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Well, I think that it's getting to be time that I replace my 12V battery. I knew when I bought the car that the battery is the original (delivered 5/02, so ~4 years of use) which would make this about the right time for recycling & replacement. This is especially important to me now that I FAS from time to time, and the ScanGauge has clued me in to just how much strain is put on the battery under those conditions.

I thought to glance at voltage before I started the engine this afternoon, which read 12.2V after sitting for 9 hours (and no FAS this morning to drain it before parking). I have also kept track of how far the voltage falls after entering a FAS, and though I haven't timed it I can tell you that things drop off pretty quickly. Sitting at a stop light yesterday with headlights on and the key in IG-II, it fell below 12V after less than a minute and got down to 11.6V by the time I was ready to start up shorthly thereafter. From what I've read, it should be able to hang on longer than that.

So what it comes to is this: I'm going to replace the battery at my leisure so that I don't end up with any unpleasant surprises. I can either go for a direct replacement or I can spring for a more expensve deep-cycle battery that might be better up to the FAS duty cycle. (I've been eyeing the Optima "Yellow Top".) Any comments on on this? Any experience with the Optima batteries vs. standard batteries would be particularly interesting.

I replaced the battery in the Del Sol in Feb. Not because it was bad but because it was oversized and I couldn't put on the battery strap that was required for the safety inspection. I got the cheapest one that Pep Boys sells and it works just fine for me. The oversized battery that came with the Del Sol was only a year old so I put it in the Outback which still had the original battery after 9 years and 120k miles. I had no problems with that battery either but I took it back to get back the core charge.

Hi Brick:

___I was on the phone speaking with Bradlee about Hybridfest 2006 plans tonight and remembered your 12V battery post earlier today. He has connections into JCI (Johnson Controls Inc. - Battery Division (http://www.johnsoncontrols.com/bg/), makers of the Optima’s here in Milwaukee) and I asked him if he could speak with the AGM experts there about a nice and lightweight AGM replacement for your Accord, my Accord, and Bradlee’s Insight as we all need them now. I mentioned the fact that us non-hybrid hypermiler’s FAS at a whim and although that does not mean deep discharge except during the winter with the lights on for FAS after FAS after FAS for an hour or so on end, we do stress our 12V’s far more then just about anybody other then those running huge current amps to Sub’s (Tom comes to mind ;)). Anyway, he said he will E-Mail those JCI experts and see what they can provide.

___While you are waiting, JCI’s Battery division’s site has a lot of info on the Yellow and Red Top Optima’s that you might be interested in reading. Tom follows the High End Stereo guys recommendations given their needs but I don’t think that is in our realm?

http://www.cleanmpg.com/photos/data/2/Optima_Yellow_Top_Battery.jpg

Red Top - 12V Starter batteries (http://www.optimabatteries.com/publish/optima/americas0/en/config/product_info/automotive/starter.html)

Yellow Top - 12V Deep cycle batteries (http://www.optimabatteries.com/publish/optima/americas0/en/config/product_info/automotive/deep_cycle.html)

___Good Luck

___Wayne

Great reply, Wayne! I look forward to hearing what the experts have to say about our application. JCI's website should keep be busy in the mean time.

Hi All:

___I just ordered an Optima - Yellow Top 51R to see how it acts given the Accord OEM 12V’s CAP is to the point I just don’t trust her anymore. Or I just wanted to try out a new high tech battery ;) It will be interesting to see how she handles extended FAS’ing with all the electronics the EX-L w/ NAVI comes equipped with over the next year or so.

___Good Luck

___Wayne

Let us know how you like it! Odds are I will do the same thing sometime this summer unless I can find a compelling reason not to.

I heard yellow tops aren't great for using as starter batteries for some reason. I don't remember why exactly. Or maybe it was blue tops. Humm. I have to look that up.

Hi Tom:

___Look it up fast as I pick it up after work in the morning.

Dual Purpose (Starting and Deep Cycle) Batteries for Professional Use

OPTIMA YellowTop is made to install and forget. No matter the conditions, be it dampness, heat, dirt or exposure to extremes in vibration or regular discharge, you can count on OPTIMA to deliver uninterrupted power. OPTIMA's ability to hold a higher voltage during the discharge cycle makes it possible to utilize more of the stored power in the OPTIMA compared to ordinary batteries. The YellowTop handles many discharges as well as re-charges without losing significant capacity. OPTIMA is also ideal for seasonal use because of its very low self-discharge rate. That means you can store your seasonal vehicles all winter without regular charging and still spring out of the starting block when winter is over.

Dual Purpose starting and deep cycling.

Lasts up to 2 times longer than other batteries.

Constant performance quality keeping your battery running at the same level even as it's being discharged.

More power in the initial 1, 3, 5, and 10 seconds of the starting process than comparably rated conventional lead acid batteries.

Ideal for seasonal use, fully charged, it can sit unused for up to 12 months at room temperature (or below) and still start a car.

15 times more resistant to vibration than other batteries.

Nonspillable and can mount in almost any position.___Possilby the same information that “All” battery manufacturers release ;)

___Thanks in advance.

___Wayne

I got the cheapest one that Pep Boys sells and it works just fine for me. Yikes! I've learned my lesson on batteries. My Boat was going through a couple cheap batteries per season. Getting stranded in a car or boat sucks! They were giving me free replacements but after 3 or 4 I spent the money and put in an Optima. I won't use anything but AGM/drycell or Optima.

Truck - Optima
Vette - Optima
Boat - Optima
Tractor - AGM "Big Crank"
Old Jet ski - "Oddesy drycell"

The HCH and new Jet ski are still on their stock batts.

hm how much did the battery cost + shipping?

I N T E R E S T I N G, but my car can still hold its 12.8 volts before starting! (after topping it up with 13.5 volts parked)

I heard yellow tops aren't great for using as starter batteries for some reason. I don't remember why exactly. Or maybe it was blue tops. Humm. I have to look that up.
http://www.optimabatteries.com/publish/optima/americas0/en/config/product_info/automotive/starter.RowPar.0005.ContentPar.0001.ColumnPar.0001.Image.0.0.gif

Hi All:

___I read quite a few end user posts on the Optima Red and Yellow tops this morning. Given the multiple FAS’s in an automobile such as mine w/ an Auto, multiple deep discharges is something I have to consider. I believe the Optima Yellow Top to be the proper choice with this in mind. The Honda OEM is a known weak battery from those that have replaced them at DriveAccord. I will be purchasing a higher CAP battery with lower internal resistance, and far greater longevity due to intentional or accidental deep discharging vs. the OEM that currently resides under the hood. I have seen availability of the specific Honda Accord - Yellow Tops from Sears Auto Center’s locally and Auto Zone’s (Accord Yellow Tops - available only online).

___For the 03 - 06 Accords, the Yellow Top 51R is the recommended size and form factor. A few months ago, there was supposedly an issue with this particular battery (the 51R) in that one of the CEL’s was possibly shorted/degraded/damaged right from the factory? They were discontinued and unavailable until just recently when they reappeared and all appears OK today?

___Sears has them listed for $149 whereas Auto Zone has them listed for $139.00 + tax shipped to your door including the core charge. I think I will hold off on tomorrow mornings purchase knowing I can have one shipped to my door by Tuesday or Wednesday of next week for even less $’s out of pocket plus the fact that it will be guaranteed factory fresh vs. one that may have been sitting on the shelf for some period of time and even possibly damaged pre-recall. About the only negative to these AGM Pb-Acid’s is that they are not inexpensive batteries by any means unfortunately :(

___As usual, hopefully everyone learned a little something from the links, graphs, descriptions, and testimonials posted here. I most certainly did. Lakedude, thanks for your personal testimonial. When I began my searches online, I saw a number of others praising these expensive little wonders too.

___Good Luck

___Wayne

Yeah AGM is not cheap but worth it if you can afford it IMO.

X you might think about a red top. Here is how I understand deep cycle (yellow) vs starting (red):

Starting batts are designed to put out a lot of amps for a very short time (seconds), perfect for a starting application.

Deep cycle batts are designed to put out less amps over a much longer time (many minutes or even a couple hours). They are used to run things like trolling motors.

A dual use starting/deep cycle is a compromise in between the two.

OK from Optima:


Remember:
A dark gray case means starting technology, a light gray case means dual purpose (engine start and deep cycle) technology.

You should be ok with a yellow/light gray. I'd stay away from yellow/dark gray for a starting app.

here we go with details from: http://www.windsun.com/Batteries/Battery_FAQ.htm



* Starting (sometimes called SLI, for starting, lighting, ignition) batteries are commonly used to start and run engines. Engine starters need a very large starting current for a very short time. Starting batteries have a large number of thin plates for maximum surface area. The plates are composed of a Lead "sponge", similar in appearance to a very fine foam sponge. This gives a very large surface area, but if deep cycled, this sponge will quickly be consumed and fall to the bottom of the cells. Automotive batteries will generally fail after 30-150 deep cycles if deep cycled, while they may last for thousands of cycles in normal starting use (2-5% discharge).

* Deep cycle batteries are designed to be discharged down as much as 80% time after time, and have much thicker plates. The major difference between a true deep cycle battery and others is that the plates are SOLID Lead plates - not sponge. Unfortunately, it is often impossible to tell what you are really buying in some of the discount stores or places that specialize in automotive batteries. The popular golf cart battery is generally a "semi" deep cycle - better than any starting battery, better than most marine, but not as good as a true deep cycle solid Lead plate, such the L-16 or industrial type. However, because the golf cart (T-105, US-2200, GC-4 etc) batteries are so common, they are usually quite economical for small to medium systems.
* Many (most?) Marine batteries are usually actually a "hybrid", and fall between the starting and deep-cycle batteries, while a few (Rolls-Surrette and Concorde, for example) are true deep cycle. In the hybrid, the plates may be composed of Lead sponge, but it is coarser and heavier than that used in starting batteries. It is often hard to tell what you are getting in a "marine" battery, but most are a hybrid. "Hybrid" types should not be discharged more than 50%. Starting batteries are usually rated at "CCA", or cold cranking amps, or "MCA", Marine cranking amps - the same as "CA". Any battery with the capacity shown in CA or MCA may not be a true deep-cycle battery. It is sometimes hard to tell, as the terms marine and deep cycle are sometimes overused. CA and MCA ratings are at 32 degrees F, while CCA is at zero degree F. Unfortunately, the only positive way to tell with some batteries is to buy one and cut it open - not much of an option.

Using a deep cycle battery as a starting battery

There is generally no problem with this, providing that allowance is made for the lower cranking amps compared to a similar size starting battery. As a general rule, if you are going to use a true deep cycle battery (such as the Concorde) also as a starting battery, it should be oversized about 20% compared to the existing or recommended starting battery group size to get the same cranking amps. That is about the same as replacing a group 24 with a group 31. With modern engines with fuel injection and electronic ignition, it generally takes much less battery power to crank and start them, so raw cranking amps is less important than it used to be. On the other hand, many cars, boats, and RV's are more heavily loaded with power sucking "appliances", such as megawatt stereo systems etc. that are more suited for deep cycle batteries. We have been using the Concorde SunExtender AGM batteries in most of our vehicles for some time now with no problems.

Hi Lakedude:

___I took all of that into consideration. The Red Tops have a deep cycle count of maybe 50 from my reads earlier this morning whereas the Yellow Tops are supposedly good out to 300 +. In terms of CCA, the Accord’s OEM is a smallish 400 CCA based unit whereas the Yellow Top 51R is a 500 CCA based one. The 720 + CCA’s of the least cap Red Tops would be nice but the 300 + Deep Cycles of the Yellow Tops are of more importance in my application while I still have far more CCA’s to perform starting duties vs. the OEM.

___Good Luck

___Wayne

Yeah after reading the difference in construction it looks like an oversized deep cycle is the way to go. I couldn't remember which kind had the thin plates. I was thinking it was the other way around.

Looks like you already knew what you were doing in the first place. Thanks for the opertunity to refresh the ole gray matter.

Hi Lakedude:

___I was just happy to hear you were a very satisfied Optima customer with great results to show for the $ outlay. Whether the Yellow Top 51R will be the most optimum battery solution for my needs is anyone’s guess? After my first series of night time Warmup P&G’s in 10 degree temps this coming winter, I will know if I made the right choice or the wrong one ;)

___Good Luck

___Wayne

Wayne,

Any verdict on the Optima battery? I saw something in your gaslog about a "reduced capacity battery" interfering with FAS and wanted to ask.

Hi Tim:

___I ordered the larger 05/06 Accord V6’s battery box 2 weeks ago which came in today actually. Since the only 51R’s available anywhere in the country are the pre-market removed ones and being > 18 months old make them as close to damaged as one could imagine, I started shopping. I found the larger D35 should fit the new box as well as being a perfect match for post matching. I don’t mind a lot more Ah and CCA’s :) although the 11 + # weight gain is not what I had intended :(

Size and post matching.

http://www.1st-optima-batteries.com/Images/schematic_D35_op.jpghttp://www.1st-optima-batteries.com/Images/schematic_51R_op.jpg


Optima Yellow Top - Dual Purpose Deep Cycle and Starter 12V Batteries

Model|Volts|Ah|CCA @ 0 F|CA @ 32 F|Reserve Cap|Case Size|Physical Size|Weight|Terminals
D51R|12|41Ah|500 CCA|625 CA|70|Small|9.25"x 5.0"x 9.0"|26.0 lbs|Top Post
D35|12|48Ah|650 CCA|810 CA|98|Med-Small|9"x 6.7"x 7.8"|37.2 lbs|Top Post

___There is an Advanced Auto as well as Sears Auto near me that supposedly have the D35’s so sometime next week, I will pick one up and let you know.

___To combat the decreased cap, I have to do one or two NICE-On’s in the middle of the warm up P&G route vs. 16 straight MS/HS P&G’s. Although not intuitive, now that we have our summer temps, my glide distances are practically ridiculous and thus the huge draw off the 12V between each FAS causing what I deem as insufficient Voltage to bring her back up via the gear reduction starter again and again and again …

___Good Luck

___Wayne

I just looked at the batteries this past weekend at Sears. I was thinking of purchasing one myself.

Have not done so yet.

Terry

I plan to replace mine this weekend.
My battery gets dangerously low. In a prolonged FAS of a few minutes my headlights dim to useless, then I switch on the highbeams which cause a surge that my radio cuts out for a moment. After a few more minutes the highbeams dim as well, then I get the battery icon on the dash.

When I arrive home is at the end of a very long FAS. I roll onto the property, down a short hill and since I park face-out I need to turn around.
While I'm rapidly spinning my steering wheel to make my turn-around the radio cuts out again, and power steering is intermittant. (At this point I'm barely rolling at all)

I stop the car from rolling, restart the car for a brief back-into the parking space and is like everything comes back to life.

At this point is really a safety issue cuz when the battery is that low my fancy new horn doesn't have enough power but to blow only one bugle and wonder about steering in an emergency, and other electrical safety items like airbags etc.

Yup, I can't put this off any longer :(

I plan to replace mine this weekend.
My battery gets dangerously low. In a prolonged FAS of a few minutes my headlights dim to useless, then I switch on the highbeams which cause a surge that my radio cuts out for a moment. After a few more minutes the highbeams dim as well, then I get the battery icon on the dash.

When I arrive home is at the end of a very long FAS. I roll onto the property, down a short hill and since I park face-out I need to turn around.
While I'm rapidly spinning my steering wheel to make my turn-around the radio cuts out again, and power steering is intermittant. (At this point I'm barely rolling at all)

I stop the car from rolling, restart the car for a brief back-into the parking space and is like everything comes back to life.

At this point is really a safety issue cuz when the battery is that low my fancy new horn doesn't have enough power but to blow only one bugle and wonder about steering in an emergency, and other electrical safety items like airbags etc.

Yup, I can't put this off any longer :(

Hey Steve,

Get a "Battery" quick: :p

Terry

Got one today at Adavnce Auto Parts for $59. It's a bit bigger than OEM but still fits in the battery box.
I knew it was time when last night the current from my brake lights cut my radio out.

I was suprised to find my SOC at zero after I put the new battery in, as it previously read full normal. As I drove it, charged until half then suddenly showed ALL SOC bars.
After about 20 miles it's back to normal.

Now I have to reset my radio stations :mad:

Got one today at Adavnce Auto Parts for $59. It's a bit bigger than OEM but still fits in the battery box.
I knew it was time when last night the current from my brake lights cut my radio out.

I was suprised to find my SOC at zero after I put the new battery in, as it previously read full normal. As I drove it, charged until half then suddenly showed ALL SOC bars.
After about 20 miles it's back to normal.

Now I have to reset my radio stations :mad:
Steve,

Way to go "Steve", Steve-Is-The-Man, :) Congrats on the Battery: :D

Terry

I think you are supposed to just have your car idle for 15 minutes or so when you replace the battery so the pack can recalibrate. I never do but I think the manual says you should.

The pack always has no bars after you disconnect the 12v. I think the computer looses the packs SoC information.

Those stock 12V Honda batts must be junk. HG your car is a 04 right? Mine is only a year newer.

So what is the word on an Optima or AGM batt for the HCH? I might as well get one now, can't stand to have a crappy batt in a car.

My 2000 Vette's batt was still fine after 5 years (replaced anyway, no since taking chances). Way to go GM! I was hard on the Vette's batt, as the car was not driven for months and then FASed when it is finally driven.

Hi Lakedude:

___I think “junk” might be too heady of a term? I was reading a good deal of information from a distributor’s site last night where they described the Optima’s as being tested out to 10,000 starts while still meeting minimum specs on voltage and cap. Most OEM’s gave up the ghost at or around 4,000 starts. The little OEM 51R in the Accord I4 has > 10,000 starts on her already and although I can tell her CAP is down somewhat from new, she is still holding her own. On the last oil change, the Honda dealership measured a solid 12.77 V and 410 CCA - ICE-Off with their new battery and alternator instrument which shows the OEM Pb-Acid still far into the “Good” range. That is one tough little 400 CCA rated battery if I do say so myself.

___Good Luck

___Wayne

Hi All:

___Since Advanced Auto Parts and Sears fell through on this, hopefully Remy Battery out of Milwaukee can come through tomorrow?

Extreme Performance > Optima Batteries > Yellow Top - Deep Cycle Batteries (http://www.remybattery.com/Yellow-Top-Br-Deep-Cycle-Batteries_263177.html)

___$119.95 + ~ $15.00 shipping is not a bad deal for the larger D35. I will try and pick one up directly as I am a bit concerned about manufacture date …

___Good Luck

___Wayne

Hi All:

---------------------------------------------------------------
Remy Batteries - Milwaukee, Wisconsin

Bill To:

Wayne R Gerdes - www.CleanMPG.com

Payment: $133.24

Promotional Code(s): none

Ship To:

Wayne R Gerdes - www.CleanMPG.com

Item Unit Price Qty Subtotal Shipped Returned
Optima Yellow Top Battery - D35 $119.95 1 $119.95 0 0

SubTotal $119.95
Tax $0.00
Shipping - UPS Ground $11.29
Handling $2.00

Order Total $133.24
---------------------------------------------------------------

___Not a bad price either ...

___Good Luck

___Wayne

I can either go for a direct replacement or I can spring for a more expensve deep-cycle battery that might be better up to the FAS duty cycle. (I've been eyeing the Optima "Yellow Top".) Any comments on on this? Any experience with the Optima batteries vs. standard batteries would be particularly interesting.

Reply:

I'm new to this group, thus a late response to an old message.

I replaced my original battery ('2000 Insight) with the yellow top Optima and have
had zero problems.

On the honda-hybrid@yahoogroups.com site, for several years there has been
intermittent discussion on what is the "best" choice of battery. Since my replacement
(about three years ago) I have read several pros & cons of using a deep discharge
battery in the Insight.

Because I've had no problem with the Optima (personally, while others may have,)
I can't give a definitive answer or other comment.

However, someone recently reported Optima is no longer making the particular
battery that fits perfectly in the Insight, so I guess you might be considering a
discontinued product.

For what it's worth, I don't see much point (now) in making a big deal out of the
selection of a battery, provided you get one with a good warranty, sufficient Cold
Cranking Amperage that fits your automobile, no matter what make/model.

I suggest readers visit the excellent discussion of batteries at www.batteryuniversity.com
You'll learn something worthwhile, from people in-the- know.

Sheafe Ewing

Doesn't look like they have an Optima suitable for the Insight. Does anyone know otherwise? I need a new one for my 01 Insight. Any other recommendations if the Optima is not available?

Someone on Prius_Technical_Stuff recently pointed out that
the yellowtops are optimized for short bursts of really
high current, aka traditional starting, which isn't the
major use in a hybrid. Marine style deep-cycles sound like
a better bet. Surf around lifelinebatteries.com or
exide.com and compare some sizes...
.
_H*

Well, my Outback's battery is finally dying. The last couple weeks I can only FAS for 2-3 minutes before it drops to a dangerous level (11.5V). I haven't been unable to start yet, but I've had a couple of close calls and monitoring the voltage like a hawk has become a PITA. Limited FAS ability has been causing my MPG to suffer noticeably, by at least 1mpg overall and much more on some trips.

This battery is of unknown age, but it wasn't new when I bought the car 4 years ago, so no surprise that it's time. Especially with the FAS abuse of the past 4 months.

So I picked up a nice Optima yellow top at Batteries Plus today. I had to special order it because I couldn't find anyone in town that stocks the D35. The NON-reversed terminal model fits the Outback properly, BTW. Everyone (including Costco) seems to have the Group 34/78 model in stock, and nothing else. Batteries+ wasn't able to even find the D35 in their computer until I gave them the exact part number recommended by the Optima website. Price was $179.95, pretty much the same as Costco IIRC.

I will install this battery tonight and report back.

I just put one of those into my Elantra about a month ago -- worth absolutely every penny. I have next to no concerns with FASing now. I have made it a habit to drop to parking lights when I'm at a stop, though. That tends to keep the battery above 12V for as long as I want to sit there. I still drop below 12V just slightly on my warmup routine to the first light (two very long FASes with only minimal runtime between to get to the speeds I want), but this battery is a CHAMP.

I think you'll be pleased. :D

I'm keeping my fingers crossed for my 4.5 year old truck battery. Any thoughts on whether/how much a solar trickle charger (like Bail Out has) would prolong battery life?

Well, the big surprise was that the Optima turned out to have been shipped fully discharged (10.5V). I don't have a plug-in charger, so I had to waste gas, running the engine for 20-25 minutes. Normally I would normally expect that to be enough.

I was wrong. When I went to start up this morning the car still wouldn't start and the voltage was in the low 11s (engine off, ignition in the RUN position)

Drove 15 minutes and the car could still barely restart, voltage in the mid 11s. Another 15 minutes and about 11.7V. Final 15 minutes to work just barely brought it up to 11.9-12.0V. Even after an hour I don't think it's quite fully charged.

My first fear was that my charging system isn't working well. But I'm getting a steady 13.9-14.0V while the engine is running, so I don't think that's it. I'm now thinking the reason this battery is taking so long to charge is simply that it has such an enormous capacity. :woot:

Update: Optima manual says at 50A charging current, battery requires 75 minutes to reach 90% charge. I've probably done just a bit less than that, so I guess it all makes sense.

I'd just like to see if anyone has any notes to add after they've been using their batteries a little longer now?

The Paseo is using equivalent of a red top optima (different brand) and has no problems, but the lights do dim on long glides with the engine off. Voltage on long engine off glides gets around 11.7-11.6 at the lowest. It doesn't seem to have any troubles at that voltage (its only a 1.5L engine), but is that abnormally low?

Sadly, the Matrix is due for a new battery. The starting is labored and on long engine off coasts the radio sometimes kicks off. I don't want to have to worry about the wife getting stuck somewhere so its time for a new battery. Looking forward, what would you recommend? The twist? I checked the optima site and there is no battery for the Matrix according to their online selection do-dad. I tried putting the Paseo battery in the Matrix this weekend and it didn't fit because the battery terminals are in the middle of the battery instead of on the edge, so the wires can't reach the terminals. The leads are so short you think it would kill them to give you an extra inch...

I've been running a Yellow Top Optima since half way through Summer and boy do I love it!

I do have issues with the Voltage getting low but that is only because most of my driving has the engine on so briefly it is tough to accumulate much charge. The problem is exacerbated by the cold -- this morning I was staring at 11.1V a bit more than I'm comfortable with. :p

The problem is easily remedied with a battery charger but I've not yet acquired one. Most days I get enough to keep the battery from trending downward TOO much simply because I don't normally use the headlights on the way home.

By the way, my Elantra has leads that are bent at right angles to hook over the sides of the battery. I straightened them to get the Optima in and haven't had any issues -- other than the positive terminal protective cap not fitting quite right.

I've been told to stay away from Optima batteries for my car as they have a weak reserve capacity and overpriced. The average gas car can get by on them, but when a FAS with 12V accessories is thrown into the picture, reserve capacity may become an issue for any car.

Here's a quick definition of reserve capacity stolen from another website: Reserve Capacity, (RC) is a battery industry rating, defining a battery's ability to power a vehicle with an inoperative alternator or fan belt. The rating is the number of minutes a battery at 80 degrees F can be discharged at 25 amps and maintain a voltage of 10.5 volts for a 12 volt battery. The higher the reserve rating, the longer your vehicle can operate should your alternator or fan belt fail.

The highest rated Optimas I could find had reserve capacities around 55 amp-hours (Ah). The OEM battery in my car had similar CCA's to the Optimas but reserve capacity was 80Ah. In other words, my OEM battery can maintain the same voltage 45% longer than the Optima if discharge rates are the same.

Batteries with good RC that have been recommended to me are Deka, Interstate, and the Bosch AGM. Some group sizes that I've been told which tend to have high RC regardless of manufacturer are 48, 49, and 94R.

That is interesting information I have not heard before, Mike!

I can't really complain much about my battery -- it is just that over the long term the SOC tends to drop slowly. Several weeks back I had to make a highway run and after that it took until just now to finally start trending down to the level I described above. I've several quite long FAS segments, too...

I see Sean, I was thinking you were near a full charge each time and still had noticeable voltage dips. You're probably right, there isn't much you could do besides get a battery charger or burn more gas.

I posted this to another thread but not to this one: I got my defective Optima replaced and the new one has been absolutely awesome for several months now. Accidentally left the parking lights on all day once, and it still started. I don't even worry about SoC when FASing anymore, even though it's winter and I may have lights, max fan and defroster running.