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Can a 12 volt regulatred power supply be used to charge car

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Unlisted
Guest

Mon Feb 11, 2019 7:45 am   



I have a 12volt regulated power supply that was probably made for using
automotive CB radios in a house. It's rated at 3 amps. Can this be used
to slow charge 12V car batteries? I have a big car battery charger,
which puts out 15 or 60 amps, but I want to trickle charge a battery in
severe cold weather.

I'm more worried about damaging the power supply than the battery.

Rheilly Phoull
Guest

Mon Feb 11, 2019 8:45 am   



On 11/02/2019 2:38 pm, Unlisted wrote:
Quote:
I have a 12volt regulated power supply that was probably made for using
automotive CB radios in a house. It's rated at 3 amps. Can this be used
to slow charge 12V car batteries? I have a big car battery charger,
which puts out 15 or 60 amps, but I want to trickle charge a battery in
severe cold weather.

I'm more worried about damaging the power supply than the battery.


Not really good for both purposes since you need higher than 12v to
charge a battery, perhaps used with a voltage booster as found on ebay
might suit you they are not expensive. You could set the adjustable
output of the booster to 13.8 or 13.6 ( according to the battery ) for a
charge and it would trickle charge when full.

Mike
Guest

Mon Feb 11, 2019 8:45 am   



On 2/10/2019 10:38 PM, Unlisted wrote:
Quote:
I have a 12volt regulated power supply that was probably made for using
automotive CB radios in a house. It's rated at 3 amps. Can this be used
to slow charge 12V car batteries? I have a big car battery charger,
which puts out 15 or 60 amps, but I want to trickle charge a battery in
severe cold weather.

I'm more worried about damaging the power supply than the battery.


If the battery is not in the vehicle, store it somewhere warmer.
IF the battery is in the vehicle, you may want to determine
the static load. You have to compensate for that too.

Severe cold weather is vague.
Go to the battery vendor site and look up the maintenance charge
voltage for your battery at the desired temperature.

12V is likely not enough to maintain full charge, but may be enough
to keep it alive.

But it's far easier to go buy a cheap trickle charger designed for the
purpose.

The biggest risk to your charger is starting the car while it's
connected.
The biggest risk to your battery is not knowing EXACTLY what the
power supply puts out at the desired temperature and what the battery
wants at that temperature.

Putting a 12V incandescent tail light in series with the power supply
will mitigate some of the issues.


Guest

Mon Feb 11, 2019 9:45 am   



On Mon, 11 Feb 2019 00:38:38 -0600, Unlisted <unlisted_at_nomail.com>
wrote:

Quote:
I have a 12volt regulated power supply that was probably made for using
automotive CB radios in a house. It's rated at 3 amps. Can this be used
to slow charge 12V car batteries? I have a big car battery charger,
which puts out 15 or 60 amps, but I want to trickle charge a battery in
severe cold weather.

I'm more worried about damaging the power supply than the battery.


If the mains fails or the mains plug is disconnected while the power
supply is connected to the battery, the power supply will get 12 V
from the battery, which may destroy the power supply, depending on the
power supply design. To be safe, put a forward biased diode between
the power supply and battery. Remember to increase the power supply
voltage to compensate for the diode voltage drop


Guest

Mon Feb 11, 2019 2:45 pm   



On Monday, 11 February 2019 07:07:56 UTC, Rheilly Phoull wrote:
Quote:
On 11/02/2019 2:38 pm, Unlisted wrote:

I have a 12volt regulated power supply that was probably made for using
automotive CB radios in a house. It's rated at 3 amps. Can this be used
to slow charge 12V car batteries? I have a big car battery charger,
which puts out 15 or 60 amps, but I want to trickle charge a battery in
severe cold weather.

I'm more worried about damaging the power supply than the battery.


Not really good for both purposes since you need higher than 12v to
charge a battery, perhaps used with a voltage booster as found on ebay
might suit you they are not expensive. You could set the adjustable
output of the booster to 13.8 or 13.6 ( according to the battery ) for a
charge and it would trickle charge when full.


13.6v is the minimum to charge a 12v car battery, more is preferable. You may be able to get that by adding diodes in the regulation feedback path if switched mode, or the linear regulator 0v connection if linear. Last time I saw a CB psu it was 13.2v.


NT

John Larkin
Guest

Mon Feb 11, 2019 4:45 pm   



On Mon, 11 Feb 2019 00:38:38 -0600, Unlisted <unlisted_at_nomail.com>
wrote:

Quote:
I have a 12volt regulated power supply that was probably made for using
automotive CB radios in a house. It's rated at 3 amps. Can this be used
to slow charge 12V car batteries? I have a big car battery charger,
which puts out 15 or 60 amps, but I want to trickle charge a battery in
severe cold weather.

I'm more worried about damaging the power supply than the battery.


Amazon has a trickle charger, with leads and all, for $9.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics


Guest

Mon Feb 11, 2019 7:45 pm   



Unlisted <unlisted_at_nomail.com> wrote in
news:a3626elig8gq8mv66muo81fb3kivf4c65k_at_4ax.com:

Quote:
I have a 12volt regulated power supply that was probably made for
using automotive CB radios in a house. It's rated at 3 amps. Can
this be used to slow charge 12V car batteries? I have a big car
battery charger, which puts out 15 or 60 amps, but I want to
trickle charge a battery in severe cold weather.

I'm more worried about damaging the power supply than the battery.



If you can set the supply voltage to 13.6 volts under the supply's
full rated load, then yes.

The problem is not you needing to worry about the supply. The
problem is that you could overcharge the battery and blow it up
(lead acid).

If you can ensure that you do not exceed the fully charged voltage
and stop charging when that is attained.

If you can't, you'd better find a way to monitor the battery's
temperature, or have some other means to determine full charge state
and turn OFF the charge device.

Mike Perkins
Guest

Mon Feb 11, 2019 7:45 pm   



On 11/02/2019 06:38, Unlisted wrote:
Quote:
I have a 12volt regulated power supply that was probably made for using
automotive CB radios in a house. It's rated at 3 amps. Can this be used
to slow charge 12V car batteries? I have a big car battery charger,
which puts out 15 or 60 amps, but I want to trickle charge a battery in
severe cold weather.

I'm more worried about damaging the power supply than the battery.


Most CB power supplies I've come across have been 13.6V or so, and so
ideal for float charging a lead acid battery.

If yours says 12V then likely not.


--
Mike Perkins
Video Solutions Ltd
www.videosolutions.ltd.uk


Guest

Mon Feb 11, 2019 8:45 pm   



On Monday, 11 February 2019 18:35:21 UTC, DecadentLinux...@decadence.org wrote:
Quote:
Unlisted <unlisted_at_nomail.com> wrote in
news:a3626elig8gq8mv66muo81fb3kivf4c65k_at_4ax.com:

I have a 12volt regulated power supply that was probably made for
using automotive CB radios in a house. It's rated at 3 amps. Can
this be used to slow charge 12V car batteries? I have a big car
battery charger, which puts out 15 or 60 amps, but I want to
trickle charge a battery in severe cold weather.

I'm more worried about damaging the power supply than the battery.



If you can set the supply voltage to 13.6 volts under the supply's
full rated load, then yes.

The problem is not you needing to worry about the supply. The
problem is that you could overcharge the battery and blow it up
(lead acid).

If you can ensure that you do not exceed the fully charged voltage
and stop charging when that is attained.

If you can't, you'd better find a way to monitor the battery's
temperature, or have some other means to determine full charge state
and turn OFF the charge device.


Old car chargers had no cut-off when full, folk just unplugged them after a while. You can do that if you don't make a habit of it. If you do it often, use a better charger. Old unregulated chargers will kill batteries if you leave them on day after day.


NT

Lasse Langwadt Christense
Guest

Mon Feb 11, 2019 8:45 pm   



mandag den 11. februar 2019 kl. 19.47.55 UTC+1 skrev jurb...@gmail.com:
Quote:
I would go higher than 13.6. Open circuit voltage is actually 12.6, leaving only a volt of headroom. When first started in cold weather a car might go up to 15.8. Of course it does not maintain that voltage, it tapers off as the temperature rises.

If you're using a solid regulated voltage with no ballast or current limit, 13.6 is almost too high.

Another thing about lead acid batteries is if you use them in the house you have to kick them around once in a while. It help knock the bubbles off the plates, as would happen when you would drive down the road. I have charged batteries in the house or garage and watched the ammeter on the charger go up as I agitated the battery.


13.6 is right around the float voltage for room temperature


Guest

Mon Feb 11, 2019 8:45 pm   



I would go higher than 13.6. Open circuit voltage is actually 12.6, leaving only a volt of headroom. When first started in cold weather a car might go up to 15.8. Of course it does not maintain that voltage, it tapers off as the temperature rises.

If you're using a solid regulated voltage with no ballast or current limit, 13.6 is almost too high.

Another thing about lead acid batteries is if you use them in the house you have to kick them around once in a while. It help knock the bubbles off the plates, as would happen when you would drive down the road. I have charged batteries in the house or garage and watched the ammeter on the charger go up as I agitated the battery.


Guest

Wed Feb 20, 2019 6:45 am   



On Mon, 11 Feb 2019 11:22:48 -0800 (PST), tabbypurr_at_gmail.com wrote:

Quote:
On Monday, 11 February 2019 18:35:21 UTC, DecadentLinux...@decadence.org wrote:
Unlisted <unlisted_at_nomail.com> wrote in
news:a3626elig8gq8mv66muo81fb3kivf4c65k_at_4ax.com:

I have a 12volt regulated power supply that was probably made for
using automotive CB radios in a house. It's rated at 3 amps. Can
this be used to slow charge 12V car batteries? I have a big car
battery charger, which puts out 15 or 60 amps, but I want to
trickle charge a battery in severe cold weather.

I'm more worried about damaging the power supply than the battery.



If you can set the supply voltage to 13.6 volts under the supply's
full rated load, then yes.

The problem is not you needing to worry about the supply. The
problem is that you could overcharge the battery and blow it up
(lead acid).

If you can ensure that you do not exceed the fully charged voltage
and stop charging when that is attained.

If you can't, you'd better find a way to monitor the battery's
temperature, or have some other means to determine full charge state
and turn OFF the charge device.

Old car chargers had no cut-off when full, folk just unplugged them after a while.
You can do that if you don't make a habit of it. If you do it often, use a better cha
rger. Old unregulated chargers will kill batteries if you leave them on day after day.


I have an old charger, a small 6A model, which only has an over current
cutout. No cut-off. I had it connected to my farm tractor last week,
when we got a huge snowstorm. The tractor and charger were outdoors, but
I had a cover over the charger. However, the plug was laying on the
ground, connected to an extension cord. That cord is plugged into a GFI
outlet on the barn. After the storm, I unplugged the charger, which had
been connected for around 36 hours. However, the GFI had tripped from
the cord being buried under the snow.

I soon found that battery was completely dead. (It was only halfway
discharged when I applied the charger). The tractor ignition switch and
lights were NOT turned on.

So, what drained the battery? It had to be the charger, which drained it
after the GFI tripped. I did not think that current is supposed to go
backwards on battery chargers, but I assume it did. With the ingition
switch and lights turned off, there is nothing to drain the battery.
(this is a simple OLD tractor, no radio or heaters or stuff).

I can only assume that the charger has a leaky diode...... I guess thats
possible????
I am not quite sure how to check this???? I can only guess to hook my
multimeter across the plus and minus clamps, then reverse it and see if
there is low resistance both ways????

Or maybe I should just put new diodes in it. 6A rated diodes cant be too
costly...

Mike
Guest

Wed Feb 20, 2019 7:45 am   



On 2/19/2019 9:13 PM, tubeguy_at_myshop.com wrote:
Quote:
On Mon, 11 Feb 2019 11:22:48 -0800 (PST), tabbypurr_at_gmail.com wrote:

On Monday, 11 February 2019 18:35:21 UTC, DecadentLinux...@decadence.org wrote:
Unlisted <unlisted_at_nomail.com> wrote in
news:a3626elig8gq8mv66muo81fb3kivf4c65k_at_4ax.com:

I have a 12volt regulated power supply that was probably made for
using automotive CB radios in a house. It's rated at 3 amps. Can
this be used to slow charge 12V car batteries? I have a big car
battery charger, which puts out 15 or 60 amps, but I want to
trickle charge a battery in severe cold weather.

I'm more worried about damaging the power supply than the battery.



If you can set the supply voltage to 13.6 volts under the supply's
full rated load, then yes.

The problem is not you needing to worry about the supply. The
problem is that you could overcharge the battery and blow it up
(lead acid).

If you can ensure that you do not exceed the fully charged voltage
and stop charging when that is attained.

If you can't, you'd better find a way to monitor the battery's
temperature, or have some other means to determine full charge state
and turn OFF the charge device.

Old car chargers had no cut-off when full, folk just unplugged them after a while.
You can do that if you don't make a habit of it. If you do it often, use a better cha
rger. Old unregulated chargers will kill batteries if you leave them on day after day.


I have an old charger, a small 6A model, which only has an over current
cutout. No cut-off. I had it connected to my farm tractor last week,
when we got a huge snowstorm. The tractor and charger were outdoors, but
I had a cover over the charger. However, the plug was laying on the
ground, connected to an extension cord. That cord is plugged into a GFI
outlet on the barn. After the storm, I unplugged the charger, which had
been connected for around 36 hours. However, the GFI had tripped from
the cord being buried under the snow.

I soon found that battery was completely dead. (It was only halfway
discharged when I applied the charger). The tractor ignition switch and
lights were NOT turned on.

So, what drained the battery? It had to be the charger, which drained it
after the GFI tripped. I did not think that current is supposed to go
backwards on battery chargers, but I assume it did. With the ingition
switch and lights turned off, there is nothing to drain the battery.
(this is a simple OLD tractor, no radio or heaters or stuff).

I can only assume that the charger has a leaky diode...... I guess thats
possible????
I am not quite sure how to check this???? I can only guess to hook my
multimeter across the plus and minus clamps, then reverse it and see if
there is low resistance both ways????

Or maybe I should just put new diodes in it. 6A rated diodes cant be too
costly...


Put the charger on a good battery.
Power it off.
Put your current meter between the battery and charger to see how much
current flow you get back into the charger.

If you are gonna replace the diodes, you should use the same technology.
Very old chargers had selenium rectifiers.

Battery chargers are dirt cheap compared to the batteries they charge.
Just get a smart one and be done with it.


Guest

Wed Feb 20, 2019 11:45 am   



On Wednesday, 20 February 2019 06:09:02 UTC, Mike wrote:
Quote:
On 2/19/2019 9:13 PM, tubeguy_at_myshop.com wrote:
On Mon, 11 Feb 2019 11:22:48 -0800 (PST), tabbypurr wrote:
On Monday, 11 February 2019 18:35:21 UTC, DecadentLinux...@decadence.org wrote:
Unlisted <unlisted_at_nomail.com> wrote in
news:a3626elig8gq8mv66muo81fb3kivf4c65k_at_4ax.com:

I have a 12volt regulated power supply that was probably made for
using automotive CB radios in a house. It's rated at 3 amps. Can
this be used to slow charge 12V car batteries? I have a big car
battery charger, which puts out 15 or 60 amps, but I want to
trickle charge a battery in severe cold weather.

I'm more worried about damaging the power supply than the battery.



If you can set the supply voltage to 13.6 volts under the supply's
full rated load, then yes.

The problem is not you needing to worry about the supply. The
problem is that you could overcharge the battery and blow it up
(lead acid).

If you can ensure that you do not exceed the fully charged voltage
and stop charging when that is attained.

If you can't, you'd better find a way to monitor the battery's
temperature, or have some other means to determine full charge state
and turn OFF the charge device.

Old car chargers had no cut-off when full, folk just unplugged them after a while.
You can do that if you don't make a habit of it. If you do it often, use a better cha
rger. Old unregulated chargers will kill batteries if you leave them on day after day.


I have an old charger, a small 6A model, which only has an over current
cutout. No cut-off. I had it connected to my farm tractor last week,
when we got a huge snowstorm. The tractor and charger were outdoors, but
I had a cover over the charger. However, the plug was laying on the
ground, connected to an extension cord. That cord is plugged into a GFI
outlet on the barn. After the storm, I unplugged the charger, which had
been connected for around 36 hours. However, the GFI had tripped from
the cord being buried under the snow.

I soon found that battery was completely dead. (It was only halfway
discharged when I applied the charger). The tractor ignition switch and
lights were NOT turned on.

So, what drained the battery? It had to be the charger, which drained it
after the GFI tripped. I did not think that current is supposed to go
backwards on battery chargers, but I assume it did. With the ingition
switch and lights turned off, there is nothing to drain the battery.
(this is a simple OLD tractor, no radio or heaters or stuff).

I can only assume that the charger has a leaky diode...... I guess thats
possible????
I am not quite sure how to check this???? I can only guess to hook my
multimeter across the plus and minus clamps, then reverse it and see if
there is low resistance both ways????

Or maybe I should just put new diodes in it. 6A rated diodes cant be too
costly...


Put the charger on a good battery.
Power it off.
Put your current meter between the battery and charger to see how much
current flow you get back into the charger.

If you are gonna replace the diodes, you should use the same technology.
Very old chargers had selenium rectifiers.

Battery chargers are dirt cheap compared to the batteries they charge.
Just get a smart one and be done with it.


Minimal chargers are just transformer & diodes. Leaky diodes yet it works are unlikely, but as Mike says measure it & see.


NT

Phil Hobbs
Guest

Wed Feb 20, 2019 2:45 pm   



On 2/11/19 2:22 PM, tabbypurr_at_gmail.com wrote:
Quote:
On Monday, 11 February 2019 18:35:21 UTC,
DecadentLinux...@decadence.org wrote:
Unlisted <unlisted_at_nomail.com> wrote in
news:a3626elig8gq8mv66muo81fb3kivf4c65k_at_4ax.com:

I have a 12volt regulated power supply that was probably made
for using automotive CB radios in a house. It's rated at 3 amps.
Can this be used to slow charge 12V car batteries? I have a big
car battery charger, which puts out 15 or 60 amps, but I want to
trickle charge a battery in severe cold weather.

I'm more worried about damaging the power supply than the
battery.



If you can set the supply voltage to 13.6 volts under the supply's
full rated load, then yes.

The problem is not you needing to worry about the supply. The
problem is that you could overcharge the battery and blow it up
(lead acid).

If you can ensure that you do not exceed the fully charged voltage
and stop charging when that is attained.

If you can't, you'd better find a way to monitor the battery's
temperature, or have some other means to determine full charge
state and turn OFF the charge device.

Old car chargers had no cut-off when full, folk just unplugged them
after a while. You can do that if you don't make a habit of it. If
you do it often, use a better charger. Old unregulated chargers will
kill batteries if you leave them on day after day.


But a lot of new ones will refuse to charge a battery that's really
flat, e.g. if you leave your headlights on. I have an ancient Sears
Craftsman 10/2 amp charger that I'm very fond of. It gets used about
once every two years--a guy I know was so annoyed with his car's
door-open chime that he disconnected it, and so lost his "your
headlights are on, dummy" chime as well.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

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