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Has anyone replaced their 51R with a larger battery?

44282 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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Maybe this explains it:
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Yep... hot weather is a primary failure accelerator on batteries... followed closely by being in a persistent undercharged state (ie: below 40% of saturation charge).

1) The amount of charge at full charge actually declines with temperature in flooded cell batteries.

2) Hot weather tends to cause evaporation of the electrolyte as well... and so the cell electrolyte in each cell needs to be monitored periodically, and topped off with a little distilled water if the levels are low.

3) Hot weather tends to also sulfate the plates a bit faster as well, and plate sulfation is slow persistent killer of all batteries.

All of the above becomes a real problem for the infrequent or short trip driver... since the battery will often not be fully recharged after a drive.

And NO... a bigger battery will not change any of the above. People keep pressing this theory but it is simply not factual, and goes to a misunderstanding of how flooded cell batteries actually work. All a bigger battery does for you is give you another 20-30% of reserve charge (good for about 10 extra days on a gen5 CRV before the battery is dead, and the extra CCA you get from a bigger battery is wasted on a CRV engine. Better to just put a higher quality 51R in that gives you more reserve capacity charge in the same footprint.

An AGM battery will address some of the issues with heat better. , but they too have their own idiosyncrasies to deal with as well... so you need to know what you are buying and what you are not. In my view.. AGMs do not provide enough benefit for the additional cost required. Better investment to simply buy a premium 51R which will have better specifications than the stock OEMs, and most after market 51Rs.

Of course there is a school of thought that just ignores the battery, then complains when it dies before it's expected life span too. :D
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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.
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.
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Unsure what group but 450 cold cranking amps and A 57Ah battery with a notification for start stop systems. I do believe that keeping any battery over 80% charge is essential for long life.

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Thanks for sharing.

I see it is labeled as a Group 4A. First time I have seen a Group 4 battery in a Honda. Group 4s are classified as heavy duty commercial and special tractor batteries, and are available in both 12vdc and 6vdc. The "A" classification is probably to note it is specified for Automobile use.

My guess is that this battery has more robust plates, to account for higher loading of start/stop cycles in 2020 CRVs. The CCA is low compared to larger batteries, but pretty close to the same as a 51R. It does however have a 57amp/hour reserve capacity, making it's reserve capacity ~ the same as the Group 24 Batteries Honda puts into all it's V6 vehicles clearly this battery is designed for numerous starts over time due to the auto start stop feature. A 51R by comparison has a reserve capacity of 40-45 amp/hours.

It looks physically very much like what Honda now puts in new generation Accords, and now Civics (both of which have a 1.5T engine)... which is labeled as an H5 Class battery. H5 is similar to Group 24 in CCA and reserve capacity.

Does anyone know for sure if this battery is also in the non-hybrid 2020 CRVs? I ask because this battery may be present for the hybrid platforms in general... rather than specifically for auto start/stop. Or perhaps the new 2020 1.5T CRVs come with an H5 as they do in Accords and Civics.

It will be interesting to see if this battery group class = fewer complaints about early dead batteries. Time will tell. I bet this battery is on the expensive side of battery pricing to replace though.
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Like I said in my original post, I am looking for greater endurance. 30% greater endurance seems significant to me.
It looks significant on first appraisal, but it really isn't. It is one more week of a CRV sitting idle before the battery depletes. To me significant would be a battery with a 70 to 80 amp/hour reserve capacity.. but that would be a huge battery as amp/hours correlate closely with physical size and mass.

If I were to upsize my battery on my CRV.. I would put the same battery Honda specifies for the Accords and Civics now ---> Group H5.

But in reality... maintaining your battery through monthly integrity checks using a consumer battery tester, checking electrolyte levels twice a year, and putting the battery on a smart charger maintainer once or twice a month will do more to prolong battery life than installing a larger battery. Even a larger battery will fail early if you literally ignore it and never check and maintain it on a regular basis.

But, as I always say.. your vehicle.. your choice. :) A group class upsizing is not hard to do, you just need a different tray and careful check to insure it fits under the hood and in the location where the battery is placed.
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Its also interesting that the newer style battery is constructed more like a deep cycle battery, thicker plates and lower CCAs for more durability and extra reserve capacity. This may have been something brought up before, but shot down.
It does have a different design profile than the classic vehicle starter battery, but it better not be an actual deep cycle battery design.. because generally those perform very poorly as starter batteries for motor vehicles.

The one advantage to more robust plates is they can take the surge cycles better, AND are more mechanically sound so they should suffer less from mechanical shocks that are common simply from driving a motor vehicle on a variety of road surfaces.

It is probably a sound path for vehicles with auto start/stop and with so many manufacturers moving in that direction.. it will likely drive a shift in battery designs by the big producers.

Thing is.. lead acid flooded cell batteries are inherently unreliable compared to the rest of a modern motor vehicle. And changing the design as the needs of vehicle manufacturers change will just introduce new weak points of failure (yet to be characterized in the field). The 51R is a poster child example of this in action..... designed and produced to reduce weight and space needed in the era of compact and subcompact motor vehicles with small engines that are easy to crank... yet carries the liability of thinner plate design and less actual amp/hrs of reserve charge capacity.
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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.
There is a group class in BCI = 4 Different alpha suffixes then sub classify the battery for a particular application. For example... Group 4 batteries appear in the BCI tables for both 6v and 12v variants.. and are differentiated by a different alpha character to the suffix. The "A" suffix is probably new and as such may not show up in many BCI tables posted on the internet yet... but that will change as the battery class proliferates in consumer vehicles and tables get updated.

The key characteristic of Group 4 = classified for heavy duty use, historically for tractors. So.. I imagine the battery companies simply leveraged that core design and modified it from there for consumer motor vehicle use.

Group 4 should perform better long term in an auto start/stop vehicle by virtue of it's heavy duty design, compared to the big H5s Honda quietly slipped into newer Hondas sporting the 1.5T in the last couple years. I like the H5 battery class a lot.. and have been very pleased having one as the stock battery in my wifes 2018 Accord with a 1.5T.

I do think the Group 4s represent a better battery group for repetitive stop/start cycles of newer vehicles. The thing I do not know though is how a Group 4 battery will perform in terms of life expectancy if the owner always disables the auto start/stop feature each time they drive. Time will tell.
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When it comes to starting and deepcycle batteries its not an either/or design.

It's a sliding scale from one design to the other based on needs of the application. As long as the CCAs and battery design meets the need it can be used for starting.

Using a small and light battery with high CCAs to reduce cost, weight and increase mileage by an imperceptible amount may work well in some applications.

As more demands are placed on the battery from software that runs even when the car isn't running the battery design needs to transition to the deepcycle design side.

This will increase cost and weight, but is a more correct design for this application.

The relatively low CCAs needed to start these engines means you aren't exceeding or stressing the DC batteries lower CCA rating (assuming its sized correctly).

This appears to be exactly what Honda has done in transitioning to the different battery.
FACT: Deep cycle batteries make poor starter batteries. They lack the CCA characteristics needed for quick starting of motor vehicle engines.

FACT: Starter batteries make poor deep cycle batteries. They lack the ability to recover from a deep discharge cycle without damage to the battery integrity.

The two classes of batteries serve widely different purposes, and as such are designed differently. There is a reason that the two different classes of batteries exist.... for different applications. Because the needs are different, so the design characteristics are also different. Using one in an application where the other is a better choice = poor design decision.

In the case of this new battery in the 2020 CRVs... clearly the need to address a much higher than normal number of start cycles over time (due to auto start/stop) puts a different demand on a battery design. And again.. what the 4A design is based on is the BCI group 4 class of batteries designed to serve the long standing heavy duty demands of the tractor class of vehicles, which are designed for lots of start and stop cycles in the use of vehicles like tractors. Deep cycle batteries on the other hand evolved from the need for long idle time and continuous power and current delivery in marine vehicles AND the ability to be completely discharged without permanent damage to the battery (ie: boats, RVs, etc).. where actual frequent and efficient engine starting is very much a secondary consideration.

If Honda just needed more reserve capacity in a battery (which I think we all agree is desirable).. they could have just stuck to the H5 they have been using in Accords and Civics successfully in recent years. The fact that they chose a battery group historically associated with heavy duty tractor class vehicle use means something... and I think that "something" goes to the higher demand in number of expected starts/stops over the life of the battery in the new 2020 CRVs.

The vote is of course still out on if this new 4A battery represents a general improvement for CRV owners, or for that matter any owner of a modern vehicle with auto start/stop features. Time will tell. It does have higher reserve capacity (which is good for serving normal higher parasitics in modern vehicles). And it does not provide the high CCA of a starter battery of the same physical profile (and that is fine because more than 400 CCA is a waste on the small engines Honda is using these days).
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Ok but what will fit in the Gen 5, does not look like much room with master cylinder there on 2.4. That is the question!
I cannot comment on a gen5 with the 2.4L in it. Show us some photos, or wait for an owner with a 2.4 who has upsized their battery. :)

But for gen5s with the 1.5T there is clearly room for a Group 24, or a group H5... and you may or may not need a new tray for these (need to actually measure and check). And of course this new 4A we have been discussing fits.... as it is the standard in the 2020s.
Hi, i replaced mine with the 35 size last week. I took out the plastic cover and tray that makes the small battery fit. I used the same top clamp and terminals from the old small battery. It’s perfect!
Did you get a thermal sleeve for it and install that? The OEMs come with one installed at the factory, but it won't fit a group 35. If not.. best to do so. It helps the battery where temperature extremes are concerned.. which helps with battery life. .
I had my battery die while flushing brake fluid. It would not take a charge. I removed it popped the caps off topped up the low cells. Bench charged it and didn’t have any problems with it 6 months later. Keep in mind mine has 80k miles on it and has been used fairly regularly since launch date. I have had bad luck with new aftermarket batteries before once your on a winning streak it keeps on coming.

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Yeah I think a lot of battery failures in CRVs are much more about the electrolyte drying out, vs actual battery integrity failures. :)

Consumers have been lulled into thinking these "capless" flooded cell batteries are maintenance free. But they do have caps, and you can check and top up the electrolyte, and should... once or twice a year.
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Thanks for posting this link. Others have mentioned this two stage charging, and have even figured a way to trick it into charging at the higher rate (by turning on the headlights during the day).
Yep.. I always drive with my headlights on. It helps insure that the battery gets properly topped up and stays that way by avoiding the low charge mode which actually depletes some charge from the battery.
Is there a post that shows the steps on how to install a NOCO Genius 5 smart battery tender ? Thanks.
Depends on how you wish to use it.

Some people permanantly install it under the hood, and then run a weather proof power port connector to an exterior mount on the vehicle (or simply under the hood). Some, like me, wired in an SAE port (since NOCOs come with SAE friendly connectors) and just plug the NOCO into that port outside the vehicle. Some just old school it by lifting the hood, and connecting the NOCO clips to the battery when they wish to do a saturation charge cycle.

As for videos... NOCO has their own youtube channel and that would be a great place to start for your video needs. Link --> NOCO If you want to do something "custom" with how you hook or install a NOCO in your vehicle.. that will require some specific searching on google.
Costco battery is great. We replaced the original battery with a Costco battery and it worked great for 7 years. Just put in another Costco battery!

I agree.. I have used Costco batteries as my replacements for many years now.

They rebrand, change suppliers from time to time and change their warranty terms from time to time as well .. but honestly I have never had to replace one before selling my vehicle and moving on to a new vehicle.. and I keep my vehicles for 10 years. So.. OEM battery, I have consistently gotten 4-5 years before replacing and the Coscto replacements still tested good years later when I sold my vehicle (ie: 5-6 years after installing).

Besides... Costco generally has competitive full replacement warranties, and Costcos return policies are also very customer friendly.
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???
He is being rhetorical... because he hates the 51R group class and makes a point to demean it every change he gets. :)
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Listen to this...if I have no Costco membership, but buy one and a battery and don't renew my membership, is warranty not going to be valid unless I renew? thx (i believe I will have too.)
As a long standing Costco member, I can't answer your question for sure. But from my understanding of Costco return policies.. you must be a member to receive return or replacement service from Costco. I do know that car batteries are sold under a product specific limited warranty, and it probably varies by state as to how that legally protects you with a membership store like Costco. Since you can literally buy a membership and cancel it anytime for a refund.. what you propose amounts to deliberate gaming of the Costco business model, which I do not condone.

You can check out this blog that covers Costco's return policies over time. 12 MUST Knows About the Costco Return Policy Before You Shop

That said.... it would be fool hardy in my view to buy a Costco membership just to buy a car battery. There are other sources for good quality batteries (since there are only a handful of actual battery manufacturers anymore in the US, they are all sourced from the same factories and then branded for the selling merchant). The advantage with Costco is their customer friendly policies and excellent prices and warranties on items they sell.

If you see no real value in a Costco membership as a whole.. seek a battery somewhere else would be what I would do.
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It would be really great if someone active on this forum had both a Gen 5 CRV with the 1.5 T engine and a Gen 10 Accord with the 1.5 T engine.
That way we could find out if the Accord's Group 47/H5/L2 battery will fit in the space allotted to the CRV’s 51R battery.

But what are the odds of that?
I have both a gen5 CRV and a gen10 Accord.

The area around the battery is different on the Accord compared to the CRV. The CRV is less cramped, as can be seen in your photos. Then again.. the Accord already has an H5 in it.

ANY battery that will physically fit in an Accord will easily fit in the CRV. Width on the H5 is the only real consideration, in determining if you even need a new tray or not.

51R 9.374 x 5.0625 x 8.8125
H5 9.565 x 6.9375 x 7.5000

Honda puts insulator sleeves around their batteries, and you would need a different one for the H5 for sure.. if you want to install a new battery with one (recommended, but not absolutely necessary).
In an Odyssey forum, someone told of an Interstate dealer who intentionally left out the box, claiming it trapped battery heat and shortened battery life. Then again, mechanics sometimes think they know more than they do. I'll go on the assumption that Honda wouldn't spend the money on that box it they didn't feel it is necessary.
Said mechanic is an idiot. An insulating sleeve will prevent thermal intrusion from the hot engine bay penetrating into the battery to begin with. And batteries on modern charging systems do not over-charge or self-heat the battery to any level that would degrade the battery life.

Aftermarket accessory manufacturers even make small heating pads for starter batteries for use in cold weather conditions to help keep the battery from suffering damage due to extreme cold.

I agree with you.. Honda spent money to put the sleeves on the batteries for a reason. Always cost conscious in the market segments they produce vehicles for.. Honda never spends money on a part for nothing. The only bad part about Honda is they do not generally communicate the "reason" to consumers very well on the various things they engineer into their vehicles.. which leaves room for wild speculation, conspiracy theories, and of course idiot mechanics who always think they know better than Honda (or any manufacturer). Please Note: this is not a dig on mechanics in general... only those that insist on telling customers foolish things.
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Been keeping smart chargers on both our Hondas for the last several months, given we only drive maybe once a week, and it is short trips. This includes a CRV with a 3 year old 51R and an Accord with 2 year old H5.

I ran my monthly maintenance checks on both batteries yesterday. Both tested good, with normal plate impedance (THE best measure of a batteries integrity) and CCA results that showed spec-CCA+~20% on each.. which is what they have tested at since they were new. I am patiently waiting to see the plate impedence tests begin to report increased plate impedance and CCA begin to decline below the spec on the battery. So far.. both have stayed consistent with the first readings on them when they were new.

Further.. I have done self discharge monitoring of them both earlier in the year... and both the 51R and the H5 have similar self discharge characteristics.... with the H5's only advantage is that it has ~ 30% more reserve capacity than the 51R. Notably though.. I observe the calculated self-discharge on the H5 (this is the inherent bleed off of charge in the battery, NOT the drain due to parasitics) is a bit more aggressive than in the 51R.. but that is simply one data point on each battery group.. so I don't draw any objective conclusion from the observation.

Beyond a certain threshold (you certainly need a battery with the capacity to properly start a vehicle.. and for Hondas with small engines.. that means ~400 CCA starting ability) ... the size of battery you put in a vehicle does not give owners the kind of additional security that they seek with a larger battery. Proper monthly checks, maintenance, and keeping a battery above 60% capacity is what ensures maximum life of a battery.

There is certainly no harm in putting a larger battery into a vehicle... just understand what you are doing, and what you gain.. and not assume that because a battery has 650 CCA that it is a better battery that will last longer in your CRV. CCA above 450 is a waste on Honda's new small engines, which is why the new battery being installed at the factory by Honda on the 2020s looks like a good upgrade. It does not provide higher CCA than a 51R, but it does clearly have more robust plate design, more reserve capacity.. and as such.. will serve the extra burden of auto start/stop well I think.
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Out of curiosity, have you done any write ups or anything on how you are testing and tracking your batteries health?

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).
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From what I've been told by my brother who is the Parts Manager at a Honda dealership, the Honda-branded batteries are crappy, no matter what the stated warranty is. How long a battery lasts has very little to do with it's group size for the most part. If it were, my Fit batteries would be dead in 2 years or less as they use the 151R battery which is about 2/3 the size of the 51R battery. No, since I switched to the Interstate brand (obtained from most Firestone and Interstate dealers) I've had typically 4-5 years of life from them. The quality of the battery is the important issue. Now I understand that Costco has switched to a Costco-branded Interstate battery which can only be warranted at Costco, but their warranty is lower than the premium Interstate battery so the choice is yours on which to get. Frankly, I always get the premium one (usually designated as MTP rather than MT).
The Costco warranty is currently 3 years... used to be 4 years. And NO prorate crap either. The last Costco battery I had in my Hondas... which was an Interstate battery (or Johnson Controls.. as Costco sources from both big suppliers) as I recall... was 5 years old when I let go of my 2008 CRV and still working fine.

You are correct that Interstate Premium batteries have a longer warranty (as do the "premium" or "gold" models from the few other big battery producers) ... but you also pay more for them too. You get what you pay for... even with starter batteries. You literally cannot beat Costcos prices on Batteries.. anywhere.. in terms of price vs performance and longevity.

If more people simply properly maintained and monitored their batteries periodically.. most owners would easily get 5 years out of their battery.. even the OEM from the factory. I stand by my view that most (not all... just most) early battery failures are due to dried out electrolyte... because the owners literally NEVER check the electrolyte levels of their batteries. Flooded cell starter batteries ARE NOT maintenance free batteries.
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