Battery Charger V/Ah

Battery Charger V/Ah

Hi!

I tested some battery chargers last night , and found "as usual"
that the amps and voltages stated on the modules were not the same as what I
found on the Volt and Amp testers....

Some 12v charging modules, would say 1.5 amp, whereas the voltage
test was 12-->17v and/or 4-->6amps on the meters....

All the "Walwart" max output 800ma (.8A) with 3 volts selected
showed 2amps on the amp meter, and almost 4amps at the 12v setting. The
inline charging modules were pretty much the same...

I have a 12v 8Ah MF SLA battery to charge at .8amp and I can't get
anything to charge as low as .8 amp from the walwarts.......when I do,
nothing happens for days, as far volt checks are concerned...

The charging volts are not higher than 12.4 volts on any of the
chargers....

Some ppl discard this discrepancy with the volts compensate for the
current, expression, but does it really, if a low charging amp can't be
achieved? I don't want to buckle cells or dehydrate the $240 MF SLA battery.

Re: Battery Charger V/Ah



"Robert LaCasse" <yamaha@here.info> wrote in message
news:363g04hkpo3a73a4ov8b2koh6vhp5t3dtv@4ax,com ...
> Hi!
>
> I tested some battery chargers last night , and found "as usual"
> that the amps and voltages stated on the modules were not the same as what
> I
> found on the Volt and Amp testers....
>
> Some 12v charging modules, would say 1.5 amp, whereas the voltage
> test was 12-->17v and/or 4-->6amps on the meters....
>
> All the "Walwart" max output 800ma (.8A) with 3 volts selected
> showed 2amps on the amp meter, and almost 4amps at the 12v setting. The
> inline charging modules were pretty much the same...
>
> I have a 12v 8Ah MF SLA battery to charge at .8amp and I can't get
> anything to charge as low as .8 amp from the walwarts.......when I do,
> nothing happens for days, as far volt checks are concerned...
>
> The charging volts are not higher than 12.4 volts on any of the
> chargers....
>
> Some ppl discard this discrepancy with the volts compensate for the
> current, expression, but does it really, if a low charging amp can't be
> achieved? I don't want to buckle cells or dehydrate the $240 MF SLA
> battery.


Your post doesn't make a whole lot of sense.

You need more than 12.4V to charge a 12V battery. If you want to limit the
current, use an LM317 wired as a constant current source, choose the
resistors accordingly to set 800mA.

Re: Battery Charger V/Ah

On Fri, 18 Apr 2008 03:35:47 GMT, "James Sweet" <jamessweet@hotmail,com >
wrote:

|>
|>"Robert LaCasse" <yamaha@here.info> wrote in message
|>news:363g04hkpo3a73a4ov8b2koh6vhp5t3dtv@4ax,com ...
|>> Hi!
|>>
|>> I tested some battery chargers last night , and found "as usual"
|>> that the amps and voltages stated on the modules were not the same as what
|>> I
|>> found on the Volt and Amp testers....
|>>
|>> Some 12v charging modules, would say 1.5 amp, whereas the voltage
|>> test was 12-->17v and/or 4-->6amps on the meters....
|>>
|>> All the "Walwart" max output 800ma (.8A) with 3 volts selected
|>> showed 2amps on the amp meter, and almost 4amps at the 12v setting. The
|>> inline charging modules were pretty much the same...
|>>
|>> I have a 12v 8Ah MF SLA battery to charge at .8amp and I can't get
|>> anything to charge as low as .8 amp from the walwarts.......when I do,
|>> nothing happens for days, as far volt checks are concerned...
|>>
|>> The charging volts are not higher than 12.4 volts on any of the
|>> chargers....
|>>
|>> Some ppl discard this discrepancy with the volts compensate for the
|>> current, expression, but does it really, if a low charging amp can't be
|>> achieved? I don't want to buckle cells or dehydrate the $240 MF SLA
|>> battery.
|>
|>Your post doesn't make a whole lot of sense.
|>
|>You need more than 12.4V to charge a 12V battery. If you want to limit the
|>current, use an LM317 wired as a constant current source, choose the
|>resistors accordingly to set 800mA.
|>

"Walwarts" = Universal Chargers

A Universal Charger's max 800mA "Walwart" will read 16v as a
charging current, when set at it's max 12v.

The current/amps will read 2--->3.5amps at 12v, which is something I
never really understood, since the Universal Charger is not rated to go or
handle more than .8amps maximum?

At the highest setting, the Universal Chargers won't do much unless
your talking days to charge an older battery at it's rating 800mA......

Are the Universal Chargers defective, most electronics shops say no,
and they are rated correctly....?

I usually put the battery on an older UPS that had the same battery
and I get good results on that....,it (voltmeter) reads 14v at 1.2amps

Am I confusing the .8aH suggested charging rate of 10% for an 8amp
battery with the Universal Chargers 800mA.

Re: Battery Charger V/Ah

Robert LaCasse wrote:

> On Fri, 18 Apr 2008 03:35:47 GMT, "James Sweet" <jamessweet@hotmail,com >
> wrote:
>
> |>
> |>"Robert LaCasse" <yamaha@here.info> wrote in message
> |>news:363g04hkpo3a73a4ov8b2koh6vhp5t3dtv@4ax,com ...
<snip>
> |>Your post doesn't make a whole lot of sense.
> |>
> |>You need more than 12.4V to charge a 12V battery. If you want to limit the
> |>current, use an LM317 wired as a constant current source, choose the
> |>resistors accordingly to set 800mA.
> |>
>
> "Walwarts" = Universal Chargers
>
> A Universal Charger's max 800mA "Walwart" will read 16v as a
> charging current, when set at it's max 12v.
>
> The current/amps will read 2--->3.5amps at 12v, which is something I
> never really understood, since the Universal Charger is not rated to go or
> handle more than .8amps maximum?

I almost responded to your first post but then I read the thread first
and James reply was everything I would have said.

What they do with cheap chargers limit the output by the windings on the
transformer and the physical size of the hunk of soft iron in it. There
typically isn't any regulation, just retification. If you really want to
see something that will tie your shorts in a knot, just charge up a high
value capacitor with the output. You may see >25V DC at no load! There
is some buzz word they use, something like 'magnetics regulated' which
just means the current drain will lower the chargers output voltage.
That is, it will put out say 16V into a 1 amp load and 11V into a 2 amp
load. I think your observation is ~'This is a wacky way to do things' is
right.

Really, go with a 317 set up as a constant current source if you want it
done right but don't want to go the $120 charger route. In a perfect
world you should set up a charger with two 317s: First one to regulate
the DC voltage to ~16V max<to allow for forward voltage drop on the 2nd
317 and still have over 14.7V you want for charging> and the second one
to limit current to the .8 amps you are looking for. It would only cost
you a couple of bucks to do it that way.

Just a couple of BTWs, I had one of those cheap 'float' chargers and it
smoked. Just no way it limited anything but its own life. I will never
buy another. My 55 amp charger will boil/melt a motorcycle battery even
when set on its lowest setting.

Rick

Re: Battery Charger V/Ah

On Fri, 18 Apr 2008 10:04:05 -0700, Rick Cortese <ricortes@earthlink,net >
wrote:

|>Really, go with a 317 set up as a constant current source if you want it
|>done right but don't want to go the $120 charger route. In a perfect
|>world you should set up a charger with two 317s: First one to regulate
|>the DC voltage to ~16V max<to allow for forward voltage drop on the 2nd
|>317 and still have over 14.7V you want for charging> and the second one
|>to limit current to the .8 amps you are looking for. It would only cost
|>you a couple of bucks to do it that way.

For some reason, the Yamaha Shop Manual's instruction from GP is
that (a constant current charger is not suitable for charging MF batteries)
and conventional chargers may harm the MF battery as well....

Your explanation on the Voltage/Amperage was quite suitable as I
have noticed and heard over and over again......so it must be true heh.....

Re: Battery Charger V/Ah

Robert LaCasse wrote:
> On Fri, 18 Apr 2008 10:04:05 -0700, Rick Cortese <ricortes@earthlink,net >
> wrote:
>
> |>Really, go with a 317 set up as a constant current source if you want it
> |>done right but don't want to go the $120 charger route. In a perfect
> |>world you should set up a charger with two 317s: First one to regulate
> |>the DC voltage to ~16V max<to allow for forward voltage drop on the 2nd
> |>317 and still have over 14.7V you want for charging> and the second one
> |>to limit current to the .8 amps you are looking for. It would only cost
> |>you a couple of bucks to do it that way.
>
> For some reason, the Yamaha Shop Manual's instruction from GP is
> that (a constant current charger is not suitable for charging MF batteries)
> and conventional chargers may harm the MF battery as well....
>
> Your explanation on the Voltage/Amperage was quite suitable as I
> have noticed and heard over and over again......so it must be true heh.....

I got tired of my Mickey Mouse wall wart charger taking forever to
charge up the power pack on my 18V portable drill. I switched to a
regulated 30V DC at 1.2 amps supply! The thing is at full charge I
figure I have ~12V at 1.2 amps or 14 Watts of power going into the
battery pack. I can tell when it has a full charge by how hot it is!

I mention this because as I said in another post, my 55 amp charger will
cook a motorcycle battery even on its lowest setting.

It really wouldn't take much to make a charger superior to most of the
junk on the market. Current limiting and voltage limiting of course,
then add something like a PIC or AVR 8 pin microcontroller. You could
have the thing put out pulsed DC at a couple of thousand Hz like some
people reccomend for rejuvinating sufated batteries and during the off
cycle check for the state of charge. A couple of LEDs could report
status like possible shorted cells and state of charge.

I have seen a couple of web sites where people have rewound microwave
over transformers to make cheap arc welders. I'm not really interested
in that since I have both wire feed and oxy acetylene set ups. Maybe a s
50 amp home brew battery charger is in order.

Rick

Re: Battery Charger V/Ah

In article <x4idnYjsJYajXY3VnZ2dnUVZ_qSonZ2d@earthlink,com >,
Rick Cortese <ricortes@earthlink,net > wrote:
> I got tired of my Mickey Mouse wall wart charger taking forever to
> charge up the power pack on my 18V portable drill. I switched to a
> regulated 30V DC at 1.2 amps supply! The thing is at full charge I
> figure I have ~12V at 1.2 amps or 14 Watts of power going into the
> battery pack. I can tell when it has a full charge by how hot it is!

Perfect way to knacker any battery. Properly looked after rechargeables
can last for many many cycles. Overcharging them can damage them
permanently in one go.

--
*Middle age is when work is a lot less fun - and fun a lot more work.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

Re: Battery Charger V/Ah

On Thu, 17 Apr 2008 22:32:56 -0700, Robert LaCasse
<scooter@yamaha.info> wrote:

>
>|>> All the "Walwart" max output 800ma (.8A) with 3 volts selected
>|>> showed 2amps on the amp meter, and almost 4amps at the 12v setting. The
>|>> inline charging modules were pretty much the same...
>|>>
>|>
>|>Your post doesn't make a whole lot of sense.
>|>
>|>You need more than 12.4V to charge a 12V battery. If you want to limit the
>|>current, use an LM317 wired as a constant current source, choose the
>|>resistors accordingly to set 800mA.
>|>
>
> "Walwarts" = Universal Chargers

I think if you spelled this with two l's it wouldn't look so much like
Walmart, which is the way I read it each time until this last one.

Besides the fact that wall-wart might not be a widespread term. And
for that matter, not all little black plug-in boxes are "universal" or
multi-voltage.

And you didn't use the word but while I'm at it, adaptor has its own
problem in that one can adapt a lot more things than just voltages.
(I don't even know how they chose that word. Changing to direct
current and changing voltage don't seem like adaption to me.)

> A Universal Charger's max 800mA "Walwart" will read 16v as a
>charging current, when set at it's max 12v.

Little black box plug-in battery charger or replacer seems to be the
words.

I haven't read much of the thread but I'm sure someone pointed out
that the 16 volts drops quite a bit when it is actually charging
something. At least with a cheap model. Doesn't that solve the
problem?

P&M

If you are inclined to email me
for some reason, remove NOPSAM :-)

Re: Battery Charger V/Ah

On Tue, 27 May 2008 13:38:38 -0400, mm <NOPSAMmm2005@bigfoot,com > wrote:

|>I haven't read much of the thread but I'm sure someone pointed out
|>that the 16 volts drops quite a bit when it is actually charging
|>something. At least with a cheap model. Doesn't that solve the
|>problem?


In a 12v, 8amp, reg charge 10%= .8amp

Sure they all do that, and on the other hand if you use a constant
charger with a 1-->>1.5 amp capacity, even a 9 volt charger will charge a
12v battery by borrowing amps<<-->>volts usually till 13.5 then drops to
regulated thermistor "overheat" setting..

I see the charger using up to an extra 5volts=1 amp if it borrows
the whole 1 amp which is why a dedicated 9 volt with high amps will charge a
higher volt less amp battery in the constant voltage system....

A 1.5 amp constant charger will charge the same battery as a
constant (current) variable volt regulated automatic charger in the same
amount of time.

The WalWart (Universal Charger) max .8 amp things would only amount
to very low trickle charge of some .2amps and might take a very long time on
a M/Cycle battery.....,it might take a week on some 10amp battery...

I figure try anything within common sense and it will work, maybe
remember to look at the charging system as watts and the charger shouldn't
over Watt the battery:

Automatic Charger MAX Quick Charge:

12v X 6amps=72watts

Small M/C battery:

12v X 8amps= 96watts

As long as the chargers watts don't overrate the battery's watts,
your fairly safe but not too prudent......since a 10% battery amp is the
best regular charge.....

Re: Battery Charger V/Ah

On Fri, 18 Apr 2008 03:35:47 GMT, "James Sweet" <jamessweet@hotmail,com >
wrote:

|>Your post doesn't make a whole lot of sense.

Well this is some kind of rocket science right???

|>You need more than 12.4V to charge a 12V battery. If you want to limit the
|>current, use an LM317 wired as a constant current source, choose the
|>resistors accordingly to set 800mA.

Oh I agree, it takes at least 13.5+ depending on the amps and what
kind of "conditioning" system the 12v charger does......

My 5amp 12v battery UPSupply puts out a constant 14.4v and
alternates up to 1.3amps (across terminal short) or .5amps of actual
charging to float, and as we all know they are the best
charger/converter/inverter systems.

I use that (UPS) to charge the battery mostly, but I still use all
kinds of other modular chargers, which are best used to run appliances or
charge RV batteries....

Most batteries shouldn't be charged for too long (except AGM) if the
electrolyte cannot be replaced, just charge/top off, then let it sit till it
needs another charge. If it's on a Motorcycle/vehicle like this 8amp, it
should recharge by the alternator easily for a long time, maybe a year or
more.

Some AGM's (made in china) require a monthly topping whether the
vehicle is charging or not.....so they claim....but that's (made in china)
stuff......you get what you pay for.....

Re: Battery Charger V/Ah

On Thu, 17 Apr 2008 20:01:08 -0700, Robert LaCasse <yamaha@here.info>
declaimed the following in alt.scooter:


> I tested some battery chargers last night , and found "as usual"
> that the amps and voltages stated on the modules were not the same as what I
> found on the Volt and Amp testers....
>
HOW did you test? Just hooking a DVM across the leads will not give
reasonable readings.

> Some 12v charging modules, would say 1.5 amp, whereas the voltage
> test was 12-->17v and/or 4-->6amps on the meters....
>
A 12V lead-acid battery tends to need >13V to charge, with 14V being
a common value.

> All the "Walwart" max output 800ma (.8A) with 3 volts selected
> showed 2amps on the amp meter, and almost 4amps at the 12v setting. The
> inline charging modules were pretty much the same...
>
Put a fully charged battery on the other end -- likely the back
pressure will reduce the actual current flowing to nil (if not actually
drain the battery due to the low voltage of the charger)

> I have a 12v 8Ah MF SLA battery to charge at .8amp and I can't get
> anything to charge as low as .8 amp from the walwarts.......when I do,
> nothing happens for days, as far volt checks are concerned...
>
.8A for 8Ah implies you are aiming for a 10hour charge rate... if
the battery were drained...

> The charging volts are not higher than 12.4 volts on any of the
> chargers....
>
Under voltage for charging -- even at trickle rates.

http :// www .batteryuniversity,com /partone-13.htm

Slow charge, risking sulfation, is 2.3V per cell... or 2.3 * 6 =>
13.8V.

Fast charge is 2.45V per cell... 2.45 * 6 => 14.7...

On low-beam (55W I believe), at freeway cruise, my Aprilia only
manages 13.5-13.8; on high-beam (35W) it achieves 13.8-14.1 -- according
the trip computer voltage display.

> Some ppl discard this discrepancy with the volts compensate for the
> current, expression, but does it really, if a low charging amp can't be
> achieved? I don't want to buckle cells or dehydrate the $240 MF SLA battery.

Then don't rely on cheap chargers -- for a $240 battery, surely you
can justify a $120 computerized charger.
--
Wulfraed Dennis Lee Bieber KD6MOG
wlfraed@ix,net com,com wulfraed@bestiaria,com
http :// wlfraed.home,net com,com /
(Bestiaria Support Staff: web-asst@bestiaria,com )
http :// www .bestiaria,com /

Re: Battery Charger V/Ah

On Thu, 17 Apr 2008 22:13:13 -0700, Dennis Lee Bieber
<wlfraed@ix,net com,com > wrote:

|>> I tested some battery chargers last night , and found "as usual"
|>> that the amps and voltages stated on the modules were not the same as what I
|>> found on the Volt and Amp testers....
|>>
|> HOW did you test? Just hooking a DVM across the leads will not give
|>reasonable readings.
|>
Right, that's my problem with some of my chargers, since "you can't
believe everything you read on the chargers" that was the best way of
checking the "real" volts/amps, but applying a known amp load might
help....

|>> Some 12v charging modules, would say 1.5 amp, whereas the voltage
|>> test was 12-->17v and/or 4-->6amps on the meters....
|>>
|> A 12V lead-acid battery tends to need >13V to charge, with 14V being
|>a common value.
|>
There seems to be no other way there, unless you wanna set the
universal Charger to 6-->9v to get a trickle charge, but even trickle
charges tend to sulphate more than just leaving the battery off a
circuit....

Re: Battery Charger V/Ah


"Robert LaCasse" <scooter@yamaha.info> wrote in message
news:uqdg04d94lfo88d0gidophu8p74frhr0f4@4ax,com ...
> On Thu, 17 Apr 2008 22:13:13 -0700, Dennis Lee Bieber
> <wlfraed@ix,net com,com > wrote:
>
> |>> I tested some battery chargers last night , and found "as usual"
> |>> that the amps and voltages stated on the modules were not the same as
> what I
> |>> found on the Volt and Amp testers....
> |>>
> |> HOW did you test? Just hooking a DVM across the leads will not give
> |>reasonable readings.
> |>
> Right, that's my problem with some of my chargers, since "you can't
> believe everything you read on the chargers" that was the best way of
> checking the "real" volts/amps, but applying a known amp load might
> help....

Most basic chargers have only rectification of the secondary voltage not
smoothing, so the reading with a DMM is likely to be very inaccurate. If you
put an electrolytic capacitor on the output it will charge to the peak
voltage (1.414 x RMS) but as others have stated battery charger transformers
are impedance regulated - that is they have a higher than stated voltage off
load which drops to around 13.8 - 14.4V on load, transformers for general
purpose power supplies (including wall warts) are definitely not suitable
for Pb battery charging unless they have electronic current limiting (like
the LM317 as others have suggested) and then the secondary voltage must be
higher by at least the minimum drop out voltage of the current limit chip.

Re: Battery Charger V/Ah

On Thu, 17 Apr 2008 22:13:13 -0700, Dennis Lee Bieber
<wlfraed@ix,net com,com > wrote:

|> On low-beam (55W I believe), at freeway cruise, my Aprilia only
|>manages 13.5-13.8; on high-beam (35W) it achieves 13.8-14.1 -- according
|>the trip computer voltage display.

That's an interesting observation.....

That's amazing, I mean the low-beam (55W), unlike the Aprilia, I
have the standard 2 halogens, and they draw 120watts so your system is
different.

Unless you have a HID lighting system...,it 's hard to beat the
battery drain from the mains....

My headlights (mains X2) don't come on till after the scooter is
started, so I'd have a very mission impossible problem to add there....I
suppose your mains work the same way....probably easier to change than a
Majesty400.

Thanx for the nfo.....

Re: Battery Charger V/Ah

Robert LaCasse wrote:
> On Thu, 17 Apr 2008 22:13:13 -0700, Dennis Lee Bieber
> <wlfraed@ix,net com,com > wrote:
>
> |> On low-beam (55W I believe), at freeway cruise, my Aprilia only
> |>manages 13.5-13.8; on high-beam (35W) it achieves 13.8-14.1 -- according
> |>the trip computer voltage display.
>
> That's an interesting observation.....
>
> That's amazing, I mean the low-beam (55W), unlike the Aprilia, I
> have the standard 2 halogens, and they draw 120watts so your system is
> different.
>
> Unless you have a HID lighting system...,it 's hard to beat the
> battery drain from the mains....
>
> My headlights (mains X2) don't come on till after the scooter is
> started, so I'd have a very mission impossible problem to add there....I
> suppose your mains work the same way....probably easier to change than a
> Majesty400.
>
> Thanx for the nfo.....

could you please delete sci.electronics.repair from this thread, as it
seems to be drifting away to a mostly 'motorcycle' issue rather than an
electronic one. I have no idea what an Aprilia is, nor any desire to know.

Generally speaking, crossposting is frowned upon.

jak