Battery Voltages
Because batteries are always referred to as 12-volt (or 6V or 24V),
it is often assumed that the normal voltage is 12V. In fact a
12V lead-acid battery only producing 12.0V is either
almost flat or is delivering a large current (under a heavy load).
In fact, a healthy 12V battery, when not being charged,
should always show 12.2 - 12.8V.

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.
But, as soon as a reasonable sized load is switched on, the voltage
drops quite quickly until it equates to the battery's actual
state of charge. Thereafter, the rate of voltage change (under
constant load) becomes linear. Thus, in practice, the voltage
of a freshly charged battery is a poor guide to its state of charge
until some of the charge has been used.

==================================================

If the part about (will slowly drop to around 13.6V over the next
few hours) is still true for small m/cycle batteries, and is not RC/Ah
specific, then I've been getting ripped of on some of the "wet' sla GS/Yuasa
batteries I've been buying..

I know, even the "agm" Chinese batts can hold these stats, but even
13.6 volt "agm" is a drag to start, whereas even a 12.6v "wet" will snap
start better.

The Chinese "agms" seem more like a "gel" battery rather than a
Starting Battery, I think an AGM with cell vent cap holes is pretty unreal
and may just be a bunch of sponge mixed with a sulphuric acid solution,
rather than a real AGM,which is much different...and Concorde pricier.

Bob

Bob wrote:
....
> You mean like a "dirty" Neg(-) terminal right, or something like
> that?...the Neg(-) terminal goes to the rectifier right?, which holds some
> up to 14.9v no load voltage, but allows you to desulfate/egualise charge at
> 16v/2Ah through it.....

I meant a copper ground wire where all the strands had turned green.

As for de-sulphating, I was taught that you need a constant-current
charger, and even then it's not always possible. The documentation for
the small Ctek charger I use specifically says that it switches
periodically from constant-voltage to constant-current mode. I'm pretty
sure it has succeeded on three different batteries but once it took
about a week. All of those batteries were MF Yuasa's, which I believe
is a fairly high-quality brand. One of them was three years old and had
sat in a neighbour's unused bike outside from October to June so it
never got very warm. On the other hand, it couldn't save a one-year old
cheap refillable import battery that sat unused just over the winter
months, even with two weeks on that de-sulphating charger. Maybe a more
expensive constant-current charger that can give larger currents for
short periods would have worked, I don't know. Or maybe the guy I got
the battery from had filled it with tap water that was full of various
metals. Around here there is a lot of iron in the water.




> I don't really understand the Rectifier's 14.0-->14.9v no
> load/22A/withstand 200volt meaning.....what is NO LOAD and why does the
> rectifier allow 16volts/2ah then.
>
> I can't figure that, when I do that, I ground on the frame/terminal,
> and no main fuse blow...lucky maybe? If I turn the ignition on even at a 2Ah
> setting I'm sure to blow the 40amp main fuse for sure.
>
> Bob
>

Well, look at psus for powering car equipment, its normally a nominal 13.8v.
Also of course all cells are not equal, and some may drop a little more
than others.

Its not just lead acid though, its all batteries and a lot of the
performance has to depend on the electrode area.
Brian

--
Brian Gaff - (E-Mail Removed)
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"Bob" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>
> Battery Voltages
> Because batteries are always referred to as 12-volt (or 6V or 24V),
> it is often assumed that the normal voltage is 12V. In fact a
> 12V lead-acid battery only producing 12.0V is either
> almost flat or is delivering a large current (under a heavy load).
> In fact, a healthy 12V battery, when not being charged,
> should always show 12.2 - 12.8V.
>
> 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.
> But, as soon as a reasonable sized load is switched on, the voltage
> drops quite quickly until it equates to the battery's actual
> state of charge. Thereafter, the rate of voltage change (under
> constant load) becomes linear. Thus, in practice, the voltage
> of a freshly charged battery is a poor guide to its state of charge
> until some of the charge has been used.
>
> ==================================================
>
> If the part about (will slowly drop to around 13.6V over the next
> few hours) is still true for small m/cycle batteries, and is not RC/Ah
> specific, then I've been getting ripped of on some of the "wet' sla
> GS/Yuasa
> batteries I've been buying..
>
> I know, even the "agm" Chinese batts can hold these stats, but even
> 13.6 volt "agm" is a drag to start, whereas even a 12.6v "wet" will snap
> start better.
>
> The Chinese "agms" seem more like a "gel" battery rather than a
> Starting Battery, I think an AGM with cell vent cap holes is pretty unreal
> and may just be a bunch of sponge mixed with a sulphuric acid solution,
> rather than a real AGM,which is much different...and Concorde pricier.
>
> Bob

My GT9B-4 12v/8ah holds a 13.2 for about 10 minutes, then drops to
13.0v about 1/2 hour, then so far 3 days @ 12.9v sitting on the bench...

This is a new battery from GS-Yuasa for Can $200.00 and I can't say
it's too **** hot....my last battery was a Chinese one proly with sponge
filled acid starved cells, but it held the voltages and not the CCA/RC....

So I might think that voltage is not the last word here, until I put
a load on it. There calcs for 1000cca=196rc(reserve capacity), but how do I
configure the 12X8=96watt battery to CCA...
I guess I'll keep looking for that one, but even then it's not
"proof in the pudding"....

ThanX for the nfo

Bob


On Sun, 29 Nov 2009 12:05:01 GMT, "Brian Gaff" <(E-Mail Removed)>
wrote:

|>Well, look at psus for powering car equipment, its normally a nominal 13.8v.
|>Also of course all cells are not equal, and some may drop a little more
|>than others.
|>
|>Its not just lead acid though, its all batteries and a lot of the
|>performance has to depend on the electrode area.
|>Brian

On Nov 29, 11:42*am, R. LaCasse <scoo...@yamaha.info> wrote:
> * * * * My GT9B-4 12v/8ah holds a 13.2 for about 10 minutes, thendrops to
> 13.0v about 1/2 hour, then so far 3 days @ 12.9v sitting on the bench...

Maybe internal cell resistance causes a drop of 0.3 to 0.4 volts
between the terminal posts after the battery has been allowed to rest
for half an hour or more?

R. LaCasse wrote:
> My GT9B-4 12v/8ah holds a 13.2 for about 10 minutes, then drops to
> 13.0v about 1/2 hour, then so far 3 days @ 12.9v sitting on the bench...
>
> This is a new battery from GS-Yuasa for Can $200.00 and I can't say
> it's too **** hot....my last battery was a Chinese one proly with sponge
> filled acid starved cells, but it held the voltages and not the CCA/RC....
>
> So I might think that voltage is not the last word here, until I put
> a load on it. There calcs for 1000cca=196rc(reserve capacity), but how do I
> configure the 12X8=96watt battery to CCA...
> I guess I'll keep looking for that one, but even then it's not
> "proof in the pudding"....
>
> ThanX for the nfo
>
> Bob

Bob, that is a pretty high quality battery and I am pretty sure from
past posts going back a year or two that the basic problem is that it
is not a very big battery and will drain in a few days under your
conditions. No amount of calculation is going to change that. Plus,
repeated full drains are not good for any lead-acid battery's longevity.
If I parked where you have to park, with the alarm on, I might
consider putting a much larger battery in that big underseat
compartment. This would involve a fair bit of thought for all the
re-wiring. Or possibly a second small battery which would require
thinking about how to charge it, maybe with some fancy electronics or
maybe with a simple switch.

(By the way, I did have a big silver scoot some years ago, but I don't
have any grey clothes. I used to see the same guy when I lived near
there. Now I'm about forty klics south and hardly ever go up there, my
only scoots now are angel blue and burgundy in colour.)

On Nov 28, 10:52*am, âÍÁ Á³Õ »Ñ·àÁ ËØÁ <macmi....@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.
>
> *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...

S'mee wrote:
>> 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 wrote:
> 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 wrote:
....
> 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.

Thanks for that link. It mentioned another Yuasa pub'n that I hadn't
seen before:

http://www.yuasabatteries.com/pdfs/2...apps_specs.pdf

Has cross-reference for some other mfrs' batteries, plus the suggested
Yuasa batteries for a lot of bikes going back for years. Come to think,
for years I've abused their batteries too, with generally better results
than I deserved.

(I don't know if there is another powersports battery company like Yuasa
in North America who are so forthcoming with their information, maybe
they are just better at knowing their market. I remember seeing a
really nice tester they made but it was a bit too much for my
pocketbook. Would have bought one of their chargers if it had been
readily available locally.)