How Fast Can an AGM Battery Be Charged..?

[Maine Sail]

Maine

At page 2, discussing bulk voltage: ". . . but once voltage is held stead or becomes "voltage limited." . . . "
At the last page, at Note concerning Lifeline: ". . . .2C charge rate as teh bare minimum . . "

Thanks all fixed!!

By the way one hopes folks take the time to understand this stuff thus to reduce battery homicides - probably should be battacides.

Me too..!

I am wrestling with why you say bulk voltage is a marketing term. Every regulator and shore charger that is programable allows one to choose a specific voltage during the bulk phase and that voltage is typically higher than the absorption voltage. Could it be lower?

You are only wrestling with it because of marketing....

• BULK charging is CONSTANT CURRENT it is not CONSTANT VOLTAGE.

• BULK charging can only occur when the charge source is in CONSTANT CURRENT.

• BULK/CONSTANT CURRENT is not VOLTAGE LIMITED it is CURRENT LIMITED

• The only time we can accurately refer to a bulk voltage is at the transition from BULK/CC to ABSORPTION/CV charging. It should properly be called a bulk transition voltage or more appropriately an absorption voltage.

The proper terminology for these marketing departments, if they cared, would be ABSORPTION 1 then ABSORPTION 2 not a voltage limited bulk voltage then absorption voltage. Heck you could even refer to it as pre-absorption and absorption. Simply put voltage limited charging is not bulk/CC charging. Voltage held constant during charging is constant voltage charging and can be absorption, float or equalization but it can not be accurately referred to as a bulk voltage.

If you have multiple CV stages then:

BULK = Constant Current
ABSORPTION 1 = Constant Voltage (could also be pre-absorption)
ABSORPTION 2 = Constant Voltage (could also be absorption)
FLOAT = Constant Voltage
EQUALIZATION = Constant Voltage

Just because big companies use fancy words to confuse the sheeple into believing they are getting something they are not, does not make it correct.

Sorry for the rant but this is like nails on a chalk board to me. Sadly it was Balmar that started this BS and everyone else seemingly followed suit....

What was the voltage during bulk at .4 and .2 in your exercise?

Charles

And here is why using the wrong terminology is entirely misleading!

The voltage during BULK was always CLIMBING towards the absorption voltage/CV LIMIT because BULK is NOT a voltage limited stage of charging it is voltage rising!

Our charge sources only do two things;

Supply all the current they are capable of = BULK = Constant Current

Limit Voltage = Absorption, Float or EQ = Constant Voltage

That's it, either they supply FULL CURRENT or LIMIT VOLTAGE they don't do both at once.

Voltage regulators, and all marine charge sources use a voltage regulator, are really nothing more than VOLTAGE LIMITERS. They don't and can't become VOLTAGE LIMITERS until the voltage limit has been reached. The voltage limit is reached by supplying constant current while the terminal voltage RISES... This is why there is no such thing as a bulk voltage, when referred to in a constant voltage sense, because in constant current, which is bulk charge, voltage is never steady and is always climbing/increasing....

EDIT: Thanks for mentioning this because if an electrically savvy guy like you can't grab onto the difference between bulk/CC and absorption/CV then it simply needed more clarification. I added this image from the Lifeline Technical Manual:

"In the first stage, a constant current is applied UNTIL the voltage REACHES a PRE-SET LIMIT."

The key words here are:

• constant current - this is BULK

• until reaches - BULK lasts UNTIL voltage REACHES the ABSORPTION limit. The word REACHES denotes voltage RISING

• preset limit. - This is the absorption or CV transition or, better stated, the bulk charge end point.

This does not denote holding voltage steady during BULK instead it clearly defines were BULK ends and that is at the "pre-set voltage limit" otherwise known as the CV or absorption.

My disagreement is with using the term "BULK" when describing a CV stage of charging, and this is simply incorrect terminology and entirely confusing to boat owners..

 

[Maine Sail]

This chart clearly shows the differences between Bulk/CC and Absorption/CV

BULK: If we start at the top left of the chart we can see that the current held rock steady at 18.75A for 1:42 minutes. This current, 18.75A, is .15C or a 15% charging current of a 125Ah battery.

VOLTAGE RISE DURING BULK: If we look at the left side of the chart we can see the voltage climbing towards the absorption set point of 14.4V. It took 1:42 minutes at a rock steady bulk/CC of 18.75A for the battery voltage to reach 14.4V.

1/3 From Left: This is the point where constant current/bulk and constant voltage/absorption flip-flop. Voltage stops climbing and is held steady, and current changes from being steady/constant to declining. Once the BULK/constant current charge has driven the battery voltage to the absorption voltage limit, the voltage is now limited or held steady and the charging current begins to decline.

CHARGE TIME: As current declines while the voltage is held steady, and the SOC rises, out towards the lower right of the chart, the time it takes to get that last few % in takes significant time. At .15C this battery took slightly over 7 hours to reach 100% SOC.

As can very clearly be seen here bulk is constant current UNTIL the voltage has risen to the absorption point where it is then held steady and current declines..

 

[JohnShannon]

Charles there are 3 step chargers first phase is constant current, till voltage builds to as they call it "bulk voltage"
Second phase is bulk charge at some regulated voltage, current decreases, once current decrease enough switch to.
Third phase is float at some regulated voltage lower than the bulk voltage.

So you can have a charger with a bulk setting, and a float setting.

 

[JohnShannon]

I wish there was a "clay tablet " font for Maine's posts

 

[Brian D]

This was Maine's first battery instructions when he invented the battery.

 

[Charles Erwin]

"In the first stage, a constant current is applied UNTIL the voltage REACHES a PRE-SET LIMIT."

So to illustrate - take the case of a programable source - perhaps a programable voltage regulator or programable shore power charger. If bv (bulk voltage) is set to 14.7 and if Av (absorption voltage) is set to 14.5 which of these two values is the 'pre-set limit'?

If the controlling pre-set limit is the Av value then why not set the bv value to that same number? For that matter why provide any ability to make these two values different?

Charles

ps - To Brian -- oh dear but I like it

 

[JohnShannon]

I dunno here is an explanation of three stage charging
http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

 

[JohnShannon]

Lifeline technical manual http://www.lifelinebatteries.com/manual.pdf page 19 has the info

They seem to imply that you can see the CC level very high indeed with the lifeline battery. Maine's data would indicate that higher CC would result in exiting bulk charge even sooner he has 0.4C exiting bulk in 20min vs over an hour for 0.2C. If you cranked it to 1C you would be out of bulk maybe almost instantly, but until your charge current had fallen to 0.4C you would be "ahead" in restoring capacity. Well as an aside, I think my 8A charger is inadequate considering my 200Ar bank. Although my typical scenario is 10% discharge during a day sail followed by 1/2 of motoring at 50+A of charge followed by 8A off the shore charger maybe not too bad.

 

[Maine Sail]

"In the first stage, a constant current is applied UNTIL the voltage REACHES a PRE-SET LIMIT."

So to illustrate - take the case of a programable source - perhaps a programable voltage regulator or programable shore power charger. If bv (bulk voltage) is set to 14.7 and if Av (absorption voltage) is set to 14.5 which of these two values is the 'pre-set limit'?

If the controlling pre-set limit is the Av value then why not set the bv value to that same number? For that matter why provide any ability to make these two values different?

Charles

ps - To Brian -- oh dear but I like it

Replace Balmars incorrect use of BV/Bulk Voltage with the words Absorption 1 or Pre-Absorption and now their terminology is no longer bastardized, misleading and incorrect.

There is nothing wrong with having additional constant voltage levels, in steps, and in fact it makes for quite an excellent charge profile, but it is simply incorrect and entirely misleading to use the term BULK for something that is CONSTANT VOLTAGE because bulk is not voltage limited...

To answer your question if the regulator or charger is set for 14.7, as the first CV limit, then CC/Bulk will drive battery voltage to 14.7V where it will then become voltage limited to 14.7V. Let's more accurately call this first CV level absorption 1. It will then limit to 14.7V for the absorption 1 programmed duration, perhaps 30 minutes. At 30 minutes the regulator will decrease the voltage limit to a lower CV limiting point of perhaps 14.5v, we'll call this absorption. The regulator will then run through that time/algorithm and finally after many more hours the regulation will again decrease the CV limit to another lower CV level called float.

A typical charge profile on a Balmar will look like this: CC, CV, CV, CV

The first CV point is incorrectly called a bulk voltage by Balmar and this is simply bad form and misleading. To my knowledge Balmar was the first to use bulk incorrectly and now we have others copying it because the confusion apparently works and folks now think they are getting a bulk constan voltage, which simply does not exist except in the eyes of the marketing departments...

 

[Maine Sail]

Charles et al.,

I am going to make a video to show bulk, absorption & float etc. or CC-CV. Don't know when I will get to it but visuals often work much better than words...

 

[jlp0217]

Main,
Usually you are spot on, but I think you're being a little too rigid here. What Balmar calls bulk voltage maybe would be better termed bulk limit, but as I understand it is the voltage that the firmware compares to current voltage to signal transition to absorbtion phase. Just because Lifeline says that trigger voltage is the same as float voltage does not make it a law of physics that charger mfgs must obey in their firmware. So what happens in a battery if the charger tries to maintain constant current longer by using a higher transition voltage?
As to Charles Erwin's question about voltages at times during bulk charging - that is exactly the subject in another thread about SOC under load.

 

[Maine Sail]

Main,
Usually you are spot on, but I think you're being a little too rigid here. What Balmar calls bulk voltage maybe would be better termed bulk limit, but as I understand it is the voltage that the firmware compares to current voltage to signal transition to absorbtion phase. Just because Lifeline says that trigger voltage is the same as float voltage does not make it a law of physics that charger mfgs must obey in their firmware. So what happens in a battery if the charger tries to maintain constant current longer by using a higher transition voltage?

I don't believe I am asking too much by suggesting companies use the correct terminology to describe charging, and lots of them do...

DIN standards actually define this very clearly. The terms bulk/CC absorption/CV have been industry standard terminology long before Balmar decided to call bulk a CV stage of charging.

As a Balmar dealer, and yes I have had this very conversation with Balmar who readily admits, when pressed, that their terminology is in fact not accurate or correct and that yes it has been misleading. My frustration lies in trying to help owners trouble shoot issues when definitions are blurred.

Balmar sets at-voltage time limits and calculates how long the regulator will stay at "bulk voltage" but this is not bulk charging it is CV charging or as DIN defines it the Uo (absorption/CV) charging. The DIN definitions are nothing new and are adapted from long held accepted industry standard definitions for charging. DIN calls this I-Uo-U charging with I being constant current or bulk.

Under DIN the definition looks like this

I = BULK / CONSTANT CURRENT = (Battery voltage rising charge source providing full current)
Uo = ABSORPTION / CONSTANT OVER VOLTAGE (they call this the constant over voltage because we are above gassing level but it is just another term for a CV stage)
U = FLOAT / CONSTANT VOLTAGE

A Balmar regulator is actually doing;
I-Uo-Uo-U not I-I-Uo-U

Put another way CC-CV-CV-CV

Put another way BULK - ABSORPTION 1 - ABSORPTION 2 - FLOAT

The Balmar regulator pushes to a higher Absorption voltage 1 (Balmar's bulk voltage) and this is good for short duration run times, and reconverting sulfation, as it gets the battery to a higher SOC & voltage level, for a short duration, before you shut down the engine. It then drops to a slightly lower absorption voltage 2 but all of these are fully programmable provided you have a .1V difference between the stages. (I have never once left a Balmar regulator using a factory pre-set)

As an example of this, for a LiFePO4 battery, I will use 13.9V for 6 minutes (Balmar calls this bulk voltage I call it Absorption 1) then I go to an absorption voltage 2 of 13.8V for a maximum of 2 hours then the voltage is dropped to a float voltage of 13.1V which essentially turns the regulator off because the voltage of the LFP battery is almost always above 13.1V...

The long and short these are excellent regulators despite the use of incorrect terminology which makes it confusing.

As to Charles Erwin's question about voltages at times during bulk charging - that is exactly the subject in another thread about SOC under load.

As I read it I thought Charles question was clearly worded and a pretty good example of where using misleading terminology leads...

"What was the voltage during bulk at .4 and .2 in your exercise?"

What was the voltage during bulk at .4 and .2 in your exercise?
Charles

 

[All U Get]

This was Maine's first battery instructions when he invented the battery.

View attachment 119450

Nice that you kept your copy Brian.

For me battery charging is like bailing the dinghy. Bulk is when its full and I use the bucket. Absorb is when the bucket isn't so good so I switch to the sponge. Finally I use the cloth to absorb too. The result is float nice and dry. I don't equalize because I don't need the center console dinghy.

All U Get