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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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"Fixing" crap Harbor Freight battery charger
Given the less-than-steller reviews and HF's reputation for electronics,
I should not have bought this thing, a 12 Volt 6 or 2 amp (switch selectable) charger for car batteries. The problem is that instead of providing the tapering charge and switch to trickle it is supposedly designed for, this "charger" discharges and kills batteries instead. (In contrast, I have a 4 amp Schauer charger that is about 40 years old which still works just fine.) Instead of throwing out the HF unit, I was thinking that it has a perfectly usable case, transformer, ammeter, and wires with alligator clips. Just the crapulent Chinese electronics are bad so I'd like to trash that stuff and turn this into an "old school" type charger like my Schauer. The transformer secondary is center tapped and reads about 28 volts AC across the ends, 14 volts on each leg from the center. The original electronics are on a small board with 7 transistors, 2 SCRs, a couple of diodes, and numerous resistors. (That's a lot of stuff just to kill batteries!) Searching online I'm finding a bewildering array of home-brew battery charger circuits, everything from simply using a bridge rectifier on the transformer secondary to more complex circuits to taper the charge and either switch off or go to trickle when the battery is fully charged. The behaviour of my old Schauer is to gradually reduces current until the battery is fully charged, where it will stay at a low level and not hurt the battery if left on overnight or even for a few days. I have not opened it up yet to see what's inside, but being an early 1970s unit I'd be surprised if there is much aside from a transformer and rectifier. Anyone have a simple circuit handy that works well for this? I've seen a few plans online that just say to use a bridge rectifier of suitable capacity, but I want to be reasonably sure that this thing won't kill any more batteries. -- Roger Blake Change "invalid" to "com" for email. Google Groups killfiled. |
#2
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"Fixing" crap Harbor Freight battery charger
On 08/05/2013 08:05 AM, Roger Blake wrote:
Given the less-than-steller reviews and HF's reputation for electronics, I should not have bought this thing, a 12 Volt 6 or 2 amp (switch selectable) charger for car batteries. The problem is that instead of providing the tapering charge and switch to trickle it is supposedly designed for, this "charger" discharges and kills batteries instead. (In contrast, I have a 4 amp Schauer charger that is about 40 years old which still works just fine.) Instead of throwing out the HF unit, I was thinking that it has a perfectly usable case, transformer, ammeter, and wires with alligator clips. Just the crapulent Chinese electronics are bad so I'd like to trash that stuff and turn this into an "old school" type charger like my Schauer. The transformer secondary is center tapped and reads about 28 volts AC across the ends, 14 volts on each leg from the center. The original electronics are on a small board with 7 transistors, 2 SCRs, a couple of diodes, and numerous resistors. (That's a lot of stuff just to kill batteries!) Searching online I'm finding a bewildering array of home-brew battery charger circuits, everything from simply using a bridge rectifier on the transformer secondary to more complex circuits to taper the charge and either switch off or go to trickle when the battery is fully charged. The behaviour of my old Schauer is to gradually reduces current until the battery is fully charged, where it will stay at a low level and not hurt the battery if left on overnight or even for a few days. I have not opened it up yet to see what's inside, but being an early 1970s unit I'd be surprised if there is much aside from a transformer and rectifier. Anyone have a simple circuit handy that works well for this? I've seen a few plans online that just say to use a bridge rectifier of suitable capacity, but I want to be reasonably sure that this thing won't kill any more batteries. Old chargers used selenium stacks, which tapered naturally. |
#3
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"Fixing" crap Harbor Freight battery charger
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#4
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"Fixing" crap Harbor Freight battery charger
Roger Blake wrote:
Given the less-than-steller reviews and HF's reputation for electronics, I should not have bought this thing, a 12 Volt 6 or 2 amp (switch selectable) charger for car batteries. The problem is that instead of providing the tapering charge and switch to trickle it is supposedly designed for, this "charger" discharges and kills batteries instead. (In contrast, I have a 4 amp Schauer charger that is about 40 years old which still works just fine.) nice. Instead of throwing out the HF unit, I was thinking that it has a perfectly usable case, transformer, ammeter, and wires with alligator clips. Just the crapulent Chinese electronics are bad so I'd like to trash that stuff and turn this into an "old school" type charger like my Schauer. The transformer secondary is center tapped and reads about 28 volts AC across the ends, 14 volts on each leg from the center. The original electronics are on a small board with 7 transistors, 2 SCRs, a couple of diodes, and numerous resistors. (That's a lot of stuff just to kill batteries!) Searching online I'm finding a bewildering array of home-brew battery charger circuits, everything from simply using a bridge rectifier on the transformer secondary to more complex circuits to taper the charge and either switch off or go to trickle when the battery is fully charged. It might be easier to fix the thing, unless you want a project. I can tell from here that it's probably using some sort of half-bridge setup. Apparently two extra diodes cost more than a smaller more efficient transformer. Heck, it's unlikely to have the correct sized transformer to start with, they just removed two diodes to save whatever it costs to keep the school kids/prisoners fed. It might be good to mod the thing to crowbar if it overshoots 13.8 or 14.1 or whatever you want your batteries charged to. There should be some sort of rectifier to prevent the battery from discharging back into the charger, check on that. I can't say they're good or bad, but I've made NiMh chargers that were just constant current sources that maxed out at the float voltage. The charging current tapers off as the thing starts to choke itself out, but it does work. The only reason I even had the constant current section was to prevent the transformer from burning out if you threw a heavily discharged cell into it. Old NiMh batteries really didnt like fast charging either. The behaviour of my old Schauer is to gradually reduces current until the battery is fully charged, where it will stay at a low level and not hurt the battery if left on overnight or even for a few days. I have not opened it up yet to see what's inside, but being an early 1970s unit I'd be surprised if there is much aside from a transformer and rectifier. Anyone have a simple circuit handy that works well for this? I've seen a few plans online that just say to use a bridge rectifier of suitable capacity, but I want to be reasonably sure that this thing won't kill any more batteries. How large are the batteries you're charging? A brute force charger may be ok for smaller batteries, but if you're trying to charge some 2 ton off the grid battery locker, you're going to have to smell that transformer burn up. What parts are on that board you have now? Can you post a photo? |
#5
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"Fixing" crap Harbor Freight battery charger
On 2013-08-07, Cydrome Leader wrote:
How large are the batteries you're charging? 12 volt lead-acid car batteries, I should have mentioned that if I didn't! What parts are on that board you have now? Can you post a photo? It does look like they cheaped out on a couple of rectifiers, hence the 28V center-tapped transformer. (The transformer looks surprisingly hefty, though.) But then again there are 2 SCRs on heatsinks and it's surprising how many discreet transistors this thing has, enough to make a decent transistor radio, but who knows how many are real. A bunch of what are probably phony 1% resistors completes the components. No ICs. No capacitors. The center tap of the transformer feeds into the center section of the board through a circuit breaker. Each side of the secondary then feeds into its own symmetrical section of the board. I tried taking a picture but my camera does lousy closeups, will have to borrow one... -- Roger Blake Change "invalid" to "com" for email. Google Groups killfiled. |
#6
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"Fixing" crap Harbor Freight battery charger
Roger Blake wrote:
On 2013-08-07, Cydrome Leader wrote: How large are the batteries you're charging? 12 volt lead-acid car batteries, I should have mentioned that if I didn't! What parts are on that board you have now? Can you post a photo? It does look like they cheaped out on a couple of rectifiers, hence the 28V center-tapped transformer. (The transformer looks surprisingly hefty, though.) But then again there are 2 SCRs on heatsinks and it's surprising how many discreet transistors this thing has, enough to make a decent transistor radio, but who knows how many are real. A bunch of what are probably phony 1% resistors completes the components. No ICs. No capacitors. The center tap of the transformer feeds into the center section of the board through a circuit breaker. Each side of the secondary then feeds into its own symmetrical section of the board. I tried taking a picture but my camera does lousy closeups, will have to borrow one... Are these "SCRs" really SCRs or just large power transistors? Did the thing sing or make horrible PWM sounds when it worked? I have seen real SCRs in telecom rectifiers (giant battery chargers/power supplies). |
#7
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"Fixing" crap Harbor Freight battery charger
On 2013-08-07, Cydrome Leader wrote:
Are these "SCRs" really SCRs or just large power transistors? Did the thing sing or make horrible PWM sounds when it worked? The board is silkscreened "SCR1" and "SCR2" in those locations - the components themselves are black plastic about 3/8" square and 1/8" thick, labeled "BT151 25J TRANSUN", metal tab at top for heat sink attachment, 3 leads on the bottom. -- Roger Blake Change "invalid" to "com" for email. Google Groups killfiled. |
#8
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"Fixing" crap Harbor Freight battery charger
Roger Blake wrote: On 2013-08-07, Cydrome Leader wrote: How large are the batteries you're charging? 12 volt lead-acid car batteries, I should have mentioned that if I didn't! What parts are on that board you have now? Can you post a photo? It does look like they cheaped out on a couple of rectifiers, hence the 28V center-tapped transformer. (The transformer looks surprisingly hefty, though.) But then again there are 2 SCRs on heatsinks and it's surprising how many discreet transistors this thing has, enough to make a decent transistor radio, but who knows how many are real. A bunch of what are probably phony 1% resistors completes the components. No ICs. No capacitors. The center tap of the transformer feeds into the center section of the board through a circuit breaker. Each side of the secondary then feeds into its own symmetrical section of the board. Why would anyone use phony 1% resistors when they are dirt cheap these days? they are pennies each in leaded, and less for surface mount in manufacturing quantities. A lot of OEMs stopped stocking 5% SMD parts, because the 1% were cheaper. We did that at Microdyne, starting in the late '90s. Cheaped out on rectifiers? They likely paid more for that CT transformer that they would save on two 30 cent diodes. The fact that there are no ICs is significant in what way? -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge. |
#9
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"Fixing" crap Harbor Freight battery charger
On 2013-08-08, Michael A. Terrell wrote:
Why would anyone use phony 1% resistors when they are dirt cheap these days? The Chinese are infamous for cheating on specifications. Whether these are actually phony or not would obviously require measuring them with an accurate meter. Cheaped out on rectifiers? They likely paid more for that CT transformer that they would save on two 30 cent diodes. The fact that there are no ICs is significant in what way? Some of the choices in the design do seem odd given that lowest possible manufacturing cost was probably the primary constraint. As far as the lack of ICs I was just describing the contents of the board, though it does seem unusual these days to see a a circuit based on discreet transistors. -- Roger Blake Change "invalid" to "com" for email. Google Groups killfiled. |
#10
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"Fixing" crap Harbor Freight battery charger
On 08/07/2013 10:07 AM, Cydrome Leader wrote:
Roger Blake wrote: On 2013-08-07, Cydrome Leader wrote: How large are the batteries you're charging? 12 volt lead-acid car batteries, I should have mentioned that if I didn't! What parts are on that board you have now? Can you post a photo? It does look like they cheaped out on a couple of rectifiers, hence the 28V center-tapped transformer. (The transformer looks surprisingly hefty, though.) But then again there are 2 SCRs on heatsinks and it's surprising how many discreet transistors this thing has, enough to make a decent transistor radio, but who knows how many are real. A bunch of what are probably phony 1% resistors completes the components. No ICs. No capacitors. The center tap of the transformer feeds into the center section of the board through a circuit breaker. Each side of the secondary then feeds into its own symmetrical section of the board. I tried taking a picture but my camera does lousy closeups, will have to borrow one... Are these "SCRs" really SCRs or just large power transistors? Did the thing sing or make horrible PWM sounds when it worked? I have seen real SCRs in telecom rectifiers (giant battery chargers/power supplies). Physicists tell me that SCRs will work as transistors. |
#11
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"Fixing" crap Harbor Freight battery charger
On Mon, 5 Aug 2013 15:05:05 +0000 (UTC), Roger Blake
wrote: Given the less-than-steller reviews and HF's reputation for electronics, I should not have bought this thing, a 12 Volt 6 or 2 amp (switch selectable) charger for car batteries.(...) Incidentally: http://802.11junk.com/jeffl/pics/drivel/slides/dead-battery-chargers.html All of them died float charging standby and backup batteries on mountain top radio sites. Mostly, the electronics on the PCB's (with the numbers ground off) were what failed. I managed to fix one or two by guessing the regulator IC that was used, but they again failed in short order. The chargers were replaced by various Statpower/Xantrex chargers, which have been working quite nicely for the last 7 years. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#12
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"Fixing" crap Harbor Freight battery charger
dave wrote:
On 08/07/2013 10:07 AM, Cydrome Leader wrote: Roger Blake wrote: On 2013-08-07, Cydrome Leader wrote: How large are the batteries you're charging? 12 volt lead-acid car batteries, I should have mentioned that if I didn't! What parts are on that board you have now? Can you post a photo? It does look like they cheaped out on a couple of rectifiers, hence the 28V center-tapped transformer. (The transformer looks surprisingly hefty, though.) But then again there are 2 SCRs on heatsinks and it's surprising how many discreet transistors this thing has, enough to make a decent transistor radio, but who knows how many are real. A bunch of what are probably phony 1% resistors completes the components. No ICs. No capacitors. The center tap of the transformer feeds into the center section of the board through a circuit breaker. Each side of the secondary then feeds into its own symmetrical section of the board. I tried taking a picture but my camera does lousy closeups, will have to borrow one... Are these "SCRs" really SCRs or just large power transistors? Did the thing sing or make horrible PWM sounds when it worked? I have seen real SCRs in telecom rectifiers (giant battery chargers/power supplies). Physicists tell me that SCRs will work as transistors. that's nice. |
#13
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"Fixing" crap Harbor Freight battery charger
Jeff Liebermann wrote:
On Mon, 5 Aug 2013 15:05:05 +0000 (UTC), Roger Blake wrote: Given the less-than-steller reviews and HF's reputation for electronics, I should not have bought this thing, a 12 Volt 6 or 2 amp (switch selectable) charger for car batteries.(...) Incidentally: http://802.11junk.com/jeffl/pics/drivel/slides/dead-battery-chargers.html All of them died float charging standby and backup batteries on mountain top radio sites. Mostly, the electronics on the PCB's (with the numbers ground off) were what failed. I managed to fix one or two by guessing the regulator IC that was used, but they again failed in short order. The chargers were replaced by various Statpower/Xantrex chargers, which have been working quite nicely for the last 7 years. were these hunk-o-junk units plugged into those hardwired site wide surge surpessors? |
#14
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"Fixing" crap Harbor Freight battery charger
dave wrote:
On 08/07/2013 10:07 AM, Cydrome Leader wrote: Roger Blake wrote: On 2013-08-07, Cydrome Leader wrote: How large are the batteries you're charging? 12 volt lead-acid car batteries, I should have mentioned that if I didn't! What parts are on that board you have now? Can you post a photo? It does look like they cheaped out on a couple of rectifiers, hence the 28V center-tapped transformer. (The transformer looks surprisingly hefty, though.) But then again there are 2 SCRs on heatsinks and it's surprising how many discreet transistors this thing has, enough to make a decent transistor radio, but who knows how many are real. A bunch of what are probably phony 1% resistors completes the components. No ICs. No capacitors. The center tap of the transformer feeds into the center section of the board through a circuit breaker. Each side of the secondary then feeds into its own symmetrical section of the board. I tried taking a picture but my camera does lousy closeups, will have to borrow one... Are these "SCRs" really SCRs or just large power transistors? Did the thing sing or make horrible PWM sounds when it worked? I have seen real SCRs in telecom rectifiers (giant battery chargers/power supplies). Physicists tell me that SCRs will work as transistors. didn't mean to be a jerk with the last reply. so I did about 3 seconds of searching and here's how that charger probably works. something is measuring the voltage of rectified DC and turning the SCRs on and off when the input voltage is just right for charging the battery. It's basically 120Hz PWM. They may even be using the negative or postive voltage from the other leg of the center tapped transformer to shut off the SCR on the opposing side. Cheap and simple. Sadly, I don't recall if you just short the gate of a SCR to something to shut it off, or if it needs a reverse voltage of some sort to really make "sure". Failure modes as imagined by me are 1) SCR shorting and outputting full voltage into your now dead battery. Seems not too likely- SCRs are pretty damn tough. 2) the gate circuitry getting botched up and the SCR NOT being shut off before the voltage hits the overvoltaged and killed battery zone. SCRs latch so if that's the case, your battery is basically being murdered 120 times as second because the gate shutoff circuity is failing 120 times a second. The of course, maybe the thing is a GTO, but the idea is the same either way. |
#15
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"Fixing" crap Harbor Freight battery charger
On Fri, 9 Aug 2013 21:00:44 +0000 (UTC), Cydrome Leader
wrote: Jeff Liebermann wrote: On Mon, 5 Aug 2013 15:05:05 +0000 (UTC), Roger Blake wrote: Given the less-than-steller reviews and HF's reputation for electronics, I should not have bought this thing, a 12 Volt 6 or 2 amp (switch selectable) charger for car batteries.(...) Incidentally: http://802.11junk.com/jeffl/pics/drivel/slides/dead-battery-chargers.html All of them died float charging standby and backup batteries on mountain top radio sites. Mostly, the electronics on the PCB's (with the numbers ground off) were what failed. I managed to fix one or two by guessing the regulator IC that was used, but they again failed in short order. The chargers were replaced by various Statpower/Xantrex chargers, which have been working quite nicely for the last 7 years. were these hunk-o-junk units plugged into those hardwired site wide surge surpessors? Sorta. All the sites were on some form of backup or emergency power, such as an autostart generator. The switching transitions are anything but graceful, with no provisions for zero voltage switching. The resultant glitches, spikes, surges, and over-voltage hiccups could easily have blown up the chargers. However, all the sites also have big MOV surge protectors and LC line filters just after the circuit breakers, which does a fine job of protecting against glitches and such. There was plenty of other equipment in the buildings, including commodity networking hardware, scanners, computahs, weather station, etc all of which are somewhat sensitive to glitches. Nothing failed except the battery chargers. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#16
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"Fixing" crap Harbor Freight battery charger
On Fri, 9 Aug 2013, Cydrome Leader wrote:
dave wrote: On 08/07/2013 10:07 AM, Cydrome Leader wrote: Roger Blake wrote: On 2013-08-07, Cydrome Leader wrote: How large are the batteries you're charging? 12 volt lead-acid car batteries, I should have mentioned that if I didn't! What parts are on that board you have now? Can you post a photo? It does look like they cheaped out on a couple of rectifiers, hence the 28V center-tapped transformer. (The transformer looks surprisingly hefty, though.) But then again there are 2 SCRs on heatsinks and it's surprising how many discreet transistors this thing has, enough to make a decent transistor radio, but who knows how many are real. A bunch of what are probably phony 1% resistors completes the components. No ICs. No capacitors. The center tap of the transformer feeds into the center section of the board through a circuit breaker. Each side of the secondary then feeds into its own symmetrical section of the board. I tried taking a picture but my camera does lousy closeups, will have to borrow one... Are these "SCRs" really SCRs or just large power transistors? Did the thing sing or make horrible PWM sounds when it worked? I have seen real SCRs in telecom rectifiers (giant battery chargers/power supplies). Physicists tell me that SCRs will work as transistors. didn't mean to be a jerk with the last reply. so I did about 3 seconds of searching and here's how that charger probably works. something is measuring the voltage of rectified DC and turning the SCRs on and off when the input voltage is just right for charging the battery. It's basically 120Hz PWM. They may even be using the negative or postive voltage from the other leg of the center tapped transformer to shut off the SCR on the opposing side. Cheap and simple. Sadly, I don't recall if you just short the gate of a SCR to something to shut it off, or if it needs a reverse voltage of some sort to really make "sure". Failure modes as imagined by me are 1) SCR shorting and outputting full voltage into your now dead battery. Seems not too likely- SCRs are pretty damn tough. 2) the gate circuitry getting botched up and the SCR NOT being shut off before the voltage hits the overvoltaged and killed battery zone. SCRs latch so if that's the case, your battery is basically being murdered 120 times as second because the gate shutoff circuity is failing 120 times a second. The of course, maybe the thing is a GTO, but the idea is the same either way. You saw that sort of thing in the early days of SCRs. There seemed to be much more use of SCRs (or at least much more application for them) when they came out, and then that faded. Not sure if there were problems, or other things came along or what. Michael |
#17
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"Fixing" crap Harbor Freight battery charger
Jeff Liebermann wrote:
On Fri, 9 Aug 2013 21:00:44 +0000 (UTC), Cydrome Leader wrote: Jeff Liebermann wrote: On Mon, 5 Aug 2013 15:05:05 +0000 (UTC), Roger Blake wrote: Given the less-than-steller reviews and HF's reputation for electronics, I should not have bought this thing, a 12 Volt 6 or 2 amp (switch selectable) charger for car batteries.(...) Incidentally: http://802.11junk.com/jeffl/pics/drivel/slides/dead-battery-chargers.html All of them died float charging standby and backup batteries on mountain top radio sites. Mostly, the electronics on the PCB's (with the numbers ground off) were what failed. I managed to fix one or two by guessing the regulator IC that was used, but they again failed in short order. The chargers were replaced by various Statpower/Xantrex chargers, which have been working quite nicely for the last 7 years. were these hunk-o-junk units plugged into those hardwired site wide surge surpessors? Sorta. All the sites were on some form of backup or emergency power, such as an autostart generator. The switching transitions are anything but graceful, with no provisions for zero voltage switching. The resultant glitches, spikes, surges, and over-voltage hiccups could easily have blown up the chargers. However, all the sites also have big MOV surge protectors and LC line filters just after the circuit breakers, which does a fine job of protecting against glitches and such. There was plenty of other equipment in the buildings, including commodity networking hardware, scanners, computahs, weather station, etc all of which are somewhat sensitive to glitches. Nothing failed except the battery chargers. It's pretty sad lead acide battery chargers were the most sensitive devices out of that mix of hardware. Any interesting lightining strike stories? |
#18
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"Fixing" crap Harbor Freight battery charger
On Mon, 12 Aug 2013 16:37:05 +0000 (UTC), Cydrome Leader
wrote: It's pretty sad lead acide battery chargers were the most sensitive devices out of that mix of hardware. I still don't know exactly what killed all the chargers. I would expect such high power devices to be built rather rugged, but apparently, that's not the case. Any interesting lightining strike stories? Nope. I live on the left coast, where we don't have much lightning. I've had some nearby hits blow up various antennas, radios, and assorted boxes, but nothing spectacular. We've eliminated most of those type of problems with careful grounding, lighting arrestors, and ritual sacrifice to the lightning god. Lighting is one problem that I don't have to deal with (much). The only interesting horror story I've heard was from another service company, where copper thieves axed the big ground wires from the tower legs to the ground rods. When lightning hit the tower, it went into the building instead of directly into the ground. I didn't see the carnage, but was told it was huge. I'm considering adding a ground wire integrity test to the SCADA alarm panel. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#19
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"Fixing" crap Harbor Freight battery charger
Jeff Liebermann wrote:
On Mon, 12 Aug 2013 16:37:05 +0000 (UTC), Cydrome Leader wrote: It's pretty sad lead acide battery chargers were the most sensitive devices out of that mix of hardware. I still don't know exactly what killed all the chargers. I would expect such high power devices to be built rather rugged, but apparently, that's not the case. Very odd. Some sort of fatal design flaw with the regulation parts is what it sounded like. Any interesting lightining strike stories? Nope. I live on the left coast, where we don't have much lightning. I've had some nearby hits blow up various antennas, radios, and assorted boxes, but nothing spectacular. We've eliminated most of those type of problems with careful grounding, lighting arrestors, and ritual sacrifice to the lightning god. Lighting is one problem that I don't have to deal with (much). The only interesting horror story I've heard was from another service company, where copper thieves axed the big ground wires from the tower legs to the ground rods. When lightning hit the tower, it went into the building instead of directly into the ground. I didn't see the carnage, but was told it was huge. I'm considering adding a ground wire integrity test to the SCADA alarm panel. I just gave this a few minutes of though and drew a blank. How do you directly test to make sure nobody stole your ground? The only thing I could come up with was run a thin wire along your ground system in a loop and assume scrappers will steal that too. If that guard wire of whatever you'd call it opens or goes missing you've triggered an alarm? |
#20
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"Fixing" crap Harbor Freight battery charger
Cydrome Leader formulerede spørgsmålet:
I just gave this a few minutes of though and drew a blank. How do you directly test to make sure nobody stole your ground? The only thing I could come up with was run a thin wire along your ground system in a loop and assume scrappers will steal that too. If that guard wire of whatever you'd call it opens or goes missing you've triggered an alarm? Measure the resistance between the tower and a separate ground connection. Leif -- Husk kørelys bagpå, hvis din bilfabrikant har taget den idiotiske beslutning at undlade det. |
#21
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"Fixing" crap Harbor Freight battery charger
Leif Neland wrote:
Cydrome Leader formulerede sp?rgsm?let: I just gave this a few minutes of though and drew a blank. How do you directly test to make sure nobody stole your ground? The only thing I could come up with was run a thin wire along your ground system in a loop and assume scrappers will steal that too. If that guard wire of whatever you'd call it opens or goes missing you've triggered an alarm? Measure the resistance between the tower and a separate ground connection. Leif That still sounds tricky as there may be multiple grounds all connected to your ground busbar. I just took a peek at the telecom room on this floor and the plate on the wall had nearly a dozen connections, of which 3 seemed to be going back to the electrical riser for the floor. You could remove most of those connections and everything would still be grounded, enough that nobody dies from a frayed power cord, but just not able to take a lightning strike or some major electrical contractor screw up. I'd love to see the AT&T manual not on how to sweep floors, but on grounding everything. |
#22
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"Fixing" crap Harbor Freight battery charger
On Mon, 12 Aug 2013 20:31:38 +0000 (UTC), Cydrome Leader
wrote: Jeff Liebermann wrote: On Mon, 12 Aug 2013 16:37:05 +0000 (UTC), Cydrome Leader wrote: It's pretty sad lead acide battery chargers were the most sensitive devices out of that mix of hardware. I still don't know exactly what killed all the chargers. I would expect such high power devices to be built rather rugged, but apparently, that's not the case. Very odd. Some sort of fatal design flaw with the regulation parts is what it sounded like. Some kind of design error might be a possibility, but why would charger from various vendors all have the same problem? I wish I had spent some time doing a post mortem, but I just wanted to get rid of them and replace them with something that works. I just gave this a few minutes of though and drew a blank. How do you directly test to make sure nobody stole your ground? The only thing I could come up with was run a thin wire along your ground system in a loop and assume scrappers will steal that too. If that guard wire of whatever you'd call it opens or goes missing you've triggered an alarm? That's exactly what I was thinking and probably the best way. I could also measure the ground resistance to another nearby ground rod, and trigger an alarm on any abrupt change in resistance. The trick will be to design it so that it will survive a lightning strike. I vaguely recall this being discussed in an article in Above Ground Level magazine, but don't recall the issue or method. http://agl-mag.com -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#23
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"Fixing" crap Harbor Freight battery charger
"Roger Blake" wrote in message ... Given the less-than-steller reviews and HF's reputation for electronics, I should not have bought this thing, a 12 Volt 6 or 2 amp (switch selectable) charger for car batteries. The problem is that instead of providing the tapering charge and switch to trickle it is supposedly designed for, this "charger" discharges and kills batteries instead. (In contrast, I have a 4 amp Schauer charger that is about 40 years old which still works just fine.) Instead of throwing out the HF unit, I was thinking that it has a perfectly usable case, transformer, ammeter, and wires with alligator clips. Just the crapulent Chinese electronics are bad so I'd like to trash that stuff and turn this into an "old school" type charger like my Schauer. The transformer secondary is center tapped and reads about 28 volts AC across the ends, 14 volts on each leg from the center. The original electronics are on a small board with 7 transistors, 2 SCRs, a couple of diodes, and numerous resistors. (That's a lot of stuff just to kill batteries!) Searching online I'm finding a bewildering array of home-brew battery charger circuits, everything from simply using a bridge rectifier on the transformer secondary to more complex circuits to taper the charge and either switch off or go to trickle when the battery is fully charged. The behaviour of my old Schauer is to gradually reduces current until the battery is fully charged, where it will stay at a low level and not hurt the battery if left on overnight or even for a few days. I have not opened it up yet to see what's inside, but being an early 1970s unit I'd be surprised if there is much aside from a transformer and rectifier. Anyone have a simple circuit handy that works well for this? I've seen a few plans online that just say to use a bridge rectifier of suitable capacity, but I want to be reasonably sure that this thing won't kill any more batteries. -- Roger Blake Change "invalid" to "com" for email. Google Groups killfiled. Harbour Frieght products are crap! You get what you pay for! Why don't you just go out a buy a new one from a reputable store. The rest of the parts in your dead battery charger are probably crap too. |
#24
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"Fixing" crap Harbor Freight battery charger
Shaun wrote: Harbour Frieght products are crap! You get what you pay for! Why don't you just go out a buy a new one from a reputable store. The rest of the parts in your dead battery charger are probably crap too. WTH is 'Harbour Frieght'? Another of your drug induced nightmares? -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge. |
#25
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"Fixing" crap Harbor Freight battery charger
"Michael A. Terrell" wrote in message
m... WTH is 'Harbour Frieght'? Another of your drug induced nightmares? Harbor Freight is a chain selling cheap tools. Some of their stuff is good, and/or good value for the money. |
#26
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"Fixing" crap Harbor Freight battery charger
William Sommerwerck wrote: "Michael A. Terrell" wrote in message m... WTH is 'Harbour Frieght'? Another of your drug induced nightmares? Harbor Freight is a chain selling cheap tools. Some of their stuff is good, and/or good value for the money. I am familiar with Harbor Freight. I have bought from them for over 30 years. I used to buy drill bits by the pound, by mail. They were all seconds, due to an uneven coloration but they were quite good. A cordless drill I bought there ten years ago ran for over seven years before the 9.6 volt battery died. I replaced it with a spare 18 V pack and still use it. I had one bad LED flashlight, and one 6in1 screwdriver in all those years. There is a local store, and I am a member of their 'Inside track Club'. In all that time I've had less than 1% defective items which is much better than my record with Craftsman. I've had their lousy screw drivers break the first time I used them to remove the screws from a computer case. The problem that I see is that most people don't know what the hell they are buying, or how to use it. A character I know bought their lightweight cement mixer. He burnt the motor up by loading too much mix & water into the drum. They replaced it twice, and he continued to overload the mixer. He says that he's an 'Idiot Savant'. I have talk to a lot of tradespeople about HF tools and they tell me they rarely break one, but they have them disappear on job sites. They will buy several sets of wrenches, and hide a spare set, just in case. -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge. |
#27
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"Fixing" crap Harbor Freight battery charger
"Michael A. Terrell" wrote in message m... Shaun wrote: Harbour Frieght products are crap! You get what you pay for! Why don't you just go out a buy a new one from a reputable store. The rest of the parts in your dead battery charger are probably crap too. WTH is 'Harbour Frieght'? Another of your drug induced nightmares? If your so ****ing stupid that you can't figure that out, you shouldn't be posting. "Harbour" is the Canadian way of spelling that word, and Frieght is just a typo, nobody is perfect, we all make mistakes - look at your parents; they had you ASSHOLE. What do you get out of critiquing someone else's spelling? Does it make you feel superior to other people, do you need to do that for your low self esteem. You are a pathetic excuse for a Human being! |
#28
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"Fixing" crap Harbor Freight battery charger
Shaun wrote: "Michael A. Terrell" wrote in message m... Shaun wrote: Harbour Frieght products are crap! You get what you pay for! Why don't you just go out a buy a new one from a reputable store. The rest of the parts in your dead battery charger are probably crap too. WTH is 'Harbour Frieght'? Another of your drug induced nightmares? If your so ****ing stupid that you can't figure that out, you shouldn't be posting. "Harbour" is the Canadian way of spelling that word, and Frieght is just a typo, nobody is perfect, we all make mistakes - look at your parents; they had you ASSHOLE. What do you get out of critiquing someone else's spelling? Does it make you feel superior to other people, do you need to do that for your low self esteem. You are a pathetic excuse for a Human being! Your the one who is brain ****ed. There is no US company named Harbour Frieght, so go **** yourself. .. -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge. |
#29
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"Fixing" crap Harbor Freight battery charger
"Michael A. Terrell" wrote in message m... Shaun wrote: "Michael A. Terrell" wrote in message m... Shaun wrote: Harbour Frieght products are crap! You get what you pay for! Why don't you just go out a buy a new one from a reputable store. The rest of the parts in your dead battery charger are probably crap too. WTH is 'Harbour Frieght'? Another of your drug induced nightmares? If your so ****ing stupid that you can't figure that out, you shouldn't be posting. "Harbour" is the Canadian way of spelling that word, and Frieght is just a typo, nobody is perfect, we all make mistakes - look at your parents; they had you ASSHOLE. What do you get out of critiquing someone else's spelling? Does it make you feel superior to other people, do you need to do that for your low self esteem. You are a pathetic excuse for a Human being! Your the one who is brain ****ed. There is no US company named Harbour Frieght, so go **** yourself. Splitting hairs proves nothing. I think the content and general idea of a message to be important unlike some anal retentive prick like you that looks for problems. -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge. |
#30
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"Fixing" crap Harbor Freight battery charger
Just as a followup here, for the moment I've solved my need for a
second automotive battery charger by picking up another 35-40 year old charger at a flea market. It works great! There's something to be said for simplicity. I'll play around with the Harbor Freight unit when I have a chance, there are a lot of possible circuits out there to play around with. -- Roger Blake Change "invalid" to "com" for email. Google Groups killfiled. |
#31
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"Fixing" crap Harbor Freight battery charger
The following link is a rough schematic of the 12V 6A-2A / 6V charger:
https://photos.google.com/search/_tr...wdPGT03vcmpefG Please note: All resistor values are measured and approximate! Theory of Operation: The input transformer has some primary side switching to change the secondary voltage for 12V 2a, 6a and 6V. SCR's AC1 and AC2 are triggered on alternate half cycles of the ac input to charge the battery. Triggering is done by P1 turning on via N1 turning on, N2 and P2 turning off. The voltage divider of 23K and the parallel 9.4k resistors sets VREF as a percentage of battery voltage. The TL431 has a nominal reference level of 2.495 volts. Therefore, V_BATTERY must be 2.495/(4.7/(23+4.7)) or about 14.7 volts to turn on VR which disables charging by turning on P2 - N2 turning off N1,P1, AC1, AC2. P3 provides hysteresis to hold VR conducting by raising VREF when VR turns on. P4 turns on when P1 is on and V_BATTERY exceeds the rectified AC from D1 D2 via P1. P4 on turns on N3 which clamps VREF low turning VR off and continuing to enable triggering. The sensing process repeats on each AC half cycle. AC1 and AC2 will turn off at the end of their positive cycle if there is no gate drive from P1. Design Notes: V_BATTERY is required to power N1,N2,P2,VR,P3,N3. Without battery voltage, N1 will not conduct and P1 will not trigger AC1 and AC2 = No battery charging. The reference voltage divider is fixed for a 12 Volt lead acid battery. Hence the note on the charger stating that 6Volt battery charging must be manually terminated. N2, N3 have no base emitter bypass resistors. Collector - base leakage current could turn them on. There is no protection for reversing the battery leads. It May be OK as is but I have not tried it. Possible failure modes: AC1 and/or AC2. would be likely candidates. BT151's are about $0.75 each in low quantities. AC1/AC2 triggering problems require chasing through the entire PC board to see where the signal is lost. Overall, the HF unit is well constructed for the price. I could envision scenarios where it would fail. YMMV ;-) AJG |
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