Auto Battery Recharging Time

Don Klipstein wrote:

> I have a friend who once had his battery prone to not charging well
> unless he had a high percentage of his engine on-time running at least
> about 2,000 RPM or something like that. Non-highway driving with lots of
> stops and lots of coasting would have his battery actually mostly
> discharge if he had his headlights on. He had an ammeter to measure net
> current to/from his battery for everything except the starter.
>
> It turns out that one of the diodes in the rectifier circuit that was
> part of the voltage regulator assembly was blown. This halved the amount
> of current delivered by the alternator. Replacing the "voltage regulator"
> (actually an assembly including a rectifier circuit, at least in his car)
> fixed the problem.

That's a good point, Don. My voltage measurement with the engine
running should tell that story, or have the alternator tested by a
competent, honest shop.

--
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

"Erehwon" > wrote in message
...
> How long should a car have to run to bring a good battery back up to full
> charge after starting? Parents have a year and a half old battery in
> their car. For the past 6 months or so, they've had frequent occasions
> when the battery hasn't had enough power to start the car, requiring a
> jump. Took it to the shop and they said the battery tests good, just
> needed to be charged, so they put it on their charger for an hour.
> According to them the short hops (3 to 5 miles) my parents typically make
> gradually run the battery down to the point that it won't start and that
> the car needs to run "at least 15 minutes at highway speed" after each
> start to bring the battery back up to full charge. Every round trip
> should be at least 30 miles? Does that sound reasonable or do I need to
> have the electrical system looked at?
>
>

firstly the answer to your initial question is that there is no accurate
answer because it depends on too many variables, secondly I can tell you
from years of experience with battery powered vehicles that battery
load-testing is a very inexact science. it will easily identify a truly bad
battery but with marginal batteries it gets a bit hit-and-miss. there are
methods for accurately testing a battery but they are too time consuming for
practical use as they involve several drain/recharge cycles and then
applying a known load over an extended time and then checking the specific
gravity of the electrolyte (assuming a non-sealed battery).

but the bottom line is that, yes, you should get the charging system
checked. if it is producing enough voltage then your problem is likely a
weak battery but don't discount the possibility of something like a bad
ground or weak starter (you didn't mention how much cranking is necessary to
get going). it is all too easy to throw a new battery in only to find you
still have the same problems a few weeks later.

also, what about the electrical draw? do your folks have the headlights on,
a/c or heater full blast, radio/cd player running, etc.? this could extend
the time taken to recharge the battery.

Simon wrote:
> "Erehwon" > wrote in message
> ...
>> How long should a car have to run to bring a good battery back up to full
>> charge after starting? ...

>> that
>> the car needs to run "at least 15 minutes at highway speed" after each
>> start to bring the battery back up to full charge. Every round trip
>> should be at least 30 miles? Does that sound reasonable or do I need to
>> have the electrical system looked at?
>>
>>
>
> also, what about the electrical draw? do your folks have the headlights on,
> a/c or heater full blast, radio/cd player running, etc.? this could extend
> the time taken to recharge the battery.
>
>

I had a 1978 VW Scirocco that had a leak in the electrical system. I
had a brand new Diehard in it, but if it sat for a week without running,
the battery would be near dead. I never did figure it out, just sold
that VW! But it wasn't the battery OR the charging system in that case.

"Jack Bauer" > wrote in message
...
> Simon wrote:
>> "Erehwon" > wrote in message
>> ...
>>> How long should a car have to run to bring a good battery back up to
>>> full charge after starting? ...
>
>>> that the car needs to run "at least 15 minutes at highway speed" after
>>> each start to bring the battery back up to full charge. Every round
>>> trip should be at least 30 miles? Does that sound reasonable or do I
>>> need to have the electrical system looked at?
>>>
>>>
>>
>> also, what about the electrical draw? do your folks have the headlights
>> on, a/c or heater full blast, radio/cd player running, etc.? this could
>> extend the time taken to recharge the battery.
>
> I had a 1978 VW Scirocco that had a leak in the electrical system. I had
> a brand new Diehard in it, but if it sat for a week without running, the
> battery would be near dead. I never did figure it out, just sold that VW!
> But it wasn't the battery OR the charging system in that case.
>

yes, that can happen. i would think most vehicles draw at least a tiny
amount of power to maintain clocks and receivers for alarms and locking
systems. obviously this shouldn't drain a battery in a week though.

did you actually have the battery tested? it is not unknown for a new
battery to fail.

Simon wrote:
> "Jack Bauer" > wrote in message
> ...
>> Simon wrote:
>>> "Erehwon" > wrote in message
>>> ...
>>>> How long should a car have to run to bring a good battery back up to
>>>> full charge after starting? ...
>>>> that the car needs to run "at least 15 minutes at highway speed" after
>>>> each start to bring the battery back up to full charge. Every round
>>>> trip should be at least 30 miles? Does that sound reasonable or do I
>>>> need to have the electrical system looked at?
>>>>
>>>>
>>> also, what about the electrical draw? do your folks have the headlights
>>> on, a/c or heater full blast, radio/cd player running, etc.? this could
>>> extend the time taken to recharge the battery.
>> I had a 1978 VW Scirocco that had a leak in the electrical system. I had
>> a brand new Diehard in it, but if it sat for a week without running, the
>> battery would be near dead. I never did figure it out, just sold that VW!
>> But it wasn't the battery OR the charging system in that case.
>>
>
> yes, that can happen. i would think most vehicles draw at least a tiny
> amount of power to maintain clocks and receivers for alarms and locking
> systems. obviously this shouldn't drain a battery in a week though.
>
> did you actually have the battery tested? it is not unknown for a new
> battery to fail.

The usual drain with the vehicle off is called IOD (Ignition Off Drain).
As an example, the FSM for the '02 LH cars said that the battery
should hold a charge for at least 21 days. The maximum drain was stated
as something like 35 mA after something like 20 minutes when the TCM
would time out and go to sleep.

--
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

"Bill Putney" > wrote in message
...
> Simon wrote:
>> "Jack Bauer" > wrote in message
>> ...
>>> Simon wrote:
>>>> "Erehwon" > wrote in message
>>>> ...
>>>>> How long should a car have to run to bring a good battery back up to
>>>>> full charge after starting? ...
>>>>> that the car needs to run "at least 15 minutes at highway speed" after
>>>>> each start to bring the battery back up to full charge. Every round
>>>>> trip should be at least 30 miles? Does that sound reasonable or do I
>>>>> need to have the electrical system looked at?
>>>>>
>>>>>
>>>> also, what about the electrical draw? do your folks have the headlights
>>>> on, a/c or heater full blast, radio/cd player running, etc.? this could
>>>> extend the time taken to recharge the battery.
>>> I had a 1978 VW Scirocco that had a leak in the electrical system. I
>>> had a brand new Diehard in it, but if it sat for a week without running,
>>> the battery would be near dead. I never did figure it out, just sold
>>> that VW! But it wasn't the battery OR the charging system in that case.
>>>
>>
>> yes, that can happen. i would think most vehicles draw at least a tiny
>> amount of power to maintain clocks and receivers for alarms and locking
>> systems. obviously this shouldn't drain a battery in a week though.
>>
>> did you actually have the battery tested? it is not unknown for a new
>> battery to fail.
>
> The usual drain with the vehicle off is called IOD (Ignition Off Drain).
> As an example, the FSM for the '02 LH cars said that the battery should
> hold a charge for at least 21 days. The maximum drain was stated as
> something like 35 mA after something like 20 minutes when the TCM would
> time out and go to sleep.
>
> --
> Bill Putney
> (To reply by e-mail, replace the last letter of the alphabet in my address
> with the letter 'x')

One more thing to worry about.

My '94 van dies off in about that 3 week timespan if I don't use it whereas
my '83 can sit outside for 3 months and start with no problem.

The price of progress.

Simon wrote:
> "Bill Putney" > wrote in message
> ...

>> The usual drain with the vehicle off is called IOD (Ignition Off Drain).
>> As an example, the FSM for the '02 LH cars said that the battery should
>> hold a charge for at least 21 days. The maximum drain was stated as
>> something like 35 mA after something like 20 minutes when the TCM would
>> time out and go to sleep.
>>
>> --
>> Bill Putney
>> (To reply by e-mail, replace the last letter of the alphabet in my address
>> with the letter 'x')
>
> One more thing to worry about.
>
> My '94 van dies off in about that 3 week timespan if I don't use it whereas
> my '83 can sit outside for 3 months and start with no problem.
>
> The price of progress.

Yep. Gotta have those memory keep alive voltages.

--
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

my rule of thumb is 1 miles of travel for each volt
"Simon" > wrote in message
...
>
> "Erehwon" > wrote in message
> ...
>> How long should a car have to run to bring a good battery back up to full
>> charge after starting? Parents have a year and a half old battery in
>> their car. For the past 6 months or so, they've had frequent occasions
>> when the battery hasn't had enough power to start the car, requiring a
>> jump. Took it to the shop and they said the battery tests good, just
>> needed to be charged, so they put it on their charger for an hour.
>> According to them the short hops (3 to 5 miles) my parents typically make
>> gradually run the battery down to the point that it won't start and that
>> the car needs to run "at least 15 minutes at highway speed" after each
>> start to bring the battery back up to full charge. Every round trip
>> should be at least 30 miles? Does that sound reasonable or do I need to
>> have the electrical system looked at?
>>
>>
>
> firstly the answer to your initial question is that there is no accurate
> answer because it depends on too many variables, secondly I can tell you
> from years of experience with battery powered vehicles that battery
> load-testing is a very inexact science. it will easily identify a truly
> bad battery but with marginal batteries it gets a bit hit-and-miss. there
> are methods for accurately testing a battery but they are too time
> consuming for practical use as they involve several drain/recharge cycles
> and then applying a known load over an extended time and then checking the
> specific gravity of the electrolyte (assuming a non-sealed battery).
>
> but the bottom line is that, yes, you should get the charging system
> checked. if it is producing enough voltage then your problem is likely a
> weak battery but don't discount the possibility of something like a bad
> ground or weak starter (you didn't mention how much cranking is necessary
> to get going). it is all too easy to throw a new battery in only to find
> you still have the same problems a few weeks later.
>
> also, what about the electrical draw? do your folks have the headlights
> on, a/c or heater full blast, radio/cd player running, etc.? this could
> extend the time taken to recharge the battery.
>

That makes no sense. That's not how battery discharge and charge curves
work. You have to define a load to talk about battery voltage at any
given state of charge. With no load at any given point of checking,
your statement makes no sense. IOW, with no load, going from partially
discharged to fully charged is not going to involve multiple volts of
change as you imply.

--
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')


man of machines wrote:
> my rule of thumb is 1 miles of travel for each volt
> "Simon" > wrote in message
> ...
>>
>> "Erehwon" > wrote in message
>> ...
>>> How long should a car have to run to bring a good battery back up to
>>> full charge after starting? Parents have a year and a half old
>>> battery in their car. For the past 6 months or so, they've had
>>> frequent occasions when the battery hasn't had enough power to start
>>> the car, requiring a jump. Took it to the shop and they said the
>>> battery tests good, just needed to be charged, so they put it on
>>> their charger for an hour. According to them the short hops (3 to 5
>>> miles) my parents typically make gradually run the battery down to
>>> the point that it won't start and that the car needs to run "at least
>>> 15 minutes at highway speed" after each start to bring the battery
>>> back up to full charge. Every round trip should be at least 30
>>> miles? Does that sound reasonable or do I need to have the
>>> electrical system looked at?
>>>
>>>
>>
>> firstly the answer to your initial question is that there is no
>> accurate answer because it depends on too many variables, secondly I
>> can tell you from years of experience with battery powered vehicles
>> that battery load-testing is a very inexact science. it will easily
>> identify a truly bad battery but with marginal batteries it gets a bit
>> hit-and-miss. there are methods for accurately testing a battery but
>> they are too time consuming for practical use as they involve several
>> drain/recharge cycles and then applying a known load over an extended
>> time and then checking the specific gravity of the electrolyte
>> (assuming a non-sealed battery).
>>
>> but the bottom line is that, yes, you should get the charging system
>> checked. if it is producing enough voltage then your problem is likely
>> a weak battery but don't discount the possibility of something like a
>> bad ground or weak starter (you didn't mention how much cranking is
>> necessary to get going). it is all too easy to throw a new battery in
>> only to find you still have the same problems a few weeks later.
>>
>> also, what about the electrical draw? do your folks have the
>> headlights on, a/c or heater full blast, radio/cd player running,
>> etc.? this could extend the time taken to recharge the battery.
>>
>

"Dennis M" > wrote in message
...
> In article >, "Simon"
> > wrote:
>
>>firstly the answer to your initial question is that there is no accurate
>>answer because it depends on too many variables, secondly I can tell you
>>from years of experience with battery powered vehicles that battery
>>load-testing is a very inexact science. it will easily identify a truly
>>bad
>>battery but with marginal batteries it gets a bit hit-and-miss.
>
> Yeah I had a strange experience concerning my battery at the local NAPA
> last fall. My car would start up fine when it was left sitting overnight,
> but sometimes when I'd drive it a few miles into town, park it, then try
> to
> start it up again it wouldn't start (wisely I carry a Victor battery
> charger around with me in the trunk at all times so I was never stranded).
>
> Did a little research on the Internet and decided on a NAPA 84 series
> battery. Some chick clerk tested it with an instrument and said it didn't
> appear to be weak (since I bought the car used in Sept. 2004 the battery
> had to be at least 4 years old), so I told her I'd "think about it." But
> the car kept doing the same thing, so about a month later I took it back
> to
> NAPA. This time a guy tested it with the same instrument and said, "Wow,
> this must be the easiest starting car ever -- this battery doesn't have
> enough power to start a lawn mower!" So I bought a NAPA 84 series, and he
> even installed it for me for no charge.
>
> He never could figure out though why it started up fine in the morning,
> but
> had problems after it was driven a short distance into town. When I first
> told him this, he was certain it must have been some other problem than a
> weak battery. But a weak battery it was as the problem has disappeared.

Batteries have internal connections that can become broken but still touch
some of the time, and plates that can become loose and short out some of the
time depending on the temperature or movement of the vehicle. These could
allow a battery to load-test OK but still cause problems.

Pat