same life or close I'd be happy.

Nice retrofit, but considering installer, I'd expect nothing less.

 

[DuckRyder]

Nice work as expected, looks like it came that way.

 

[LazyDog]

I did the same ro fit on 2004 CRV and just modify the battery tray only. I can find a group 35 more easily at my local Menard's and does why the change.

 

[Tdbo]

Did this years ago on my '12.
The 51 was totally inadequate in my climate (even when new.)
With a remote start, the 51 made it a one hit wonder.
If it didn't start the first time, you knew that you had to go get the jump box.
The 35 is the easiest to go with.
I spent absolutely zero on mine to modify it.
The only thing that was required was a pair of pliers to bend back the tab that held the 51 tight.
Still plenty of room, even with a 35.
Took care of the starting issue easily.
Another advantage of making the swap: a wider array of batteries to choose from, sometimes at a lower cost.

 

[Tundragod]

I did this about 11 years ago and still in my 08 Accord I4 today. I did not spend any extra cost, just bent the top hold down as seen in the picture.

 

[Bottom_Feeder]

Nice job. I did essentially the same thing on my '15 Accord using a 24F (link to my thread might even be below for you) a few years ago. OEM parts makes the swap look stock and clean. Not sure why the pics in my thread are now gone.

 

[JeffKeryk]

I wish there was room for the larger battery in the 2006 and 2007 TSXs I service. I replaced 1 51R 2 weeks ago and the one in our car, a 2018 date, is not long for the world. The smaller TSX vs Accord makes the upgrade inpossible.

@The Critic corrected me; I am gonna stuff a group 35 into our TSX. The TSX has 212K and has been a joy to own. It's still perfect.
I got almost 5 years out of the current 51R. I have been topping it up with the battery tender as of late.

 

[The Critic]

Could a 24F be squeezed in for even more CCA?

It appears so. I originally wasn’t sure if it would fit.

 

[Hall]

When my daughter had her 2015 Civic, it had a 51R and to put in a Group 35 would have been extremely tight.

I think our '12 Civic is the identical layout and yeah, I'm not sure a 35 would fit.

 

[FZ1]

Could a 24F be squeezed in for even more CCA?

This^^^^^^^^^^^. My Camry 4 specs a 24F. 725 cca on my WM max

 

[CharBaby]

I like upping to a Group 24F whenever possible as it is the same price (often le$$) and free extra power (CCA/CA).

 

[Hall]

I like upping to a Group 24F whenever possible as it is the same price

Do you see lower prices for 24F vs 35 ? It seems like more and more applications are switching to 35 group size, especially with ones that used to spec 24F. Why ? The 35 is slightly smaller and more importantly, lighter. The difference in CCA and/or Ah is negligible as well.

 

[The Critic]

Do you see lower prices for 24F vs 35 ? It seems like more and more applications are switching to 35 group size, especially with ones that used to spec 24F. Why ? The 35 is slightly smaller and more importantly, lighter. The difference in CCA and/or Ah is negligible as well.

In all honesty, how much much juice do you need to crank over a 2.4L 4-cyl engine running 20/30wt oils? Obviously some reserve would be nice and a 35 seems like a reasonable balance.

I think another consideration is the alternator's output; if we deviate too far from the OE size, I am concerned that the alternator is not large enough to keep a monster battery topped up.

 

[brianl703]

I think another consideration is the alternator's output; if we deviate too far from the OE size, I am concerned that the alternator is not large enough to keep a monster battery topped up.

Why? The alternator only needs to put back into the battery what has been taken out. Barring something like a completely dead battery that was jump-started, or a faulty battery with a shorted cell, a larger battery would not be expected to require any more out of an alternator than a smaller one.

EDIT: From what I've observed there isn't much correlation between the alternator size and the battery capacity. Alternator size is based on presence of things like electric cooling fans, and battery size is based on engine displacement.