Easy Question: Charging Car Battery Removed From Vehicle?
quentinm...@gmail.com
charging owners manual states that you need to "attach at least a
24inch (60cm) long, 6 gauge (AWG) insulated battery cable to NEGATIVE
battery post", then later states "connect the black NEGATIVE output
clamp to the free end of the cable".
Ive used battery chargers in the past, but Ive never done this step
before. How important is it to use an insulated cable between the
batter charger's negative clamp and the battery's negative post?
I tried to google for more information, and I see the same
instructions explained here:
http://www.battery-chargers.com/charging_instructions.htm (scroll down
half way until you find "B. CHARGING BATTERY OUTSIDE VEHICLE".
Could anyone explain to me why a jumper cable or insulated battery
cable is required to be placed between the charger's negative clamp,
and the battery's negative post? How important is it to do this? I
have charged batteries in the past and have never done this. What
problems could occur if I did not use a jumper cable or insulated
cable and instead just attached the battery charger's NEGATIVE clamp
to the battery's NEGATIVE post?
quentinm...@gmail.com
> Could anyone explain to me why a jumper cable or insulated battery
> cable is required to be placed between the charger's negative clamp,
> and the battery's negative post? How important is it to do this? I
> have charged batteries in the past and have never done this. What
> problems could occur if I did not use a jumper cable or insulated
> cable and instead just attached the battery charger's NEGATIVE clamp
> to the battery's NEGATIVE post?
I should add to this:
I removed the car battery from my car for the winter since it is not
going to be driven. I wanted to store the battery in my basement
connected to a slow charging system to keep the battery alive and well
all winter. Should I use a jumper cable between my battery post and
batter charger's NEG output clamp as described in the owners manual
and website URL posted in my original message?
M.M.
> When you charging a car battery removed from your vehicle, my battery
> charging owners manual states that you need to "attach at least a
> 24inch (60cm) long, 6 gauge (AWG) insulated battery cable to NEGATIVE
> battery post", then later states "connect the black NEGATIVE output
> clamp to the free end of the cable".
>
> Ive used battery chargers in the past, but Ive never done this step
> before. How important is it to use an insulated cable between the
> batter charger's negative clamp and the battery's negative post?
>
Perhaps it's for the same reason that it's recommended to connect the
negative jumper cable to the engine block instead of directly to the
negative post when jump starting...to prevent a possible spark from
igniting any gases from the battery? I can't think of any other reason
why you'd want to do that.
If you connect the charger to the battery and then plug the charger in
(or turn it on) you'd probably accomplish the same thing. It's probably
just CYA for the charger manufacturer...
Don Bruder
<58b76562-f7a0-4f25...@p69g2000hsa.googlegroups.com>,
quentinm...@gmail.com wrote:
<snip>
> Could anyone explain to me why a jumper cable or insulated battery
> cable is required to be placed between the charger's negative clamp,
> and the battery's negative post? How important is it to do this? I
> have charged batteries in the past and have never done this. What
> problems could occur if I did not use a jumper cable or insulated
> cable and instead just attached the battery charger's NEGATIVE clamp
> to the battery's NEGATIVE post?
It's not "required", it's just fairly intelligent.
The purpose of the "extension", whether it be a set of jumper cables, a
hunk of insulated wire, or whatever else, is to move the
connect/disconnect point away from the battery, so that any spark that
may happen when connecting/disconnecting the charging apparatus is
distant from the (possible) cloud of explosive hydrogen gas produced by
the battery as it charges. The extension cable serves *ABSOLUTELY NO
ELECTRICAL OR FUNCTIONAL PURPOSE* beyond moving the physical
(dis)connection point away from the battery - omitting the extension
will have no effect whatsoever on the actual charging process. On the
other hand, omitting it *MAY* result in a trip to the hospital to have
pieces of the battery surgically removed from various parts of your
anatomy...
It's the same principle as when you jump-start a car - You hook up to
the positive posts on both vehicles (no particular order - it isn't
important), then you connect to the negative post of the "live" battery,
and finally, you connect the other end of the negative cable to
"someplace as far away from the battery as practical". The last
connection made is the one that's going to cause the spark, so you want
to make that connection as far away from the batteries as you can.
Similarly, the first thing you disconnect is going to be the one that
makes the spark - So you want it to be far from the battery and the
likely cloud of hydrogen. Thus, you disconnect the "someplace far from
the battery" connection first. Once you've done that, the disconnect
sequence is irrelevant, although most folks agree that the next one to
be removed should be the other end of the negative cable (because doing
so makes it impossible to accidentally short the positive and negative
clamps on the "far end" of the cable to produce a spark)
Whether charing out of the vehicle, or setting up for a jump-start,
connecting directly to the battery is perfectly functional, but may be
unsafe due to the potential for explosion.
--
Don Bruder - dak...@sonic.net - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info
tn...@mucks.net
battery out of a vehicle is safety.
If the battery is outside of the vehicle chances are that the battery
is indoors and away from air movement. If this is the case explosive
battery fumes may be present at the battery itself. If your last
connection was made at the battery site the spark resulting may cause
an explosion.
The use of the extra cable nullifies this scenario by taking the
inevitable spark and moving it away from the battery, providing your
last connection is the negative charger to the free end of the extra
cable.
Tim
Make it easy on your self and make sure your battery charger is turned
off , Hook up the Battery and then turn it on!!!
Don't need to nullify (Sigh) justify or anything else. people sometimes
forget to turn off the charger before they unhook them and thats why the
recommend the cable.
If you wanna go pro on it,,, buy yourself a Battery tender (not a
trickle charger) and use that during the storage period. It will save
you battery life by not over charging and keep sulfation to a minimum
Later
Tim
PASCO we are your starting and charging specialists
410-546-2041
tn...@mucks.net
>Make it easy on your self and make sure your battery charger is turned
>off , Hook up the Battery and then turn it on!!!
>
>Don't need to nullify (Sigh) justify or anything else. people sometimes
>forget to turn off the charger before they unhook them and thats why the
>recommend the cable.
So no spark will occur with most chargers unplugged? Think again.
Don Bruder
wrote:
Precisely...
A spark *DOES NOT NEED TO BE VISIBLE* to be plenty adequate to touch off
a hydrogen explosion.
*EVERY* time a circuit is made or broken, *THERE IS A SPARK*. Hooking
the final clamp of a charger to the terminal of a battery is closing a
circuit, and even if the charger is unplugged, *THE BATTERY* is
extremely unlikely to be so dead that it doesn't make at least a
micro-spark (small, perhaps even invisible, but perfectly capable of
igniting a cloud of hydrogen if it's there) as the connection is made.
Likewise, disconnecting the clamp after the battery is charged, even
with the charger powered down, or unplugged from the wall, causes a
spark as the circuit is broken. At this point, though, the chances are
*MUCH* higher of getting an explosion, because the battery has been
charged, which has generated hydrogen, which may be hovering around the
battery just waiting for something to ignite it. Which, incidentally, is
the reason that they'll tell you to charge a battery in a well
ventilated location - minimize hydrogen build-up, minimize chance of
Kevin Bottorff
news:475dc26b$0$36412$742e...@news.sonic.net:
while all this safety info is mostly true, a good batt charger, not a
cheepe, will not spark while off. It does not conplete a circuit as that
means that it would discharge the batt if left conected but off. The
cheep ones will do that but most comercial ones will not. KB
--
Thunder Snake #9
"Protect" your rights or "lose" them.
Steve
I thought again, and the answer is still the same. With the charger
unplugged- no spark because the diodes in the charger don't allow
reverse current flow through it.
Don Bruder
Kevin Bottorff <kevyN...@netins.net> wrote:
Actually, the "good ones" contain a diode (or work-alike circuitry) that
stops the discharge, but even there, a circuit *IS* being made, and for
a tiny instant prior to the diode (or work-alike) "noticing" and
operating to cut it off, juice flows. Which means spark is possible.
Don Bruder
Steve <n...@spam.thanks> wrote:
Once the circuit is completed and everything is up to high enough
potential to forward-bias the diode...
Until it hits that potential (Which varies from diode to diode) there is
current flowing in the circuit. (Different diodes also have different
"response speeds" when it comes to stopping current flowing in reverse,
as well)
Never mind that any capacitance or inductance in the output circuit is
going to "fill up" by drawing from the battery when the connection is
made.
In both cases, current flow equals possibility of spark sufficient to
ignite hydrogen.
tn...@mucks.net
A diode will stop all current flow? I thought only a open circuit
could do that.
AZ Nomad
diodes only conduct in one direction.
Don Bruder
AZ Nomad <azno...@PremoveOBthisOX.COM> wrote:
True, but only *AFTER* the circuit has "charged up", so to speak. For a
brief instant, they conduct either way. Once the circuit hits *ROUGHLY*
(exact number varies by diode type) 2 volts, they stop conducting in
reverse until the voltage exceeds the diode's back voltage. (At which
point, all the "magic smoke" usually leaks out of the diode)
Don't take my word for it, though - Set up a rig so you can watch things
happen on a fast oscilloscope. Start with the O-scope set to the highest
input impedance it can do, then connect the unplugged charger's positive
cable to the battery's positive terminal, the O-scope ground to the
battery's negative terminal, and watch the display as you touch the
O-scope probe to the (still unplugged) charger's negative cable.
The momentary reverse voltage will show up "loud and clear" as the
circuit formed by touching the probe to the cable "charges up".
(You may need to do some tweaking to get it in a range where you can see
it - start with lots of attenuation so you don't blow the 'scope, and if
you can't see the spike the first time around, start dialing down the
attenuation until you get it into a range the 'scope can display)
tn...@mucks.net
Usually by a ratio, not infinity.
Scott Dorsey
>True, but only *AFTER* the circuit has "charged up", so to speak. For a
>brief instant, they conduct either way. Once the circuit hits *ROUGHLY*
>(exact number varies by diode type) 2 volts, they stop conducting in
>reverse until the voltage exceeds the diode's back voltage. (At which
>point, all the "magic smoke" usually leaks out of the diode)
I don't think so.
There is a certain FORWARD voltage required for turn-on.... the diode
remains nonconducting until the forward voltage is about 0.6V. But
nothing will make it conduct in reverse.
if you don't believe me, look at the I/V plot on the diode data sheet.
>Don't take my word for it, though - Set up a rig so you can watch things
>happen on a fast oscilloscope. Start with the O-scope set to the highest
>input impedance it can do, then connect the unplugged charger's positive
>cable to the battery's positive terminal, the O-scope ground to the
>battery's negative terminal, and watch the display as you touch the
>O-scope probe to the (still unplugged) charger's negative cable.
I bet you see a big FORWARD inductive kickback, if the charger doesn't
have much shunt capacitance.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
AZ Nomad
>True, but only *AFTER* the circuit has "charged up", so to speak. For a
>brief instant, they conduct either way. Once the circuit hits *ROUGHLY*
bullshit.
When reverse biased, they never conduct; when forward biased, silicon
diodes have a 0.7V drop.
AZ Nomad
cite, please.
The conduction in reverse is close enough to zero that you can ignore it.
a few microamps don't matter in an automotive charging circuit.
tn...@mucks.net
>>>diodes only conduct in one direction.
>
>>Usually by a ratio, not infinity.
>
>cite, please.
>
>The conduction in reverse is close enough to zero that you can ignore it.
>a few microamps don't matter in an automotive charging circuit.
Take any electronics coarse and you'll see that a typical diode has
as low as a 10:1 forward to reverse resistance. Any resistance less
than infinity can cause a spark across a voltage source. It would be
irresponsible to say that all one has to do to hook up a battery is to
just have the supply turned off.
Don Bruder
AZ Nomad <azno...@PremoveOBthisOX.COM> wrote:
The point is that even a small amount of current can cause a spark - and
it doesn't matter which way the juice is flowing. And even a small
(invisible to the naked eye) spark can be sufficient to touch off the
hydrogen explosion that's the reason behind the method originally being
asked about.
Don Bruder
wrote:
Precisely... Which is *EFFECTIVELY* what the original poster was asking
about - "Why does it say to do the hookup by connecting an extension to
the negative post, then connecting the charger to the far end of the
extension?"
The answer, when boiled down, is "To get the inevitable spark away from
the stuff that it could ignite, causing the battery to blow up in your
face."
How well or poorly a diode conducts, in which direction, or at what
voltage, has little or nothing to do with it. When you make or break a
connection to the battery, even if what you're (dis)connecting is an
unplugged charger, THERE WILL BE A SPARK. That spark MAY be enough to
ignite the cloud of hydrogen that could be hovering around the battery.
So you want to make/break the connection at a distance from the battery.
Steve
>>>So no spark will occur with most chargers unplugged? Think again.
>>
>>I thought again, and the answer is still the same. With the charger
>>unplugged- no spark because the diodes in the charger don't allow
>>reverse current flow through it.
>
>
> Once the circuit is completed and everything is up to high enough
> potential to forward-bias the diode...
>
> Until it hits that potential (Which varies from diode to diode) there is
> current flowing in the circuit. (Different diodes also have different
> "response speeds" when it comes to stopping current flowing in reverse,
> as well)
>
> Never mind that any capacitance or inductance in the output circuit is
> going to "fill up" by drawing from the battery when the connection is
> made.
>
> In both cases, current flow equals possibility of spark sufficient to
> ignite hydrogen.
>
I just don't buy it. The capacitance of a reverse-biased diode is so
tiny that you're talking microamps for microseconds. That would be such
a vanishingly small spark that the concentration of hydrogen and oxygen
at the point of spark would have to be absolutely PERFECT for ignition.
Just aint gonna happen in the real world. The fact that it is
theoretically possible at million-to-one against odds is the only reason
that the CYA language is there at all in the charger instructions. If
some dumb-cluck blows up a battery in his own face by connecting with
the charger powered, the language is there to protect the manufacturer.
They can say, "see, we TOLD you to use an insulated pigtail and you
didn't." Which is as it should be.
Steve
> Don Bruder <dak...@sonic.net> wrote:
>
>>True, but only *AFTER* the circuit has "charged up", so to speak. For a
>>brief instant, they conduct either way. Once the circuit hits *ROUGHLY*
>>(exact number varies by diode type) 2 volts, they stop conducting in
>>reverse until the voltage exceeds the diode's back voltage. (At which
>>point, all the "magic smoke" usually leaks out of the diode)
>
>
> I don't think so.
>
> There is a certain FORWARD voltage required for turn-on.... the diode
> remains nonconducting until the forward voltage is about 0.6V. But
> nothing will make it conduct in reverse.
For all pracitcal purposes, you're right. There is a tiny reverse
leakage current that can practically be measured in number of electrons
per minute, which is for all intents and purposes zero.
And there IS the "junction capacitance" that Don is talking about, but
its a tiny, tiny, tiny capacitance. Not enough to produce a spark-
because the capacitance of the air gap as you move the charger lead up
to the battery post (right before you connect it) is comparable to the
diode junction capacitance and appears in series with it- in essence the
diode "charges" before the physical connection is even made.
Scott Dorsey
>
>For all pracitcal purposes, you're right. There is a tiny reverse
>leakage current that can practically be measured in number of electrons
>per minute, which is for all intents and purposes zero.
In this case yes, but the leakage on a diode can actually be a useful thing
in high-Z circuits. If you look at an anti-knock sensor, for instance, it
usually has a FET front end with a reverse-biased diode fabricated on the
same substrate, to provide a very teeny path to ground for the FET gate.
Piezo element flexes, voltage on the gate changes, and the ground path
is enough to keep the FET biased right when it's idle but not enough to
sink much of the tiny low-current signal from the piezo.
>And there IS the "junction capacitance" that Don is talking about, but
>its a tiny, tiny, tiny capacitance. Not enough to produce a spark-
>because the capacitance of the air gap as you move the charger lead up
>to the battery post (right before you connect it) is comparable to the
>diode junction capacitance and appears in series with it- in essence the
>diode "charges" before the physical connection is even made.
Junction capacitance can be pretty large on huge selenium stacks,
like your local theatre used to use for projection arcs. Now it's a
non-issue except in the RF world.
Steve
Steve
>
>
> Junction capacitance can be pretty large on huge selenium stacks,
> like your local theatre used to use for projection arcs. Now it's a
> non-issue except in the RF world.
> --scott
And there are all kinds of cool things to do with junction capacitance
in the RF world. Since capacitance is related to reverse bias voltage, a
reverse-biased diode makes a handy voltage-controlled capacitor
(Varactor diodes are optimized for that purpose). Which is the
technology that gave us radio and TV tuners without knobs or other
moving parts.
tn...@mucks.net
>> In both cases, current flow equals possibility of spark sufficient to
>> ignite hydrogen.
>>
>
>I just don't buy it. The capacitance of a reverse-biased diode is so
>tiny that you're talking microamps for microseconds. That would be such
>a vanishingly small spark that the concentration of hydrogen and oxygen
>at the point of spark would have to be absolutely PERFECT for ignition.
>Just aint gonna happen in the real world.
Micramps for a few milliseconds? Have you ever measured the current
flow when hooking a unplugged charger up to a charged battery?
Diodes are not the perfect switch you seem to imply. In order for
a diode to pass large amounts of current it is required to have a
minimal resistance in the forward direction. Since a typical power
diodes used in battery chargers have about a 10:1 resistance ratio
that means it still passes current in the reverse direction. Just not
at the same level.
You also seem to forget that many chargers have accessory circuits
like voltmeters that draw 20 milliamps or so when the leads are hooked
up. 20 milliamps will cause a spark.
Again, it would be irresponsible to suggest that all one has to do is
have the charger unplugged in order to hook a battery up.
Tim
> In article <w7OdnaDHiK2cLsPa...@texas.net>,
> Steve <n...@spam.thanks> wrote:
>
>> tn...@mucks.net wrote:
>>
>>>> Make it easy on your self and make sure your battery charger is turned
>>>> off , Hook up the Battery and then turn it on!!!
>>>>
>>>> Don't need to nullify (Sigh) justify or anything else. people sometimes
>>>> forget to turn off the charger before they unhook them and thats why the
>>>> recommend the cable.
>>>
>>> So no spark will occur with most chargers unplugged? Think again.
>> I thought again, and the answer is still the same. With the charger
>> unplugged- no spark because the diodes in the charger don't allow
>> reverse current flow through it.
>
> Once the circuit is completed and everything is up to high enough
> potential to forward-bias the diode...
>
> Until it hits that potential (Which varies from diode to diode) there is
> current flowing in the circuit. (Different diodes also have different
> "response speeds" when it comes to stopping current flowing in reverse,
> as well)
>
> Never mind that any capacitance or inductance in the output circuit is
> going to "fill up" by drawing from the battery when the connection is
> made.
>
> In both cases, current flow equals possibility of spark sufficient to
> ignite hydrogen.
>
long and TRUST me there's no science to it any more!!! The only time I
have ever seen a battery "explode" was when a crew hooked up a bettery
reversed polarity with a bad alternator putting out 22V. Don't make it
hard on a person who is just trying to get general info... just give
them the basics... I've been doing this for years. Just make sure the
switch is off before hookup. And besides if you want to scare the hell
out of someone who is trying to save money by doing it themselves,,, why
don't you tell them if there battery has a short in it ,, it could
sizzle, smoke and really cause a fire! The best bet is make sure you
have a good battery charger!!!
At PASCO, We are the Charging and Starting Specialists
Steve
>>>In both cases, current flow equals possibility of spark sufficient to
>>>ignite hydrogen.
>>>
>>
>>I just don't buy it. The capacitance of a reverse-biased diode is so
>>tiny that you're talking microamps for microseconds. That would be such
>>a vanishingly small spark that the concentration of hydrogen and oxygen
>>at the point of spark would have to be absolutely PERFECT for ignition.
>>Just aint gonna happen in the real world.
>
>
> Micramps for a few milliseconds? Have you ever measured the current
> flow when hooking a unplugged charger up to a charged battery?
Since I'm 50 feet from a lab where I can actually make that measurement,
and its my lunch hour, I will go do that within an hour. I'll let you
know- but I don't think my lab has a meter that can measure that small
of a current.
>
> Diodes are not the perfect switch you seem to imply. In order for
> a diode to pass large amounts of current it is required to have a
> minimal resistance in the forward direction. Since a typical power
> diodes used in battery chargers have about a 10:1 resistance ratio
> that means it still passes current in the reverse direction. Just not
> at the same level.
I don't know where you get this "10:1 resistance ratio" business. Its
certainly not valid. I have pulled from my shelf and opened on my desk
right now the textbook "Solid State Electronic Devices, 2nd Edition"
(published 1980- darn I'm getting old) by Ben G. Streetman, presently
chairman of the Electrical Engineering department at the University of
Texas at Austin. Section 5.3 "Forward- and Reverse-biased junctions" is
applicable. Page 150 defines the components of current that can cross a
P-N junction (aka a diode), primarily the "drift current," the
"diffusion current" and the "generation current" components. All 3
contribute to current flow under forward bias. However, page 151 states
clearly:
"Under reverse bias, both diffusion currents are negligible and THE ONLY
CURRENT (my emphasis) is the relatively small and VOLTAGE INDEPENDENT
(my emphasis again) generation current from n to p."
Note that the reverse bias current flow across a diode doesn't even
depend strongly on the applied voltage, therefore it doesn't even begin
to have a curve that looks like a "resistance," and therefore the "10:1
resistance ratio" doesn't even exist at all.
"Generation current" is due to the quantum effect of electron-hole pairs
spontaneously appearing in the junction region of a diode, and the
electron being swept one direction and the "hole" the other due to any
applied voltage at all. Photodiodes use the fact that light can cause
hole-pair generation, but in regular rectifier diodes its just a
probabalistic event, with a super-low probability. The reverse current
flow is TINY, up until you exceed the reverse breakdown voltage of the
diode... and a 12v battery aint gonna do THAT to a charger rectifier diode.
>
> You also seem to forget that many chargers have accessory circuits
> like voltmeters that draw 20 milliamps or so when the leads are hooked
> up. 20 milliamps will cause a spark.
>
> Again, it would be irresponsible to suggest that all one has to do is
> have the charger unplugged in order to hook a battery up.
If I'm a corporate lawyer knowing that some goober will hook it up live,
backward, or whatever, then I force my tech writers to put in the
requirement for a long insulated lead to cover my company's ass. Someone
WILL blow up a battery with one (or more) of the chargers my company
sells, so its imperative that I make it clear that my company explained
all precautions, both reasonable and unrealistic.
On the other hand if I'm out in my garage and all I care about is my
own life (which I value greatly) then I have NO problem hooking up with
the charger unplugged, because the odds of me getting hit by lighting
inside my garage are FAR greater than the odds of connecting this way
causing the battery to blow up. IOW, a rational and competent user only
cares about the REALISTIC precautions.
Steve
>>
>>
>> Micramps for a few milliseconds? Have you ever measured the current
>> flow when hooking a unplugged charger up to a charged battery?
>
>
> Since I'm 50 feet from a lab where I can actually make that measurement,
> and its my lunch hour, I will go do that within an hour. I'll let you
> know- but I don't think my lab has a meter that can measure that small
> of a current.
>
Measurement complete. Interesting results, actually.
The first test I did was with a 10-amp fully automated (fast then
maintain) electronic battery charger that's about 10 years old. Its got
dual-color LEDs on front to indicate "charging" or "charged." The LED
turns amber ("charging") when the charger is unplugged but connected to
the battery, so I knew it was going to have a measurable reverse current
because that is what lights the LED. It did- 17 milliamps. Personally, I
consider that completely safe to connect while unplugged- the
probability of a spark that could ignite hydrogen from the battery would
be vanishingly small. But there IS a current. I turned out all the
lights and tried to see a spark- no dice.
The second charger I measured was a newer fully automatic fast/maintain
charger. It was even better than I claimed- when connected to a fully
charged battery but unplugged from the wall, it showed a whopping 0.2
MICROamps of reverse current. Yes, 200 NANOamps. The meter I was using
only goes down to 10ths of a micro-amp, so really the measurement's at
the limit of the meter's- it could be even less than that. Absolutely
ZERO chance of that charger causing a spark if you connected it (while
its unplugged) to a fully charged 12v battery.
Finally, I dug up the oldest-style charger we have. Its a semi-automatic
Dayton, meaning that it charges until it senses 13.8 volts, then shuts
off (a mechanical relay clicks open) and won't kick back on until the
voltage falls WAY down to something like 11. It also has a 55-amp
"start" setting. When unplugged, it draws about 30 mA reverse current
from a fully charged 12v battery, and that might, conceivably, remotely,
create a spark when hooked up unplugged. Yet its instructions don't say
*anything* but pretty much hook it up, positive first and then negative"
and then plug it into the outlet. Nothing about a long insulated lead or
anything. Since Dayton is still in business without having killed or
maimed any users, and this was the "worst" reverse current of the
chargers I had on hand, I think I will rest my case here.
tn...@mucks.net
>
>Measurement complete. Interesting results, actually.
>
>The first test I did was with a 10-amp fully automated (fast then
>maintain) electronic battery charger that's about 10 years old. Its got
>dual-color LEDs on front to indicate "charging" or "charged." The LED
>turns amber ("charging") when the charger is unplugged but connected to
>the battery, so I knew it was going to have a measurable reverse current
>because that is what lights the LED. It did- 17 milliamps. Personally, I
>consider that completely safe to connect while unplugged- the
>probability of a spark that could ignite hydrogen from the battery would
>be vanishingly small. But there IS a current. I turned out all the
>lights and tried to see a spark- no dice.
At 20ma I can see a spark in the dark. At 17ma I would suggest you
look again.
>The second charger I measured was a newer fully automatic fast/maintain
>charger. It was even better than I claimed- when connected to a fully
>charged battery but unplugged from the wall, it showed a whopping 0.2
>MICROamps of reverse current. Yes, 200 NANOamps. The meter I was using
>only goes down to 10ths of a micro-amp, so really the measurement's at
>the limit of the meter's- it could be even less than that. Absolutely
>ZERO chance of that charger causing a spark if you connected it (while
>its unplugged) to a fully charged 12v battery.
>
>Finally, I dug up the oldest-style charger we have. Its a semi-automatic
>Dayton, meaning that it charges until it senses 13.8 volts, then shuts
>off (a mechanical relay clicks open) and won't kick back on until the
>voltage falls WAY down to something like 11. It also has a 55-amp
>"start" setting. When unplugged, it draws about 30 mA reverse current
>from a fully charged 12v battery, and that might, conceivably, remotely,
>create a spark when hooked up unplugged. Yet its instructions don't say
>*anything* but pretty much hook it up, positive first and then negative"
>and then plug it into the outlet. Nothing about a long insulated lead or
>anything. Since Dayton is still in business without having killed or
>maimed any users, and this was the "worst" reverse current of the
>chargers I had on hand, I think I will rest my case here.
I have made connections to batteries also without blowing anything up.
It just makes more sense if you completely remove the possibility by
'use of the extra cable.
Bob Flumere
Modern auto and marine battery chemistry is such that not a lot of
"gassing" occurs unless seriously overcharging.. not the case here and
second, the vents are ususally equipped with some sort of flame trap
type arestor in the openings.
I used to work at a shop where oddball sized, heavy duty, lead acid
batteries were "rebuilt", and before leading the terminal connections
or heating the tar that was used in those days to seal the cells into
the case, the tech used to wave the torch over the open cells to get
any little hydrogen "pop" out of the way so that it wouldn't startle
him later on!.
In my opinion (only), the danger of a hydrogen explosion is MANY times
greater after the battery has been on charge, has reached full charge,
is gassing freely and the charger is REMOVED without turning off the
power... creating a spark when there would likely be gas in the
vicinity of the battery terminals.
This "extra lead on the negative terminal" sounds like someones idea
of a legal CYA more than an absolute requirement if common sense is
used around a lead acid battery that has been gassing.
Bob