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Has anyone replaced their 51R with a larger battery?

44285 Views 134 Replies 41 Participants Last post by  BobInPa
I’ve had it with the 51R battery size chosen by Honda for the Gen 5 CRV. I am on my second Honda battery, the first one was replaced under my New Car Warranty in September 2018. I know that it is totally my fiscal responsibility to replace my current battery, so I’m not going to mess around with another Honda battery. My 2017 EXL has been jump started 7 times in the last 3.5 years, way too often as far as I’m concerned. Actually each of my Honda batteries made it one whole year before they started failing, so it is really 7 jump starts in 1.5 years. So I want to replace my 51R battery with a larger battery with greater endurance.

Has anyone replaced their 51R with a larger battery that does not require any modifications to the existing battery containing hardware? Hardware like tie-downs, trays, cables, hood, etc.

I know this subject has been discussed many times before in the last 3.5 years but I don’t remember reading an actual answer to my question.
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Yup. The 51R is a lawnmower battery. It comes standard in many riding mowers, and the CR-V. In this case, bigger does mean better. I just finished upgrading my '07 to a Group 24F. The write-up is here: Gen 3 Group 24F Battery Upgrade .

Of course, my '07 is going to be a little different from your 2018. You can find all you need to know for your late model V in this main thread here:

Larger Group 24 Battery Install .

It will not void your warranty, and it will not harm your alternator, which cannot tell what size the battery is, and will behave normally. I went with an AGM battery. My two previous 512R's lasted less than 1.5 years each. I'm also installing a NOCO Genius 5 smart battery tender. Since I retired, I don't drive as often, so I will keep this plugged in to 110v, and it will keep the battery healthy all the time. All I have to do is unplug it when I go out, or else get a really, really long extension cord. :cool:

Actually, I think the install is easier for the Gen 5 than for my Gen 3. Read through the above thread's 14 or so pages and you'll find info for Gen 4 and 5 installs that should give you all you need to know. It does require a little work, but it's not brain surgery. I even used Odyssey parts to make it all officially Honda issue. Good luck, and let us know what you decide to do.
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Of course you can put any battery in your vehicle that you like, your vehicle, your choice. :)

But a Group 24 (or similar) is not going to buy you much in your gen3 CRV. A) you do not need the extra CCA, so that is a waste. B) a 24 only gives you about 25% more reserve charge capacity. C) gen3s have pretty low normal parasitic.. so the only thing you really have to deal with in a gen3 is the normal slow self-drain characteristics of the battery itself and the fact that every battery made is a ticking clock that ticks down persistently until it fails some years after the electrolyte is activated.

A gen5 benefits more from installing a larger battery, simply for the extra reserve capacity, which can extend the period of time before a sitting CRV depletes it's battery due to normal power down parasitics. But even then, the difference is small... 40-45 days idle vs 30-35 with a stock 51R installed.

Early battery failure is much more about allowing a battery to sit at a persistently low charge state, which accelerates plate sulfation + lack of any periodic checks and maintenance on these batteries.. which are not actually maintenance free. This is true.. regardless of the size battery you choose to install. Which is why periodic maintenance checks and use of a smart charger is such a benefit for motor vehicle battery life expectancy.
It will buy me what I want (along with the NOCO Genius 5 smart batter tender I am installing with it), which is better tolerance for sitting between trips without becoming too critically discharged, and more reserve, since I am planning an audio upgrade that will include amps. I also went with an AGM this time, my first. Hopefully, together, the new setup will work better for me. I do have to deal with high summer temps and infrequent trips, so I can use all the help I can get, especially when the audio upgrade is done. Also, Those "on-paper" numbers (40-45 days idle vs 30-35) are a fantasy here, where my 51R's (all 3) would last no more than 4-5 days to maybe 7 idle before needing a jump. That's with no measurable parasitic draw, an otherwise healthy alternator, starter, and electrics, and using top-shelf quality batteries. I suspect it is just down to the much lower quality of current batteries being produced today. Even the big-a** batteries in my '91 big block F250 never lasted more than 18 months at a time. I don't know anyone here who isn't experiencing the same issues. Our tropical heat is a big factor, but I remember them lasting much longer in the good old days. I suspect makers have tripled their sales since they adopted the "new" lower quality in the last 5-7 years. It hasn't made them cheaper, though, has it? Battery life just isn't what it used to be.

My only concerns with the new AGM are whether it has better heat tolerance and better quality. I also hope the upgrade helps to preserve starter life. For the price, I certainly hope so, but only time will tell.
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Interesting! I l looked up the 4A designation and it shows a small motorcycle battery. According to the Advance Auto Parts site, the correct battery for the 2020 1.5Lt is the Group Size H5. Most of the online sites do not yet show a listing for this vehicle, and the ones that do show the A4, which is not a BCI number as far as I can find, and also not the correct battery for the car. I'm sure the A4 designation has some significance, but all else I've found shows the Group SIze H5. THe H5 appears to be a bit smaller than the Group 35 but very close. Same on specs.
Here's a link: Advance Auto Parts - Down for Maintenance .

That's the only listing they showed for the car. Still, a considerably larger battery than the 51R.
No, the original battery is sufficient. To install a bigger battery, you need to get a bigger base plate to house the bigger battery. I am not sure it is worth the cost.
Actually, it isn't, for many here, including me. The group 24 size battery tray, box, hold down clamp, etc., used for the 24F swap runs about $30 or so for the kit. My new 24F AGM battery has 75% more reserve than the tiny 51R lawnmower battery.

I haven't seen anyone yet post having done the 24F swap for a Gen 5, but it has worked for all previous generations. Should be good for all Gen 5's with 51R's in them. The newest models with this larger battery will likely render the swap moot.
Is there a post that shows the steps on how to install a NOCO Genius 5 smart battery tender ? Thanks.
Yes sir! Right here: Gen 3 Group 24F Battery Upgrade . It is included in my Gen 3 battery thread, right after the battery. Of course, it can be done any way you want, but you'll see how I chose to do it.
Is there a specific tray kit for the 24F swap or is that something generally available at auto parts stores? I have a 2018 CRV EXL
There is. In my thread on the Gen 3 upgrade I did I have all the details listed on all that - here: Gen 3 Group 24F Battery Upgrade .
The parts are OEM Honda, from the 2014 Odyssey. I have them all listed there, along with a link, prices, and an explanation. For your 2018 the process will no doubt be a little different than it is for the Gen 3, so please, when you do yours, post that in the main battery thread with a couple of pictures and tell us how it went. That main thread is here:

Larger Group 24 Battery Install .
We don't have many lawns here in southern Arizona, but when i lived elsewhere, i mowed plenty of lawns. I'm trying to figure out how a lawn mower can use a battery as big as the one in a CRV, or any battery for that matter. Well, I have seen some rechargeable electric mowers, but???
So, you've never seen a riding lawnmower? They generally have a 10-20 hp engine, are electric start, and have a belly mounted mower head. They come in many different sizes and capacities. The average and larger sized ones will have this same 51R battery in them.
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Not much to connect a maintenance charger to a battery and there's a few different ways to do it. I just connect a SAE fused pigtail to the battery and plug the charger in when the car is not in use. If you do it this way the only thing to know is that the nut on the negative battery clamp is not meant to be completely removed, they distorted the threads to prevent this. So to put the pigtail's ring terminal on the negative clamp you need to cut the ring. Open the ring up and slip it under the nut.
No, That's not necessary at all. Just turn the nut off, it will repair the threads as it comes off, as they are just slightly staked. Do NOT cut or split the ring terminal. I just did this two days ago on mine, and have done many, many others. It's easy. Splitting or cutting the terminal will likely lead to it corroding prematurely, plus it looks sloppy.
captainbeandip and williamsji know what they're
Welcome to the forum! Actually, those numbers may be true for the minimal low-price batteries, but I went from a 51R with 410 CCA to a 24F AGM with 710, which is more like a 75% increase, not 25%. But the real point is that the 51R is simply inadequate for many of us, and more is always better. Especially when you live in a more extreme climate, and/or plan an audio upgrade, like me, and similarly don't drive daily. The numbers don't lie, and neither does the result.
The thing we are discussing here is the fact that. for many owners, the CR-V's Group 51R battery is simply inadequate, because it is too small. This has been a common complaint for the entire run of CR-V's all the way back to the beginning. Honda chose to install a battery that is just not large enough to be dependable. It's not about battery condition, or care. It's about the fact that many owners need more from the system, because of their particular driving needs. I'd go so far as to say I consider it a defect. After all, in my case, I took good care of 3 Group 51R batteries in a row in the space of less than 2 years, and all 3 went bad. At that point, doing the same thing again and expecting a different result is the definition of insanity. So I upgraded.

If your situation means that you live in the right climate, and do the right amount of driving, the stock battery will probably be fine. But, if your use falls the slightest bit outside those parameters, the battery is just not good enough. If you want to keep throwing money after more 51R's, I'm sure the battery makers will appreciate it. But it will be expensive, troublesome, and will likely cost you a starter sooner too. Not to mention all the hassles of frequently being stranded, always at the worst possible times. Or, you can realize that it's just a machine, and you can outsmart it!
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There's no way to put in a larger battery without additional hardware and have the battery protected against heat and held down properly. What it came with fits the 51R and nothing larger. But why does that matter, since the cost is negligible for the extras?

We now know that the brand new 2020 with the 1.5L has a new larger battery, Group 4A/5H. That battery is essentially the same size as the Group 35 battery. What does that tell us? It tells us the earlier Gen 5 has room for a larger battery. So, to do this swap in your 2017-19, you'll need to do some measuring. I suspect the 24F might be tight. This is the picture posted earlier by Nuke of the new 2020 battery in situ:


Hmmm. Looking closely, it appears this battery has an insulation wrap on it instead of a box. Anybody else see that? If so, maybe you could get the tray, hold-down, bolts, and wrap, and just use this same 4A/5H battery.

It would be handy if someone with a 2017-19 could post a picture similar to the one above but showing their 51R battery.
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The insulating box is for heat protection, as the battery is close to the engine and the whole compartment is very compacted and full and subject to getting very hot. I'd put that box back in ASAP. They never used to cram the battery in such a tiny space so close to the engine, but they do now. Engines run hotter now too.

From what I can see in the pictures above (Thanks Bob!) there is room to put in a 24F, but I think I'd try to get the newer parts and go with the 4A or 5H.
I'm not so sure about that. Remember all the concerns about some CRV's engines not getting hot enough to provide cabin heat?

With that said, Honda installed the battery insulating box for a reason, probably a good idea to keep it there, even if one changes to a bigger battery (which in my humble opinion), is not needed.
Cabin heat is not related to and has little to do with engine compartment heat. However, even a defective engine would get hot at some point. You know, like the fact that even a broken clock is right twice a day. Heat is a byproduct of internal combustion, so that battery needs to be protected. And normally functioning engines do get quite toasty, especially here, in the summertime.
My process, regardless of the battery group or brand is as follows:

- Once a month, I use this Ancel battery tester to preform a battery integrity test, and also a charging system test and check for any leaking diodes in the alternator (a notorious source of high discharge parasitic). The results will let me know the CCA, plate impedance, and charge state on the battery, as well as confirming that the charging system is operating normally.

- Once or twice a month, I put hook up one of my smart chargers... currently using this one NOCO over night to perform a nice full saturation charge on the battery. Currently, I keep on on each vehicle 7/24 since we are not driving much at all in our household.

- Twice I year, I pop off the rectangular caps and shine a light down into each battery cell to check the electrolyte levels and top them up if needed with a little distilled water.

Though not really necessary, I also keep one of These permanently connected to each of my vehicles batteries so that I can record and monitor the charge characteristics of my batteries over time while sitting idle. It only puts a 1 ma burden on the battery, so it does not contribute any measurable drain on the battery as long as you do not keep the App that it communicates with on all the time. It keeps a record, on one minute intervals, of your battery voltage and it downloads it to your phone app when you connect to it and you can see the data logs in graphic format.

And when driving, I always drive with my headlights on as this overrides the low charge state in the Honda dual mode charging system. The low charge state of the dual charge mode in Hondas is, I believe, the number one cause of undercharged batteries in Hondas... so I never let it take over when I drive, unless it is a long drive planned. I mostly do short trips, in town though.. hence I want the charging system at 14.5vdc ... NOT 12.4vdc (low charge mode in Hondas).
I really like the Noco G5. Just got it hooked up last week to the new 24F AGM battery, and, though the battery was new and fired the car right up when installed, the Noco took about 15-18 hours to decide it was fully charged. I'll be watching how it all goes now, as this is my first tender on a car (had them on bikes for years), and also my first AGM battery. Considering what the dang thing weighs (and costs), I hope it's worth its weight in something good. :) Interestingly, I've always driven long trips with lights on, but never short ones. After this I think I'll do it your way.
You also check the condition of the battery by load testing it frequently.

This is correct maintenance for a battery, but is a routine never required in the past, so it isn't something that the average car owner has been conditioned to do.

And really isn't something that a person should need to monitor this closely.

The battery and charging system should be designed and sized accordingly to be able keep the battery fully charged, and then hold that charge for a reasonable amount of time, as in a few months, not a few weeks.

The parasitic draw on the battery from the system should be accounted for, in either a larger battery designed for the low long term draw, or reduce the load until the small battery can deal with it.

Both the charging system and battery aren't optimized for this result, their design goal was to get that last .002 mpg, and a lower cost.

The system works exactly like it was designed to, which doesn't work that well for a significant number of the owners.
Agreed. They really don't make batteries like they used to. It's almost as if they now come with a built-in self-destruct. Up to about ten or so years ago I always got 5-8 or more years out of all my batteries. After that, I have not had a single one last more than 18 months. Not one. Also the two-stage charging system. I wonder, now that they have upgraded the battery in the 2020's, if there are any changes to that system. I would hope so, as it seems to me the new ones will be more dependent on battery health.
I've heard good things about those Panasonic batteries, couldn't find one around here. Battery covers are critically important to protect the battery from engine compartment heat under the tightly packed CR-V hood. Especially with newer batteries, which simply are not the same quality of the old days any more. As long as the battery's top is open, it is not "smothered." It's the sides that matter, where the heat damage gets in. IMO the 51R is a lawnmower battery, not near large enough, but the engineering department never wins against the cost-cutting department.
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I gotcha! Nolo Contendere. When I mentioned the top being open, I just meant with no cover or anything blocking the battery's access to ventilation. The CR-V's bottom and side covers act as shields to help protect the battery from engine heat, as it is located very close to the engine in a tightly packed engine compartment. The insulation pads, both aftermarket and the ones that come on the new CR-V's, provide the same function. The only time a car battery burns/explodes (obviously not counting a fire) is when it is being subjected to a severe overcharge from a malfunctioning alternator or other major electrical issue. Just living in a high heat environment will only shorten its life.
No, but I do have some experience with batteries, having been a truck driver. Years ago I was very happy to receive a brand new tractor. It was a Mack Day cab, with the big motor and fully loaded, a very nice one. First night, I set out for DFW, with about 45k on. Got up there, no issues. Smooth and fast. On the way back I stopped for fuel at the Knox. When I was done and ready to leave, I went to fire it up and the right side battery box exploded when I engaged the starter. This one had battery boxes on both sides, as it had a full complement of 6 batteries - the heavy duty version of the truck. When I say it exploded I mean it went off like a bomb. People came running out to look. Luckily the explosion ruptured the main cables on that side. It caught fire, had to put that out with the extinguisher. I had to be towed in. $9,000 later it had a new battery box, fuel tank, one air tank, cables and wiring harness, alternator, and 3 batteries.Cause? The alternator. Brand new truck, too. I had a ruptured eardrum and a lovely headache. Never had any other trouble out of that tractor for the two years I drove it. Years later I had a new Cascadia pulled in for a week while they replaced and rerouted the battery cables due to a fire hazard issue recall. De ja vu. 24v systems can get away from you pretty quickly when they malfunction.
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Yep. The sulfur smell was strong but only after the event. Of course, it was a brand new truck - still had the plastic on the seats - so there was that smell. So it could have been there and I just didn't smell it. But it was summertime and I had the A/C going, so who knows. I'm thankful it happened after I climbed back in and had the door shut and cranked it, instead of while I was putting fuel in the tank on that (right) side. Interestingly enough, it didn't damage the 3 batteries in the left side battery box, just the 3 in the right side, closest to the alternator.

It's an odd thing that some innovations are implemented on big trucks for years before ever being seen on cars, and yet with others it's the opposite. This truck was pre-computer-age, so I'm sure the big high output alternator didn't have that, but I'd bet most of them do now, since everything is computerized, especially the super-finicky and troublesome emissions systems and computer-controlled injector solenoids, etc. But there are still a lot of truck fires caused by this stuff. Expensive!
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