Battery Charging Questions

3. Is wrong.
A 20A current source will keep pushing in 20A regardless of the battery state (0% to 100% and then onwards to explosion/meltdown).
It would need a voltage limit (at which point it would switch to a trickle charge mode)
Del

I don't think 3 is wrong. You seem to be restating what the OP said: that a constant current source will charge at 20 amps at the start of charge and continue at that amperage throughout the charge, until the battery boils dry, etc. A voltage limit would be needed, such as the 14V the OP mentions.

Only if the voltage is substantially higher than the battery enough to "take" a 20 amp current, otherwise the current wil just reduce.......

If the electronics are organized to do this accurately, substantial and dangerous gassing may result....

Assuming a LA battery type of course......constant current charging is for most non LA types of battery "the norm".....

ur battery is 12 V

a 14V Dc source is ideal for charging the battery

the ampere out put of the source is decided by the load or u can say resistance, when the battery is discharged the resistance is low and your 14V/20A source may start giving current upto 18A

but with the time the resistance will increase with charging of battery and current will come down...

if your source is powerful enuf to pump any amount of current.. obviously nt 20A but may be even 4A or 6A which will damage battery cells

so for that u need an over charging protection

Also be careful with (2). The current limiter will probably introduce a voltage drop - how much will depend on the type of current limiter.

_{It's been our experience that some readers of these pages get quite excited at the suggestion of anything of such nature being inserted between the voltage source and the battery .}

thats right

u need to check the voltage ur charger is giving at battery terminal while its charging

not with open terminals!!

Hi

actually your decision to charge the battery using 14v,it is ideal for your battery if you are using 12v battery.The charging current will decided by battery.and you can charge the battery using the source from alternator of car.

offcourse by battery but ur source shud b able to give that much current to battery if ur source has abelity to deliver 10A and battery need 15 at some moment than it will b over loaded... so the source shud b able to give maximum current drawn by a battery

how ever a partialy discharge battery will draw less current as compare to fuly discharged one which is a rare case

but once battery is charged ur charger will still try to inject some current.. shich is very low but dangeros fr battery so.. u need over sharging protection

First off if the batteries have 0% charge the most chargers will not charge them.

The proper voltage for charging a lead acid battery is 2.5 volts per cell. So at 14 volts they will not be 100% charged.

The proper voltage for charging a lead acid battery is 2.5 volts per cell. So at 14 volts they will not be 100% charged.

This could be misleading. Many lead acid batteries, especially AGMs, should never be allowed to get above 14.5 volts during the charge. (In fact, many
AGMs will, in 70AH size, tolerate charge rates of over 100 amps if voltage is kept no higher than 14.5.)

A fully-charged battery is typically 12.7 volts, after it has been disconnected from the charger for a day or so. Maintenance (trickle) charge voltage is generally 13.8 V.

Just gave him what the design voltage is for the charge on a wet cell. AGM may not be able to handle it because of the restriction the glass mat makes on the fluid just as a jel cell does. But it's no more miss leading the letting him think it's 100% charged at 14 volts. You are correct in that the finished voltage from most chargers is around 14.5 volts for 12 volt battery. The main reason being your not charging a single cell at a time. They are connected in series. If pushed to the design charge voltage of 15 volts on 12 volt battery one of the cell would have more the 2.5 volts on it. The internal resistance of a cell is independ of the other cells.

Buy already manufactured Battery Charger,the time of building your own charger is over, it costs you much more and it will not be the same by any way.

3. by using current source ( is there any example of current source? ) that pumps out 20A constantly, it will charge at 20A to 20A (0% to 100% full).

Yes, the standard example of a constant current source is a modern battery charger. They charge at constant current for the bulk charge, then switch to constant voltage to finish the charge. In the constant current phase, voltage will fluctuate. As the charge progresses, the voltage would eventually get too high, which would cause the battery to gas. Short of that point, the transition to constant voltage is made.

For a lead acid cell of 2V,70AH we give 2.5V,70/20=3.5A for charging. Please keep it in mind lower than 3.5A is to be given.(1 to 3.5) lower the charging current longer the life of cell. Get educated -Hit

The answer is generally NO.

If you are talking about Lead Acid batteries, they are only voltage charged, not current. The current taken is due to the difference in the battery's terminal voltage and the charge voltage and the internal resistance of the charger/battery in series.

The supply current will be limited initially by the power supply maximum, but as the charging battery's voltage rises, the charge current will reduce, till a point of equilibrium is met, where both are at the same voltage. In practise as the current drops and drops, you theoretically never get a true equilibrium.

Which is why a good charger supplies at a higher voltage than required (allows a higher current to flow) and when the battery achieves a preset voltage level, the charging current is either severely reduced to a trickle (trickle should roughly balance out the losses - or not quite. It should not cause the charge to still climb, albeit slowly) or cut off completely....depending upon the design of the charger....

To get a good battery life, you should consider NOT to fully 100% charge as this promotes gassing and eventually will reduce the full life expectancy of the battery, especially if its a cheap car type battery.

70-80% full should be considered and if its a car type battery, start recharging at 12.6 volts....as car batteries do not take kindly to deep discharging.

Leisure batteries can handle that far better. In fact, other than "cranking amps", they handle most things better than a car type battery...

Other battery types are current charged, in fact I believe its true to say "all other battery types are current charged!" Voltage charging will often just damage them or cause a possible fire!!!

GA from me.

Is the Car Battery considered float battery ?

Float is a state of charge not a battery. A car battery is a start battery and is usually always a lead acid (flooded) battery.

OK,does the float charger never charge the battery fully?

Float chargers do just that, they keep a battery basically fully charged and use a minimum amount of mains current to do that.

They can be seen in emergency light fittings all around the world.

The idea is to keep a battery charged up as most LA batteries have a "bad" shelf life and self discharge slowly all the time.

This method actually does the battery little good in the long run and the life is not prolonged in any way and the lights still need to be tested regularly to enable the defective ones to be replaced asap.....I would recommend testing at least once a month....

I personally build "ON/OFF" LA Battery chargers that allow the battery to charge then discharge then charge, but discharge only down to 12.6 volts.

This appears to keep them "happy" longer, though I have not done proper testing per se.....its partly my personal impressions and the fact that I do not like float or trickle charging......

I liken it to a boxer or some other sportsman "flexing his muscles"!! How true it is I cannot say!!!

chrisg288

Great link thanks

From that link:

"Float Charge: The 3rd stage of 3-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2 volts) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it's main purpose is to keep an already charged battery from discharging."

Is not "float charger" then a synonym for "trickle charger", or indeed "maintenance charger"?

It seems to me that there's a bit of wordplay going on, resulting in multilateral incomprehension.

What a perfect word combination (that I must never forget!):-

"multilateral incomprehension"

Thanks John.

I am sure that many of us will get to use that on CR4 from time to time. On this blog it fits perfectly into place, like a central diamond in a beautiful(?) ring setting!!!

As for charging the battery, the general rule-of-thumb for alternator output to battery size ratio is 4:1. In other words, if your anticipated ideal battery capacity is 400 amp-hours, your alternator's rated output should be 100 amps or greater.

You've reversed your own ratio from one sentence to the next.

But in either case, the ratio is not typical. A 60 AH battery is very common for automotive use. A 100 amp or 150 amp alternator is typical, with 200 amp alternators being not uncommon (considered heavy-duty for car use), even when the battery is 60 AH. 400 AH batteries are never found in cars, and rarely found in even large trucks. Even if they were found, a 100 amp alternator would be far too small for such a huge battery.

When I hear someone talking in AH instead of CCA or MCA they are not or should not be talking about a regular car battery...

CCA and MCA are completely different concepts than AH. It is not the case that these figures are used in car batteries instead of AH ratings. All car batteries are rated in AH (for energy capacity) and CCA (for power output). Obviously, MCA (marine cranking amps) is not a typical spec for car batteries.

I guess for some I should have said battery to alternator. I did not reverse anything in the definition it is clearly stating 4:1 meaning 4 being battery capacity and 1 the alternator output.

It is obvious that I was pointing out the difference in CCA, MCA and AH to the originator of the question. He was asking about AH and asking about charging it with a car alternator. A car alternators charge profile is meant to charge a start battery not a deep cycle battery. A start battery is not designed for repetitive cycling in a situation where amp hours are the concerned.

You could try contributing to the thread instead of attempting to be an editor.

Could you please inform me what is most reliable chargers available today you prefer for large Lead Acid Batteries (520AH and larger):

1-High frequency charger

2-Linear charger

Thanks

If you are using an AC charger I have used the following manufacturers on systems up to 2000 AH

Xantrex

Magnum

For an engine driven system the following link can supply alternators and regulators.

Balmar

To obtain maximum life out of your battery it should be charged using maker's recommended charger for type of battery- this will have the correct amp/voltage/feedback/regulator to ensure overcharging does not occur. Now as to car batts using wet lead acidthe car makers supply inbuilt alternator charging at 14 odd volts(regulating amps)- this is a good all around compromise for performance & batt life- a car batt starts gassing at 14.2v increasing as volts rise- but to get specific gravity of 1.266 a charge voltage of 15.3 v is needed & some gassing(don't believe me?- try it with a good hydrometer). Apart from this there is ambient temp, batt faults(like shorts in 1 or more cells, or open conn, or lead plate shedding-etc-etc-etc)- anyway-most car batts will last up to 7 years(if not abused- which includes over drain by over using starter, or over charging if charging system develops fault, or overcharging by using unregulated external charger etc etc etc) the biggest killer of wet & sealed lead acid batts is sulphation which occurs if batt is allowed to sit for extended periods(all rechargeable batts self discharge) without recharging. These days we have a zapper unit which dissolves sulphation & can get more life from otherwise useless batts(wet & gel& sealed& valve reg). It is only the modern car which needs a good batt/ starter to start- older cars had a manual crank handle- as long as batt provided enough current for coil(4> amps)- away you went!. Now as to charging batts out of car- you must have a regulated charger- I use a design which adds on to any unregulated charger- adjustable - (as wet car batts age = diff impedances affecting charge rate) - puts in initial 6 amps at up to 14.6v, then drops to 14v, then slowly rises to 14.3v at @1amp = batt fully charged(averaged using 10 wet lead acid car batts of diff caps & age)- proved using a 200 amp high rate discharge tester(also home made). So there we are dear friends.

What is the problem of the gassing in the wet Lead Acid battery as long as distillation water is added from time to time?

Gassing does not add to the charge of the battery. Its just getting rid of the extra "energy" being put into it.

You could liken it to continued boiling of a kettle, the water does not get any hotter than boiling point.....

Once its full, it gases.....

Also the battery starts to warm up when its full, this degrades the paste on the plates.

Gassing is a lose, lose situation.

LA Batteries are when used 100% correctly only about 70% efficient. Overcharging just uses up energy needlessly and reduces this already low efficiency even further....

Thanks for reply.

You mentioned "this degrades the paste on the plates", actually there is no paste on the plates,it is made of sulphur and sulphur oxide without any paste on it ?

I just watched the making of deep cycle batteries on "How It's Made" (S8, E4, P1)

it definitely mentions the use of paste (lead oxide I believe. about the 1:55 minute mark in the video)

Chris

Many thanks.

I have no idea why he suddenly took offense at the wording, perhaps he can tell us why? But as he signed on as a guest, its hardly likely that he has the manners to do that!!!

But it is soft when "pasted" into position.

You don't want it softening and dropping off as eventually it builds up to a level where it shorts that cell out completely.

You are only arguing semantics......

You didn't really get much right in this post! Bad hair day?

Sorry on my last post, I screwed up real good!!!

How about "coming out" (or "in")?

Maybe you're registered, & didn't sign in - but if you're an unregistered guest, you're one of the few who has come back and 'fessed up to getting it wrong.You're the kinda people CR4 needs, so get registered & join in. (Pretty please).

Where the 30% losses go ?

http://wiki.xtronics.com/index.php/Sealed_Lead_Acid_Battery_Applications#Battery_Efficiency

Great link John, many thanks.

That means that you need to charge a LA Battery with 130% more energy, to get 100% back out.....

You can start reading here to learn just how innefficient some batteries and power generation systems are:-

http://www.blogonsmog.com/motor-monday/?currentPage=7

ELVs (Electric Vehicles)are at best 24% efficient......

Hello

In the old days (could be 10 years ago) LEA batteries used to be charged in a equalize mode for short time every while.

Is that charging mode is still used today.

I am a retired man (73 years old) and i would like to know what is going on today.

Cheers

I think this mode is still used in some special cases in addition to the normal steps of charging the battery.

Have a long life,God bless you and America as well.

thsnk all for the advice.... really gimme a good view of the charging thingy..

I was exploring different types of charging method in term of constant voltage (with or without current limit) and constant current (with or without voltage limit) ** ya, i miss out the voltage limit in my original q ~~ *

I have this in my spec sheet:

Charger rating in amps: 25A and Battery :PC1700 or smaller battery.

My questions is, can i safely say that when i put a voltage source (no current limit) to charge this particular battery PC1700, it will draw less than 25A (probably 20A)because the manufacturer of the battery recommended charger to be able to deliver 25A?

Use any commercial 20A battery charger-it will do every thing for you automatically.

My questions is, can i safely say that when i put a voltage source (no current limit) to charge this particular battery PC1700, it will draw less than 25A (probably 20A)because the manufacturer of the battery recommended charger to be able to deliver 25A?

No, you can't safely say that. Assuming your PC 1700 is the Odyssey of that model designation, the charging current can be much higher than 25 amps if the state of charge is low (and if charging current is not limited). The owner's manual highlights the importance of voltage limiting, but (correctly) states that as long as 14.7 volts is not exceeded (15 = absolute max, at which damage starts to occur) there is no limit on charge current. These batteries are perfectly happy accepting 200 - 300 amp charge currents when used in electric vehicles with regenerative braking, for example.

Note that the manual says:

• In order to achieve the full design cycle life of ODYSSEY batteries in cyclic applications the charge current must be a minimum of 40% of the battery's 10-hour rating (column 8 of the chart on page 5).

So for the PC1700, 26 amps is the minimum recommended charge current. If your charging source is a car alternator, it will provide far more than this minimum, and it will incorporate voltage limiting which will probably be OK for the Odyssey -- but it should be checked. There are some car alternators which are voltage limited to 15 or even 15.5 volts -- too high for the Odyssey (and in my view, to high for any lead-acid car battery.)

Good quality battery chargers will limit voltage to 14.5 - 14.7 during the bulk charge, and there is no need to go beyond that for any lead acid battery.

If your charging source is a power supply (not recommended) with good voltage limitation, then the power supply (if it can put out 20 amps or so) will not damage the battery (they are not that sensitive to being charged at lower-than-optimum rates) but the battery could damage the power supply, if it is not sufficiently overload protected. These batteries have very low internal resistance, and so can draw a lot of amperage from a charging source.

Best bet is to go with a good modern three stage charger of 25 - 30 amps. If it is charged mainly by a vehicle, check that the voltage cannot exceed 14.7.

GA

I liked you "Bumble" Mr Moronic!!

Good quality battery chargers will limit voltage to 14.5 - 14.7 during the bulk charge, and there is no need to go beyond that for any lead acid battery.

While I agree with the bulk of your comments I only have the following to add.

With Lead Acid or Lead Calcium "Deep Cycle" batteries during "Equalization" the voltage will be raised to approximately 2.7 volts per cell which is about 16.2 volts for a 12 volt battery and the current output of the charger should be limited to 5% of the battery capacity. Another name for Equalization is "Controlled" Overcharging "emphasizing controlled".

I have used "Equalization" to save "start" batteries that had been improperly charged, but must admit that when start batteries get to a point that they no longer hold a charge they are usually beyond help.

Car alternator regulators do not have Equalization capabilities nor do some AC chargers. "External regulators" on engine driven alternators will usually have this feature (for example marine diesel driven alternator and regulator charging an 800 Ah house bank).

Balmar Extenal RegulatorXantrex

Xanterx AC Marine Multi-Chemistry charger This charger allows you to charge individual banks all different chemistry at the same time. Great if your start battery is lead acid and the house is AGM. No need for separate chargers.

Whether it is an AC charger or regulated alternator the Equalization feature will be disabled on AGM or Gel batteries due to the danger of explosion from gassing. (They are sealed). Manufacturers of these batteries for liability reasons will not recommend equalizing these batteries. Although with "experience only" they too can be equalized as I have done it on many occasions to save large banks of batteries. "This only to be done by experienced individuals only". For obvious reasons I will not state how to do this. I learned it during an unofficial conversation with a Powerline AGM battery engineer. (In his words if you have a few thousand dollars invested in deep cycle AGM batteries and they are not holding a charge, what do you have to loose). If not done correctly it could be devastating, in any case with that particular job I was successful at restoring the batteries and they are still in service 5 years later. (The cause of the AGM battery failure that lead to sulfating was undercharging).

As lead acid batteries are voltage devices, I cannot for the life of me understand your statement here:-

"the voltage will be raised to approximately 2.7 volts per cell which is about 16.2 volts for a 12 volt battery and the current output of the charger should be limited to 5% of the battery capacity."

As to get to that voltage, you will need a high current at the same time.....

To anyone who has not spent a lot of time with such batteries, my comment may not be understood, sorry to them.....so I will attempt to explain the problem a little better in a simple format:-

Here is a simple representation of the charger and battery as two resistances in series:-

Now say I want to get 12 volts across the battery, what voltage must I apply to the circuit as a whole?

Well if I want 12 volts across the battery, I use simple Ohm's law to find the current, which I = V/R = 12/2.5 = 4.8 amps.

Now I want to find the voltage that I need to allow 4.8 amps to flow through BOTH resistances. This is also simple:-

V = I X R = 4.8 X 7.5 = 36 volts.

So I must supply 36 volts across the two resistances to get 4.6 amps to flow which means I will have 12 volts across the Battery.......

If I apply more voltage, the voltage across the battery will rise as will the current.

If I apply less voltage, I will have less than 12 volts across the battery and less current!!!!

I cannot change one without changing the other......simple!

Forgetting for a moment that as a battery receives current when charging, the battery's voltage will rise and the current will drop, this is an "instantaneous example" only...but shows the principle clearly.

My question is how will you get to 2.7 volts per cell AND keep the current to less than 5%?

That is completely impossible on every sort of LA battery that I have ever seen, as the battery has a resistance, depending upon the state of the charge. Having the luck that at 2.7 volts per cell AND 5% or less current, MAY happen only when the battery is already fully charged and in a really good condition, MAYBE!

It will certainly gas like crazy and get very hot as this implies putting 16.2 volts over a 12 volt battery......as you cannot keep voltage up and current down in the manner you describe. Simple Ohm's law.

It may be worth trying on an otherwise dead battery ( I admit we used to do this to try and rejuvenate old car batteries in the 50 and 60's, before I was 15 years old!)......but there are far better methods in general usage nowadays....The old method only worked occasionally even then......more by luck than judgement!!

Now other battery technology (not LA), you probably could do this as they are "current charged", but not LA!

May I suggest that you read the following .pdf, it states quite clearly that what you suggest will only reduce the life of the battery:-

http://www.power-sonic.co.uk/downloads/Battery_Guide.pdf

Have a great day in spite of me.

I did not make this up. This absolutely common sense in the industry.

I install these systems in yachts and home solar systems and I live on 12 volts full time and have been for the past 9 years.

You are correct that the battery has to be fully charged. As far as reducing the life of the battery, in some cases it is not an issue because it is normally done when the batteries are sulfated and not holding a charge and your are faced with Equalizing or buying new batteries. On yachts with lead acids batteries equalizing is used as a preventative measure every month.

The following research argues that it will extend battery life.

It does gas like crazing and the electrolyte levels and temperatures need to watched carefully. This is why they don't recommend it on sealed batteries. The high volts/low amps reconverts the lead sulfate back back into lead and sulfuric acid and off of the plates. (simplified).

Check out the links I posted on this and my last post and read it for yourself and if you have a problem contact the manufacturers of batteries, chargers and regulators. All of this is achieved in the regulators and charger programing. Better yet just type in the search engine "Battery Equalization".

This is the real world when you are living on 12 volts. Not some theoretic mumble jumble. Why do you think the option to Equalize is built into chargers and regulators. Don't shoot the messenger!

The statement "the voltage will be raised to approximately 2.7 volts per cell which is about 16.2 volts for a 12 volt battery and the current output of the charger should be limited to 5% of the battery capacity." was taken directly out of the operation manual for Xantrex and Balmar and is also discussed in books by Nigel Calder and the "12 volt bible" by Ed Sherman.

As far as I am concern I have beat this dead horse long enough. Good luck!

Believe me, those/that company is talking through its hat.

If a battery is gassing violently, then its getting a far higher current through it than 5%.......

5% is ALMOST not charging!!!Thats more like a "trickle" which WON'T gas till the battery is fully charged which on most car batteries will take a long time to achieve. Certainly not violently......and for a 100amp battery, its almost a "maintenance" charge....

One should not believe marketing literature, its there to grab the gullible ones only with no accurate knowledge!!! It was always like that and will never change.....

The .pdf I posted is a very good and reasonably accurate document, but even so, I bet it has a couple of points that I could query on!!

Andy - be careful.

Did you read through the manual cited in the link? Several things puzzled me before reading parts of it carefully. I may be speaking out of turn, but they seem to know what they're on about. That or it's a very good scam (which I doubt).

Cheers,
John.

[Edit - the phrase "5% of the battery capacity" is a bit vague, to say the least. What does it mean?. I suspect it's quite a hefty current - way more than trickle/maintenance etc.]

John, its actually physically impossible to drive such a low current through a LA battery at the same time such a high voltage. Mr Ohm will not let you as he made a simple law about it long ago!!

Violently gassing is another tip that the current is high when you do this!!! Low currents do not cause batteries to violently gas......the energy input is simply too low!!!

Also mentioned was the possibility that a SLA battery might explode........

All of these point to a high energy transfer, only achieved with high currents.

Anyone who does not believe that, is entitled to his own opinion.....but that does not make it true!!

How much is "5% of the battery capacity" (in amps)? What current are we actually talking about?

On a 100 amp/H battery, 5 amps....... = 5% = C/20. A relatively low rate of charge....

When the battery is 100 % charged, the Battery terminal voltage will be around 14.3 volts at 20°C.....

This stuff is often misworded. You hear electric vehicle people and others talking about putting "amps" back into a battery (when they really mean amp-hours). As you know, amp-hours and amps are different things. If a battery is rated 100 AH, 5% of that would be 5AH, not 5A. But what is meant is 5 amps. As Andy wrote, they are referring to a C/20 charge rate.

Charge rate, C is understood to be referenced to the battery's AH rating (which itself should be specified in terms of the number of hours of discharge). Charging at 1C rate means charging at an numerical amperage value equal to the numerical value of the battery's AH rating. (Mathematically, the charge rate is really AH/H... and the H's cancel.)

John, its actually physically impossible to drive such a low current through a LA battery at the same time such a high voltage. Mr Ohm will not let you as he made a simple law about it long ago!! Violently gassing is another tip that the current is high when you do this!!! Low currents do not cause batteries to violently gas......the energy input is simply too low!!! Also mentioned was the possibility that a SLA battery might explode........All of these point to a high energy transfer, only achieved with high currents. Anyone who does not believe that, is entitled to his own opinion.....but that does not make it true!!

The key is the battery internal impedance is not constant. If the battery resistance was constant your logic would prevail but the internal resistance of all lead-acid cells changes with the cell's state of charge.

Current and Batteries and Ohm's Law

Battery voltage can be affected by three factors — state of charge, current, and temperature. State of charge is what we are trying to find out, so that leaves current and temperature as factors to reckon with.

Current means the rate of electron flow through the battery caused by either charge or discharge. Every electrochemical cell has internal resistance. As current moves through the cell, the cell's voltage changes because of this internal cell resistance. When the cell is being recharged, current flow causes the cell's voltage to rise. The higher the recharging current the higher the voltage rise. As the cell is discharged, the discharging current causes the cell's voltage to drop. The higher the discharging current, the greater the battery's battery depression. This holds true for all electrochemical cells regardless of type, size, or environment. While absolute values vary widely between different acid and alkaline technologies, the relationship between current flow and cell voltage remains constant. The graphs show a variety of recharge and discharge rates from C/5 to C/100. This C/XX number is actually a rate of charge or discharge in Amperes proportioned to the capacity of the battery. For example, consider a battery of 100 Ampere-hours. If you divide this Ampere-hour capacity by 10 hours, then you get a charge (or discharge) rate of 10 Amperes. Ten Amperes is a C/10 charge (or discharge) rate for a 100 Ampere-hour battery. Consider another battery of 500 Ampere-hours capacity. Here a C/10 rate would be 50 Amperes. While the absolute values of the charge (or discharge) currents are different between the two batteries of different capacity, their effect on the batteries voltage is the same. The currents are in the same proportion to the batteries capacity. If voltage is to be related to battery state of charge, then we must compensate for voltage variation due to current movement through the battery. Hence there are a variety of curves on both the charge and discharge graphs.

Lead-acid Internal Resistance and State of Charge (SOC)

In lead-acid cells, the electrolyte (sulfuric acid) participates in the cell's normal charge/discharge reactions. As the cells are discharged, the sulfate ions are bonded to the plates — sulfuric acid leaves the electrolyte. The process is reversed when the cell is recharged. A fully charged lead-acid cell has an electrolyte that is a 25% solution of sulfuric acid in water (specific gravity about 1.26). A fully discharged lead-acid cell has virtually no sulfuric acid in its almost pure water electrolyte (specific gravity about 1.00). As the sulfuric acid concentration in the electrolyte changes so does the electrical resistance of the electrolyte, which in turn changes the internal resistance of the entire cell. The bottom line is that the internal resistance of all lead-acid cells changes with the cell's state of charge. This characteristic gives the lead-acid reaction its particular shape or signature on the voltage vs. SOC graphs. This signature is unique — very different from alkaline cells whose electrolyte resistance remains constant regardless of SOC. The shape of the lead-acid curves makes it possible to use a voltmeter to determine a battery's state of charge.

Reading the Curves

The data presented here on the graphs was generated from a set of Trojan L-16W deep cycle lead-acid batteries. Each Trojan L-16 battery is composed of three series connected, 350 Ampere-hour, lead-acid cells. The graphs and the data here relates to six of these lead-acid cells in series forming a 12 Volt battery. Those of you using a 24 Volt system with twelve lead acid cells in series must multiply the voltage in the text and on the charts by two. The voltage versus state of charge (SOC) profiles will match those of similarly constructed cells. Other types of lead acid cells, like car batteries, lead-calcium cells, and "RV deep cycle" batteries will have different charge/discharge curves. I offer these graphs as examples of what to look for with your battery. While specific voltage vs. SOC points will vary from battery type to battery type, the shape and relationship of the curves is similar for all deep cycle lead-acid technologies.

From article Titled Lead-Acid Battery State of Charge vs. Voltage

By Richard Perez

The other article I posted was not a product brochure, it was a research paper that you obviously did not read before closing your mind.

If you look at the bottom of the graphs, you can quite quickly see what you are doing to the battery.....severely reducing its life with drastic overcharging. Up to 130% of overcharge. THIS NEEDS A HEAVY CURRENT, far more than the C/20 (5%) bandied about earlier, which was the point I was trying to make and of course nobody read and fully understood what I was talking about (I did think that I put it very simply.........)

I would be most grateful to ANYONE who can show that a battery being charged to OVER 130% AND only done at C/20 or 5%......as of now, nobody has managed to demonstrate that in anyway shape or form!!! I say it cannot be done.....you appear to feel that it can, so please supply proff. Thanks in advance!!

The last 30% demonstrated in your graphic, has only resulted in large quantities of water being turned into an explosive hydrogen/oxygen mixture, which the smallest spark from clothing or a cigarette will cause a massive explosion, usually sending large pieces of battery case, sulphuric acid and lead in all directions at very high speed. Many have lost their sight in this way.....

Furthermore, leave the 130% charged battery for a few hours doin nothing and the voltage drops back to normal values AT BEST. If the battery is now damaged, they will drop even further!!! So all the extra energy put in is simply lost, it is certainly not ever available at the terminals.....

LA Batteries are remarkably inefficient, I forget exactly but a ball park figure will probably be around 70% FOR A BATTERY CHAGED TO 70% CAPACITY. Once beyond 70% capacity, the efficiency drops and drops. Its a wellknown fact....you can even see the point where the efficiency drops on the graph you displayed quite easily.

But showing this graph as proof that the severe overcharging is OK has no logic or good use to it. Occasional "light" gassing and a charge to 100% will keep a battery fit, but anything more is both wasteful and can be dangerous as I mentioned earlier....

As I also said before, each to his own on this matter. You screw your batteries the way you see fit, I look after mine in the manner I see fit.

My test battery (120 A/H Leisure battery) is now about 9 years old and shows no signs of losing capacity and has only needed water once (a tiny amount, it was still within the allowed tolerance) 2 years ago, in spite of being used in Mediterranean countries with day temperatures up to 48°C, when on holiday each year and very hot summers here in Germany too like this year for example.........

But I do design and build my own chargers since around the year 2000....they do not work in the way that many others do, nor do they charge to 100% unless I program it to.....which I only do occasionally when we are going to be several days away from a possible charging source....running a car engine just to charge a battery is simply a waste of fuel.....

Please do try and read "between the lines" in such documents as you printed here (I know the source, its a good source, but not to be taken literally as being the correct way to handle a battery, particularly if you want your battery to last a long time), they only tell a one sided version of what can be done/is required and lead many from the "straight and narrow"!!!

They are not advocating anything to do with battery life expectancy, nothing about safety, they are only showing you what can be done.....

Modern battery "Zappers" seem to work well, though the full understanding of "why" does not seem to have been written yet. I use one on my caravan battery and it does its job as expected.....just HOW good it is I can only say when the battery is finally defective......you will be one of the first to know!!

Have a great day.

My test battery (120 A/H Leisure battery) is now about 9 years old and shows no signs of losing capacity and has only needed water once (a tiny amount, it was still within the allowed tolerance) 2 years ago, in spite of being used in Mediterranean countries with day temperatures up to 48°C, when on holiday each year and very hot summers here in Germany too like this year for example.........

You may be on a holiday in a hot climate for a short time but I am in the Caribbean full time every day 365 days a year, where it is hot all the time. My batteries are 9 years old and they were discarded by someone else. They are 6 gel batteries and I equalized them after getting them out of the trash and have run them steady for 5 years as I live full time on my yacht. These batteries show no sign of letting up yet.

I have saved many sulfated batteries for customers over the years who would have disposed of them and I have never had a catastrophic failure. As I said in an earlier post the batteries need to be monitored while Equalizing.

Out of the entire world using chargers to equalize deep cycle batteries and out of the many papers published on the subject of "Equalizing" you are alone in your believes.

It was people like you that told my partner and I that was impossible to arrest a detonation, he went a head invented the first detonation flame arrester in the world and I have since gained 5 patents on various designs.

As you said you make your own chargers and in your own words "One should not believe marketing literature, its there to grab the gullible ones only with no accurate knowledge!!! It was always like that and will never change....."

So lets just agree to disagree!

Good day to you too!

Thats a way to end an argument when you can't answer the question, ramble on about something else that has almost nothing to do with the question and then simply stop.

OK.

Its not what I would do......but then thats just me!!

Bye.

Andy,if you charge the battery every time to only 70% of its full capacity that causes the remaining part(30%) to sulphate and becomes damaged part.

That single sentence shows your level of knowledge of LA Batteries to be simply zero!!!

I expect it is also your level of knowledge for batteries as a whole.......as it is also not true for all the battery types that I can think of......

TIP!! It is not like a petrol tank, where the fuel fills from the bottom up!!!!

WOW!! How embarrassing for you (if you had properly signed on and not just as a guest!!)....

But I guess you already knew that you didn't know much about this subject, which proves that you know one thing only here!!!

By the way, if you had read my posts more carefully you would see two exceedingly important points:-

1) I charge to 100% when we are going to a camping site with no electricity.

2) There is a small electronic unit (often called a Zapper), permanently connected across the battery, to give it little nudges of high voltage from time to time, this is believed to stop sulfation, I believe it too.....though I have to admit that the chemistry is mostly not understood, even by the companies that make them.

I have yet to note any loss of capacity up to now.....

"That single sentence shows your level of knowledge of LA Batteries to be simply zero!!!"

Haughtiness is the first step towards the big fall.

But it does not help you to know more it would appear......so if I were you (thank God above I am not!) I would endeavour to learn more and reduce the haugtiness factor as well, as it hasn't heped you in the slightest!!!

Its just like in Rome, a messenger brings you bad news, so you kill the messenger!!!! As if that would help anyone.....

It would have been better if you had read ALL the relevant posts before "sticking your neck out" for me to "whop" off.....and studied more at school!

Laughable and exceedingly petty......

With such posts one "knows" who has an engineering background or not rather quickly!!!!

So what i understand so far is the equalization mode is good only for flooded battery and not for sealed Lead Acid battery.

Is i am wright ?

Oo...Yes, i was refering to the oddesey batteries...But the manual that i hav does not have the 40% thingy... guess mine is not updated ~~ Thsnk a lot for the infor ~

I would like to know the differences between using the recommended charger and NOT using the charger.

For eg:

1. Car Alternator (say, 100A) + charger + battery (oddesey PC1700)--- The charging will be taken care by the charger. Voltage and current limit is done by the charger. Correct? If yes, then the alternator need to sized up to total load capacity + limited current of the charger + some safety factor.

2. Car Alternator (say, 100A) + battery (Oddesey PC1700) --- Directly connect the alternator to the battery. The battery will draw max capacity of the alternator (meaning it draws more than 40% of the 10-hr rating) ? OR the battery will draw max of what the batt needs (equal or below 40% of the 10-hr rating). For this case,can the alternator be sized up to total load capacity + 40% of the 10-hr rating + some safety factor?

I'm not sure what you mean by "charger" in the context "Car Alternator (say, 100A) + charger + battery (oddesey PC1700)---."

Ordinarily, a battery is charged by an alternator when the vehicle is running, and sometimes (depending upon application) charged by an external charger (generally AC-powered) when the vehicle is not running. When an Odyssey battery is installed in a car or power boat (in which it is used as a starting battery) the battery might never be charged by an external charger. Equalizing is generally (although not always) not employed with AGM batteries, so there is not much that an external charger offers that the alternator (with its voltage regulator) does not offer.

However, some vehicles sometimes sit unused for long periods. Then an external charger can be used to keep the battery from developing recalcitrant sulfation (crystallized sulfates that cannot be redissolved). Often, only a maintenance charger (float charger) is required in this situation.

Sailboats, RVs, etc sometimes use the term "charger" to mean an external charge regulator. Perhaps this is what you have in mind? (Ordinarily you would not use a car alternator and an external, (i.e., AC/mains) charger at the same time.)

2. Car Alternator (say, 100A) + battery (Oddesey PC1700) --- Directly connect the alternator to the battery. The battery will draw max capacity of the alternator (meaning it draws more than 40% of the 10-hr rating) YES ? OR the battery will draw max of what the batt needs (equal or below 40% of the 10-hr rating). NO

I am assuming by "directly connect" you mean through the diodes and with the internal regulator intact.

For this case,can the alternator be sized up to total load capacity + 40% of the 10-hr rating + some safety factor?

Whether or not this is required would depend upon how the battery is being used. It is certainly permissible, however (and common) to have a large alternator installed in a car to deal with unusually heavy electric loads (AC running all the time on high, huge stereo, battery-powered winch, etc.) How are you using this battery?

there is not much that an external charger offers that the alternator (with its voltage regulator) does not offer.

MoronicBumble, I know that you know this but I wanted to clarify it for others. An external AC charger, in most cases (not all) are configurable for different battery chemistry (AGM, Gel, LA etc...) equalizing and other features. An Alternator with a built in regulator cannot be adjusted for anything other than their factory settings which is normally for Lead Acid batteries. Having said that an Alternator can be altered to use an external configurable external regulator that has all of the features of external AC charger. You can also purchase the Alternator that is already set up for this.

(Other topic, do you live or own a boat as I seen your "Sailing News Letter" post?)

Ooo...Now i understand better. thsnk ~

Lets say the battery usage is like a normal car usage. crank start engine + occasionaly use to supply the car system when the alternator is not running.

About the "charger", the mastervolt alternator has this regulator/battery charging controller or dunno what they call it (thats the "charger" i was talking about, not the AC-DC external charger used when alternator not running), actually read the states of the battery (batt temperature, voltage) and controll the charging stage (like bulk charge etc etc) of the battery.

MoronicBumble, i was reading the manual that u posted. Quote from the manual " with simple constant voltage charging (alternator or independent charger), there is no limitation on the inrush current".

Does this mean that, if i just connect alternator to the battery (no charger), the battery will just draw what it needs ( what it needs based on the state of charge) ? E.g it might be drawing max of alternator capacity during (let's say) 25% charged state?

Does this mean that, if i just connect alternator to the battery (no charger), the battery will just draw what it needs ( what it needs based on the state of charge) ? E.g it might be drawing max of alternator capacity during (let's say) 25% charged state?

Yes, that is essentially correct. The term "needs" is not exactly correct, though. The battery doesn't have any knowledge of what it needs in term of charge rate -- it only has an internal resistance that varies with state of charge. For your battery, the amperage can be very high without damaging the battery. For other batteries, high amperage can cause plate overheating and warpage. So some batteries would be damaged or have their life shortened by high charge rates, even though their internal resistance will cause such charge rates (given a source capable of high amperage). For these other batteries, the battery "needs" a lower rate, but the charging source can deliver a higher rate than needed.

"For your battery, the amperage can be very high without damaging the battery."

Oo.. that means, i need to limit this current, if i dun wanna damage my alternator.....

Edit: And this current limit will hav to set it to above the recommended 40% of the 10-hr rating....

After this very long discussion about battery charger believe me i got completely confused information, i don't know what is right and what is wrong.