On Tue, 04 Nov 2003 15:50:45 -0600, "Clifton T. Sharp Jr."
wrote:

Bruce W...1 wrote:
The car is in a garage in a good neighborhood but the owner of the
garage is on and extended vacation. The theives I'm worried about are
neighborhood children. Actually it's the homeowner's car, I'm just
doing them a favor, and saving myself from having to go there to start
the car once a week.

Keeping the battery charged is not the only reason to start the car once
a week.

Suppose it means that a car battery won't last long if you keep it
steady at top charge level, instead of decharge it down towards 50%,
sense the voltage level and charge it up to 14.4V (for this cold
area), and switch off the charger until it is down to 50% again....

I was told that a car battery wouldn't last long anyway for this
application, so even when my car battery is 6-7 years old, it
wouldnt't last more than a year when trickle charged, while it is far
better economy to buy a leisure type battery

73
Jan-Martin, LA8AK
http://home.online.no/~la8ak/
--
remove ,xnd to reply (Spam precaution!)

In article ,
J M Noeding wrote:

Keeping the battery charged is not the only reason to start the car once
a week.

Suppose it means that a car battery won't last long if you keep it
steady at top charge level, instead of decharge it down towards 50%,
sense the voltage level and charge it up to 14.4V (for this cold
area), and switch off the charger until it is down to 50% again....

As I understand it, that's exactly the opposite sort of regime that a
car battery prefers.

Car batteries are designed to provide large amounts of current for
engine cranking, even when cold. One of the tradeoffs in this design,
unfortunately, is that they do not tolerate deep (or even heavy)
discharge at all well. Discharging a car battery down to 50% and then
recharging it, repeatedly, is likely to greatly shorten its life. The
plates will quite literally fall apart.

Batteries having a different internal construction can handle deep
discharge quite a bit better. The older sort of "marine
deep-cycle" battery (designed for electric trolling motors) were
quite good - but I'm told that modern "marine deep-cycle" batteries
are more like car batteries in their design and no longer have a big
advantage in terms of deep-discharge life.

The best ones for deep discharge, today, seem to be the
starved-electrolyte (glass mat), and spiral-cell types. These are
often used for telecom backup applications, large UPS systems,
wheelchair motor, and electric-tractor/golfcart applications.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

In article ,
J M Noeding wrote:

Keeping the battery charged is not the only reason to start the car once
a week.

Suppose it means that a car battery won't last long if you keep it
steady at top charge level, instead of decharge it down towards 50%,
sense the voltage level and charge it up to 14.4V (for this cold
area), and switch off the charger until it is down to 50% again....

As I understand it, that's exactly the opposite sort of regime that a
car battery prefers.

Car batteries are designed to provide large amounts of current for
engine cranking, even when cold. One of the tradeoffs in this design,
unfortunately, is that they do not tolerate deep (or even heavy)
discharge at all well. Discharging a car battery down to 50% and then
recharging it, repeatedly, is likely to greatly shorten its life. The
plates will quite literally fall apart.

Batteries having a different internal construction can handle deep
discharge quite a bit better. The older sort of "marine
deep-cycle" battery (designed for electric trolling motors) were
quite good - but I'm told that modern "marine deep-cycle" batteries
are more like car batteries in their design and no longer have a big
advantage in terms of deep-discharge life.

The best ones for deep discharge, today, seem to be the
starved-electrolyte (glass mat), and spiral-cell types. These are
often used for telecom backup applications, large UPS systems,
wheelchair motor, and electric-tractor/golfcart applications.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

In normal operation a car battery doesn't get discharged to 50% and
then recharged. The starter draws a large amount of current for a very
short time and then the alternator keeps the battery charged and
supplys the current for the vehicle. It seems to me like this would be
very close to keeping the battery on a trickle charge.

In normal operation a car battery doesn't get discharged to 50% and
then recharged. The starter draws a large amount of current for a very
short time and then the alternator keeps the battery charged and
supplys the current for the vehicle. It seems to me like this would be
very close to keeping the battery on a trickle charge.

"Bruce W...1" wrote:


You guys are getting unnecessarily complex me thinks.

Then you think wrong. Your own reference tells you to use
a regulated voltage for float charging.


Yes a voltage regulator would be nice but not really essential.

No, a voltage regulator is essential for float charging.

And
this might get stolen too. Besides, if I was going to go to that effort
I'd just buy a float charger (about $25).

And if you build a voltage regulator using the recommended
LM317 and one of the wall warts you already own, you'll spend
less than 5 dollars. If you don't have a suitable wall wart,
adding the cost of that will still leave you WAY under 25 bucks.


The car is in a garage in a good neighborhood but the owner of the
garage is on and extended vacation. The theives I'm worried about are
neighborhood children. Actually it's the homeowner's car, I'm just
doing them a favor, and saving myself from having to go there to start
the car once a week. So I'd rather not spend money when I have a
plethora of wall warts.

The car does have an alarm but I don't know how much current it pulls.

And "keep alive" current for the radio and microprocessors
and clock and ?? totals how much?


Case, I've got one wall wart which has a 17V open voltage. When I pull
it down to 12.0 volts the current is 120 mA. Might this work?

Yes - if the battery starts out fully charged, and if the
current drain on the battery is only a few mA, and if you
add an LM317, a resistor and a pot and a diode to make a
protected (by the diode) voltage regulator. See the datasheet
at http://www.national.com/ds/LM/LM117.pdf for a diagram
(minus the diode). Add a diode between the input and
output of the LM317, banded end toward the input.



I could increase the size of the transformer if needed. It's just that
I haven't yet figured out what's needed.

Lead-acid batteries have a rated current at which they can be float
charged without causing any damage.

No - not a current. You want a regulated voltage for float
charging.

This is the number I need, but have
not been able to find it.

Read the article you mentioned (below). It says:
"Next comes the Float Step. This is a regulated voltage
of not more than 13.4 volts and usually less than 1 amp
of current."


Here's a related article:
http://www.4unique.com/battery/battery_tutorial.htm

"Bruce W...1" wrote:


You guys are getting unnecessarily complex me thinks.

Then you think wrong. Your own reference tells you to use
a regulated voltage for float charging.


Yes a voltage regulator would be nice but not really essential.

No, a voltage regulator is essential for float charging.

And
this might get stolen too. Besides, if I was going to go to that effort
I'd just buy a float charger (about $25).

And if you build a voltage regulator using the recommended
LM317 and one of the wall warts you already own, you'll spend
less than 5 dollars. If you don't have a suitable wall wart,
adding the cost of that will still leave you WAY under 25 bucks.


The car is in a garage in a good neighborhood but the owner of the
garage is on and extended vacation. The theives I'm worried about are
neighborhood children. Actually it's the homeowner's car, I'm just
doing them a favor, and saving myself from having to go there to start
the car once a week. So I'd rather not spend money when I have a
plethora of wall warts.

The car does have an alarm but I don't know how much current it pulls.

And "keep alive" current for the radio and microprocessors
and clock and ?? totals how much?


Case, I've got one wall wart which has a 17V open voltage. When I pull
it down to 12.0 volts the current is 120 mA. Might this work?

Yes - if the battery starts out fully charged, and if the
current drain on the battery is only a few mA, and if you
add an LM317, a resistor and a pot and a diode to make a
protected (by the diode) voltage regulator. See the datasheet
at http://www.national.com/ds/LM/LM117.pdf for a diagram
(minus the diode). Add a diode between the input and
output of the LM317, banded end toward the input.



I could increase the size of the transformer if needed. It's just that
I haven't yet figured out what's needed.

Lead-acid batteries have a rated current at which they can be float
charged without causing any damage.

No - not a current. You want a regulated voltage for float
charging.

This is the number I need, but have
not been able to find it.

Read the article you mentioned (below). It says:
"Next comes the Float Step. This is a regulated voltage
of not more than 13.4 volts and usually less than 1 amp
of current."


Here's a related article:
http://www.4unique.com/battery/battery_tutorial.htm

Stupid question but is there any possible way to get to the vehicle at least
once a month or can someone you know and trust gain access to the car at
least once or twice a month??? Unless you have a problem with your battery
and/or charging system, having someone start the vehicle and let it run for
roughly 10-15 minutes seems like an easier solution.


--
Ryan KC8PMX

Why is it one careless match can start a forest fire, but
it takes a whole box to start a barbecue?

"Bruce W...1" wrote in message
...
This is not ham radio related but I know you guys have the answer.

I need to store a car unattended for a winter in the midwest. And I
want to put a tricke charge on the battery.

I'd rather not buy a fancy trickle charger because it would probably get
stolen. On the other hand I have a vast array of wall wart
transformers.

If I connected one of these transformers how many milliamps should it
put out at 12V? Or rather what's the least current that would do the
job?

It seems that lead acid batteries can dissipate too much current as
heat. In other words I could probably feed it one amp continuously.
But would 100 mA at 12V do the job? I'd hate to lose a 1-Amp wall wart.

Thanks for your help.

Stupid question but is there any possible way to get to the vehicle at least
once a month or can someone you know and trust gain access to the car at
least once or twice a month??? Unless you have a problem with your battery
and/or charging system, having someone start the vehicle and let it run for
roughly 10-15 minutes seems like an easier solution.


--
Ryan KC8PMX

Why is it one careless match can start a forest fire, but
it takes a whole box to start a barbecue?

"Bruce W...1" wrote in message
...
This is not ham radio related but I know you guys have the answer.

I need to store a car unattended for a winter in the midwest. And I
want to put a tricke charge on the battery.

I'd rather not buy a fancy trickle charger because it would probably get
stolen. On the other hand I have a vast array of wall wart
transformers.

If I connected one of these transformers how many milliamps should it
put out at 12V? Or rather what's the least current that would do the
job?

It seems that lead acid batteries can dissipate too much current as
heat. In other words I could probably feed it one amp continuously.
But would 100 mA at 12V do the job? I'd hate to lose a 1-Amp wall wart.

Thanks for your help.

I was told that a car battery wouldn't last long anyway for this
application, so even when my car battery is 6-7 years old, it
wouldnt't last more than a year when trickle charged, while it is far
better economy to buy a leisure type battery
====
A leisure type (deep cycle) battery is fine for a moderate load for a
relatively long time ,since the plates are relatively thick.
However they are not suitable for engine starting purposes ,since brief
demands for a high starting current cannot be met reliably over time.
That's why car batteries have relatively thin plates with a large area
capable of supplying the high starting current.

If a car is kept outdoors it is worthwhile employing a small solar panel
positioned near the south face of the car with its lead plugged into the
cigarette lighter socket. This will keep the battery in a healthy condition.
I have seen these solar panels advertised by the car accessories trade.

Frank GM0CSZ / KN6WH