Battery 27R vs ?

Nov 9, 2008
Drained the battery in my Tundra last winter, but it managed to make the rest of winter (slower cranking when cold). Picked it up from the mechanic last night and it went "click-click-click" but decided to crank over a minute later before I had a chance to jump it. Going on 8 years old, so... it's time. But it says on it 27R and it seems 27F is more common? I'm a little confused as 24 size apparently was also offered, and comes up a lot in searches; but I have I have the cold weather package and tow package, and well, bigger is better. Is 27F = 27R?
An R at the end means that the + and - terminals are reversed. In a lot of cases the cables aren't long enough if you use the other version. Otherwise the battery is the same, it is just built in a mirror image.
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27 is the battery group, the size of the case. 27F and 27R are a group 27 case with the F and R indicating the terminal locations. As mk says, the only difference is which side the + and - are on. Group 24 batteries are a different case size. Here's a chart: Battery sizes Bigger does not always mean more capacity. It depends upon the plates, etc.
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Finally figured out that R and F are the same. Just means that + and - are swapped; I guess Ford started that trend, and apparently some OEM's object to using F as a result. Anyhow... a 24F would work, but is smaller. And cheaper. I'll poke around a bit more, took way too long to figure out the R and F issue.
I spent some time with a measuring tape and that BCI chart and squeezed a larger battery into mine for a bit for reserve capacity. It's half inch shorter but the full width of that plastic tray. So if you do some homework you can upsize. I don't recall the size I put in, and won't have access to it until late tonight, in case you wanted the number.
'tis ok. Comes down to paying $130 or so for a 27F at Autozone, or $100 or so for a 24F at Walmart. Will probably just do Duralast from Autozone, it's the right size and nearly the availability of Walmart.
27R = 27F just different brands do different naming schemes. While you can use a 24 in the same space, I'd go with the 27, from what I've seen at work they tend to last longer - generally, the bigger the battery the more durable it is.
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Went to Autozone, pulled the battery (breaking one bolt in the process), and while the label says 27R it is molded as 27F! Tested 98%, so back in it went. Grr, had I known... I remember when this used to be a 5 minute job. But I guess back then I never wore dress clothes either.
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So it tested all right after all??? Hmmmm. How old is this battery?? Depending upon that I would possibly consider just prophylactically replacing it. Given just how cold it can get up your way.. I would being thinking of doing that. Hope that you have been doing all right man. Good to see ya on here.
When a vehicle needs a jumpstart, thinking that the alternator will return the battery to full charge, is unwise in the extreme. Under Ideal charging voltages, it could not get near 100% charged, in less than 6.5 hours. The alternator's voltage regulator will NOT hold ideal voltages for fastest recharging. In reality at the voltages the voltage regulator will allow, 10+ hours of highway driving will only have the jumpstarted battery in the 85% to 95% range. it does not matter if you just polished your alpha and Omega chromed 300 amp alternator, the battery cannot be recharged from 10% to 100% in less than 6.5 hours. a lead acid battery would preferably ALWAYS be at 100% state of charge. Driving around with it at less than 80%, which is high likely for a long time after junmpstarting, is very hard on the battery. Also, taking it to a store to be load tested is basically a joke. I can take my 4 year old deeply cycled and abused marinne battery, put it on a charger for an hour, load test it on such machines, and it would read well into the green. yet I know for a fact that this battery has no more than half of its original capacity and I have been expecting it to short a cell for years now. Actually starting an engine requires very little of the battery capacity and little of the CCA rating of the battery. it is only when the battery and engine are cold to very cold, and the battery somewhat discharged, that being able to actually start the engine becomes questionable. And taking it in for a load test is largely a waste of time. the results that are told are largely determined by the label on the battery. And if it is still under warranty of the people who are testing it, and if they have an excess number of older batteries in that particular size they need to move. Digital multimeters might not refresh quick enough, but an analog meter, placed on a battery terminals, should stay above 9.5 volts cranking the engine. If and when a voltmeter placed on battery terminals drops well below 10v when cranking a fuel injected engine, then it is nearing the end of its useful life. No way would I ever trust any load tester or tech at any autoparts store to tell me if a battery is good or bad. Each and every turn of the key can be considered a load test, if one is watching a voltmeter during engine cranking. And those who really want to eek out maximum battery longevity do not rely on the vehicles charging system to insure a full charge of the battery. And any time the battery is discharged to any significant degree with the engine off. Plug it into a charger. Do not rely on the alternator/ vehicles voltage regulator, to fully charge the battery. While 95% charged is ore than good enough to start the engine, a battery kept at 95% charged its whole life, would live half as long as one that lived at 100% charged its whole life. The Longer any lead acid battery remains less than fully charged, and the lower state of charge it remians, the faster it degrades/loses capacity. loses its cranking amps. And on an Aged battery, the green light on a charging source is not indicative of a 100% charged battery, it is indicative that the charger held its charge algorithm for the programmed amount of time. Will the green light on a charger indicat a battery charged enough to start a vehicle, yes. Will it indicate the battery is indeed fully charged, fat chance. Full charge is determined by a hydrometer, measuring specific gravity, compnesated for temperature of the electrolyte, and compared to a previous reading on THAT specific fully charged battery, when it was new. In hot climates battery acid specific gravity might max out when new atr 1.260, and a battery made for a cold climate might max out at 1.310, or in the interests of maximum profit and a who cares anyway, they might be 1.275 intended for hot or cold climates. Just do not believe that 12.7 means it is fully chrged, or that a few floating balls in a 99 cent hydrometer really indicate much of anything, or that the load tests perfomred by AP store halfwits, on a battery that was recently chrged by a vehicle, have much if any meaning as to the state of health of the battery. There are so many factors which can influence these load tests towards good or bad, besides the everpresent human greed/ maximum profit factor it is a bit ridiculous. A simple voltmeter wired to the actual battery terminals and regularly observed when the engine is cranking, will easily allow one to know when the battery is getting weak enough that replacement will be required in the near future. Obviously not everybody is going to want some aftermarket voltmeter and watch it religiously every engine start, but the person wondering if their battery is weak, or not, can easily put a voltmeter on the battery terminals and watch it while someone else cranks the engine. Then try it again after leaving the lights on for 10 minutes. When it starts dropping below 10 volts when cranking then keep an eye on it. The state of chrge of the battery will also greatly affect the voltage seen during engine cranking. So while the green lighted charger might not indicate a true full charge, it is way way better than thinkng I just drove for a half hour so therefore the battery must be fully charged. I bet many battery's which tesst good in AP stores are at or near end of life, and many which test bad are simply in need of an extended and full charge and could go for another year or 2 as long as attempts are made to regularly fully charge the battery. A vehicles chargngt system is most concerned with not overcharging a battery. this is done with charging voltage. Voltage is electrical pressure. The lower the pressure, the slower the recharging. the lower the pressure, the less the chance of overcharging. The less chance of overchrging the happier the accountants and the laywers for the automaker are, but this is usually at the expense of batery longevity, especially if the battery is discharged regularly via prasitic loads, or by listeningto the radio with the engine off. No lead acid battery is immune to chronic undercharging, and almost every vehicle's voltage regulator is programmed for exactly that, as it is safer than insuring the battery is returned to and kept at full charge, as fast/often as possible each and every time it is driven. Batteries are just rented, but a wise renter can seriously extend the rental contract simply by knowing that the automaker, simply does not care about achieving excellent battery longevity, but they sure as hockeypucks do care if a battery is continuously overcharged and offgassing a lot producing oxygen and hydrogen drying out. A regularly overcharged battery has a much higher chance of having those offgasses meeting a spark and going kaboom. Much much safer to regularly undercharge and require car owners to replace batteries more often.
Originally Posted By: bbhero
So it tested all right after all??? Hmmmm. How old is this battery?? Depending upon that I would possibly consider just prophylactically replacing it. Given just how cold it can get up your way.. I would being thinking of doing that. Hope that you have been doing all right man. Good to see ya on here.
Yeah I thought it odd, but I didn't read up on testing, so... shrug Been doing ok. Busy fall, kids in school and all. Needed to spend less time online.
Originally Posted By: wrcsixeight
Yeah, in hindsight I should probably get a float charger--this truck is not getting driven much these days. Few miles per week, gets filled up about once a month it seems. For the record, I drained the battery to 8 or 9 volts last year. A door got left open. I jumped it then and it's been fine since. Been a slow cranker in cold weather last few years, but always started. Anyhow, last night I got clicks on the first key then on the second keying it decided to start--must not have been able to run the fuel pump and starter at the same time, I guess. Been started thrice since and it starts fine--but it's been pretty warm, 30-40F.
I let it sit for a few days and it was 12.37V when it was about 15F outside. Took it for a 20min drive, it's been sitting over an hour (off), and it reads 12.37V. I have a cheapo 2A Sears charger/maintainer so I'll let it do its thing for a few hours and see what happens.
Give 2A all night. A lot of its power is just going to keep the battery warm, not really charge it. Size 24 is one of WM's $49 specials, FWIW. You have a gear reduction starter so it's not really that demanding an application.
Poking around I found a 2/6/10 amp charger lurking in my basement. Brand new, in the box--barely remember buying it. Open it up and it comes with a pre-broken clamp, but I have some. Might use that instead. No, it definitely isn't a demanding application, so I've thought about going group 24 and calling it a day--then I could always play magical battery with my other two cars, if I ever needed to. Going to charge this up and monitor health, and wait it out. There's a chance I might trade out of it in a year or so. frown
Nah, that's how one can economize. wink I actually don't know how old the battery is. Says Toyota on it but I don't see a date. Maybe it was replaced before I got the truck five years ago? Charger kicked off after 4 hours. Was 12.95V off the charger. Maybe I can milk another winter out of it.
Remember my friend not to trust that battery charger kicking off.... Unplug and plug back in. And do this several more times. To get that battery truly up to 100%. It can take 2-3 hrs of additional charging to get to true 100% after the chargers green light comes on or kicks off.
I'm testing a batteryMINDer now. They slow charge, float and desulfate. I did charge my battery first with a prologix 2320 on 10A, then on 2A the next night after driving it. The sulfation I can see through the watering holes is much reduced from just a proper full charge. The last 5% topping charge takes several hours. I'm going to take some photos of the sulfation when I get some time