Concern about battery depletion

[Luciano151]

Maxie, my van, carries four, six volt batteries. Currently I only use them to charge up my cell phone and related electronic gadgets and to run my vent fan; which I don't do very often. Within eight days, my batteries went down to 11.3 which is basically exhausted. I was wondering how on earth I could use so much juice up, if I'm not running anything that could even be remotely considered a juice sucker. I was advised to connect it to shore power overnight, which I'm currently doing, and pay attention to what I'm running for a few days and keep an eye on the gauge. I believe that a completely full bank of batteries would be considered full at 14.5? I don't know as I'm not an expert on this. If somebody does, I'd appreciate your input and your ideas on why these batteries are depleting so quickly. Thanks!

 

[SternWake]

Maxie, my van, carries four, six volt batteries. Currently I only use them to charge up my cell phone and related electronic gadgets and to run my vent fan; which I don't do very often. Within eight days, my batteries went down to 11.3 which is basically exhausted. I was wondering how on earth I could use so much juice up, if I'm not running anything that could even be remotely considered a juice sucker. I was advised to connect it to shore power overnight, which I'm currently doing, and pay attention to what I'm running for a few days and keep an eye on the gauge. I believe that a completely full bank of batteries would be considered full at 14.5? I don't know as I'm not an expert on this. If somebody does, I'd appreciate your input and your ideas on why these batteries are depleting so quickly. Thanks!

How old are these batteries?  What are these 'related electronic gadgets'?

What Vent fan?

Fully charged batteries, well rested, many hours after removing from the charging source, should read 12.8v or so.

14.5 is up in the absorption voltage range.  One needs to get the battery up to this voltage for a certain duration to fully charged it, but after the charger is turned off, and no Loads are present, voltage will quickly decline to 13.3 or so, and in an hour could be 13.15, and in 6 more hours 12.93v and in 24 hours could be 12.8v, all with no electrical loads on the batteries.

So either you are using more electricity than you think, or your battery capacity is compromised, Or you started out well less than fully charged, or most likely,  some combination of all three of these possibilities.

PLugging in overnight might not be enough to fully charge the batteries.

Do you know the type of charger/ converter?  What is the voltage as they are now charging?

Often the charger/converters provided in RV's are quite poor at actually recharging the battery to full.

Better options exist which will take better care of the batteries when plugged in than the Wfco converter or Magnatek converters often supplied with RV's

Iota and progressive dynamics will do a pretty good job when their charge wizard/pendant/IQ4  option is employed.

4, six volt gc-2 batteries  at ~450AH capacity total should get a 50 to 60 amp charger for around a ~10 to 13% charge rate such as Trojan recommends for their flooded batteries.

If you run a generator to recharge to 80% you can apply a higher amp charger to save some gas and reduce noise longevity, but no point in buying any lesser amperage charger/converter for that much battery capacity.

http://www.amazon.com/DLS-55-AUTOMATIC-BATTERY-CHARGER-SUPPLY/dp/B0074JVO0A

Shop around for somewhat better pricing.

 

[Luciano151]

How old are these batteries?  What are these 'related electronic gadgets'?

Wow, you know your stuff. I already learned quite a bit. Thanks. Related electronic gadgets include: Kindle, Nook and lap top.

What Vent fan?

I have a Fan-tastic van. The one with a thermostat and the ability to blow air in and out of the van.

Fully charged batteries, well rested, many hours after removing from the charging source, should read 12.8v or so.

So for clarification, if my meter shows 12.8v, that is for all four batteries combined, not just one, correct?

14.5 is up in the absorption voltage range.  One needs to get the battery up to this voltage for a certain duration to fully charged it, but after the charger is turned off, and no Loads are present, voltage will quickly decline to 13.3 or so, and in an hour could be 13.15, and in 6 more hours 12.93v and in 24 hours could be 12.8v, all with no electrical loads on the batteries.

So for clarification, if I charged my battery all night and it is only 12.9, and it should be at 14.5 or so, should I charge it overnight again, leave it charged longer than overnight, or is there something else I should do? In other words, if I want the batteries to be fully charged they need to be in the "absorption" range for a while and what do I need to do to get me there?

So either you are using more electricity than you think, or your battery capacity is compromised, Or you started out well less than fully charged, or most likely,  some combination of all three of these possibilities.

I'm positive I'm not using more electricity than I realize. There is a possibility that the batteries weren't fully charged. If the battery capacity is compromised how can I fix that or check to see if they are compromised?

PLugging in overnight might not be enough to fully charge the batteries.

Do you know the type of charger/ converter?  What is the voltage as they are now charging?

All I know is that I have a 3000 watt converter in my van. I'm not sure of the name brand. I can find out if it will help me with this issue.

Often the charger/converters provided in RV's are quite poor at actually recharging the battery to full.

I had the electrical system put into my van. It's my understanding that I have a heavy duty set up. I guess that's why I'm kind of concerned that with four batteries and that size converter (by the way, the converter has been off. I've been running mainly from the 12 volt sockets)

Better options exist which will take better care of the batteries when plugged in than the Wfco converter or Magnatek converters often supplied with RV's

Iota and progressive dynamics will do a pretty good job when their charge wizard/pendant/IQ4  option is employed.

These last two paragraphs went over my head...

4, six volt gc-2 batteries  at ~450AH capacity total should get a 50 to 60 amp charger for around a ~10 to 13% charge rate such as Trojan recommends for their flooded batteries.

I don't know what this means either.... The batteries I have are zero maintenance. I think they have a three letter name. I was told I don't have to worry about them for at least a couple of years or so. 

If you run a generator to recharge to 80% you can apply a higher amp charger to save some gas and reduce noise longevity, but no point in buying any lesser amperage charger/converter for that much battery capacity.

I'm sorry, but I didn't understand this either. lol. I have a generater by the way, but have not used it yet. I want to methodically go through everything one thing at a time. Good learning opportunity. Thanks!

http://www.amazon.com/DLS-55-AUTOMATIC-BATTERY-CHARGER-SUPPLY/dp/B0074JVO0A

Shop around for somewhat better pricing.

 

[Luciano151]

Forgot something. The batteries are brand new. Two months old.

How old are these batteries?  What are these 'related electronic gadgets'?

What Vent fan?

Fully charged batteries, well rested, many hours after removing from the charging source, should read 12.8v or so.

14.5 is up in the absorption voltage range.  One needs to get the battery up to this voltage for a certain duration to fully charged it, but after the charger is turned off, and no Loads are present, voltage will quickly decline to 13.3 or so, and in an hour could be 13.15, and in 6 more hours 12.93v and in 24 hours could be 12.8v, all with no electrical loads on the batteries.

So either you are using more electricity than you think, or your battery capacity is compromised, Or you started out well less than fully charged, or most likely,  some combination of all three of these possibilities.

PLugging in overnight might not be enough to fully charge the batteries.

Do you know the type of charger/ converter?  What is the voltage as they are now charging?

Often the charger/converters provided in RV's are quite poor at actually recharging the battery to full.

Better options exist which will take better care of the batteries when plugged in than the Wfco converter or Magnatek converters often supplied with RV's

Iota and progressive dynamics will do a pretty good job when their charge wizard/pendant/IQ4  option is employed.

4, six volt gc-2 batteries  at ~450AH capacity total should get a 50 to 60 amp charger for around a ~10 to 13% charge rate such as Trojan recommends for their flooded batteries.

If you run a generator to recharge to 80% you can apply a higher amp charger to save some gas and reduce noise longevity, but no point in buying any lesser amperage charger/converter for that much battery capacity.

http://www.amazon.com/DLS-55-AUTOMATIC-BATTERY-CHARGER-SUPPLY/dp/B0074JVO0A

Shop around for somewhat better pricing.

 

[SternWake]

2 month old AGM golf cart batteries dropping that far indicates your electrical loads are far greater than you think. A laptop is an Ampwhore. Mine consumes ~3.5Ah each hour if the laptop battery is already full and it is just on the internet.

Your make and model charger/converter would be helpful, but basically batteries need a certain amperage applied until battery voltage rises to the mid 14 level, then the voltage held in the mid 14 level until amps needed to maintain that mid 14 area taper to a certain level. and a 50% charge to 100% charge simply cannot be accomplished in less than 6 hours, and that is with a high amp charging source that seeks and holds the correct absorption voltage.

AGM batteries also have this minimum charge rate issue when depleted to 50% or below regularly.

But if my previous post went over your head I am going to step back and let others answer your questions.

YOu do NOT want to deplete your batteries that far. recharge at 12.2v or the battery capacity will be compromised quickly, especially with AGM batteries.

recovering lost capacity on new batteries stands a better chance than old, but if you keep on keeping on with your same depletion levels your batteries will not last a year.

 

[29chico]

Please give us the make and model of both the converter and the batteries.  All four batteries should be identical, please confirm this.

Honestly, without that info, trying to give a quality response is not possible.

 

[Luciano151]

I have four of the same batteries, 6 volt, AGM batteries. I have a Xantrex Freedom SW 3102 3000 watt converter.

Based on what you gentleman told me, as soon as I got home today, I plugged in my batteries to shore power and plan to leave them until they reach the "threshold" level that was mentioned at which point I'll leave it charged another few hours. Is this what you recommend, or is there something else that I could or should be doing? Thank you!

P.S. The last I looked the battery indicator was full and the indicated stated I was at 13.2.

 

[SternWake]

That is a very good charger with many options to fine tune the charge profile to the batteries you have.

All AGMS are not the same, with a wide variance in acceptable absorption voltage, So which Brand batteries do you have?

resting voltage is applicable to state of charge on a rested battery. DO not get hung up on voltage = %, it takes a long time for voltage to stabilize before voltage=%.

http://rollsbattery.com/uploads/pdfs/documents/user_manuals/Rolls_Battery_Manual.pdf

http://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf

http://lifelineb.wpengine.com/wp-content/uploads/2015/12/manual.pdf

Lifeline AGM says when amps taper to 0.5 per 100Ah of capacity at 14.4v and 77 degrees fahrenheit, then Their batteries can be considered fully charged. It is especially important to fully charge AGMS as often as possible, holding 14.4 for as long as it takes for amps to taper to 0.5% of total capacity.

Your charger can be programmed to meet Lifeline's specs.

You can achieve pretty much Ideal battery charging with that unit, you just need to learn to program it correctly.

I don't have the manual.

 

[29chico]

AGM is a an absorbed glass mat battery.  Not a brand or model but a type.  

I would suggest getting the manual for the Xantrex and the manual for the battery.  By reading up on the charging requirements of the battery you can determine the charging info that will allow you to program the Xantrex to correctly charge your battery bank.  Both Xantrex and the battery mfr. should have a tech line to help you out with questions.

Without the brand and model or part number of the battery, I can't provide any more information.

 

[Luciano151]

AGM is a an absorbed glass mat battery.  Not a brand or model but a type.  

I would suggest getting the manual for the Xantrex and the manual for the battery.  By reading up on the charging requirements of the battery you can determine the charging info that will allow you to program the Xantrex to correctly charge your battery bank.  Both Xantrex and the battery mfr. should have a tech line to help you out with questions.

Without the brand and model or part number of the battery, I can't provide any more information.

Hello. I opened up the box holding the batteries. All of the batteries are blue. They Say, DC Series 2 and then some other numbers that are covered by a cross piece of wood that covers all four batteries. I didn't want to mess with. Each battery says, "Blue Fullriver Battery manufacture LTD, Deep Cycle 

I took a picture of it, but can't figure out how to upload it.

I also took a picture of what I believe is the fuse box, that is located right next to the inverter. It shows two switches. 1 and 2. Switch 1 is on the Off position. Switch 2 is on the TRIP position. Is this the way they are supposed to be? 
Lastly, I have had Maxine plugged in for two days now, but it is still just showing 13.4. When will it get to the "fully charged stage." I think one of the gentleman who posted stated it was the "threshold" stage. At which point I'm supposed to leave it there for a few hours???

I'm learning a lot. Thanks.

P.S. I have the manuals, but probably am not reading them correctly. The inverter just looks like a horizontal silver box with some wires coming out of it. I didn't see any place to program anything. Nor did I see anything on the batteries either.

 

[SternWake]

Hello. I opened up the box holding the batteries. All of the batteries are blue. They Say, DC Series 2 and then some other numbers that are covered by a cross piece of wood that covers all four batteries. I didn't want to mess with. Each battery says, "Blue Fullriver Battery manufacture LTD, Deep Cycle 

I took a picture of it, but can't figure out how to upload it.

I also took a picture of what I believe is the fuse box, that is located right next to the inverter. It shows two switches. 1 and 2. Switch 1 is on the Off position. Switch 2 is on the TRIP position. Is this the way they are supposed to be? 
Lastly, I have had Maxine plugged in for two days now, but it is still just showing 13.4. When will it get to the "fully charged stage." I think one of the gentleman who posted stated it was the "threshold" stage. At which point I'm supposed to leave it there for a few hours???

I'm learning a lot. Thanks.

P.S. I have the manuals, but probably am not reading them correctly. The inverter just looks like a horizontal silver box with some wires coming out of it. I didn't see any place to program anything. Nor did I see anything on the batteries either.

Full river make a good AGM battery

http://www.fullriverbattery.com/series/batteries/dc-series#view-models

According to this link:

http://resources.fullriverbattery.com/fullriver-battery/spec-sheets/DC224-6.pdf

Absorption voltage is listed at 14.7v@77f

Float voltage is to be 13.6 at 77f

http://www.batterien-mueller.de/uploads/media/Fullriver_Lade-Anweisung.pdf

INitial amperage is to be 0.15 to 0.35% of battery  capacity.

That is 15 to 35 amps per 100aH  of capacity.  You had ~450Ah of capacity when the batteries were new.

YOur charger might be holding a lower float voltage because it is hotter than 77F.

YOur charger likely already held the batteries at 14.x for some period of time and then dropped to float voltage, so it will likely not attempt to achieve absorption voltage again until restarted with battery voltage below 12.6v or so.

They might be fully charged right now and not need more time ata absorption voltage.

The Full river spec sheets give you all the info you need to recharge the batteries according to their specific manufacturer recommendations.  You can not do any better than achieving their recommendations.

Your inverter/charger, can somehow be programmed to meet the exact  charge profile recommendations.

I have no idea how to program your charger, i've never seen it.

Your batteries and charger indicate it was set up by somebody with a fairly good idea of a very capable system.  Most people here have a plug in charging source some small percentage as capable as your charging source. 

Unless you want to kill those batteries prematurely, you need to make sure that charging source is applied before the batteries go below 12 volts under normal loads, preferably 12.2 volts.

If you continue to drain them to 11.3 volts time and again you will be forced into replacing them far sooner than desirable, which is a shame considering the capability of your charging source.

 

[highdesertranger]

sure wish we could see pics of your charger and switch. instead of typing in the "quick reply" window, hit the little green box that says "new reply", it's on the lower right of the last post. that will open a new page, below the box you type in it says add attachments this is where I add pics. try it it's easy. if I can do it anybody can. highdesertranger

 

[29chico]

I'm pretty sure that you will need to have the remote meter for that Xanterex inverter/charger to program it.

The best way to properly charge an AGM battery is to hold them at absorption voltage until the charge amps taper down to a given amount.  The correct absorption voltage and the amps at which to terminate the charge should be given in the Fullriver manual.

That inverter/charger should have a remote temperature sensor on one of the batteries so that it can temperature compensate the voltage that it feeds into your battery bank.  Verifying this would be a good idea.

 

[Luciano151]

     

Thank you sir for the tip on how to upload pics.

I didn't know that my Inverter/charger came with a control to regulate it if I use a certain kind of battery. I have to investigate that.

In regards to the "floating" charge that was mentioned. In layman's terms, how is that different than the "threshold" charge?

I have a small monitor that shows quite a bit of information, but I've only really paid attention to the battery charge because the rest of the information looks like Russian. I've made an attempt to go on-line to understand everything about watts, volts, ah, ect. but it's really difficult to understand. It bothers me because I want to understand what I'm working with. I designed everything, but I stated that I wanted four batteries and I wanted a 3000 watt inverter. I didn't specifically ask for anything in particular; mainly because I don't understand what to ask for other than in generalities. It's something I really need to learn. You gentlemen are really sharp and I'm picking up a lot of pointers that I wish I new when I was first getting into this. It's the one thing in Maxie's setup I just don't get and it's pretty frustrating.

Based on what has been stated, I am going to unplug the battery and use it as before. As soon as I get to 12.4 or so, I'm going to recharge it again to see if I can get it to threshold capacity and from then on, when I get to 12.4 or so (feel free to chime in if the number is wrong) I will recharge it again until I'm back to threshold capacity.

Thanks!

 

[29chico]

     

Thank you sir for the tip on how to upload pics.

I didn't know that my Inverter/charger came with a control to regulate it if I use a certain kind of battery. I have to investigate that.

In regards to the "floating" charge that was mentioned. In layman's terms, how is that different than the "threshold" charge?

I have a small monitor that shows quite a bit of information, but I've only really paid attention to the battery charge because the rest of the information looks like Russian. I've made an attempt to go on-line to understand everything about watts, volts, ah, ect. but it's really difficult to understand. It bothers me because I want to understand what I'm working with. I designed everything, but I stated that I wanted four batteries and I wanted a 3000 watt inverter. I didn't specifically ask for anything in particular; mainly because I don't understand what to ask for other than in generalities. It's something I really need to learn. You gentlemen are really sharp and I'm picking up a lot of pointers that I wish I new when I was first getting into this. It's the one thing in Maxie's setup I just don't get and it's pretty frustrating.

Based on what has been stated, I am going to unplug the battery and use it as before. As soon as I get to 12.4 or so, I'm going to recharge it again to see if I can get it to threshold capacity and from then on, when I get to 12.4 or so (feel free to chime in if the number is wrong) I will recharge it again until I'm back to threshold capacity.

Thanks!

The commonly used terms for stages in charging a lead acid battery are bulk, absorption and float.

As I have no idea what a threshold charge is we might was well get on the same page please.  The link below will help with the terminology of battery charging stages.

Link:  http://www.trojanbattery.com/pdf/U.S. Battery Charge Profile Full 11-12-13.pdf

The above link uses the term finish instead of float, but otherwise it is some good input

 

[Luciano151]

Thanks Chico, I am going to read up on this. I contacted K and asked them to verify the two things you mentioned.

In regards to being on the same page. I used the wrong terminology. I should have used absorption rate rather than threshold. I guess threshold would be used when you maintain the absorption rate until the amps taper to 0.5 of the total capacity of the batteries. It almost sounds like I know what I'm doing. lol.

 

[SternWake]

Thanks Chico, I am going to read up on this. I contacted K and asked them to verify the two things you mentioned.

In regards to being on the same page. I used the wrong terminology. I should have used absorption rate rather than threshold. I guess threshold would be used when you maintain the absorption rate until the amps taper to 0.5 of the total capacity of the batteries. It almost sounds like I know what I'm doing. lol.

Hey at least you are not one of those who use volts amps and watts interchangeably.

Basically Bulk, is when depleted batteries can accept everything the charging source can make.  Generally a constant current phase.

Once the voltage rises upto 14.x volts under bulk charging, the charging source makes sure not to cross this max voltage threshhold.  this absorption voltage.  and so the absorption stage begins.  The amps required to maintain absorption voltage will taper.  When amperage tapers to a certain threshhold, while still held at absorption voltage, then they can be considered fully charged. A constant voltage phase of charging


The time at which absorption voltage is to be held can vary widely depending on many factors. Most automatic chargers use a time base algorithm, such as 2 hours.  but 2 hours is generally only half the time required, and as such the batteries do not get fully charged, their owner mistakenly believes otherwise, and they degrade and lose capacity faster than they otherwise could, if absorption voltage were held as long as required to get the batteries to 100%.  98% is not good enough, and 98% to 100% can take 2 hours as the battery simply cannot accept much current in this state of charge range

The better way to trigger float mode is when the amps required to hold absorption voltage taper to a certain level.


Float voltage can be anywhere between 13.06 and 13.6volts, depending on battery, and of course battery temperature.  Generally very little amperage is required to hold a fully charged battery at float voltage.  If a battery is still accepting a lot of amperage at float voltage, then the battery IS NOT anywhere near fully charged and would benefit from the charging source seeking to bring them upto 14.x volts.

Many times chargers need to be tricked into seeking absorption voltage, especially when they see voltages over 12.8v when first hooked up.  Tricking is accomplished by lowering voltage by using large loads on the battery to lower its voltager to ~12.6v or less then restarting charger quickly, then removing loads, quickly.

Your charger if programmed correctly for those full river AGMs could easily double the total number of cycles you get from the batteries.  The key to battery longevity in deep cycle applications is a true 100% recharge applied as often as possible, as quickly as possible after any depletion.  There is a huge difference in longevity between the battery that gets recharged to 96% and the one which gets to 100% each recharge

 

[highdesertranger]

that box with the breakers is just that, a box with circuit breakers. that is not your converter/charger. keep searching and get us a pic of the converter/charger. glad to help with the picture thing. highdesertranger

 

[Luciano151]

that box with the breakers is just that,  a box with circuit breakers.  that is not your converter/charger.  keep searching and get us a pic of the converter/charger.  glad to help with the picture thing.  highdesertranger

Hello hightdesertranger,

I think that I'm good to go now with my system. I know enough to make better decisions in regards to how I use my batteries. What I have learned.

1. If I run my batteries to 11.3 often I will ruin them within a year.
2. The absorption/threshold rate is 14.7 for my batteries.
3. I should charge my batteries at 12.4 and not let them get any lower.
4. The float on my batteries is 13.4, which means that I can't charge them up any farther than that unless I use the batteries down to 12.4, and then quickly charge up again, fooling my batteries so that they go up to their absorption rate of 14.7.
5. When I am at the absorption rate of 14.7, I should keep them there until the capacity of my batteries reaches .05 of capacity.

The only thing that would be helpful to me would be to know the correlation between a number and
it's percentage. For example, 14.7 is 100% and 11.3 is probably 10% or less. What do the numbers in-between represent in terms of percentage? With this information I am going to copy/paste to a word document and laminate to keep in Maxine so I can remember.

I greatly appreciate all the help I received from each of you that posted. You're a great bunch of guys. I do feel like I'm in a tribe and I'm glad I joined this board.

 

[SternWake]

1. correct.
2.  absorption voltage is 14.7.  quit obsessing on the word 'threshold'
3. Recharge when batteries fall to ~ 12.2v.  you can of course charge at 12.4
4. You are hung up on voltage equaling a state of charge.  Float voltage is when  a charging source is  keeping a fully charged battery, fully charged.  Chargers are supposed to be smart.  They are not.
5.  You are hung up on voltage equalling a state of charge.  This is not accurate.  Voltage only can relate to state of charge when the battery has not seen any loads, or charging sources for many many many hours.  As this never happens in actual use, one must divest themselves from the notion that a certain voltage absolutely equals a state of charge.  Voltage can give a vague range as to state of charge when discharging, but it really helps to know the amperage load on the battery at the time, and have experience in watching the voltmeter and the ammeter as they discharge.

To know an accurate % remaining in batteries, one needs a battery monitor.  these are about 200$ and require all electricity flow through a Shunt, which then counts the amps in and out of the battery, makes some calculations and will give to a %, which is about 90% accurate, and can drift over time and or be completely inaccurate if programmed incorrectly.

Using voltage as a state of charge is wildly inaccurate. It is like throwing a rock at a rubber band and judging the weight of the rock by how far the rubber band stretched.

But I fear you do not want to believe this.

I despise the above chart as it is taken as verbatim for each and every 12v battery, when they vary widely, and AGM batteries tend to old higher voltages for longer in the first 50% of discharge.  

12.6+ = 100% is absolute BS.  My AGM battery at a rested 12.6v is about 75%, and 12.11v rested is 50%.  Note the word rested, meaning many many hours after all loads and charging sources have been removed and voltage has stabilized, and yes it takes this long and is different on each battery and the time for stabilization changes  as the battery ages

Full River likely has in their documentation a voltage/state of charge graph, but please remember it is only accurate on a rested battery, one which has not seen any loads for an hour or more and one who has not seen a charging source for many many hours or more.

UNless you really want to learn more about living on battery power, all you really need to know is recharge when batteries fall to 12.2v in your regular usage, and hope your very expensive charger's preset algorithm makes your batteries somewhat happy, which is a shame as it could be programmed to 'ideal' specifications.

I fear going into any more specifics will just lead you down a dark road of confusion, and sorry to adding to your confusion by using the word 'threshold' near the word voltage once or twice.

I am not sure I can clear it up.  When a battery is charged its voltage will rise.  Hopefully it rises to the absorption voltage dictated by the battery manufacturer, adjusted for battery temperature.  One it reaches absorption voltage it must be held there for a certain amount of time.  This time is variable.  When amps required to hold absorption voltage taper to a certain limit, then the threshold has been reached.  The automatic  charging source either holds absorption voltage for a set time period, or it uses amperage at absorption voltage to trigger float mode.  14.7v in itself is not indicative of anything.  I could get my depleted battery to 14.7v in 15 seconds application of 120 amps.  Does this mean the battery is fully charged.  Absolutely not, it would required ~6 more hours being held at 14.7 until amps tapered to 0.4amps

Divest yourself of the notion that voltage absolutely = a certain %.  Voltage = % with a 30% or larger margin for error.