My latest battery load test

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Battery is the 5 year old OE in the 2015 Altima in my signature, mfg'd in Oct 2014. So, this battery is just 5 yrs old. I often keep the battery on maintain/tender when we're not using the car often. I use a (not a BatteryTender Brand) but a 4 Stage Battery Maintainer. IDK the brand of maintainer(not marked), as it's from a previous Flo-Tech backup sump pump not being used any longer. I had the battery load tested at AAP ~ 5pm, from an afternoon of running around doing errands. So I stopped in AAP as I saw frew cars in the parking lot and figured it's a good change they're not too busy. So, here's the test printout and I find it a bit odd. ------RESULTS------ *GOOD BATTERY* TEMP: 67 *F VOLTAGE: 12.79 V RATED: 550 CCA MEASURED: 607 CCA..................WHAT? When having a battery load tested, I've never had an older battery measure a higher CCA than the rated CCA. I've had them read sorta close but never higher! Any thoughts, questions or needed information? CB
 
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Cranking amps are rated at 32F, Cold Cranking Amps are rating at 0F. It shouldn't be unusual to see higher than rated cranking amps when measuring at temps higher than 0 and 32
 
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What does this reading mean to you in regards to the battery condition? Do you suggest having it tested again? Next month when our temperatures drop even more, I'll have the battery tested again. I mean, yesterday was a warm day for our October(pushing 70*F) as we should be in the low 50s*F
 
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You got a conductive battery test not a load test. A load test puts 1/2 the CCA load on the battery for 15 seconds and you read the voltage on a temp compensated scale. Did AAP enter or check the temp of the battery. The better Midtronics testers can accept a temp reading to compensate the measured CCA.
 
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That is probably an uncompensated cranking amp result just labeled "CCA" to reduce customer confusion. A battery ought to meet its CCA rating in a real cold test throughout the warranty period or it is defective. So they overbuild them some.
 
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The conductive testers can test a battery that is not fully charged and give an accurate readout. So its fast for the places that want to sell you a battery. A true load test requires the battery to be fully charged and takes more time. The test results you got are fine. Retest next fall.
 
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Originally Posted by Donald
The conductive testers can test a battery that is not fully charged and give an accurate readout. So its fast for the places that want to sell you a battery. A true load test requires the battery to be fully charged and takes more time. The test results you got are fine. Retest next fall.
Thanks! I will continue to plug in the "Maintainer" at least once per week(or more often) when the car is not in use(weekends etc.).
 
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Lead acid batteries always desire to be absolutely fully charged, so any charging source applied to an undercharged battery is a good thing, as long as it is not overcharging it. Maintainers are not intended to top charge a depleted battery, but they can do so, when it is still healthy. When the battery is aged, a maintainer might not be able to produce enough amperage to keep the battery at the correct 'float' voltage. Float is basically to hold the battery at full charge with minimal overcharging occurring, and ideally is temperature compensated for battery temperature. I don't have experience using load testers, whether conductive or carbon pile so no comments from me on the validity of their readings, but I do view every engine start as a load test, by watching a digital voltmeter as the starter motor is turning with an overnight cold engine. How many times the voltmeter updates during the engine cranking can change the reading one sees, obviously one which samples 5 times a second is better than one which samples voltage 2 times a second. When newer my 930CCA AGM battery was always able to remain over 12v cranking the overnight cold engine, now approaching 6 years and over 1200 deep cycles, this is dropping into the mid to low 9's. I can tell it is not cranking nearly as fast, yet it is in no danger of not being able to start the engine. My battery gets deep cycled, and I often ask it to start my overnight cold engine with half or more of its capacity removed from it, and voltage falls even lower during cranking, and it is obviously slower too, but it still easily starts. Regarding a maintainer's ability to keep a battery top charged, or to bring it to near full charge, there are a whole bunch of variables involved. My AGM battery when new, I could hold it at 14.7v, and amperage required to maintain this voltage would eventually drop to 0.0x amps, but now, at the end of its life, amperage tapers to 4.7 amps, then starts rising again. Technically when amperage would taper to 0.4amps at 14.4 to 14.7v this battery is considered fully charged, but now amperage never tapers that low, so I consider full charge when amps stop tapering and begin rising instead, when held at 14.4 to 14.7v. Meaning a maintainer, capable of only 1 amp of output, could never get my current aged end of life battery to absorption voltage, and while float voltage for an 77f AGM battery is 13.6v, my aged end of life battery is still requiring over 1.4 amps to be held at 13.6v, meaning a 1 amp maintainer could not hold my aged near end of life battery at 13.6v, nor hold it fully charged, it would just be turning that 1 amp into heat and perhaps be able to maintain 13.2v. So plugging in a 1 amp maintainer on a less than fully charged aged battery might be fully inadequate not only for top charging, but holding an aged battery near full charge. These 'end amps' is a sure sign my battery is nearly done, as is the voltage falling to the mid 9's cranking my overnight cold engine in mild ambient temperatures. I'd be interested to see the readings on an conductive tester and a carbon pile, but neither is going to tell me anything I don't already know by observing how many amps flow at what voltage, and what voltage falls to during X amount of load. Since I do deep cycle my 90AH AGM battery nearly nightly, I also watch the voltage it can maintain powering this laptop or other things while an amp hour counter records the usage from the battery. Interestingly, the voltage it maintains during these light loads is still impressive when still over 50% charged. It is still retaining higher voltage than a big new 130AH group 31 flooded marine battery did when it was new when powering light loads, upto abut 50 to 60 amp hours from full. If i were to base battery health only on voltage maintained powering light loads, I would not know this battery is at end of life. While I will be getting a new battery soon(ish), I am doing it as the end amps being nearly 5 amps, is wasteful of electricity. it is taking nearly twice as much time and electricity to bump this battery back up to fully charged. The charge efficiency factor is now horrible, whereas when new it is one of the best of any lead acid battery. I carry a fully charged jumper pack 18AH battery/~170CCA(Ub12180), which by itself has started my cold engine in warm ambient temps, and will have zero issues assisting my weakened aged battery to do so when that day comes, if it comes before I decide to replace it. Readers not wanting to deal with AP personell, or acquiring their own carbon pile or conductive battery testers, can simply watch a cheap voltmeter while they crank their engine and have their own 'load test' on every cold engine start Warm restarts on my own engine happen so quick that the voltage reading is mostly meaningless. When one regularly starts seeing voltage dropping into in the mid to high 9's or less when cranking the overnight cold engine, time to consider shopping for a new battery deal at your convenience. Readers in colder climates this time of year, might wish to make this threshold in the low 10's instead of high 9's. Voltage at a 12v powerport/ciggy plug receptacle inside the vehicle can be significantly lower than actual battery terminal voltage though, depending on the vehicle and how many other circuits share power from the battery to the fuse block, and how many accessories are sharing that wiring at the time. One of the dashboard ciggy plug digital voltmeters is still better than nothing, and better than an analog dashboard gauge where it is nearly impossible to tell the difference between 12 and 13 volts. A 3 wire digital voltmeter with its sense and ground wired directly to the battery terminals is best, but impractical for most. Having a digital voltmeter visible is also great to see what the vehicle's voltage regulator is allowing as one drives. Most people have taken a voltage reading right after engine starting, and see a number in the 14's and assume that is what it always allowed by the voltage regulator, but they generally will drop into the mid 13's once things warm up. Fine for a fully charged and still healthy battery, but not so fine for an undercharged and aged one. The dashboard voltmeter can easily alert one to a failed charging system, or if they have one of the newer vehicles that decide to keep the battery at around 80% charged, sacrificing its longevity to save a few tenths of a MPG. One might see battery voltage highway cruising drop to 12.6v or less, occassionally jumping to mid 14's. In a 1980's vehicle this would point to a bad connection somewhere in the charging circuit, but today its normal on some vehicles. So while a carbon pile load test a standard test, or should be, one can view their own starter's load, and thus each cold engine start, as a load test, by seeing how much voltage the battery can maintain when starting the cold engine. Most will easily see when it is time to replace by this method, but a small % of batteries under 80% health/original capacity, can kick the bucket without warning too. For best lead acid battery longevity and reliability, get them and keep them as fully charged as possible, and do not expect that the vehicle itself is capable, or trying to achieve this 'ideal'. It takes no less than 3.5 hours to charge a battery from 80% to 100%, assuming a voltage held in the mid 14's for those 3.5 hours. One can deplete a 100% charged battery to 80% in a few minutes blasting a powerful stereo with engine off, yet would have to drive for no less than 3.5 hours to return that battery to near full charge. Today's modern vehicles keeping lights on after engine shutdown, and high parasitic loads, ensure the battery is never fully charged, and its charging system is hardly optimized to fully recharge it in the minimum time possible, and this time would still likely be measured in hours, if it were optimized for fastest possible safe battery charging, which it is not. Honestly I think that a 2 year lifespan of batteries in some modern vehicles is impressive seeing how chronically undercharged they always are. Maintenance minded Bitogers seeking maximum battery longevity would ensure and verify absolute top charge as often as possible. Achieving absolutely 100% top charge is not easy, nor is verifying it. Just know the green light on smart chargers is not that benchmark. Good enough? perhaps, but 'Ideal' is several steps above the capabilities of smart chargers, as their primary mission, is to not overcharge, and as such they fall well short of achieving a true full charge. The green 'full charge' light is a liar, 99% of the time, but any charging of a less than fully charged battery is better than no charging.
 
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Originally Posted by Char Baby
IDK the brand of maintainer(not marked), as it's from a previous Flo-Tech backup sump pump not being used any longer.
My Flotec FP2000 backup sump pump has a charger/maintainer part # PS117-77FP, that looks like the following (faceplate label differs) and is a relabeled Schumacher, from their Signature Series. It doesn't have the clamp style shown, just spade connectors. It has the maintenance mode and a 3rd sensing wire but it is a 10A charger, not just a maintainer. It did a great job keeping the pump battery topped off, till a 6 cent transistor in it failed and left the battery sitting low for a long time before anyone noticed. I replaced the 6 cent transistor with a 10 cent transistor and it's still humming along today. [Linked Image from cdn3.volusion.com]
 
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Originally Posted by Dave9
Originally Posted by Char Baby
IDK the brand of maintainer(not marked), as it's from a previous Flo-Tech backup sump pump not being used any longer.
My Flotec FP2000 backup sump pump has a charger/maintainer part # PS117-77FP, that looks like the following (faceplate label differs) and is a relabeled Schumacher, from their Signature Series. It doesn't have the clamp style shown, just spade connectors. It has the maintenance mode and a 3rd sensing wire but it is a 10A charger, not just a maintainer. It did a great job keeping the pump battery topped off, till a 6 cent transistor in it failed and left the battery sitting low for a long time before anyone noticed. I replaced the 6 cent transistor with a 10 cent transistor and it's still humming along today. [Linked Image from cdn3.volusion.com]
I have a smaller 1.5 amp maintainer with mine. I also have a Schumacher battery mounted/under hood "maintainer" atop the battery in the Firebird in my signature. This battery is at least 15 yrs old. I bought this battery & maintainer together. I also keep it plugged all the time when not driving the car. And I have yet another exact maintainer(as mentioned in my OP) that is in fact connected to my current Flotec backup sump pump with its 9 yr old deep cycle marine battery. As long as I keep up the acid level, the posts and terminals clean & lubed and the maintainer ON, it's anyones guess how long these batteries will last.
 

JHZR2

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Batteries are usually built/delivered with excess energy and lower impedance than needed so that it delivers nameplate after some degradation. 12.79V means it had surface charge unless it was really hot out. Open circuit voltage at reasonable temperatures should be mid 12.6-low 12.7V.
 

JHZR2

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Originally Posted by wrcsixeight
Lead acid batteries always desire to be absolutely fully charged, so any charging source applied to an undercharged battery is a good thing, as long as it is not overcharging it. Maintainers are not intended to top charge a depleted battery, but they can do so, when it is still healthy. When the battery is aged, a maintainer might not be able to produce enough amperage to keep the battery at the correct 'float' voltage. Float is basically to hold the battery at full charge with minimal overcharging occurring, and ideally is temperature compensated for battery temperature. ... My AGM battery when new, I could hold it at 14.7v, and amperage required to maintain this voltage would eventually drop to 0.0x amps, but now, at the end of its life, amperage tapers to 4.7 amps, then starts rising again. Technically when amperage would taper to 0.4amps at 14.4 to 14.7v this battery is considered fully charged, but now amperage never tapers that low, so I consider full charge when amps stop tapering and begin rising instead, when held at 14.4 to 14.7v. Meaning a maintainer, capable of only 1 amp of output, could never get my current aged end of life battery to absorption voltage, and while float voltage for an 77f AGM battery is 13.6v, my aged end of life battery is still requiring over 1.4 amps to be held at 13.6v, meaning a 1 amp maintainer could not hold my aged near end of life battery at 13.6v, nor hold it fully charged, it would just be turning that 1 amp into heat and perhaps be able to maintain 13.2v. So plugging in a 1 amp maintainer on a less than fully charged aged battery might be fully inadequate not only for top charging, but holding an aged battery near full charge. These 'end amps' is a sure sign my battery is nearly done, as is the voltage falling to the mid 9's cranking my overnight cold engine in mild ambient temperatures. I'd be interested to see the readings on an conductive tester and a carbon pile, but neither is going to tell me anything I don't already know by observing how many amps flow at what voltage, and what voltage falls to during X amount of load. ... Readers not wanting to deal with AP personell, or acquiring their own carbon pile or conductive battery testers, can simply watch a cheap voltmeter while they crank their engine and have their own 'load test' on every cold engine start Warm restarts on my own engine happen so quick that the voltage reading is mostly meaningless. When one regularly starts seeing voltage dropping into in the mid to high 9's or less when cranking the overnight cold engine, time to consider shopping for a new battery deal at your convenience. Readers in colder climates this time of year, might wish to make this threshold in the low 10's instead of high 9's. ... For best lead acid battery longevity and reliability, get them and keep them as fully charged as possible, and do not expect that the vehicle itself is capable, or trying to achieve this 'ideal'. It takes no less than 3.5 hours to charge a battery from 80% to 100%, assuming a voltage held in the mid 14's for those 3.5 hours. One can deplete a 100% charged battery to 80% in a few minutes blasting a powerful stereo with engine off, yet would have to drive for no less than 3.5 hours to return that battery to near full charge.
Ive run ammeters in series with run of the mill maintainers, and have observed current to reduce sufficiently as a percentage of Ah to be considered full charge. What you describe as a sign of end of life in your AGM battery, I'd define as a high impedance internal short. Yes, indicative of EOL, but the reason why you're seeing that amount of current needs to be defined. Unless you held the battery, open circuit, in a controlled atmosphere, and watched the voltage/SOC drop, versus when new, it would be tough to determine. Condemnation should be doubling impedance or 20% capacity loss. You're right that you should be able to observe voltage under load, but ideally you would know new and used parameters. Keeping conduction voltage above some level is a good surrogate though. I agree that it takes a LONG time to charge a battery full, and cars won't really do it...
 
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One cannot determine full charge by amperage accepted as a percentage of capacity at typical maintainer voltages. 13.6 to 13.8v. Only at absorption voltage,14.2 to 14.8v. Ive not tested the voltage output of every maintainer and wont, but few are going to achieve mid 14s, and most cant if they only have 1.5 amps maximum to work with. Earlier in my agm's life I could plug in and could charge my 50% depleted agm battery at 13.6v for days and days. Until amps taper to near zero. But when i'd spin that voltage dial to 14.7v, it would then take several more hours, accepting 8 to 15 more amp hours, for amps to taper back to or below 0.5% of capacity, and only then indicating true full charge. Ive done the same with a flooded battery mid life. 13.6v for held days and days, until amps tapered to very low levels.with no dc loads running, then dipped a temp compensated hydrometer and found cells at. 1.255 and less. It took several hours more at 14.7v to get them to 1.270 and then 45 minutes at 16.2v to get all but one stubborn cell to read a temp compensated 1.280. This clearly indicated full charge was not possible to achieve at 13.6 no matter how long it was applied on a less than perfectly healthy battery. Many maintainers will never exceed 13.6v and as such will not be able to fully charge a mid life battery. Ever. Whether a human decides to consider it fully charged, or good enough, is subjective opinion. Ill trust tools properly used to collect actual data instead to form my opinion on state of charge, and state of health. I suggest readers not assume their maintainer is capable of charging their battery fully. Not without verification. Meaning a good hydrometer on a flooded battery whose cells can be dipped, and on an agm, by the amperage accepted.at 14.4.to.14.7v. You cannot determine full charge on an agm when itis held at lesser voltages. You can guess of course. Or assume and hope. Can't achieve 14.4 to 14.7v on demand in order to see how many amps the agm battery accepts....... Then you cant determine true full charge of an agm. Period. Even if one has a coloumb counter and has returned 115%that which was removed. Good luck trying to get a smart.charger or maintainer to seek and hold absorption voltage in order to check amperage, after it has already decided 13.6v or less is fine dandy. Again any charging of a less than fully charged battery is better than no charging. But ideal is a true full charge, and this takes a long time at higher voltages and exponentially longer. If ever, at lesser voltages typical of maintainers. Achieving Full charge takes longer and longer as the battery ages. It ages faster and faster and loses.capacity and cranking amps faster and faster when it does not get truly fully charged, and this is not reversable, but rate of decline can be slowed. With true full charges. Achiever revularly thereafter. If it does get truly fully charged regularly and never overdischarged, it can last a very long time. Even in south Texas. Is it worth your effort? Perhaps. Perhaps not. But 'good enough' battery life is different for everybody. Ideal/maximum battery life is achieved by true full charge achieved as often as possible, but assumptions of true full charge being achieved by products which claim to do just that, should be verified before they are trusted. If chargers and vehicles had their voltages and durations of higher voltages optimized for achieving max battery life by achieving true full charge, we'd all be spending much less to replace batteries, and not concerned with the warranty length. As only the rare defective battery would fail within it. What other warrantied product could the consumer intentionally or ignorantly destroy, and demand another for free, and get it?
 

JHZR2

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I don't know what maintainers you're talking about. Mine take CV charge up to the 14.4-14.7V range, while current decays (which is what I noted that I observed), before transitioning over to a temperature compensated float voltage. Of course current will be lower at float voltage, since there's less over potential. My point was if you're still seeing amps of current at 14.4-14.7V, and it's starting to rise, that energy is going somewhere slowly (high impedance short). Otherwise it should decay. The energy can't go nowhere.
 
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A maintainer which seeks to bring battery to and then hold it at 14.7v for a period of time, and then drops to a temperature compensated float voltage is obviously much better than a single voltage max 13.6v maintainer. But its foolish to believe 'ALL' maintainers out there, are 2 or 3 stage 1.5+amp capable chargers seeking to hold 14.4 to 14.7v for a period of time before reverting to float. How many amps the maintainer has available in order to seek 14.4 to 14.7v, is a big issue. Both batteries I am now using both deep and shallow cycling regularly, now require way more than 1.5 amps to reach 14.7v. The one starting my engine now, for the last year, has required more than 1.5 amps to reach and maintain 14.7v when fully charged. so a 1.5 amp maintainer, even if it is seeking 14.7v, will never get either of these batteries to 14.7v, as the one battery requires 4.7 amps to get to and be held at 14.7v and the other requires 5.4 amps when they are very near or at full charge. Both these batteries are end of life, and have many hundreds of deep cycles on them and thousands and thousands of engine starts and are both a month shy of 6 years. They have delivered many hundreds of KWH over their lifetime, whereas the average starter battery will have delivered a tiny fraction of that when they are too weak to do their job. They could indeed have 'high impedance shorts' As I've watched these batteries age I've seen that amps stop tapering at higher and higher levels when fully charged, then starts rising, along with battery temperature. They are still being cycled and charged. One of them is still easily able to start my engine, the other, I'll not bother trying. It hasn't since June 2015. A 1.5 amp maintainer placed on either of these two batteries would not be able to get them near full charge, even if it was a maintainer capable of seeking 14.4 to 14.7, which not all do. ALL lead acid batteries, as they age, will require more and more amperage to be held at the same voltage when they are fully charged. These 'tail' amps at absorption voltage, are indicative of age/ condition and when the battery requires more than 1.5 amps to reach 14.5v, and the maintainer only has 1.5 amps available, then the battery will not reach 14.5v and as such it will likely not be able to achieve full charge. Some say a failing battery will take out an alternator. I don't know how much a shorted cell sucks up. But the extra 4 to 5 amps my alternator now has to produce to maintain my aged battery at 14.7v is not going to push my alternator or external voltage regulator over the edge. I got plenty of alternator temperature data( and voltage regulator temperature data) at different output and speeds. 18 more amps of output ( blower motor on high) at 65mph makes the alternator stator 2.5 degrees hotter. Under 25mph is a different story. So trying to fully charge a battery with a maintainer is unwise. Can some maintainers achieve full charge given enough time? Sure, on a newer healthy and generally smaller battery. Can every 'maintenance' charger sold since they came out, achieve full charge of a depleted battery when given enough time on a larger mid life battery, NO. Easily Provable with a hydrometer, but few to none bother. I have, I do, Its obvious. When one wants to see 1.280 on all cells and sees 1.255 instead, the battery is NOT fully charged, no matter what voltage it might hold. If 14.7 or higher voltages applied and held, never raises specific gravity over 1.255, then the battery is sulfated, and is fully charged to its maximum remaining capacity. I've not used the impedance testers. I've not used carbon pile load testers, but few can actually load half the CCA figure of the battery and hold it for 30 seconds. According to the SAE J537 CCA test, the fully charged battery is to maintain more than 7.2v after 30 seconds when loaded to half the CCA rating of the battery, not 10.5v as stated in another thread.... https://batteryuniversity.com/learn/article/how_to_measure_cca_cold_cranking_amp Half the CCA figure of a battery, is a big amperage number, asking the battery to deliver this, for 30 seconds, is very hard on the battery. A true load test is damaging to the battery, to some degree. The voltage the battery can maintain under load, ANY load, is a load test. Obviously bigger loads are more revealing. My starter draws nearly 1800 watts when i last measured it. Its rated to output 1400watts. 1800 watts at 10 volts is 180 amps. 1800 watts at 11 volts is ~163 amps 1800 watts at 12 volts is 150 amps. The voltage as the battery ages keeps dropping when starting the overnight cold engine. Higher amperage causes more voltage drop on the cabling leading from battery to starter. Each time I start my engine therefor is a 150 to 180 amp load test. Seeing how low voltage falls each overnight cold engine start, as the battery ages, at different temperatures and state of charge, is very enlightening, and I have been doing this for many years now. This equals Thousands of observations of voltage maintained during engine cranking. The voltage falling lower and lower during engine starting, has been a steady decline over the nearly 6 years I've been using this battery. One does not need to purchase an impedance tester, or a carbon pile load tester, or take their battery to an autoparts store to have it tested. They can simply watch a voltmeter every time they crank their engine instead. An analog needle would be better than a digital voltmeter which samples voltage 2 times a second or has a delay. When voltage drops to a certain level while cranking the engine, it is obvious the battery is weak, or perhaps just undercharged, and one should recharge and try again hoping to see a higher voltage held while the starter is spinning, or begin shopping for a battery, and carrying their fully charged jumperbox, or cables, or just replace the battery. I am carrying a fully charged jumper battery, and have been, for nearly a year. Glad I did not buy a new full size battery a year ago, as this one can obviously still do its job. The money saved by not buying a carbon pile or impedance tester can be put toward a good quality maintenance charger and the hardware to easily/conveniently plug it in, or a bigger battery. That said if I owned either, I'd definitely use them, as another data point, but neither are going to tell me what my other observations of performance, already have. But I'd rather spend that money elsewhere.
 

JHZR2

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The strange part of all your logic is this - power supplies can current limit at a set voltage. So even a chintzy little maintainer could get the voltage up to where you want, question being if it can handle the total power... something in there is a limiting step... but doesn't mean that some low rating supply couldn't give it... we're talking a few watts max. Whether or not the battery will stop absorbing current and decay to a lower amount is a different story... Volts drive amps, not the other way around. You need overpotential to overcome the internal impedance on charge. You just can't push more current without more voltage. But a power supply can current limit and give whatever voltage it is designed for.
 
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I am building a 24vdc fan to have infinite speed control from 8 to 28 volts. At 8 volts this fan draws 0.16 amps. At 28 volts it draws 2.45 amps. I am using a power supply that can either lower or raise the output voltage from the voltage it is fed. This power supply has a current limiting potentiometer. If i limit current to 2.0 amps when powering this fan, Then i cannot get more than 25.4 volts. No matter how much higher i crank the voltage potentiometer. If i limit the voltge to 25.4v and crank the current pot as high as it will go. 10 amp on this particular supply, Then voltage stays put and fan speed does not change and amperage rises no further. If i instead lower the current pot with voltage pot still set at 25.4, Then voltage falls with the current being limited as this fan requires 2 amps.at 25.4v and 1.2 amps at 21 volts. I can limit max voltage achievable by the current potentiometer. This power supply will go as high as 36 volts. I dont ever want the fan to see 36 volts. So i use the current potentiometer to limit amperage to 2.45 volts, then voltage cannot ever exceed 28 volts when powering this fan.no matter how high i crank the voltage potentiometer. Its the same thing with a battery. A new healthy battery when fully or near full charge might require 1 amp to attain 14.7v. A mid life battery might require 1.75 amps to attain and be held at 14.7v when fully charged. A 1.5 amp limited source will then on this battery never be able to achieve 14.7v. An un loaded.power supply /charger might be seeking a constant voltage of 14.5,but hook it to a 12.2vbattery and the voltage at power supply and at battery terminal falls to much closer to battery voltage, Than the power supply set voltage. As the battery charges. The shared voltage rises. Slow.with fewamps available much faster with higher amperage available. But if there is only 1.5 amps to work with, and the fully charged battery requires more than 1.5 amps to reach 14.7v. Then it will never reach 14.7v. There is no flaw in my observations. There is a glaringly obvious misunderstanding on your part about the relationship between voltage and amperage when charging batteries. Or powering a load. Thats the problem with book learning and no experience, combined with insecurity and ego. Guess ill be taking a vacation or something more permanent now. I Waste way too much time here anyway.
 

JHZR2

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A motor and an electrochemical system are not the same thing. A motor in the case you describe has a set resistance, inductance, back EMF and torque. V=I*R+L*dI/dt+E Where I is related to the motor's torque and E to the angular velocity (RPM). In a battery, it's related to the thermodynamic characteristics of the reaction (feasibility at conditions), and the kinetics of the reaction. Vt=I*R+Voc Voc is set by thermodynamics of the half cell potentials. So while in your motor case, EMF is related to angular momentum, and varies with speed, in the case of a battery, Voc varies with what the relative ratios of the reagents are inside. Because in the battery, amps are a quantity of charge, related by coulombs and time, we can know exactly how many atoms can be reacted with these parameters, we can actually track the quantities of reagents and thus the electrochemica potential change with time. Thus why state of charge and voltage are linked. With the battery, you can drive the electrochemical potential higher, and restrict the reaction rate, because the I term is going into the chemical reaction. With insufficient voltage you can't overcome polarization, but with sufficient voltage you can then meter in just how many moles of electrons you wish to dose to change the reagents. With the fan, the I*R term is dissipated by shaft work, so insufficient torque and the motor can't keep up the angular velocity thus less back EMF... vicious cycle. The linkage in the battery isn't the same.
 
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