Charging the car battery? help

Ok the car is an '90 Accord 4DR EXR.
-The battery is fairly new about 2 months
-Its not a top-of-the-line battery, just an economical one
-It died after helping a friend jump start his car,

My question is when I put the battery on charge am I suppose disconnect it from the car terminals or should I leave them on?

Leave them on.

And hope you didn't fry your alternator. A service manual will actually tell you to disconnect the ground to prevent voltage spikes from getting to your electronics..

Leave them on.


Deffinitly DO NOT LEAVE THEM ON.

That sort of stupid advice will get you banned.

Deffinitly DO NOT LEAVE THEM ON.

That sort of stupid advice will get you banned.

Well then everyone around here that I know must be doing it wrong. EVERYONE I know does that. Well I guess you learn something new everyday.

Well then everyone around here that I know must be doing it wrong. EVERYONE I know does that.

Yes, they're all doing it wrong.

Deffinitly DO NOT LEAVE THEM ON.

That sort of stupid advice will get you banned.
ooh....I want to hear the theory on THIS!

I've yet to see a alternator that wasn't switched via the ignition switch. How does a charger magically turn on the ignition, and when it does, what bad things does that cause?

(if I see the words "flux capacitor" in your reply, I'm taking your title away from you) :lol:

I've yet to see a alternator that wasn't switched via the ignition switch. How does a charger magically turn on the ignition, and when it does, what bad things does that cause?

there's still power in the computers and circuitry when the ignition's off. chargers make more current that batteries, as they charge them, and can damage the electronics.

there's still power in the computers and circuitry when the ignition's off. chargers make more current that batteries, as they charge them, and can damage the electronics.
ah....CURRENT is higher? Current to what? To the computer? How?

Sorry. No lame answers here. You'll have to show your smarts.

electricity doesn't make decisions. If current is higher to the computer, its higher to everything else in the circuit. So IF thats the case, then everything else is at risk.

I'm leading you. I want to see a better answer. What is the REAL risk here, and what causes it, specifically.

it's 7:05am here. i haven't slept and i'm embarking on a 12-hour day at college, purely physical work.

sorry to be so blunt, but right now i don't care...

hehehe....you get an F! But thanks for trying!

Next!

:lol:

The laws to electicity are very simplistic, but the understanding of them, are not.

(don't take this to mean I'm some kind of expert....I'm far far from an EE, I'm just a dumb car mechanic who knows just enough to get into trouble diagnosing cars)

here's my solution. when i charge the battery on MY car, i'll disconnect the batter.

what other people decide to do is purely up to them. if they cook something, not my problem.

Wait isn't there a diode in the voltage regulator or somewhere around there that blocks electricity coming from the direction fo the battery just for that purpose or if the battery does get overcharged it won't destory the electronics.

yes take cables off to charge. could lead to big problems leaving them on while charging...

Many warnings are pretty simple: why not to look for a leaky propane line with a lighter. The explanation on why is easy to understand.

I'd like to hear the WHY for this one. Not the popular "belief".

If charging a battery was a problem, then I would think the car wouldn't have an alternator

A battery charger puts out AC voltage, as well as DC. AC is bad on electronics built for Low ripple DC..
Plus some battery chargers are poorly regulated, voltage-wise.

alternators have voltage ripple also. A common failure of an alternator is the diode bridge, which puts large AC voltage into the circuit. I've never seen such a failure do anything other than damage a battery though.

Basically, what you're saying is, some battery chargers are cheap and/or faulty. I still don't see what this will do to the rest of the system though. If a charger isn't regulating the voltage correctly, the battery could very well get damaged whether you have the car cables hooked up or not.

There should not be any problem leaving the battery cables on when charging the battery. That's what we did at the dealer with very expensive cars all the time, not waste our time taking the battery out to charge them.
1. if the ignition switch isn't on, the power isnt going to go through most of the circuitry anyway.
2. even if you do leave the switch on, the electronics are only going to use as much power as they always have. The rest of the current is going into the battery.... charging it.

Now. If you try to charge the battery by putting 100 VOLTS to the system, then you'll have problems.

ok if you say so BOB...you think the dealer ship's going to agree probably not??? if you get a good 1 he'll tell you the truth....BOB......

I'v never taken them off, and never had a problem. Mine also has a jump start mode, that would be hell-of hard to do with them disconected.

ok if you say so BOB...you think the dealer ship's going to agree probably not??? if you get a good 1 he'll tell you the truth....BOB......

um, I've worked at dealerships.

I don't want the "truth". I want the "why". Truth is colored by opinions

ok if you say so BOB...you think the dealer ship's going to agree probably not??? if you get a good 1 he'll tell you the truth....BOB......

Wow. Great rebuttal. I suggest that anyone who wants to respond to this thread brush up on their basic electrical theory.

There should not be any problem leaving the battery cables on when charging the battery. That's what we did at the dealer with very expensive cars all the time, not waste our time taking the battery out to charge them.
1. if the ignition switch isn't on, the power isnt going to go through most of the circuitry anyway.
2. even if you do leave the switch on, the electronics are only going to use as much power as they always have. The rest of the current is going into the battery.... charging it.

Now. If you try to charge the battery by putting 100 VOLTS to the system, then you'll have problems.

Exactly. The charger may be able to supply 40 amps of current to charge the battery but that doesn't mean it will force those 40 amps through every single piece of electonic circuity in the car. Each individual device will only draw what it needs. If the computer needs to draw .01 amps to retain its memory that's all it will draw regardless of how many amps are available to the entire electrical system. As long as the voltage output of the charger is matched to the electrical system on the car everything will be ok.

ooh....I want to hear the theory on THIS!

I've yet to see a alternator that wasn't switched via the ignition switch.


To be honest, Iv simply always been told to disconnect the Earth.
I can think of two reasons: Yes, there have been cars built where the alternator was not switched off the ignition.
My old Herald based kit car was one, the Herald loom it used was so old (circa 1950's) it didn't even have any fuses. (yes it had an electrical fire, which is how I discovered the lack of fuses, yes this was fixed)).
Now, imagine one of these cars, but its an MG, or a Rover, and has a positive earth because some English engineer wanted to be different?

Second reason, what would happen if you were to start the car, while it was connected to a charger? It dosn't sound like it would be healthy for the alternator or the charger?



I work on the theory that until its proven safe to leave it connected, its safer to disconnect the earth from the battery when hooking up a charger.

I would rather to something I know causes no harm, that something I don't if it could cause harm. Flux capacitors are expensive and sensitive to current flow.

some rather....extreme examples. I'm just guessing here, but the original poster of this thread doesn't have a pre-50's era car, and it has fuses and all that fancy jaz.

as for the car starting with the battery charger connected....I don't know if you've bought a charger since the 50's....? But most of them have a switch for "starting". Its a high amp circuit to help get enough amperage to the starter when theres a dead battery in the circuit.

They don't put that feature on the chargers in hopes of you foolishly believing it so that they can catch your car on fire.

I'm all for the "I've always done it this way and it works" method. But you are operating off of a belief with no "why".

Lets really tear up this thread. Lets get some dialog going here.

Lets hear a story about an attempt to charge a battery, and something bad happened. I want to hear what has happened when uneducated poor saps didn't follow such beliefs. Hopefully, we'll get some gory details.

granted....I can tell you all sorts of stories about people jumping batteries incorrectly, hooking up batteries backwards, etc. then trying to get it covered under warranty (not!). But I don't count those.

I've personally never seen a "failure" from charging a battery on the vehicle.

Now I CAN relate one story, where my battery charger helped me diagnose a problem. I had a Jeep Cherokee that was giving me fits with a problem. I can't even remember what it was, as far as symptoms. But the battery was low on charge. We have an ancient charger at work, it does not regulate voltage. (probably from the 70's). I accidently put it on too high of a setting and so a puff of smoke come out of the junction box. I traced it and found the problem that was causing all the other symptoms. A bad terminal connection on the ASDL relay. But no harm was caused by the charger....only a small puff of smoke on a pre-existing bad circuit. The voltage spiked to over 20V

Ever measured the voltage produced by a charger on the boost setting? I've seen 18-20 volts on most 200 amp boosters. Makes all the lights bright as hell! I'm not worried about current biting my electronics, just voltage...and spikes. Every service manual (Ford, GM, Chrysler, Honda, etc..) I dug up today said to at least disconnect ground, preferrably both cables if possible. I just don't leave anything to chance..

not all chargers are the same. As I mentioned, most "modern" chargers are much better at regulating voltage. It really depends one what charger is in question.

If you have an ancient charger from WW2, then I agree. Be worried. Anything that smells vaguely like "electronics" will be smarter than the operator. Liability has a habit of causing such corrections in application

I just don't leave anything to chance..


Exactly.
Iv seen a PC blow up because the transformer in the back of the power supply decided life was no longer worth living. It fried everything in the PC, even destroyed the HDD controller board.
Iv seen a house worth of electronics written off because of a voltage spike from the mains.
Imagine either of those two things happening while your car battery is on charge? How are you going to go to the shops to spend the insurance money and buy a new TV and PC?

Exactly.
Iv seen a PC blow up because the transformer in the back of the power supply decided life was no longer worth living. It fried everything in the PC, even destroyed the HDD controller board.
Iv seen a house worth of electronics written off because of a voltage spike from the mains.
Imagine either of those two things happening while your car battery is on charge? How are you going to go to the shops to spend the insurance money and buy a new TV and PC?

so....why do you believe your alternator is safer?

Why is one form of charger not a concern, and another is?

I dont' mind the anal level, but lets be consistant.

so....why do you believe your alternator is safer?

Why is one form of charger not a concern, and another is?

I dont' mind the anal level, but lets be consistant.


Because one can spike at over 240volts, and the other can't?

ah. And what do 200 amp capable car alternators peak at in AC voltage?

it really doesn't matter. They prefer to avoid damage to the system(s). So we are left with considering the likelyhood of it. I don't think it's likely with a remotely modern charger or alternator. They design fail-safes into them even if they fail. They don't like being sued.

Did you have a worse Friday than I did?


I don't think it's like with a remotely modern charger or alternator. They design fail-safes into them. They don't like being sued.

Ahh, now this is an interesting point.
In the states or UK that might be an issue, in the rest of the world its pretty mute. I would have hard time suing my chargers manufacturer, not only do my own country's laws make it difficult, the charger was made in China, and their laws are totally different again.

ah. And what do 200 amp capable car alternators peak at in AC voltage?

Anything more than .5 AC volts and an alternator is considered defective. An average battery charger puts out waaay more than ten fold this number.

you are correct.....

let rephrase it then.

I've been a full time mechanic for 12 years. I've never worked at a shop that worried about disconnecting the battery first. I've never seen any failure that wasn't improper use of the equipment. Some days I'll personally charge 3 or 4 batteries.

Thats a lot of batteries I've charged on a very wide variety of chargers. Never had a single issue.

ah....CURRENT is higher? Current to what? To the computer? How?

Actually he is correct. Depending upon the charge rate and how he is charging it. The voltage at the charger connections can be much higher than 12.6 (a fully charged battery) And the computer is connected (along with a few other devices) so, it is law that I = E/R. :grinyes: The load remains the same, the voltage is higher and thus the current to the computer is higher. Nothing secret about this. However, the risk while finite, is small. The manufacturers were well aware of this and the ECM can handle it fine. There is also some remote possibilty of large voltage spikes due to inductive loads in the circuit. This can occur when connecting and disconnecting a charger. (It doesn't matter whether you disconnect the negative or positve terminals first.) However, the manufacturers also prepped for this with decoupling capacitors in all the high impedance devices like the ECM. So it is also a very small risk.

If current is higher to the computer, its higher to everything else in the circuit. So IF thats the case, then everything else is at risk.

And it is., albeit a small risk.

I'm leading you. I want to see a better answer. What is the REAL risk here, and what causes it, specifically.

I just gave it to you. AND, all other things being equal... it is not a bad idea to disconnect the battery when charging. But almost not worth the effort.

Jim
EE/ME

Actually he is correct. Depending upon the charge rate and how he is charging it. The voltage at the charger connections can be much higher than 12.6 (a fully charged battery) And the computer is connected (along with a few other devices) so, it is law that I = E/R. :grinyes:

The very next line of my post that you quoted said all that, without being specific.

I was trying to cut through the mystical beliefs and get someone to actually say what can cause dangerous currents to the computer.

Which is simple: too much voltage. In otherwords, improper voltage regulation. Either due to a faulty charger, or due to operator error. The latter being far more likely IMO.

There are some very bizarre concepts being pushed around this thread.

So I'll throw in some of my own.

Chargers provide voltage, the current through the battery is the result of this (not the cause).

Chargers and alternators all push a similar voltage to charge the battery, 14.2-14.7v is the range for all the vehicles I've tested.

Car electronics are safe to beyond this level and will not be damaged by a healthy charger. Of course a dodgy charger could kill anything (including you)!

The only times I've bothered to disconnect a battery for charging were:
1. When the power cord wouldn't reach the car.
2. When I have had electrical leakage (the cause of the flat battery).

You can even jump modern cars without problems, my jumper leads have a capacitor between the wires, damps out voltage spikes.

Chargers and alternators all push a similar voltage to charge the battery, 14.2-14.7v is the range for all the vehicles I've tested.

Car electronics are safe to beyond this level and will not be damaged by a healthy charger. Of course a dodgy charger could kill anything (including you)!


Yep


my jumper leads have a capacitor between the wires, damps out voltage spikes.

Few do. (if any)

To the contrary, some use a pulsed DC to supposedly break up sulfation.
However the battery is, for all practical purposes, a capacitor and it tends to filter spikes.

Try running your car radio off the charger alone without the battery. On most chargers all you will get is a loud hum... That's because it is a 1/2 wave 120cycle pulsed voltage. (No filtering caps.)

You will often see this same effect when the car has a totally bad (open) battery.

The main point to this thread though... If you are real anal, pull the battery to charge it. :grinyes:
If you are pretty normal, charge it while connected.

Jim

Try running your car radio off the charger alone without the battery. On most chargers all you will get is a loud hum... That's because it is a 1/2 wave 120cycle pulsed voltage. (No filtering caps.)

My charger cost less than $US20 and it produces good DC. But I can see why others would take the cheapest way to charge a battery.

I have used my charger to run a car radio before. I pulled the radio to sell it and realised there was still a CD in there. Connecting up the charger was enough to wake it up and eject the CD.

Big relief.

My charger cost less than $US20 and it produces good DC. But I can see why others would take the cheapest way to charge a battery.

I have used my charger to run a car radio before. I pulled the radio to sell it and realised there was still a CD in there. Connecting up the charger was enough to wake it up and eject the CD.

$20 US? You can't get much cheaper than that. I think you have a trickle charger there. (Or a wall wart DC power supply).

Most real chargers put out either a pulsed DC or a ripple DC. They charge better in theory at least.

BTW, pulsed DC or ripple DC would still eject your CD. However if you tried to play the audio it would probably be just a hum...

i learned my lesson. i put my charger on boost to charge my battery not taking cables off. went to start my car and had a puff of smoke come out of air vent. car started but i toasted by radio. had to buy another radio for my car. if your driving a newer car take charger off after battery is charged when cranking car .