Re: Can a 12 volt regulatred power supply be used to charge car batteries?

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On Mon, 11 Feb 2019 11:22:48 -0800 (PST), snipped-for-privacy@gmail.com wrote:

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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...



Re: Can a 12 volt regulatred power supply be used to charge car batteries?
On 2/19/2019 9:13 PM, snipped-for-privacy@myshop.com wrote:
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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.



Re: Can a 12 volt regulatred power supply be used to charge car batteries?
On Wednesday, 20 February 2019 06:09:02 UTC, Mike  wrote:
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Minimal chargers are just transformer & diodes. Leaky diodes yet it works are unlikely, but as Mike says measure it & see.


NT

Re: Can a 12 volt regulatred power supply be used to charge car batteries?
wrote:

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How are you going to simulate a 3 stage charge cycle?
<https://batteryuniversity.com/learn/article/charging_the_lead_acid_battery
or deal with changes needed by temperature extremes?
<https://batteryuniversity.com/index.php/learn/article/charging_at_high_and_low_temperatures
I don't think it can be done correctly with a (roughly) 12V 60A power
supply.  The 3A charger might work, but you'll need some kind of
regulator and charge controller.  Most CB radio power supplies that
I've seen use linear regulators, which means that the unregulated
voltage is probably about 15V.  Rip out the linear regulator, install
a lead-acid battery charger circuit, and you might have something that
works.  Something like this PCB:
<https://www.ebay.com/itm/3A-12V-Lead-Acid-Battery-Accumulator-Storage-Cell-Charger-Module-UPS-Car-Solar/282699952196
Or, just buy a battery maintainer and be done with the project.

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Normally, I would suggest you run out and buy a proper battery
charger.  However, my luck hasn't been too good with some products.
Six out of these seven charges died or went insane while charging
fairly new lead-acid batteries.  The seventh charger died a few months
later after boiling the water out of 2 expensive batteries:
<http://www.learnbydestroying.com/jeffl/pics/drivel/slides/dead-battery-chargers.html>
I'll spare you the details, but basically these were an attempt to
save money by not buying a proper charger.  I donated my Statpower
Xantrex 10A charger to the cause and had no further problems that
required long drives to various mountain top sites:
<http://www.xantrex.com/power-products/battery-chargers/overview.aspx

You mention something about wanting to trickle charge a lead-acid car
battery.  That will not work.  Automotive lead-acid batteries are NOT
made for stationary use.  Ask in any of the wind, solar, or
alternative energy forums about how well car batteries work for
stationary use.  Car batteries were made to deliver a large amount of
current quickly when starting a car and then recharge quickly.  
<https://www.stationary-power.com/landing/blog/the-difference-between-stationary-batteries-and-engine-start-batteries/



--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Can a 12 volt regulatred power supply be used to charge car batteries?
snipped-for-privacy@downunder.com writes:

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+1


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