Where did you read that "Honda Dual Mode charging circuitry (attached to the battery) is pre-programmed for the RC value of the original battery size/type and if you substitute a different RC battery, over/undercharging might occur." I think all voltage regulators change the charging voltage based on condition of the battery and amount of current being drawn by the vehicle's electrical devices. They vary the voltage from between about 12.5 volts to around 15 volts. Usually the voltage regulator is inside the alternator housing, or near the alternator. It is always attached to the battery electrically, but not usually physically. Many times one battery size may have different electrical characteristics depending upon brand, and upon a brands "class" such as regular, or "gold." The "gold" class will have greater Reserve Capacity. According to my understanding, Reserve Capacity is not even a real battery characteristic, but is rather a marketing term. The real characteristic is the battery's ampere-hour rating, and whether it is deep cycle or regular cycle. The the marketing ranks will come up with a RC based on the ampere-hour rating. Ampere-hours are the number of hours that the battery will supply a certain number of amps, before it becomes too discharged to easily do much work. It is figured at a certain ambient temperature. The more ampere hours the more hours a battery can function, at a specified current in amperes,, before it needs to be charged up again. The more ampere hours, the longer it takes to charge the battery fully, once it has been discharged. RC is basically ampere hours figured at a differernt ampere rate than ampere hours. For example if it supplies 1 amp for 100 hours, it will have 100 ampere hours. It will put out 25 amps for 4 hours – approximately. For various reasons, slightly less hours. .So then its RC rating will be 4 hours. This is all approximate as changing in temperature and discharge rate will affect the actual number of hours at 25 amps rather than 1 amp. But basically it is just a different way of providing the same info as ampere hours.

 

We were taught at UTI that Honda, Audi, BMW, and MB cars with controlled charging circuits used the RC value of the battery as part of the charging curve. In general it was taught that it was a like for like replacement for the battery's RC value. If you have other details - please include them here. I'm no longer working in automobile repair and these items may have changed.

 

I installed the 51R battery a few months ago to replace the original 151R.

I noticed immediately that the car starts much quicker, almost immediately, whereas with the 151R battery, it took a few seconds.

I wonder if installing the 51R takes some load off the starter, and would actually prolong starter life over the smaller battery.

 

Google found several references to Honda's dual mode charging system and these pages they say the same thing that you said, about how the dual mode charging system works. However I can't find anything in these articles about the dual mode system. that says you have to use the same RC battery, with it. This may be a separate issue. There is nothing in the articles that relates to the capacity of the battery. They say the dual mode system is a fuel-saving system, it just means that the ECM will cause the voltage regulator to almost stop charging under the conditions described, and go into a charging mode that resembles a trickle charger, because this uses less gasoline. The alternator will require less force to turn it when it is putting out less voltage through the voltage regulator, and therefore engine will not be working as hard to turn the alternator, and not using as much fuel. The battery is temporarily not getting charged, it is basically being just maintained, as if connected to a trickle charger.

here might be something else though, other than the dual charge system, that works better with an orig equipment sized battery.

I did notice that there is nothing in the owners manual about replacing the battery with an exact equivalent battery. The manual says use honda branded brake fluid and definitely use the correct Honda CVT oil, and use Honda branded coolant, but nothing about using a Honda branded exact equivalent battery.

Note that, except for "engine is being stared," the conditions for putting the regulator into low mode are AND conditions. All of them have to be met to put the regulator in low mode.

Therefore, If there is a load on the system more than 15 amps, OR the vehicle speed is above 45 mph, OR the engine speed is above 3000 RPM, OR the coolant temperature is above 167 deg F (which it always is, after the engine has been running for about 3 minutes) OR the air conditioner compressor is on, then the ECM will put the regulator in normal charging mode. Basically it looks like only when the engine is cold, will the regulator go into low mode. On my car what I observed is that if my car is cold when I start it, that the coolant temp very quickly goes to up about 167 deg F, it takes about 5 minutes, at which point the blue coolant-cold light goes off. Then a minute or 2 later the coolant temp is up to 180 deg F, and it always remains above 180 deg as long as the engine is running, whether the car is idling, or the car is being driven.

 

Not true as I drive that amount and still the batteries go dead, this never happened on the Civic it replaced, nor on my Passport, Accord, all from the same location and usage.

 

Not true as well as not practical for those of us with a short commute. I am 1 mile from my basic grocery store. So when I am working hard, I am limited to lots of short trips.

 

After 5 years 9 months, my 2016 Fit 6MT battery was showing signs of trouble: Clutch in, turn key, hear a click but the starter would not turn. Not even a slow, laboured starter sound, just nothing. Clutch in, then out, repeat, and it would eventually start. I'd trickle charge it overnight and it would start the the next day, but a few more starts and it would return to the previous behaviour. it was time for a new battery.

The 51R is a much bigger battery, but it fits snugly in into the allotted space, like it was designed for it. My local store, Canadian tire, told me that if I bought the 51R for my Fit they would reduce my warranty to 6 months. I told them I have a Civic 2006 that uses a 51R. Dumb policy. The 151R costs $144CAD 360CCA 3 yr warranty, while the larger 51R costs $130CAD for 450CCA 3 year warranty, or $146CAD 500CCA 4 year warranty. I opted for the 4 year warranty.

The battery switch was pretty easy and took me 45 minutes. The 51R fits like a glove. I had to cut the odd shaped battery tray with tin snips and some side cutters. The finish was not the smoothest, but no one will see it. The hardest part was that the positive cable was very tight and needed wiggling to loosen. You only need a 10mm open ended hex wrench. I liberally added dielectric grease to both posts. The radio was unaffected and I did not lose any station info. The radio graphic that I uploaded was not lost. Fuel data such as odometers and such were also unaffected. The new battery was not topped up, so I trickle charged it for a little over a day.

Overall, this was pretty easy. I took my time. Nothing broken, the car survived, I just wonder who was the engineer that approved the Fit's dinky 151R? At least they left enough space for the 51R, thank goodness.

 

It's cheaper, it's lighter, and it works.

 

Thanks for posting this.

 

You might have been able to use something like a soldering iron to melt the plastic more cleanly and more easily instead of having to cut it.

 

After loosening the positive clamp from the positive post of the original battery, using a 10mm hex wrench, I had trouble lifting the cable up and off of the positive battery post. If I recall correctly, the cable was just too stiff. To solve that problem, I detached the cable clamp from the cable, by loosening the 12 mm hex screw that held the cable clamp to the cable. If I recall correctly it was a screw with a 12mm hex, that screwed into a captive nut at the bottom of the screw.

Another difficulty I had was removing the yellowish nylon clamp that holds the positive cable conduit above the battery. I had trouble removing this nylon thing from the top of the left j-hook, I wasn't able to pull it straight up and off of the j-hook, as some people have said to do. Instead, to remove the nylon clamp from the top of the left j-hook I loosened the nylon 10mm hex while holding the remainder of the conduit clamp from turning. Putting the nylon conduit clamp back onto the j-hook was accomplished by simply pushing the 10mm hex straight down over the threads of the j-hook.The shape of the "barbs" below the nylon 10mm hex made it easy to push the nylon hex down onto the threads, but hard to pull it up off of the threads.

 

Any bet the reason that Honda provided most Fits with 151R batteries but left space for the larger 51R battery, was that new Fits or Jazz's sold in arctic climates would come with the larger battery.

 

No, I think they got a good deal on those larger battery trays and took advantage of it.

 

I'm glad you figured out how to remove it. Taking it slow and figuring out things one at a time is the best approach. If something is tight, you can often pry it loose. I remember the old days with just a large clamp and a large nut holding the clamp on.

 

Replaced my battery last month with the larger Costco 51R. According to the date code the Costco 51R was only 1 month old. Relatively easy project, took about an hour.


Honda OEM 151R battery compared to the larger Costco 51R battery which I bought.

Tray.

Tray after using a soldering iron to cut away the side to accommodate the larger battery. Had to be careful not to breathe in fumes from plastic.

New battery mounted as far to the left as it will go to give about a 3/8" air gap between the battery and the heat sink on the right.

Like I said, not a difficult project and many others have done it before me.

 

Thanks, woof. It's raining in California today, but I might do the battery replacement this week. Gonna cut the plastic tray with a hack saw (just cause I'm too lazy to buy the correct tool for the job). We have Costco here, but I'm not a member. Finding a battery isn't as easy as it used to be.

 

Has anyone noticed any issued with using the larger 51R battery (that fills in the wider air gap between the ECM heat sink and the battery) from a battery life or ECM issue?

 

It took me only a moment to figure out how to remove the positive cable from the battery, to see how detaching the clamp from the cable, by turning the screw with the 12mm hex head, would enable me to lift the cable out of the way. But the nylon fastener that secujres the conduit to the left j-hook – I spent maybe 2 years looking on line for tips on how to remove nylon fastener from the top of the j-hook. I saw one or 2 youtube videos that said to just pull the thing off of the j-hook by pulling straight up. But id didn't come off that way. I pulled fairly firmly, but it didn't come off. It seemed to me that I would not be able to pull it up and often the threads, without damaging it. Also, looking at it, it appeared to me as if it had "barbs" that enabled it to be easily pushed down, but hard to pull up. Finally I figured out that you could unscrew it by turning the 10 mm hex counter-clockwise (lefty loosey) – but only if you held rest of the fastener from turning along with the hex. For 2 years, it just didn't occur to me to do it that way. I was all set to just cut the stupid thing off, and then after the new battery was in, use a simple zip tie to hold the conduit to the battery clamp, in order to keep it from banging against the clamp and wearing..

 

Fit made in Japan = Comes with tray that fit the 51R battery, though they only provided you with the 151R. When you replace the battery with 51R, you won't need to cut/modify the tray.

Fit made in Mexido = Comes with tray that fit the 151R only. 1) Modify/cut the tray to fit the 51R 2) Find/replace the tray that allows the 51R without cutting/modifying to fit.

 

Yeah I had heard that there was a larger tray out there and I kind of suspected it was for the Japan market. I wonder though which battery the Japanese actually got in their cars to go with those trays.

Incidentally, watch the first minute of this Scotty Kilmer video where he talks about OEM batteries and tires, specifically mentioning Toyota and Honda: