How can I go about making a car battery charger, I need it to charge a battery to play music at home rather than a psu maybe with with potentiometer to adjust voltages an all
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Ok, here's a simple one. Beware of overcharging, though.
http://www.next.gr/circuits/how-to-make-car-battery-charger-l32739.html
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Oh, wow, that 18v design post #5 is an invitation to short battery life.
The chargers sold in stores now all have electronic controls that blow up when there is a lightning strike within two miles. So I build battery chargers now. A centertapped 28 v E core transformer, or a transformer with two 14 vac windings hooked up top to bottom to make a center tap. If you can get 24 v center tap transformer that will work and be even safer on the battery, but nobody stocked one when I was buying. Peak volts is 1.4 times rating volts (half winding) minus .7 v for the diode.
Two > 3 amp diodes like MR502 with unline ends soldered to the end windings and line ends soldered together make the plus cable terminal. A three ohm 50 W resistor between diodes & plus cable can keep a 4 amp rated transformer from burning up if the battery has a short. The center tap of the transformer connects to the minus cable. A circuit breaker or fuse on the input AC is traditional. Calculate the breaker current at divide by 5 the output current of the transformer. In the western hemisphere, the 120 vac one. I used a triad E-core 4 amp transformer but they are about $80 now. Use a case with vents for the heat, but enclosed to keep fingers out of the 120 vac terminals. If the case is metal connect it to safety ground with a star washer and machine screw and nut. You can buy the electronic parts from farnell that probably operates in Jamaica but in the US I've found Alliedelec is cheaper on e-frame transformers. If you can figure out a way to mount a toroid transformer the inexpensive reliable ones used on the NA continent are antekinc.
My old charger shorted a strand of hay laying across the diode from a lightning strike, and the carbon track burned up the transformer. The shed was full of hay strands from the previous owners livestock hobby when I bought it. I put the new transformer & diodes in the old charger case. You may mount the diodes on insulated board drilled for diodes resistor & mount screw, or on a cinch solder terminal strip. A >3 amp >200 piv diode is a lot less lightning sensitive than some microprocessor.
Honestly, they stuff microprocessors in the most inane products these days so they will blow up in less than a year and you have to buy another one. I cut up a room fan with a microprocessor last month where the TO92 triac for the oscillate motor had blown up & 120 AC had taken out the processor. Totally unnecessary intelligence for a room fan but a LCD display sells more product at trivial cost and great markup I suppose.
The chargers sold in stores now all have electronic controls that blow up when there is a lightning strike within two miles. So I build battery chargers now. A centertapped 28 v E core transformer, or a transformer with two 14 vac windings hooked up top to bottom to make a center tap. If you can get 24 v center tap transformer that will work and be even safer on the battery, but nobody stocked one when I was buying. Peak volts is 1.4 times rating volts (half winding) minus .7 v for the diode.
Two > 3 amp diodes like MR502 with unline ends soldered to the end windings and line ends soldered together make the plus cable terminal. A three ohm 50 W resistor between diodes & plus cable can keep a 4 amp rated transformer from burning up if the battery has a short. The center tap of the transformer connects to the minus cable. A circuit breaker or fuse on the input AC is traditional. Calculate the breaker current at divide by 5 the output current of the transformer. In the western hemisphere, the 120 vac one. I used a triad E-core 4 amp transformer but they are about $80 now. Use a case with vents for the heat, but enclosed to keep fingers out of the 120 vac terminals. If the case is metal connect it to safety ground with a star washer and machine screw and nut. You can buy the electronic parts from farnell that probably operates in Jamaica but in the US I've found Alliedelec is cheaper on e-frame transformers. If you can figure out a way to mount a toroid transformer the inexpensive reliable ones used on the NA continent are antekinc.
My old charger shorted a strand of hay laying across the diode from a lightning strike, and the carbon track burned up the transformer. The shed was full of hay strands from the previous owners livestock hobby when I bought it. I put the new transformer & diodes in the old charger case. You may mount the diodes on insulated board drilled for diodes resistor & mount screw, or on a cinch solder terminal strip. A >3 amp >200 piv diode is a lot less lightning sensitive than some microprocessor.
Honestly, they stuff microprocessors in the most inane products these days so they will blow up in less than a year and you have to buy another one. I cut up a room fan with a microprocessor last month where the TO92 triac for the oscillate motor had blown up & 120 AC had taken out the processor. Totally unnecessary intelligence for a room fan but a LCD display sells more product at trivial cost and great markup I suppose.
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I'm going to check local stores to see if I get said parts and let you kno
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Sandre, I guess you are selling nothing but want own use, have to keep it cheap and can not order from USA.
Above suggestions are well intentioned but not adjusted to your situation.
1) you omitted most important information:
a) what size is your battery? Very different answers for a small 7AH one than for a car type 40 to 70 AH type.
b) what is your music equipment consumption in Amperes or Watts?
If small, you can recharge overnight and use it during the day; if large you may need frequent recharges or a more powerful charger to reduce reload cycle to a couple hours.
2) if a small battery, a simple recharger is fine, somewhat halfway between both suggestions above: asimple14 or 16VAC transformer, a diode bride, some means to limit current, maybe a power resistor or couple car lamps and you will have to moitor charge voltage regularly, stopping when you reach 13.8 or 14.4V , depending on how alert are you to stop charging.
Ok, provide us with data ande wemight suggest something.
PS: that said, I bet you can get a second hand car battery charger for less than what you´d spend on a transformer/diodes/cabinets/plugs-wires-switches-clamps/etc.
Above suggestions are well intentioned but not adjusted to your situation.
1) you omitted most important information:
a) what size is your battery? Very different answers for a small 7AH one than for a car type 40 to 70 AH type.
b) what is your music equipment consumption in Amperes or Watts?
If small, you can recharge overnight and use it during the day; if large you may need frequent recharges or a more powerful charger to reduce reload cycle to a couple hours.
2) if a small battery, a simple recharger is fine, somewhat halfway between both suggestions above: asimple14 or 16VAC transformer, a diode bride, some means to limit current, maybe a power resistor or couple car lamps and you will have to moitor charge voltage regularly, stopping when you reach 13.8 or 14.4V , depending on how alert are you to stop charging.
Ok, provide us with data ande wemight suggest something.
PS: that said, I bet you can get a second hand car battery charger for less than what you´d spend on a transformer/diodes/cabinets/plugs-wires-switches-clamps/etc.
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As well as a car charger out here would be like a aprox 120 dollars used... and I may can build it cheaper?
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I still think the best and easiest charger for 12V lead acid batteries is a 13.8v power supply.
You can leave it hooked up indefinitely; it can´t over charge.
It´s the same way the charging system in a car works.
You can leave it hooked up indefinitely; it can´t over charge.
It´s the same way the charging system in a car works.
The dual 14 v winding transformer or 28 center tap produces 13.4 v at full charge current because of the diode drop on each side. This is what it will put into a discharged battery.
However if there is no current draw this transformer diode arrangement will creep up to 18.7 at no current. Lead acid batteries don't like much more than 15 v continuously.
The dual 12 v winding transformer 24 v center tap will only max out at 15.8 v which is safe for tickle charge, but at full power only puts out 11.3 volts. That makes motor performance listless and may make your music system a bit low powered.
That is where the microprocessor comes in. One can be used to sense the 28 v ct rig, and cut off the input power with a traic when the battery reaches full charge. Unfortunately these devices & sensors and the triac are sensitive to lightning surges, so if one leaves them unattended in my summer camp location, that is plugged up all the time. they are prone to becoming a dead steel box with a blown fuse. That makes schauer auto-zone wall-mart etc very happy because they sell a new battery charger every 18 months, but doesn't make me happy at all. My country property is particularly prone to hits because the electric lines have about 3000 ' between houses with a nice safe air conditioner or refrigerator motor to bleed off the energy of the lightning. I unplug the refrigerator in my trailer when I'm not there 8 months a year, so that source of surge supression is not there even 1/5 the time when it was running.
If you live in a dense city with lots of refrigerators and fan motors running, then lightning is not the problem and a commercial electronic control battery charger should be fine. One rated above your system draw current.
If you left your music player on all the time and only turned down the volume when you were listening, then the 28 vct system would be the way to go. If the transformer were rated slightly higher current than the music system drew.
However if there is no current draw this transformer diode arrangement will creep up to 18.7 at no current. Lead acid batteries don't like much more than 15 v continuously.
The dual 12 v winding transformer 24 v center tap will only max out at 15.8 v which is safe for tickle charge, but at full power only puts out 11.3 volts. That makes motor performance listless and may make your music system a bit low powered.
That is where the microprocessor comes in. One can be used to sense the 28 v ct rig, and cut off the input power with a traic when the battery reaches full charge. Unfortunately these devices & sensors and the triac are sensitive to lightning surges, so if one leaves them unattended in my summer camp location, that is plugged up all the time. they are prone to becoming a dead steel box with a blown fuse. That makes schauer auto-zone wall-mart etc very happy because they sell a new battery charger every 18 months, but doesn't make me happy at all. My country property is particularly prone to hits because the electric lines have about 3000 ' between houses with a nice safe air conditioner or refrigerator motor to bleed off the energy of the lightning. I unplug the refrigerator in my trailer when I'm not there 8 months a year, so that source of surge supression is not there even 1/5 the time when it was running.
If you live in a dense city with lots of refrigerators and fan motors running, then lightning is not the problem and a commercial electronic control battery charger should be fine. One rated above your system draw current.
If you left your music player on all the time and only turned down the volume when you were listening, then the 28 vct system would be the way to go. If the transformer were rated slightly higher current than the music system drew.
A bit of Googling tells me that a U1-9MF battery is typically about 24Ah, so a 30A current draw would last for 48 minutes under ideal conditions. In reality most batteries can't be repeatedly emptied of charge, and you probably don't have ideal conditions, so maybe 30 mins running? 220A will be the current it can supply for a few seconds to run a starter motor.
If you can build a charger, then you can probably build a mains PSU instead - then you won't need the battery.
If you can build a charger, then you can probably build a mains PSU instead - then you won't need the battery.
I've heard that computer ATX power supplies can be used to run car amps. But if you must have a charger, how about a 15V laptop power pack with a rectifier and a resistor in series to drop the voltage and limit the current?
No, many laptops are 19 v open circuit. You're talking a 12 v car equivalent battery. Once the battery reaches full charge the resistor won't drop voltage and the battery will deteriorate. V=I*R where V is the voltage drop of the resistor and I is the current, which drops to near zero at full charge. Overvoltage producing power supplies require a sensor to shut it off after the current drops too low, when charging lead acid car batteries.
lead acid battery charging is simple.
use a basic transfomer plus selenium rectifier and let the characteristics of the pair control maximum current and maximum charged voltage.
or
use a PSU that outputs an excess of DC voltage and current. Attach a current limiter followed by a voltage regulator.
You select the current limit to suit the battery size. You select the voltage regulator output to suit the battery technology.
Old lead acid with the ability to top up the lost water need ~14 to 14.5Vdc for full charge.
low maintenance lead acid need a bit lower voltage.
maintenance free lead acid need lower still. ~ 13.8Vdc
The battery manufacturers give guidance on charge rates and charge voltages vs temeprature for all their product. Follow the guidance they give.
use a basic transfomer plus selenium rectifier and let the characteristics of the pair control maximum current and maximum charged voltage.
or
use a PSU that outputs an excess of DC voltage and current. Attach a current limiter followed by a voltage regulator.
You select the current limit to suit the battery size. You select the voltage regulator output to suit the battery technology.
Old lead acid with the ability to top up the lost water need ~14 to 14.5Vdc for full charge.
low maintenance lead acid need a bit lower voltage.
maintenance free lead acid need lower still. ~ 13.8Vdc
The battery manufacturers give guidance on charge rates and charge voltages vs temeprature for all their product. Follow the guidance they give.
If you choose a 15v laptop supply, the diode will drop it by about 0.6 volts, and a 1 ohm resistor will limit current to what the supply can handle. If the supply output goes above 15v at low currents, add an incandescent pilot light or a resistor upstream from the diode.
About the ATX supply, Google and you'll find tips on how to use them for bench power supplies or running car amps.
About the ATX supply, Google and you'll find tips on how to use them for bench power supplies or running car amps.
I've done exactly that in a pinch - but microprocessor-controlled, SMPS chargers that can handle the whole charging cycle from deep discharge to 'float' operation for different vehicle battery types and capacities, (eg AGM motorcycle and SLA car batteries) can be so cheap these days, there's no reason not to just buy one.
I think mine was under £15/$20 from Lidl; it's made in Germany, delivers >4A stone cold even over 24hrs restoring a flat 100ah battery; also works on the AGM bike battery in my ex-hillclimb toy car; and the charge profiles/management are easily the equal of the more boutique CTEK and similar.
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