Re: Do you beleive these stats on Battery Voltages?
โอม มณี ปัทเม หุม
> Very conveniently, the relationship between a battery's state
> of charge and its voltage is linear (10% per 0.10V) between about 90%
> (12.70V) and 20% (12.0V). However, when a battery has been on
> charge, even if its not fully charged, the voltage will be up
> around 13.8V. This will slowly drop to around 13.6V over the next
> few hours, but even if left overnight it shouldn't drop below
> 13.0V unless the battery was only partly charged or is on the way out.
Battery manufacturers would disagree slightly.
If you charge up a sealed AGM battery, you may read
14 ~ 15 volts when you first take it off the charger, but the resting
voltage will drop down to 12.8 volts and stay there in about half an
hour, assuming that the battery was in good condition and took a full
charge.
Bob
<macm...@gmail.com> wrote:
|>On Nov 28, 3:26�am, Bob <r...@armageddon.info> wrote:
|>
|>> Very conveniently, the relationship between a battery's state
|>> of charge and its voltage is linear (10% per 0.10V) between about 90%
|>> (12.70V) and 20% (12.0V). However, when a battery has been on
|>> charge, even if its not fully charged, the voltage will be up
|>> around 13.8V. This will slowly drop to around 13.6V over the next
|>> few hours, but even if left overnight it shouldn't drop below
|>> 13.0V unless the battery was only partly charged or is on the way out.
|>
|>Battery manufacturers would disagree slightly.
|>
Yer sure right about that, it's a 3 ring circus of dis/informations all
over.
It may depend on were they were made, but I did use some Chinese
"AGMs" with a holding 13.6 volts 2 hours after charging but no load....it
started with about the same cca as a 12.8 "wet" sla battery.
|> If you charge up a sealed AGM battery, you may read
|>14 ~ 15 volts when you first take it off the charger, but the resting
|>voltage will drop down to 12.8 volts and stay there in about half an
|>hour, assuming that the battery was in good condition and took a full
|>charge.
This battery is on the vehicle circuit, and not a stand alone battery on a
table....right?....a GT9B-4 12v/8Ah wants a charge at 12.v, and the Majesty
Yamaha yp400ts manual considers 12.8v as a minimal voltage, but AGMs can go
down to 12.5v before needing a recharge.
I prefer using a Shumacher 4 stage smart charger with blinding LEDs,
and it equalise/bulk/absorb charges to 12.9v/%100 and then goes into a float
maintenance mode, and goes up to a possible 17v (stubborn batt) to maintain
at least a 13.2v for regular MF/Marine/DeepCycle, and 13.4v for agm/gel
status for a specified time.
The 12.9v full charge is referred as %90 by other chargers, most
chargers, all have a slightly different but very consistent preference.
.
This float *topping mode* is good if you have time/patience with a
passive/auto smartcharger....wereas an active/constant charger feeds the
battery what it is supposed to be with no time consuming battery queries.
Bob
โอม มณี ปัทเม หุม
> |> If you charge up a sealed AGM battery, you may read
> |>14 ~ 15 volts when you first take it off the charger, but the resting
> |>voltage will drop down to 12.8 volts and stay there in about half an
> |>hour, assuming that the battery was in good condition and took a full
> |>charge.
>
> This battery is on the vehicle circuit, and not a stand alone battery on a
> table....right?....
No, that is the open circuit voltage while the battery is sitting on
the table half an hour after charging it.
The manufacturer's literature that comes in the box with the battery
tells exactly how to fill it with the supllied electrolyte and how
long to charge it and at what rate.
Then the literature says to measure the resting *open circuit* voltage
and specifies that 12.8 volts indicates a full charge for the AGM
battery.
If the manufacturer doesn't know the right information, who on earth
would know?
If I can't trust the manufacturer to give me correct information, then
I'm at their mercy...
The last two AGM batteries I've owned lasted 8 years without problem.
S'mee
If you posted it it's either a LIE or you plagerized it...
Bob Myers
>> Battery manufacturers would disagree slightly.
>>
>> If you charge up a sealed AGM battery, you may read
>> 14 ~ 15 volts when you first take it off the charger, but the resting
>> voltage will drop down to 12.8 volts and stay there in about half an
>> hour, assuming that the battery was in good condition and took a full
>> charge.
>
> If you posted it it's either a LIE or you plagerized it...
He no doubt did a cut-and-paste of this info, but at
least this time he used a source that was correct. Per the
basic chemistry, one lead-acid cell should provide a
nominal voltage of somewhere around 2.1, so for
a six-cell-in-series battery, you should see somewhere
around 12.6V. The "13.X" volt reading that we're used
to seeing in charging situations (including what you'd
see on a voltmeter on your car dash, since presumably
the engine is running and the system is in the "charging"
condition when you'd see this) is because you have to
use a slightly higher voltage per cell to charge the thing.
But 14-15V is high; exceed about 2.4 V/cell (14.4V across
a "12V" six-cell battery, and a lead-acid cell will start
outgassing. Typically, a charger is set to deliver something
like 2.2-2.3 V/cell, or 13.2-13.8V across the battery - and
that's the highest you should ever be reading across the
battery terminals.
Bob M.
Mark Olson
Mostly correct if you are talking conventional lead-acid batteries, but
for many new bikes that come with sealed VRLA (valve regulated lead acid)
batteries, the lead-calcium chemistry is different, and the voltages are
a little higher. According to Yuasa,
When considering upgrading to a sealed VRLA
battery that did not come OE in your vehicle, check
to make sure your charging system has a
regulated output between 14.0 - 14.8v.
Of course this applies to vehicles that came from the factory with sealed
VRLA batteries too, not just older vehicles that are being retrofitted.
Also, the _fully_ charged voltage of a sealed VRLA battery is 13.0V, not 12.6V:
Check voltage using a voltmeter. Readings for a charged, newly-activated
battery should be 12.8v or higher after the battery is charged and sits for
at least 1 - 2 hours. If less, it needs an additional charge.
I strongly recommend that anyone who has an interest in taking the best
possible care of their motorcycle battery, no matter what style or type,
to download and read Yuasa's excellent technical manual.
http://www.yuasabatteries.com/pdfs/TechMan.pdf
It has enough detail and enough plain language to satisfy both picky chemists
and curious ignotes.
Bob Myers
> Mostly correct if you are talking conventional lead-acid batteries,
> but for many new bikes that come with sealed VRLA (valve regulated lead
> acid) batteries, the lead-calcium chemistry is different, and the
> voltages are a little higher. According to Yuasa,
I stand (well, sit) corrected, or at least amended, however
please let me add that "VRLA" does not necessarily imply
a different cell chemistry (the name itself simply means
"valve-regulated lead-acid," and refers to any of the
construction types where the battery is "sealed" and will not
vent excess gas until/unless a pressure relief valve is triggered.
These are also generally classed as "acid-starved" and/or
"recombinant" types, as they (a) generally contain less acid
than a conventional design, and (b) are constructed such that
generated hydrogen and oxygen gases will recombine rather
than vent, as long as the pressure remains below the relief
valve's trip point. However, while this permits a somewhat
higher charge voltage (and therefore faster charging) to be
safely used, the cell chemstry is very often exactly the same
as in conventional types, and so the voltage of a charged
cell or battery would in those cases also be the same. So
in the case of a VRLA type, you will often see somewhat
higher charging voltages, but the same voltage as in a conventional
type when you simply check the battery voltage on its own.
In any event, we certainly agree that one should not exceed
the recommended maximum charging voltage per the
battery manufacturer's recommendations; Bad Things can
happen if you do. 15V is high for any of these types.
Bob M.
Mark Olson
No, according to Yuasa, that is not the case with their sealed VRLA
batteries. Perhaps it is true of other makes, but I doubt it.
> In any event, we certainly agree that one should not exceed
> the recommended maximum charging voltage per the
> battery manufacturer's recommendations; Bad Things can
> happen if you do. 15V is high for any of these types.
I'm not a chemist nor do I play one at weekends, but if you read the
Yuasa technical manual, I think all or most of your concerns about
sealed VRLA batteries and their electro-chemistry will be addressed.
I strongly doubt that any VRLA batteries sold to the general public are
anything other than a lead-calcium chemistry. Here's what Yuasa has to
say about their sealed VRLA batteries:
1. The plates are comprised of special lead-calcium
alloy grids and charged active material. Lead-calcium
reduces self-discharge – the battery holds its charge
longer. The construction of the sealed VRLA battery
causes freed gas to recombine inside the battery instead
of being vented… allowing the battery to be sealed.
...
During discharge, sulfuric acid electrolyte solution reacts
with the lead plates, turning them into lead sulfate. The
electrolyte – sulfuric acid solution made up of hydrogen,
sulfur and oxygen – gives up its sulfur and some of its
oxygen and turns to water.
PbO2 + Pb + 2 H2SO4 → 2 PbSO4 + 2 H2O
The process reverses with charging. Electrolytes and
plates return to their original composition. The charging
current breaks down water into its component gases:
hydrogen (from the negatively charged plate) and oxygen
(from the positive plate). Gases escape out the vent
tube. With a conventional battery, water is added to
replace that loss.
Here’s the real secret of a sealed VRLA battery: the negative
plate never becomes fully charged… so, no hydrogen
gas. The positive plate still makes oxygen, but instead of
being forced out the vent tube, it reacts with the charged
active material to become water again. That’s “gas
recombinant technology.” That’s the magic of YUASA’s
non-spillable, sealed VRLA battery.
Really, download that PDF and read it, I found it fascinating.
ralleyrat
wrote:
Manufactueres would not disagree.
It's called 'surface charge' and 'pros' will lightly load a battery
for a minute or so to
drain it before they take voltage to estimate the 'state of charge' to
which you refer.