Easy Question: Charging Car Battery Removed From Vehicle?

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?

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...

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.

The only reason they tell you to use a extra cable when charging a 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.

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

So no spark will occur with most chargers unplugged? Think again.

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 explosion.

Don Bruder wrote in news:475dc26b$0$36412$ snipped-for-privacy@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

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.

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.

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.

A diode will stop all current flow? I thought only a open circuit could do that.

diodes only conduct in one direction.

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)

Usually by a ratio, not infinity.

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.

I bet you see a big FORWARD inductive kickback, if the charger doesn't have much shunt capacitance.

--scott

When reverse biased, they never conduct; when forward biased, silicon diodes have a 0.7V drop.

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.