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'[OT] BATTERY CHARGER'
R. I. Nelson
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I have about 8 different 12 volt led acid batteries that I wish to
charge. some are deep cycle some are regular. They are all lead acid
type. None of them are the sealed maint. free type.
I also have a 50 amp 24 volt DC power supply that a friend gave me. (He
needed the space, no longer needed it and did not want to throw it out.)
The question does nay one know of plans for a multiple battery charger
that I could make. I would love to have something I could just hook up
the wires to the batteries and not have to worry if I forget them for a
day or 2.
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fn:Robert I. Nelson
adr:;;P.O. BOX 373;RIPON;WI;54971;USA
note;quoted-printable:Custom design and building of small electro mechanical devices.=0D=0A=
AUTOCAD work ver2002
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R. I. Nelson wrote:
> I have about 8 different 12 volt led acid batteries that I wish to
> charge. some are deep cycle some are regular. They are all lead acid
> type. None of them are the sealed maint. free type.
> I also have a 50 amp 24 volt DC power supply that a friend gave me.
> (He needed the space, no longer needed it and did not want to throw it
> The question does nay one know of plans for a multiple battery
> charger that I could make. I would love to have something I could
> just hook up the wires to the batteries and not have to worry if I
> forget them for a day or 2.
I wrote because I dont see any replies to your mail .......
(and because I just read this now)
The cheapest way time-wise and money-wise to get your batteries charged
is to hook them up via a big resistor.
And buy a watch with alarm.
You can guess the charging time for a battery from the battery-terminal
General: If you dont have the possibility to switch off in time (auto or
manual), do not go over 1/10 AH charge current. It is dangerous.
"1/10 AH current" for a 100AmpHour battery is 1/10 x 100 that is 10 Amp
Automation 1: Use a timer (and high-contact-current relay) to switch-off
after/at an estimated time. One for each charger, or charge one battery
at a time.
Automation 2: Measure the voltage at the terminals and switch off when
the fully-charged-voltage has been reached. It works much better (and it
is good for your batteries) if you combine this with 'Improvement 1'
below (tapered-off charging current).
You can keep this simple or make it more sophisticated. (simple is
Improvement 1: Taper the current after bulk-charge. Lower the current
once the terminal-voltage is over 12.8 Volt or so. (the lead-acid
batteries I have charged all accept their bulk-charge around 12.6 - 12.7
Volt so cut the bulk-charge-current above that voltage).
Switching off in time is not critical for non-sealed lead-acid batteries
(it IS for sealed batteries). You can be several hours late switching
off) if you limit the current below 1/10 AmpHour rating (max. 10 A
charging-current for a 100 AH batt).
With a little experience it is also possible to estimate the charging
time from the voltage at the terminals. And set a timer for
auto-switch-off. You can check afterward if the battery is fully charged.
Battery chargers often have few controls because charging is a
non-critical proces. There are clear limits though.
Automotive battery-chargers (manual and automatic) limit their max
charge-current by selecting a transformer with the right voltage. To be
used without filtercapacitor.
This causes auto-taper-off of the charging current. As the
battery-voltage increases the current reduces (as the charger is
As the design is fixed (as per the above) the process produces
It is possible to switch off at the familiar voltage of 13.8 Volt. For
one-time charging, followed by auto-charger-disconnect a higher voltage
is used. Like 14.5 Volt.
If your 24VDC powersupply has a way to lower the voltage, you save energy.
Removing the filter-capacitor in the powersupply will help to lower the
More details for more specific situations.
Herman in PHL (Philippines).
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