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Have replaced OEM type 51 battery 3 times in 10 years in our ’08 CRV. #4 starting to go bad. Read about upgrading to a larger capacity battery. After reading different threads in this forum, bought a Duracell 35/85 AGM @ local Sam’s Club. Type 35 battery is slightly smaller than the type 24R & has terminals in correct position for CRV. Ordered Odyssey tray & box from new Honda dealer on 1604 in far west San Antonio. Arrived 2 days later. Parts & price list below.

While on lot, checked out new CRV’s. Saw an “added” feature posted on each vehicle: nitrogen in tires for $199. Salesman said that the price was “negotiable”. I told him the only negotiation that I want is to completely remove that spurious “upgrade”.

Removed type 51 battery, box, & tray. Wire-brushed metal battery stand to remove old crud. Used Dremel to cut several notches in J-bracket holder. Used the following to flatten edge of stand nearest air filter box: small crescent wrench & a section of 1” dowel & 3 lb. sledge hammer. Spray painted battery stand & let dry.

The space allotted for the battery in the CRV required minimal adjustment to tray and box. Tray adjustment consisted mainly of cutting a notch to fit against the bracket near the radiator and another notch for the J-bracket tie down next to the air filter box. Box adjustment consisted of trimming off all bottom tabs, making a similar notch in same corner as tray, & cutting small notch in top of box to fit battery clamp to battery.

1 Battery info.jpg
Battery info.png
2 Oddy battery box.jpg
Oddy battery box
3 Oddy battery tray.jpg
Oddy battery tray
4 Notched, flattened, painted tray.jpg
Adjusted CRV battery tray
5 Notch in tray.jpg
Tray corner notch
6 Notch against bracket.jpg
Tray notch under bracket
 

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Discussion Starter #2
51 battery replacement, pt 2

Duracell AGM battery is manufactured by East Penn. Size of battery is smaller than 24R that others have recommended. No other modifications were needed on the CRV except for the bending of the support tray edge closest to the air filter box - pic #4, I think.

Box tray adjustments.jpg
Oddy box with tabs cut off & corner notch
9 Box top notch for clamp.jpg
Finished project!
 

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Cool! I think I will do this on my '07 when I need a new battery. Thanks for all the helpful hints and part IDs.
 

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Delayed reply here but Very nice Upgrade...... Can't have too many CCA's for a car with so many different electrical draws these days. Seems the stock battery in my '19 is taxed heavily with all the "sensing" gear running. Would like to see a little excess or reserve capacity but I get it - They are in business to make a profit not just to make good cars. Thanks for sharing your upgrade. Boat is NOT a car given all the extra BIG DC loads, but I have a boat and I installed 2 x Group 31 AGM starting batteries (1 for each 8.1 Liter Port and Starboard engines, and 1 Group 8D AGM battery for house DC loads and they work hard when we are aboard. I planned to change after 5 years but they are still going strong at 12 years now. Sometimes simple upgrades that cost a little more than the MFG's recommendation translate to added security, less taxing and greater longevity. Love what you did here.
 

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Delayed reply here but Very nice Upgrade...... Can't have too many CCA's for a car with so many different electrical draws these days. Seems the stock battery in my '19 is taxed heavily with all the "sensing" gear running. Would like to see a little excess or reserve capacity but I get it - They are in business to make a profit not just to make good cars. Thanks for sharing your upgrade. Boat is NOT a car given all the extra BIG DC loads, but I have a boat and I installed 2 x Group 31 AGM starting batteries (1 for each 8.1 Liter Port and Starboard engines, and 1 Group 8D AGM battery for house DC loads and they work hard when we are aboard. I planned to change after 5 years but they are still going strong at 12 years now. Sometimes simple upgrades that cost a little more than the MFG's recommendation translate to added security, less taxing and greater longevity. Love what you did here.

It's not CCA that matters for these modern vehicles with small engines ... it is reserve capacity. Generally, more CCA goes along with more reserve capacity as well.. but not always.. have to actually check the specs on the specific battery to be sure.

CCA is all about starting power for the engine.. and the 1.5T starts snappy and puts a fairly small load demand on the battery. Whereas all those electronic systems (which are largley powered by the charging system when the engine is running) result in a modest parasitic draw on the battery even when fully powered down correctly after parking. But that modest draw on a gen5 CRV would take down a fully charged battery in about 35 days of sitting (which is why you can sometimes see the dealer service staff out on the new car lines checking and charging batteries on vehicles that have been sitting for a while).

One other factor that leads to premature battery death is sufation due to the way the dual charging system in Hondas work (been like this for a couple decades.. so this is nothing new). Effecitvely, your battery is often not fully charged when you park your car and stop the engine. It totally depends on how much driving you have done, and what state the dual charge system is in when you turn off the engine. If the battery was fully charged while driving... then the charging system drops down to about 12.4-12.5 volts and modest discharge of the battery results in the process. The dual charge system will cycle back and forth as you drive (between 12.4 and 14.5) so it really depends where in the cycle the charging system was when you turn off your engine. This can be defeated by simply driving with your lights on which forces the charging system into the high state.... and vehicle lead acid batteries thrive longest when kept fully charged. Undercharging subjects them to mild to moderate sulfation in the plates.
 

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Lead acid batteries are charged at 2.3v per cell. That's 13.8v give or take a bit. Oh wait, probably thought it was a good idea to have my CRV windows remotely open for the convenience of thieves and errant precipitation. I have a cigarette, ahem... sorry, AUXILIARY convenience outlet (must remain PC here) voltmeter. I'm a gonna slap that in and check this out. Considering the inteligence of the Honda engineers, I don't doubt this one bit!

Many thanks for posting this very important bit of intel!

Concerning engineering acumen:
Shakes head in total disbelief. We call them "fresh outs" for a reason.
A flooded cell 12V battery may peak charge to 2.3V per cell.. but it won't hold that. As soon as you pull the charge and let it sit.. it will fairly quickly loose the "float" and setting out around 12.7 to 12.8. I personally have seen this effect when I put my CRV battery on my NOCO smart charger, and when tested my battery still shows 120% of rated CCA at full charge and battery voltage settles at 12.75 once the float charge bleeds off .. so the battery remains solid.

If you look up battery charge level charts for vehicle batteries... you will find most show 12.7 = 100% charge and 12.4 = 80% charge. So.. what Honda does is not unreasonable with their dual charge system.. but with ever increasing standby parasitic currents in these modern vehicles.. they are going to have to abandon that at some point, or put in batteries with much larger reserves. They already have moved to an H5 battery on the new Accords.. so it would not surprise me if we see H5s or similar in the next gen CRV too.

The real problem with parking your vehicle for the day with only an 80% charge is you shaved a week off your battery reserve just for the parasitics that are normal for a gen5 CRV. For the short trip driver.. it gets worse.. because they generally do not drive enough to get the battery fully back to 100% charge most days.. and as such.. slowly over a period of weeks.... the battery will be a bit lower each day when you start your vehicle.. and when it goes down to 12.2 or below... flooded cell batteries begin to sulfate their plates.. and if that persists.. it kills the battery prematurely. Yet a CRV will continue to start fine on a 12.2V charge.. as long as the CCA is normal... so some owners have silent premature death taking place on their battery but are unaware of it until it fails.
 

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A flooded cell 12V battery may peak charge to 2.3V per cell.. but it won't hold that. As soon as you pull the charge and let it sit.. it will fairly quickly loose the "float" and setting out around 12.7 to 12.8. ...
YES. I was just referring to the charge voltage. Anyway I agree totally with what you said. Excellent and well thought out post BTW.

Many moons ago I had to fly and stayed at the customers site for a month. My car was in the lot discharging from those parasitic currents you mentioned. I had a smaller version of this:

It kept the battery charged, but after 4 weeks I think it overcharged it as there is no voltage limiting circuit on the array. In my Odyssey all the accessory outlets disconnected with the ignition in off position. I would be a bit hesitant to recommend this as a solution to the problem we are discussing.
 
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