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Charging a car battery with 14V AC?
Hi everyone!
Any reason why AC can't be used to charge a car battery? Reason I'm asking is that I have an old Fedtro Powerhouse charger which is outputting AC. |
Charging a car battery with 14V AC?
On Sat, 24 Mar 2012 12:12:39 -0400, Gary wrote:
Hi everyone! Any reason why AC can't be used to charge a car battery? Reason I'm asking is that I have an old Fedtro Powerhouse charger which is outputting AC. More likely, the charger puts out rectified but unfiltered DC. Put a 100mf 30 volt capacitor on the output of the charger (watch polarity) then measure the DC voltage. If there is no DC voltage across the capacitor, then the rectifier(s) in the charger are toast. |
Charging a car battery with 14V AC?
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Charging a car battery with 14V AC?
On Sat, 24 Mar 2012 12:39:01 -0400, Gary wrote:
On Sat, 24 Mar 2012 12:25:02 -0400, wrote: On Sat, 24 Mar 2012 12:12:39 -0400, Gary wrote: Hi everyone! Any reason why AC can't be used to charge a car battery? Reason I'm asking is that I have an old Fedtro Powerhouse charger which is outputting AC. More likely, the charger puts out rectified but unfiltered DC. Put a 100mf 30 volt capacitor on the output of the charger (watch polarity) then measure the DC voltage. If there is no DC voltage across the capacitor, then the rectifier(s) in the charger are toast. OK, except I can't see anything inside the charger that looks like a rectifier: aside from the main transformer, there is just a small coil of wire (the buzzer?) and a 6V/12V switch. Depending on the age of the charger, it could have a selenium rectifier (looks like a stack of square or round metal plates wih washers between them) or it could use solid state diode(s). Depending on the amp rating of the charger, a solid state diode(usually silicon) coud be stud mounted or it could look like a "blob" on a wire. When the selenium rectifier in an old adjustable EICO 6/12 volt battery eliminator/charger (that I've had for years) finally died, I replaced it with a silicon bridge rectifier on a heat sink. The maximum output voltage is now higher, thanks to the differece in voltage drop across a silicon diode (0.6 volt reardless of load) versus the several volt drop (that increases with load) across the original selenium rectifier. You need DC (even if it's unfiltered) to charge a battery - AC won't work. |
Charging a car battery with 14V AC?
Any reason why AC can't be used to charge a car battery?
No, not if you don't mind the battery exploding and spraying hot sulfuric acid in your face. |
Charging a car battery with 14V AC?
OK, I will try as you suggest. You said something about watching the
polarity across the output of the charger -- what exactly did you mean? The plus output of the charger goes to the plus terminal of the battery. I urge you NOT to do this. There is no guarantee this charger will correctly charge your battery. Find someone knowledgeable to help you. Or pay a service shop to charge the battery. Or buy a new, working charger. |
Charging a car battery with 14V AC?
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Charging a car battery with 14V AC?
On Mar 24, 9:39*am, Gary wrote:
On Sat, 24 Mar 2012 12:25:02 -0400, wrote: On Sat, 24 Mar 2012 12:12:39 -0400, Gary wrote: Hi everyone! Any reason why AC can't be used to charge a car battery? *Reason I'm asking is that I have an old Fedtro Powerhouse charger which is outputting AC. More likely, the charger puts out rectified but unfiltered DC. Put a 100mf 30 volt capacitor on the output of the charger (watch polarity) then measure the DC voltage. If there is no DC voltage across the capacitor, then the rectifier(s) in the charger are toast. OK, except I can't see anything inside the charger that looks like a rectifier: *aside from the main transformer, there is just a small coil of wire (the buzzer?) and a 6V/12V switch. Think: If you attempted to charge a battery with AC, the charge deposited when the current swung positive would be discharged when the current swung positive. All you would be doing is heating the battery, not charging. Take out your ohmmeter and look to see if there's a diode between any two points. Also, look for modifications. When I was a sprout, we had a battery charger purported to rejuvenate the carbon zinc cells of the day. The light went out, and the charger quit charging. Not knowing any better, to make it work, I jumpered the light, which apparently acted as the charge current regulator. At which point the diode went "Sproing." Somebody might have taken your charger's diode out in the belief it would improve things. |
Charging a car battery with 14V AC?
Gary wrote:
Hi everyone! Any reason why AC can't be used to charge a car battery? Reason I'm asking is that I have an old Fedtro Powerhouse charger which is outputting AC. yeah sure, put the battery on a turn table and electrodes off the side and the spin the table at 50/60hz, what ever your country system is. Have this magical little charger of yours make contact on the electrodes at the appropriate time. :) or, one could simply get a bridge rectifier and maybe a resistor (ballast) for current limiting. Jamie |
Charging a car battery with 14V AC?
On Sat, 24 Mar 2012 10:39:01 -0700, mike wrote:
On 3/24/2012 9:25 AM, wrote: On Sat, 24 Mar 2012 12:12:39 -0400, wrote: Hi everyone! Any reason why AC can't be used to charge a car battery? Reason I'm asking is that I have an old Fedtro Powerhouse charger which is outputting AC. How do you know it's putting out AC? For an AC input, a typical voltmeter will show the voltage on an AC scale, but about zero on a DC scale. That's what I'm getting. Rectified, but unfiltered DC will show significant readings on both AC and DC scales. More likely, the charger puts out rectified but unfiltered DC. Put a 100mf 30 volt capacitor on the output of the charger (watch polarity) then measure the DC voltage. If there is no DC voltage across the capacitor, then the rectifier(s) in the charger are toast. This is a risky experiment. OP says he thinks it's putting out AC. If that's an accurate statement, like due to a shorted diode, be prepared for an exploded cap. I tried to come up with an answer to the original question, "why AC can't be used to charge a car battery?" I couldn't think of an answer that would not require a complete explanation of the difference between AC and DC. Closest thing I could think of was, "AC goes negative every cycle and batteries can't." I knew there was a good reason. |
Charging a car battery with 14V AC?
Gary wrote:
Hi everyone! Any reason why AC can't be used to charge a car battery? Reason I'm asking is that I have an old Fedtro Powerhouse charger which is outputting AC. If this thing is ac, you need a rectifier. Need more info. You also might need current limiter. I'm reminded of some old chargers we had in the army, in the battery room. Big box with switched levels of pulsating voltage to control charge rate. I think the transformer had multiple taps. Charged and cycled batteries about the size of motorcycle batteries. These were for RCAT's , remote controlled aircraft targets. Greg |
Charging a car battery with 14V AC?
On 3/24/2012 10:32 AM, William Sommerwerck wrote:
OK, I will try as you suggest. You said something about watching the polarity across the output of the charger -- what exactly did you mean? The plus output of the charger goes to the plus terminal of the battery. I urge you NOT to do this. There is no guarantee this charger will correctly charge your battery. Find someone knowledgeable to help you. Or pay a service shop to charge the battery. Or buy a new, working charger. I agree ...why not just buy one? A real charger is not that expensive: http://www.amazon.com/b?ie=UTF8&node=15707061 |
Charging a car battery with 14V AC?
On Sat, 24 Mar 2012 10:32:31 -0700, "William Sommerwerck"
wrote: OK, I will try as you suggest. You said something about watching the polarity across the output of the charger -- what exactly did you mean? The plus output of the charger goes to the plus terminal of the battery. I'm aware of that. I was asking about how the polarity of the AC output affects how the capacitor should be placed? I urge you NOT to do this. There is no guarantee this charger will correctly charge your battery. Find someone knowledgeable to help you. Or pay a service shop to charge the battery. Or buy a new, working charger. You're missing the point. Sometimes we play around with old, obsolete kit, just to see if it'll work. |
Charging a car battery with 14V AC?
You said something about watching the polarity across
the output of the charger -- what exactly did you mean? The plus output of the charger goes to the plus terminal of the battery. I'm aware of that. I was asking about how the polarity of the AC output affects how the capacitor should be placed? AC has no polarity. |
Charging a car battery with 14V AC?
gregz wrote in
rg: Gary wrote: Hi everyone! Any reason why AC can't be used to charge a car battery? Reason I'm asking is that I have an old Fedtro Powerhouse charger which is outputting AC. If this thing is ac, you need a rectifier. Need more info. You also might need current limiter. I'm reminded of some old chargers we had in the army, in the battery room. Big box with switched levels of pulsating voltage to control charge rate. I think the transformer had multiple taps. Charged and cycled batteries about the size of motorcycle batteries. These were for RCAT's , remote controlled aircraft targets. Greg you want to regulate the charge voltage,too. go too high and you boil your electrolyte away,ruin your battery. -- Jim Yanik jyanik at localnet dot com |
Charging a car battery with 14V AC?
On Mar 25, 6:13*pm, Jim Yanik wrote:
gregz wrote rg: Gary wrote: Hi everyone! Any reason why AC can't be used to charge a car battery? *Reason I'm asking is that I have an old Fedtro Powerhouse charger which is outputting AC. If this thing is ac, you need a rectifier. Need more info. You also might need current limiter. I'm reminded of some old chargers we had in the army, in the battery room. Big box with switched levels of pulsating voltage to control charge rate. I think the transformer had multiple taps. Charged and cycled batteries about the size of motorcycle batteries. These were for RCAT's , remote controlled aircraft targets. Greg you want to regulate the charge voltage,too. go too high and you boil your electrolyte away,ruin your battery. The car's electrical system is designed around a standard of 13.8 V, I was always told. That's what one should shoot for, I would think. |
Charging a car battery with 14V AC?
Jim Yanik wrote:
gregz wrote in rg: Gary wrote: Hi everyone! Any reason why AC can't be used to charge a car battery? Reason I'm asking is that I have an old Fedtro Powerhouse charger which is outputting AC. If this thing is ac, you need a rectifier. Need more info. You also might need current limiter. I'm reminded of some old chargers we had in the army, in the battery room. Big box with switched levels of pulsating voltage to control charge rate. I think the transformer had multiple taps. Charged and cycled batteries about the size of motorcycle batteries. These were for RCAT's , remote controlled aircraft targets. Greg you want to regulate the charge voltage,too. go too high and you boil your electrolyte away,ruin your battery. We used to have regulated supplies on some battery backup gear on NASA equipment. We adjusted by the bubble method. You were supposed to cycle them once in a while . Greg |
Charging a car battery with 14V AC?
spamtrap1888 wrote:
On Mar 25, 6:13 pm, Jim Yanik wrote: gregz wrote rg: Gary wrote: Hi everyone! Any reason why AC can't be used to charge a car battery? Reason I'm asking is that I have an old Fedtro Powerhouse charger which is outputting AC. If this thing is ac, you need a rectifier. Need more info. You also might need current limiter. I'm reminded of some old chargers we had in the army, in the battery room. Big box with switched levels of pulsating voltage to control charge rate. I think the transformer had multiple taps. Charged and cycled batteries about the size of motorcycle batteries. These were for RCAT's , remote controlled aircraft targets. Greg you want to regulate the charge voltage,too. go too high and you boil your electrolyte away,ruin your battery. The car's electrical system is designed around a standard of 13.8 V, I was always told. That's what one should shoot for, I would think. That's true, but any electronic item must be designed to live at 16 volts. I remember the specs on my datsun mechanical regulator, got up over 15 volts. 13.8 is maximum long term use, but you need higher voltage to fully charge or overcharge to clear contamination. Greg |
Charging a car battery with 14V AC?
On Sun, 25 Mar 2012 15:36:44 -0700, "William Sommerwerck"
wrote: You said something about watching the polarity across the output of the charger -- what exactly did you mean? The plus output of the charger goes to the plus terminal of the battery. I'm aware of that. I was asking about how the polarity of the AC output affects how the capacitor should be placed? AC has no polarity. Exactly my point. So does it matter how the capacitor is placed across the output leads? |
Charging a car battery with 14V AC?
"Gary" wrote in message
... On Sun, 25 Mar 2012 15:36:44 -0700, "William Sommerwerck" wrote: You said something about watching the polarity across the output of the charger -- what exactly did you mean? The plus output of the charger goes to the plus terminal of the battery. I'm aware of that. I was asking about how the polarity of the AC output affects how the capacitor should be placed? AC has no polarity. Exactly my point. So does it matter how the capacitor is placed across the output leads? You wouldn't normally place a capacitor across /any/ device with an AC output. The only obvious uses that come to mind would be for stability, or to mop up high-frequency junk. Neither would be likely in a charger. |
Charging a car battery with 14V AC?
In article ,
Gary wrote: I'm aware of that. I was asking about how the polarity of the AC output affects how the capacitor should be placed? AC has no polarity. Exactly my point. So does it matter how the capacitor is placed across the output leads? No. If it's truly an AC output, the capacitor will explode equally well with either orientation. Unless I am missing something here, you're trying to do something futile... you *cannot* charge a car battery using an AC waveform of the sort you'd get out of a transformer. The net amount of charge delivered into the battery will be zero, with or without a filter capacitor... all you'll do is heat up the battery to no good effect, and (if you install a filter capacitor) overheat the capacitor and make it blast its guts out all over the room. This is spectacular but not terribly useful :-) You *must* rectify the AC (either half-wave or full-wave rectification). Once you do so, you no longer have AC - you have a pulsed DC. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
Charging a car battery with 14V AC?
Dave Platt wrote:
In article , Gary wrote: I'm aware of that. I was asking about how the polarity of the AC output affects how the capacitor should be placed? AC has no polarity. Exactly my point. So does it matter how the capacitor is placed across the output leads? No. If it's truly an AC output, the capacitor will explode equally well with either orientation. Unless I am missing something here, you're trying to do something futile... you *cannot* charge a car battery using an AC waveform of the sort you'd get out of a transformer. The net amount of charge delivered into the battery will be zero, with or without a filter capacitor... all you'll do is heat up the battery to no good effect, and (if you install a filter capacitor) overheat the capacitor and make it blast its guts out all over the room. This is spectacular but not terribly useful :-) You *must* rectify the AC (either half-wave or full-wave rectification). Once you do so, you no longer have AC - you have a pulsed DC. Gary keeps ignoring this. Greg |
Charging a car battery with 14V AC?
On Sun, 25 Mar 2012 17:42:53 -0400, Gary wrote:
On Sat, 24 Mar 2012 10:32:31 -0700, "William Sommerwerck" wrote: OK, I will try as you suggest. You said something about watching the polarity across the output of the charger -- what exactly did you mean? The plus output of the charger goes to the plus terminal of the battery. I'm aware of that. I was asking about how the polarity of the AC output affects how the capacitor should be placed? I urge you NOT to do this. There is no guarantee this charger will correctly charge your battery. Find someone knowledgeable to help you. Or pay a service shop to charge the battery. Or buy a new, working charger. You're missing the point. Sometimes we play around with old, obsolete kit, just to see if it'll work. To cut out a lot of the BS, there is a simple test you can perform. Set a DMM to the 20VDC range and connect it to the output of the battery charger. If you get a reading of over 14VDC the charger is probably good. If you get a reading of a lower voltage, suspect the charger is bad (unless there is a 6/12 switch). If you get a reading of 0 VDC, but a reading of 12 -15 VAC, the rectifiers are shorted. It MIGHT be possible that selenium rectifiers are so leaky that you would not get a DC reading, but I would doubt it. PlainBill |
Charging a car battery with 14V AC?
On Saturday, March 24, 2012 12:12:39 PM UTC-4, Gary wrote:
Hi everyone! Any reason why AC can't be used to charge a car battery? Reason I'm asking is that I have an old Fedtro Powerhouse charger which is outputting AC. You cannot charge a battery on AC. Battery chargers have to be properly current regulated at the nominal charging voltage for the battery. You do not want to have any kind of battery rupture, and especially a car battery! The acid will do a lot of damage. Invest in a proper safe battery charger! Jerry G. |
Charging a car battery with 14V AC?
"Gary" wrote in message ...
OK, I will try as you suggest. You said something about watching the polarity across the output of the charger - what exactly did you mean? I have rigged up all kinds of circuits as an elec tech, but this would be too risky for me. I would only use a commercial charger and even then would not make any modifications to it. Charging lead-acid batteries always produces hydrogen. Even a little spark or high temp can ignite an explosion which can spray sulfuric acid mist all over. I have never seen an explosion first hand, but have talked to a fellow who is super careful and even he blew one up years ago. Too many warnings probably, but be sure and connect to the batter first before connecting the charger to the AC source. I also connect the charger to an ext cord, and then (several feet away) connect to the AC receptacle. FYI, here's a photo of a $25 battery charger I have used for 10+ years. a good investment for other projects. Battery exploding http://www.youtube.com/watch?v=d_TnsHu2u4c Battery getting damaged from improper charging http://www.youtube.com/watch?v=1APmCDhnuVU Schumacher 1.5A On-Board Charger Model SE-1-12S. Input 120VAC 4A 60HZ. Output 12VDC 1.5A: http://imageshack.us/f/205/chargerki.jpg/ |
Charging a car battery with 14V AC?
On 03/24/12 16:12, Gary wrote:
Hi everyone! Any reason why AC can't be used to charge a car battery? Reason I'm asking is that I have an old Fedtro Powerhouse charger which is outputting AC. Hopefully your face is in the car battery when it explodes, you stupid *******. |
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