# Battery/Alternator charging question

Assuming an electrically sound Alt and Batt about how much driving/runtime is needed to recharge what is drawn/lost to start the car? Alternatively ....how long
will the car need to be run to recharge the battery to where it was before the car was started?
I know this is not easy to answer becuase it depends on so much but just ballpark estimate here would be fine..ie is it 1 or 5 minutes at idle etc.
Let's also assume that the car starts in about 2 or less seconds... hence no starting problems or extended turnover times just to keep this simple.
Thanks
MB
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Some very rough guesses:
200A cranking current for 2 seconds = 10A charging current for 40 seconds. Closer to 1 minute than 5, certainly.
About 5.2kJ of energy, and assuming the gasoline engine is about 25% fuel efficient, that is approximately 1/50 of an ounce of gasoline[1]. That's not including the amount of extra fuel used during starting vs. running, which probably puts that 1/50 of an ounce down into the noise.
[1] http://hypertextbook.com/facts/2003/ArthurGolnik.shtml
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Interesting to see 10 amp charge. I think that's considered fast. I have two old battery chargers which run at 5 and 6 amps.

To put it into perspective it takes 8 hrs at 5 amps to recharge a dead battery.
-- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned
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William R. Watt wrote:

I have driven quite a few older vehicles equipped with ammeters; it is not unusual to see charge currents of >10A immediately after starting. Fairly soon after, they generally settle down to a constant 1-2A. Unfortunately, the one in my current project ('55 Studebaker) is not calibrated; however I suspect that full scale is 60A as it was originally a 6V car (currently running a Delco 10SI internally regulated alternator) so the readings I get on that setup appear to be consistent with what I've stated above.
Were I a true geek, I would hook up my Fluke meter and check it, but I have other issues I'd rather deal with, that are more important to making it a safe, reliable driver :)
nate
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A good battery / alternator will charger at about 30 amps after a start, tapering down after a few seconds to a few minutes, depending on the condition of the battery and how much it was discharged.
"William R. Watt" wrote:

--
Mike Walsh
West Palm Beach, Florida, U.S.A.
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Dilemma on my hands is along the same lines
I just got finished importing a 1971 Citroen 2CV from France, to my home in the desert of California. I drove the car 300 miles in France before leaving her in the hands of the freight forwarder. She ran great, no issues at all. The boat trip and wait time on both shores inclusive was 4 weeks. When I picked the car up in Baltimore, however, she wouldn't start at all. No click, no sound, nothing
I got a jump start and she started right up, sounding great. Until we disconnected the jumper cables, when she would almost immediately sputter and die. She's stay on a few moments longer if we let her run for a few minutes before disconnecting the cables, but then would die again, and wouldn't start on its own again at all
Thinking "charging system problem", I ran off to replace the battery -- kicking myself in hindsight for not getting the old one tested before I handed it off to the recylclers -- dumb dumb dumb of me!! At least with a new battery I should be able to start the car and drive it back to the parts store to hopefully get the charging system diagnosed. Did all that, and the parts store (incorrectly) reported no charging system trouble at all. Their meter showed the alternator to be charging at 13.57, healthy enought to be charging the battery on the brand new battery for this 12V system, very simple two-cylinder vehicle
So, I stupidly left Baltimore on that rainy evening to begin driving as far West as I could get. Fifty miles outside of Baltimore, as the rain got more intense in the darkness of night, I noticed the dash lights were certainly VERY dim, if not completely gone. And then people behind me were flashing their brights -- how rude of them, I thought, since I was going as fast as I could up these winding steep mountain curves. Well, these people were trying to signal me that I was driving with no lights on at all!! In the driving rain!! On mountain curves no less. That would explain why my wipers kept going off and on and why playing with the light switch (off-on-off-on) seemed to make my engine either gain or lose power, accordingly
To make an incredibly long story shorter, I got her to Palm Springs, not running, and had an alternator guy bench test the alternator. He found it to not be working at all, took the cover off, and found a lead completely missing. Soldering on a new lead, the bench test passed this time. Reinstalled the alternator, I got the car back home (still in tow, though ). He recommended I charge the battery by connecting it to the battery of my car which did run -- with both vehicles off -- for an hour. Then disconnect the cables and start the car
Did that, but the Citroen did not start up at all. So reattached cables, started the car with the good battery (which is a 1972 Totota Land Cruiser FJ40, btw), and started the Citroen right up. Perfect, great. But then after disconnecdting the cables, the Citroen died again. (which is what it had done in Baltimore, too, before I replaced the battery... which I now realize was most likely unnecessary. Crap!!
So at this point... I have had somewhat better luck by leaving the Toyota off, starting the Citroen, letting her run for a good 5 minutes while connected. Then disconnecting the cables. Last time I did that she ran for a full 5 minutes before sputtering and dying. And then trying to start the car on its own showed the battery had no charge at all. No power for wipers, lights, nothing.
So do I need a new voltage regulator, too, or maybe instead of the new battery? And why would this all happen suddenly, after just travelling by ship?
I think tomorrow I can get her to the parts store by asking a friend to follow me and we'll bring the jumper cables along. I haven't tried charging while driving, but am hoping more power going through the system will be enough to charge the battery. As you can tell, I'm no expert in these matters, so any suggestions/alternatives, ideas, kind words for a frustrated dude will all be welcome and appreciated
Thanks
-- cyclometric
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cyclometric wrote:

the desert of California. I drove the car 300 miles in France before leaving her in the hands of the freight forwarder. She ran great, no issues at all. The boat trip and wait time on both shores inclusive was 4 weeks. When I picked the car up in Baltimore, however, she wouldn't start at all. No click, no sound, nothing.

disconnected the jumper cables, when she would almost immediately sputter and die. She's stay on a few moments longer if we let her run for a few minutes before disconnecting the cables, but then would die again, and wouldn't start on its own again at all.

kicking myself in hindsight for not getting the old one tested before I handed it off to the recylclers -- dumb dumb dumb of me!! At least with a new battery I should be able to start the car and drive it back to the parts store to hopefully get the charging system diagnosed. Did all that, and the parts store (incorrectly) reported no charging system trouble at all. Their meter showed the alternator to be charging at 13.57, healthy enought to be charging the battery on the brand new battery for this 12V system, very simple two-cylinder vehicle.

West as I could get. Fifty miles outside of Baltimore, as the rain got more intense in the darkness of night, I noticed the dash lights were certainly VERY dim, if not completely gone. And then people behind me were flashing their brights -- how rude of them, I thought, since I was going as fast as I could up these winding steep mountain curves. Well, these people were trying to signal me that I was driving with no lights on at all!! In the driving rain!! On mountain curves no less. That would explain why my wipers kept going off and on and why playing with the light switch (off-on-off-on) seemed to make my engine either gain or lose power, accordingly.

running, and had an alternator guy bench test the alternator. He found it to not be working at all, took the cover off, and found a lead completely missing. Soldering on a new lead, the bench test passed this time. Reinstalled the alternator, I got the car back home (still in tow, though ). He recommended I charge the battery by connecting it to the battery of my car which did run -- with both vehicles off -- for an hour. Then disconnect the cables and start the car.

started the car with the good battery (which is a 1972 Totota Land Cruiser FJ40, btw), and started the Citroen right up. Perfect, great. But then after disconnecdting the cables, the Citroen died again. (which is what it had done in Baltimore, too, before I replaced the battery... which I now realize was most likely unnecessary. Crap!!)

starting the Citroen, letting her run for a good 5 minutes while connected. Then disconnecting the cables. Last time I did that she ran for a full 5 minutes before sputtering and dying. And then trying to start the car on its own showed the battery had no charge at all. No power for wipers, lights, nothing.

me and we'll bring the jumper cables along. I haven't tried charging while driving, but am hoping more power going through the system will be enough to charge the battery. As you can tell, I'm no expert in these matters, so any suggestions/alternatives, ideas, kind words for a frustrated dude will all be welcome and appreciated.

Check ALL wiring between the alternator, voltage regulator, and battery. Make sure that the voltage is actually getting out of the alternator, and subsequently out of the regulator. (I assume from your description that it is externally regulated.) Also the points in the voltage regulator may be dirty, they can be cleaned with an ignition points file.
13.5V is not a whole lot from a full-fielded alternator (I assume when testing it on the bench it was full-fielded and not going through the regulator. If you were testing the alt. and reg. as a unit disregard.)
I had a similarly frustrating issue with my '55 coupe, everything bench tested OK but whenever I left it sit for a week it wouldn't crank over. Finally in desperation I got it started and drove it to the parts store where I'd bought the battery. It tested bad, and I left with a new battery. D'oh! We will see if it starts tomorrow AM. Last time I drove it was Sunday so this will be a good test...
I need to get me a battery load tester one of these days...
nate
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On Fri, 4 Nov 2005 11:05:11 +0100, cyclometric

desert of California. I drove the car 300 miles in France before leaving her in the hands of the freight forwarder. She ran great, no issues at all. The boat trip and wait time on both shores inclusive was 4 weeks. When I picked the car up in Baltimore, however, she wouldn't start at all. No click, no sound, nothing. i don't know about anybody else but when i see a usenet posting by someone who doesn't use carriage returns, i don't read it. ...thehick
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This morning I'm going to remove the battery from the Citroen and drive it to the parts store for testing -- but they'll have to charge it first, before it can be tested, right? Or, I suppose that if it doesn't take a charge at all, that's enough to prove that it's a defective battery, huh
Thanks
-- cyclometric
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If they do it right, it should take an hour or so to charge and test if it's good. If it's really bad it might take less time, as they'll be able to tell if it won't take a charge etc.
nate
cyclometric wrote:

the parts store for testing -- but they'll have to charge it first, before it can be tested, right? Or, I suppose that if it doesn't take a charge at all, that's enough to prove that it's a defective battery, huh?

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OK, AutoZone charged the battery -- which had not been done since I bought it in Baltimore -- and now the car starts and runs fine. I drove it to AutoZone and they tried to test the charging system, but their testing equipment kept saying I wasn't running at 2000 rpm, even when I had the choke completely open and the throttle completely open via the gas pedal. So I think I'll have to test the battery's charge now by hooking it up to a manual battery charger I bought -- I guess I can tell if the system is working by noticing whether the charge is deteriorating after running the car medium distances, eh
Thanks
-- cyclometric
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You're talking about a Deux Chevaux, right? You probably weren't running at *4000* RPM - their test equipment has probably never seen a two-cylinder car.
nate
cyclometric wrote:

in Baltimore -- and now the car starts and runs fine. I drove it to AutoZone and they tried to test the charging system, but their testing equipment kept saying I wasn't running at 2000 rpm, even when I had the choke completely open and the throttle completely open via the gas pedal. So I think I'll have to test the battery's charge now by hooking it up to a manual battery charger I bought -- I guess I can tell if the system is working by noticing whether the charge is deteriorating after running the car medium distances, eh?

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cyclometric wrote:

in Baltimore -- and now the car starts and runs fine. I drove it to AutoZone and they tried to test the charging system, but their testing equipment kept saying I wasn't running at 2000 rpm, even when I had the choke completely open and the throttle completely open via the gas pedal. So I think I'll have to test the battery's charge now by hooking it up to a manual battery charger I bought -- I guess I can tell if the system is working by noticing whether the charge is deteriorating after running the car medium distances, eh?

To respond to the rest of your post why don't you just buy a good Fluke meter? sure it will cost you a couple hundred bucks but it will save you endless frustration. You can then check both voltage and current which you will need to do to properly troubleshoot your problem.
nate
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N8N wrote:

it in Baltimore -- and now the car starts and runs fine. I drove it to AutoZone and they tried to test the charging system, but their testing equipment kept saying I wasn't running at 2000 rpm, even when I had the choke completely open and the throttle completely open via the gas pedal. So I think I'll have to test the battery's charge now by hooking it up to a manual battery charger I bought -- I guess I can tell if the system is working by noticing whether the charge is deteriorating after running the car medium distances, eh?

Or he can simply buy a \$10 meter at the hardware, Wal-Mart, ACO, etc. and read the voltage with all of the lights, radio, heater and other turned on. If the voltage still holds 14+_.5V, that's a pretty good load test for the alternator. He can check the battery voltage to see if it's holding 12.6V when the engine is off. A fluke meter is not a substitute for knowledge, but I'd like to have on anyway.
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Al Bundy wrote:

it in Baltimore -- and now the car starts and runs fine. I drove it to AutoZone and they tried to test the charging system, but their testing equipment kept saying I wasn't running at 2000 rpm, even when I had the choke completely open and the throttle completely open via the gas pedal. So I think I'll have to test the battery's charge now by hooking it up to a manual battery charger I bought -- I guess I can tell if the system is working by noticing whether the charge is deteriorating after running the car medium distances, eh?

The last time I bought a cheap multi-meter I took it back the same day because it didn't work. My ancient Fluke, which was bought at a pawn shop for maybe \$25, still works fine, so long as I don't do something stupid and blow the (hard to find) fuse.
nate
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i'd be lost without my cheap multimeter.got 2 or 3 just so i dont have ta go lookin.
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