mcalhoun wrote:

Harbor Freight $7.99 float chargers:

You don't say! Have you ever measured their voltage? Or is it written
on the case?

I never had, so I went out (to the garage; brrrr!) and measured one:
13.58 volts. FWIW, the wallwart says "15VAC at 600 ma", but there's a
little plastic box on the wires between the wart and the battery clips.

--Myron.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

================================================== ========

Now we're getting somewhere. Myron said 15VAC at 600 ma. C/100 is
about 700 mA. Any idea what's inside the little voltage adjustment box?

On Wed, 05 Nov 2003 18:09:46 -0500, Bruce W...1 wrote:
mcalhoun wrote:
Although their normal price is about $15, float battery chargers (wall
wart, coiled cord, little black box with LED, two cords with large
alligator clips on the ends) are often advertised in Harbor Freight
catalogs for $7.99. I must have half a dozen of them now, keeping
batteries here and there up to snuff. I've never measured them, but
they seem to do a real good job, and they're hard to beat at that price!

I have no connection to Harbor Freight except as a satisfied customer,

Ditto to all of the above.

You don't say! Have you ever measured their voltage? Or is it written
on the case?

Mine vary between 13.5v to 13.6v. If you open the little plastic
box between the transformer and the battery terminals you will find
a little adjustment that will let you tweak the voltage.

I have two different styles, one with curly coiled leads and one
with straight leads. I think the straight lead is older and has
been obsoleted. Too bad, because they made a nice low-current
adjustable power supply. The curly lead ones don't. But they
both seem to do a fine job of keeping lead acid batts up to snuff.

I have a couple on my bench. One set to 13.6v and one to 14.1v. I
put a gel cell on the 14.1v to charge after use, then on to the
13.6v to maintain ready for next time.

I have one in the barn. I cut off the clamps and put on a pair of
anderson powerpole connectors. A matching connector on my lawn
tractor allows me to easily attach with no concern for polarity
mismatch whether it is me or anyone else. I got 5 seasons from the
last battery, which is pretty good for a lawn tractor that sits
pretty much unused october thru april.

sdb
--
| Sylvan Butler | Not speaking for Hewlett-Packard | sbutler-boi.hp.com |
| Watch out for my e-mail address. Thank UCE. change ^ to @ |
It may be better to live under robber barons than under omnipotent moral
busybodies. The robber baron's cruelty may sometimes sleep, his
cupidity may at some point be satiated; but those who torment us for our
own good will torment us without end, for they do so with the approval
of their consciences. -- C. S. Lewis

On Thu, 6 Nov 2003 14:15:17 -0700, Sylvan Butler
d wrote:

On Wed, 05 Nov 2003 18:09:46 -0500, Bruce W...1 wrote:
mcalhoun wrote:
Although their normal price is about $15, float battery chargers (wall
wart, coiled cord, little black box with LED, two cords with large
alligator clips on the ends) are often advertised in Harbor Freight
catalogs for $7.99. I must have half a dozen of them now, keeping
batteries here and there up to snuff. I've never measured them, but
they seem to do a real good job, and they're hard to beat at that price!

I have no connection to Harbor Freight except as a satisfied customer,

Ditto to all of the above.

You don't say! Have you ever measured their voltage? Or is it written
on the case?

Mine vary between 13.5v to 13.6v. If you open the little plastic
box between the transformer and the battery terminals you will find
a little adjustment that will let you tweak the voltage.

I have two different styles, one with curly coiled leads and one
with straight leads. I think the straight lead is older and has
been obsoleted. Too bad, because they made a nice low-current
adjustable power supply. The curly lead ones don't. But they
both seem to do a fine job of keeping lead acid batts up to snuff.

I have a couple on my bench. One set to 13.6v and one to 14.1v. I
put a gel cell on the 14.1v to charge after use, then on to the
13.6v to maintain ready for next time.

I have one in the barn. I cut off the clamps and put on a pair of
anderson powerpole connectors. A matching connector on my lawn
tractor allows me to easily attach with no concern for polarity
mismatch whether it is me or anyone else. I got 5 seasons from the
last battery, which is pretty good for a lawn tractor that sits
pretty much unused october thru april.

sdb

I just picked up a couple of the float chargers from Harbor Freight.
They measure 13.55 no load. 13.55 at 130 ma, 13.4 at 175 ma, 12.9 at
230 ma, 12.8 at 250 ma.

Looks like they will only supply about 175 ma max and still be above
13.4 volts. At over 500 ma they will shut down and won't restart until
the load is removed completely.

One problem I see with them is that they draw 36 ma from the battery
if they are hooked up to the battery (at 12.9 battery volts) but not
plugged into the wall. If you loose AC power that will quickly kill
the battery!

They measure 3.6k both ways when you check the resistance but when
hooked to the battery they cause much more draw than 3.6 ma.

These are the ones with the curly cords. Are these internally
adjustable ?

I wonder if there is enough range to add a series diode?

Thanks
Gary K4FMX

On Thu, 6 Nov 2003 14:15:17 -0700, Sylvan Butler
d wrote:

On Wed, 05 Nov 2003 18:09:46 -0500, Bruce W...1 wrote:
mcalhoun wrote:
Although their normal price is about $15, float battery chargers (wall
wart, coiled cord, little black box with LED, two cords with large
alligator clips on the ends) are often advertised in Harbor Freight
catalogs for $7.99. I must have half a dozen of them now, keeping
batteries here and there up to snuff. I've never measured them, but
they seem to do a real good job, and they're hard to beat at that price!

I have no connection to Harbor Freight except as a satisfied customer,

Ditto to all of the above.

You don't say! Have you ever measured their voltage? Or is it written
on the case?

Mine vary between 13.5v to 13.6v. If you open the little plastic
box between the transformer and the battery terminals you will find
a little adjustment that will let you tweak the voltage.

I have two different styles, one with curly coiled leads and one
with straight leads. I think the straight lead is older and has
been obsoleted. Too bad, because they made a nice low-current
adjustable power supply. The curly lead ones don't. But they
both seem to do a fine job of keeping lead acid batts up to snuff.

I have a couple on my bench. One set to 13.6v and one to 14.1v. I
put a gel cell on the 14.1v to charge after use, then on to the
13.6v to maintain ready for next time.

I have one in the barn. I cut off the clamps and put on a pair of
anderson powerpole connectors. A matching connector on my lawn
tractor allows me to easily attach with no concern for polarity
mismatch whether it is me or anyone else. I got 5 seasons from the
last battery, which is pretty good for a lawn tractor that sits
pretty much unused october thru april.

sdb

I just picked up a couple of the float chargers from Harbor Freight.
They measure 13.55 no load. 13.55 at 130 ma, 13.4 at 175 ma, 12.9 at
230 ma, 12.8 at 250 ma.

Looks like they will only supply about 175 ma max and still be above
13.4 volts. At over 500 ma they will shut down and won't restart until
the load is removed completely.

One problem I see with them is that they draw 36 ma from the battery
if they are hooked up to the battery (at 12.9 battery volts) but not
plugged into the wall. If you loose AC power that will quickly kill
the battery!

They measure 3.6k both ways when you check the resistance but when
hooked to the battery they cause much more draw than 3.6 ma.

These are the ones with the curly cords. Are these internally
adjustable ?

I wonder if there is enough range to add a series diode?

Thanks
Gary K4FMX

Harbor Freight $7.99 float chargers:

You don't say! Have you ever measured their voltage? Or is it written
on the case?

I never had, so I went out (to the garage; brrrr!) and measured one:
13.58 volts. FWIW, the wallwart says "15VAC at 600 ma", but there's a
little plastic box on the wires between the wart and the battery clips.

--Myron.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

On Wed, 05 Nov 2003 18:09:46 -0500, Bruce W...1 wrote:
mcalhoun wrote:
Although their normal price is about $15, float battery chargers (wall
wart, coiled cord, little black box with LED, two cords with large
alligator clips on the ends) are often advertised in Harbor Freight
catalogs for $7.99. I must have half a dozen of them now, keeping
batteries here and there up to snuff. I've never measured them, but
they seem to do a real good job, and they're hard to beat at that price!

I have no connection to Harbor Freight except as a satisfied customer,

Ditto to all of the above.

You don't say! Have you ever measured their voltage? Or is it written
on the case?

Mine vary between 13.5v to 13.6v. If you open the little plastic
box between the transformer and the battery terminals you will find
a little adjustment that will let you tweak the voltage.

I have two different styles, one with curly coiled leads and one
with straight leads. I think the straight lead is older and has
been obsoleted. Too bad, because they made a nice low-current
adjustable power supply. The curly lead ones don't. But they
both seem to do a fine job of keeping lead acid batts up to snuff.

I have a couple on my bench. One set to 13.6v and one to 14.1v. I
put a gel cell on the 14.1v to charge after use, then on to the
13.6v to maintain ready for next time.

I have one in the barn. I cut off the clamps and put on a pair of
anderson powerpole connectors. A matching connector on my lawn
tractor allows me to easily attach with no concern for polarity
mismatch whether it is me or anyone else. I got 5 seasons from the
last battery, which is pretty good for a lawn tractor that sits
pretty much unused october thru april.

sdb
--
| Sylvan Butler | Not speaking for Hewlett-Packard | sbutler-boi.hp.com |
| Watch out for my e-mail address. Thank UCE. change ^ to @ |
It may be better to live under robber barons than under omnipotent moral
busybodies. The robber baron's cruelty may sometimes sleep, his
cupidity may at some point be satiated; but those who torment us for our
own good will torment us without end, for they do so with the approval
of their consciences. -- C. S. Lewis

mcalhoun wrote:

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

Although their normal price is about $15, float battery chargers (wall
wart, coiled cord, little black box with LED, two cords with large
alligator clips on the ends) are often advertised in Harbor Freight
catalogs for $7.99. I must have half a dozen of them now, keeping
batteries here and there up to snuff. I've never measured them, but
they seem to do a real good job, and they're hard to beat at that price!

I have no connection to Harbor Freight except as a satisfied customer,

--Myron.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

================================================== =====

You don't say! Have you ever measured their voltage? Or is it written
on the case?

Bruce:

As others have indicated, you really want to use a regulated charging
voltage to keep the battery up... The voltage is important, however, more
important to getting the design right is knowing how much of a drain the
automobile puts on the battery when "nothing" is going on... Many cars will
drain a good battery in about a month, just from the residual drain that is
the result of such things as clocks and memories in radios and such. Add
anything else and you've got a good chance of needing significantly more
charging current than you might at first think.

You mention that you are worried about using a fancy trickle charger because
it may get stolen, which implies that the car is outside in the elements,
and not in a protected or secured environment. I'd be willing to bet that
if you have to worry about someone stealing a trickle charger, you should
probably be concerned about just about everything else too, once someone
notices the car isn't moving and has a power cord going to it....

In addition, being concerned about a 1-amp wall wart, which are nearly a
dime a dozen, may be false economy, considering the value of the car and
items built or installed in it. Why wouldn't the tires and wheels
disappear, or the battery itself? Same for radio and/or other
accessories... or even perhaps the car itself.

If you do go and build something to keep the battery up, bear in mind that
you are probably going to need something with a voltage around 16 volts or
so, given that most regulators require a couple of volts of headroom over
the regulated voltage. This may take you into a range of supplies or wall
warts that is higher than you may have on hand anyway.

--Rick

"Bruce W...1" wrote:

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.

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

Wow, that is a revelation. I hope most people reading this group would know
that.
73 Gary N4AST

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

Although their normal price is about $15, float battery chargers (wall
wart, coiled cord, little black box with LED, two cords with large
alligator clips on the ends) are often advertised in Harbor Freight
catalogs for $7.99. I must have half a dozen of them now, keeping
batteries here and there up to snuff. I've never measured them, but
they seem to do a real good job, and they're hard to beat at that price!

I have no connection to Harbor Freight except as a satisfied customer,

--Myron.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)