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 Automatic 12V Lead Battery Charger		  New Topic  Reply to Topic
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hanz360
Apprentece

Philippines
7 Posts
Posted - Jan 22 2008 :  09:27:51 AM  Show Profile  Reply with Quote
moderator pls help me w/ this., it possible to connect a diode at positive/negative side of the output to prevent the current from battery entering the circuit? if yes is there any effect to the circuit? thanks in advance
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zouzanda
Apprentece

Lebanon
8 Posts
Posted - Jan 24 2008 :  11:18:19 AM  Show Profile  Reply with Quote
man ofcourse u can't cz this circuit needs to test the voltage on the battery so if u used a diode ull prevent that from happening so Q2 will never turn on
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Aaron Cake
Administrator

Canada
6718 Posts
Posted - Jan 27 2008 :  10:35:30 AM  Show Profile  Visit Aaron Cake's Homepage  Send Aaron Cake an ICQ Message  Send Aaron Cake a Yahoo! Message  Reply with Quote
What he said. A diode at the output will prevent the circuit from seeing the voltage of the battery.
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pebe
Nobel Prize Winner

United Kingdom
1078 Posts
Posted - Jan 27 2008 :  10:55:33 AM  Show Profile  Reply with Quote
quote:
Originally posted by zouzanda

man ofcourse u can't cz this circuit needs to test the voltage on the battery so if u used a diode ull prevent that from happening so Q2 will never turn on

That's only partially true. With a diode fitted the circuit will see 0V battery volts so it will assume the battery is flat and switch on the charger. Once the circuit is charging and the diode is conducting then it will 'see' battery volts plus 0.7V.

All you need to do is set up the potentiometer to give a charger output 0.7V higher than without the diode.
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hanz360
Apprentece

Philippines
7 Posts
Posted - Feb 01 2008 :  10:14:01 AM  Show Profile  Reply with Quote
what i mean is a "blocking Diode",preventing the current entering the circuit when you unplug the charger and the battery still connected to the charger, so that the battery will not be drain...

Thanks for the info guys..
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hanz360
Apprentece

Philippines
7 Posts
Posted - Feb 02 2008 :  07:28:54 AM  Show Profile  Reply with Quote
another question.., i have a NiCd and NiMH batteries and it's require a 12V charger to charge it, so its possible that i can use this 12V Lead Battery Charger to charge my NiCd and NiMH batteries? thank's in advance
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audioguru
Nobel Prize Winner

Canada
4218 Posts
Posted - Feb 02 2008 :  7:02:46 PM  Show Profile  Reply with Quote
Ni-Cad and Ni-MH batteries need a completely different charger circuit from the lead-acid battery charger.

Usually a regulated current is used and the small voltage peak-dip is sensed or the rapid rise in battery temperature is sensed to stop the charging when the battery is fully charged. ICs are made to charge these batteries.
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hanz360
Apprentece

Philippines
7 Posts
Posted - Feb 02 2008 :  10:52:10 PM  Show Profile  Reply with Quote
thank's audioguru for the info.

Any body knows the schematic diagram for 12v NiCd and Ni-MH batteries charger?
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audioguru
Nobel Prize Winner

Canada
4218 Posts
Posted - Feb 02 2008 :  11:55:40 PM  Show Profile  Reply with Quote
A 12V Ni-Cad or Ni-MH battery is fully charged at 14.0V to 15.0V depending on the charging current.
Maxim-IC have some battery charger ICs and the schematic for the battery charger is in their datasheets.

The charger circuits are automatic to charge quickly but avoid the battery exploding if it is overcharged.
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carlmaggott
New Member

South Africa
1 Posts
Posted - Feb 11 2008 :  03:09:00 AM  Show Profile  Reply with Quote
What can I use as replacements for the BT136 and the BRX49??
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Aaron Cake
Administrator

Canada
6718 Posts
Posted - Feb 18 2008 :  09:51:13 AM  Show Profile  Visit Aaron Cake's Homepage  Send Aaron Cake an ICQ Message  Send Aaron Cake a Yahoo! Message  Reply with Quote
Go to your favourite semiconductor manufacturers website and look it up in the substitution charts.
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vicky
Apprentece

Kenya
6 Posts
Posted - Mar 11 2008 :  07:04:02 AM  Show Profile  Reply with Quote
can i use the circuit on the http://www.aaroncake.net/circuits/charger2.asp to charge a 24v battery? If yes, what changes should i make.
Please help, its urgent
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kivdenn
Nobel Prize Winner

Uganda
535 Posts
Posted - Apr 25 2008 :  09:49:21 AM  Show Profile  Reply with Quote
Why should resitors R4,R5,R7 and R8 be of high wattage yet they send current to the gate and the gate draws little current and also why are they four in number cant two of them of 2watts connected in series serve the purpose? Also these resistors are always very hot why is this? Thanks
Dennis
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Aaron Cake
Administrator

Canada
6718 Posts
Posted - Apr 27 2008 :  10:54:24 AM  Show Profile  Visit Aaron Cake's Homepage  Send Aaron Cake an ICQ Message  Send Aaron Cake a Yahoo! Message  Reply with Quote
Ohm's law will show you how much power they must dissipate.
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kivdenn
Nobel Prize Winner

Uganda
535 Posts
Posted - May 16 2008 :  08:52:21 AM  Show Profile  Reply with Quote
How can I modify this charger to charge a 24V battery bank? Thanks
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