Car battery charger, not working.
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I have 3 dead harbor freight chargers. wish I knew how to fix them. they are the 6v/12v 2/10/55 ones.
after the 3rd one I bought a schumacher based on the recommendations here. Its still going good.
after the 3rd one I bought a schumacher based on the recommendations here. Its still going good.
Taking a voltage reading on an unloaded charger won't prove too much. It must be in a balanced circut.
If you are well-versed in how to use a multimeter and such (taking readings for AC/DC, etc.) and assuming that you are able to pull off the cover off the charger and it's deemed transformer based, you can take some measurements to see if the transformer secondary is putting out some readings (typically in excess of 12VAC). If this is true (getting >12VAC reading but no DC reading from your clamps), then you know that somewhere along the way, your bridge rectifiers, etc. maybe faulty.
If you can't get a reading off of your transformer secondary windings, and yet you can get 120V AC on the input (primary) side of the transformer, then your transformer is deemed faulty.
IF your charger is switcher based, that's a different (advanced) subject.
**Sorry, switcher-based charger is an advanced electronics subject that is out of this board's discussion...if you didn't pay too much for it, might as well chuck it and get a new one instead of trying to fix it....***
Q.
If you can't get a reading off of your transformer secondary windings, and yet you can get 120V AC on the input (primary) side of the transformer, then your transformer is deemed faulty.
IF your charger is switcher based, that's a different (advanced) subject.
**Sorry, switcher-based charger is an advanced electronics subject that is out of this board's discussion...if you didn't pay too much for it, might as well chuck it and get a new one instead of trying to fix it....***
Q.
JHZR2
Staff member
Originally Posted By: Smoky14
Taking a voltage reading on an unloaded charger won't prove too much. It must be in a balanced circut.
+1. Often the chargers have a delay before they start to put out any voltage/current, so that they can determine if the connected load is the right voltage, determine what they need to put out, etc. 1.8V may just be some leakage.
Id do this:
-Obtain a multimeter, use it for voltage readings.
-Read the battery voltage without the charger attached, report.
-Attach the charger, read the battery voltage, report.
-Start up the charger with the right voltage and current settings utilized. Measure voltage after a few minutes, report.
If your battery is bad, like it has a shorted cell, the voltage of the charger may drop, or it may get cut via a current limit because the battery is accepting too much too fast. There are all kinds of schemes that are used...
A slow rate (low current) charger will not take the voltage too high for a while. It may even just float at a single voltage and just limit the current it provides. So some may just be a 13.5 or so voltage source.
Taking a voltage reading on an unloaded charger won't prove too much. It must be in a balanced circut.
+1. Often the chargers have a delay before they start to put out any voltage/current, so that they can determine if the connected load is the right voltage, determine what they need to put out, etc. 1.8V may just be some leakage.
Id do this:
-Obtain a multimeter, use it for voltage readings.
-Read the battery voltage without the charger attached, report.
-Attach the charger, read the battery voltage, report.
-Start up the charger with the right voltage and current settings utilized. Measure voltage after a few minutes, report.
If your battery is bad, like it has a shorted cell, the voltage of the charger may drop, or it may get cut via a current limit because the battery is accepting too much too fast. There are all kinds of schemes that are used...
A slow rate (low current) charger will not take the voltage too high for a while. It may even just float at a single voltage and just limit the current it provides. So some may just be a 13.5 or so voltage source.
Originally Posted By: expat
Thanks, that's about what I expected.
Any idea on what rating of Diode I should look for.
What's the peak current rating of the charger? I'd use a diode in each secondary leg that can handle 2X that current.
For voltage, 50 PRV is borderline marginal, and anything 100 PRV will be fine.
You can parallel diodes to increase their current capability, series them to increase the voltage rating.
Also, don't overlook the real possibility of a high resistance connection where the output leads attach to the alligator clamps. I'd cut the leads, and carefully reattach the alligator clamps making sure you have good low resistance connections at the clamps before you rip the diode pack out of it. That may be all that's wrong with it.
If it's one of the dirt simple transformer, voltage switch, rectifier type charger, there's really nothing to go wrong except the clamps or the diodes. I've never seen a bad transformer on one.
Thanks, that's about what I expected.
Any idea on what rating of Diode I should look for.
What's the peak current rating of the charger? I'd use a diode in each secondary leg that can handle 2X that current.
For voltage, 50 PRV is borderline marginal, and anything 100 PRV will be fine.
You can parallel diodes to increase their current capability, series them to increase the voltage rating.
Also, don't overlook the real possibility of a high resistance connection where the output leads attach to the alligator clamps. I'd cut the leads, and carefully reattach the alligator clamps making sure you have good low resistance connections at the clamps before you rip the diode pack out of it. That may be all that's wrong with it.
If it's one of the dirt simple transformer, voltage switch, rectifier type charger, there's really nothing to go wrong except the clamps or the diodes. I've never seen a bad transformer on one.
Originally Posted By: Quest
...then you know that somewhere along the way, your bridge rectifiers, etc. maybe faulty ...
All of the "basic" ones I've seen are just as cheap as cheap can get, and use a two diode full wave rectifier, where ( on 12 volt output ) alternate diodes conduct on alternate halves of the ac cycle. There's no need to filter the pulses, since the load is a battery.
I like the basic ones because a lot of times they will charge batteries my fancy computerized charger rejects.
...then you know that somewhere along the way, your bridge rectifiers, etc. maybe faulty ...
All of the "basic" ones I've seen are just as cheap as cheap can get, and use a two diode full wave rectifier, where ( on 12 volt output ) alternate diodes conduct on alternate halves of the ac cycle. There's no need to filter the pulses, since the load is a battery.
I like the basic ones because a lot of times they will charge batteries my fancy computerized charger rejects.
Thanks guys, I hope to get to it this weekend.
I'm pretty sure it's just an Old, Dumb, Battery charger.
Which is what I want! the sort where I can test 12v electrical components as well charge the Lawnmower battery etc.
Sure, I could just buy a new one, But I have the time, and like to know what makes things tick.
I've never happened get into a charger before.
I'm pretty sure it's just an Old, Dumb, Battery charger.
Which is what I want! the sort where I can test 12v electrical components as well charge the Lawnmower battery etc.
Sure, I could just buy a new one, But I have the time, and like to know what makes things tick.
I've never happened get into a charger before.
JHZR2
Staff member
Originally Posted By: Win
There's no need to filter the pulses, since the load is a battery.
I like the basic ones because a lot of times they will charge batteries my fancy computerized charger rejects.
Maybe they do have use with charging bad batteries (which may or may not have any retained capacity, or may have other issues), but the AC ripple can be harmful to batteries too, so lack of filtering may not be the best thing either...
There's no need to filter the pulses, since the load is a battery.
I like the basic ones because a lot of times they will charge batteries my fancy computerized charger rejects.
Maybe they do have use with charging bad batteries (which may or may not have any retained capacity, or may have other issues), but the AC ripple can be harmful to batteries too, so lack of filtering may not be the best thing either...
Originally Posted By: expat
... I'm pretty sure it's just an Old, Dumb, Battery charger.
Which is what I want! the sort where I can test 12v electrical components as well charge the Lawnmower battery etc.
...
Well, as noted ^^^^^ the output of the dumb chargers is pulsed DC, so it's best not to attach it directly to anything that uses 12 VDC because of the complete lack of filtering.
In my older, poorer, college days, I used them as 12 volt supplies with an old car battery as the filter element, which works pretty well, actually.
... I'm pretty sure it's just an Old, Dumb, Battery charger.
Which is what I want! the sort where I can test 12v electrical components as well charge the Lawnmower battery etc.
...
Well, as noted ^^^^^ the output of the dumb chargers is pulsed DC, so it's best not to attach it directly to anything that uses 12 VDC because of the complete lack of filtering.
In my older, poorer, college days, I used them as 12 volt supplies with an old car battery as the filter element, which works pretty well, actually.
Originally Posted By: JHZR2
.... but the AC ripple can be harmful to batteries too, so lack of filtering may not be the best thing either...
I don't recall seeing an ac ripple spec for my Schumacher smart charger, but it wouldn't surprise me if it's not all that great. It uses a switcher type power supply.
I have a small handheld digital scope, so next time I'm bored watching a battery charge, I might have a go at measuring it.
Speaking of scopes, good luck finding a U.S. made one
. Last weekend I was in Dallas looking at scopes, not the cheap ones either, $1K plus digital Tektronix and LeCroy scopes - all made in China now.
.... but the AC ripple can be harmful to batteries too, so lack of filtering may not be the best thing either...
I don't recall seeing an ac ripple spec for my Schumacher smart charger, but it wouldn't surprise me if it's not all that great. It uses a switcher type power supply.
I have a small handheld digital scope, so next time I'm bored watching a battery charge, I might have a go at measuring it.
Speaking of scopes, good luck finding a U.S. made one
JHZR2
Staff member
What else would we expect!!!! Frustrating.
until expat reports back with pictures to share, otherwise, we are at best--just guessing.
speaking of scopes, you get what you pay for, period.
(*I'm a big fan of older teks or Rhode and Schwartz scope, or Japanese ones such as Hitachi, Trio, National or even Meguro; for digital LCD scopes, any Chinese ones or even Agilent (pretty much Chinese made these days) will get my vote*)
HP modular types are great but can be a bit of a pain to acquire and get them calibrated...definitely laboratory-grade stuff though..
Q.
speaking of scopes, you get what you pay for, period.
(*I'm a big fan of older teks or Rhode and Schwartz scope, or Japanese ones such as Hitachi, Trio, National or even Meguro; for digital LCD scopes, any Chinese ones or even Agilent (pretty much Chinese made these days) will get my vote*)
HP modular types are great but can be a bit of a pain to acquire and get them calibrated...definitely laboratory-grade stuff though..
Q.
Originally Posted By: Win
Originally Posted By: expat
... I'm pretty sure it's just an Old, Dumb, Battery charger.
Which is what I want! the sort where I can test 12v electrical components as well charge the Lawnmower battery etc.
...
Well, as noted ^^^^^ the output of the dumb chargers is pulsed DC, so it's best not to attach it directly to anything that uses 12 VDC because of the complete lack of filtering.
In my older, poorer, college days, I used them as 12 volt supplies with an old car battery as the filter element, which works pretty well, actually.
Thank you, I had never considered that.
I the past I have typically tested light bulbs.
But what might be adversely effected by pulsed DC?
Regardless, I will use a filter from now on.
Would a capacitor work?
Originally Posted By: expat
... I'm pretty sure it's just an Old, Dumb, Battery charger.
Which is what I want! the sort where I can test 12v electrical components as well charge the Lawnmower battery etc.
...
Well, as noted ^^^^^ the output of the dumb chargers is pulsed DC, so it's best not to attach it directly to anything that uses 12 VDC because of the complete lack of filtering.
In my older, poorer, college days, I used them as 12 volt supplies with an old car battery as the filter element, which works pretty well, actually.
Thank you, I had never considered that.
I the past I have typically tested light bulbs.
But what might be adversely effected by pulsed DC?
Regardless, I will use a filter from now on.
Would a capacitor work?
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@expat:
don't get carried away RE: whether it's pulsed DC, non-filtered DC (ripples within) or not.
At this stage, you should try to focus on the fact as to why your output side voltage reading is low.
Why don't you find yourself a load (a 12V automotive lightbulb,e.g. brake light or similar, with at least10Watts or more) to load test your output side and see if you get a reading of 12V DC or higher?
If you still getting low voltage reading (waaay lower than 12VDC, I mean you mentioned you got something like 1.x volts, right?!), your secondary is shot.
No need to dwell/spend time on technical perspectives like "...should I add a filtering capacitor?..."
And please! when you have a moment: please take some photo shots and upload to share. We are still playing guessing game here...
Q.
don't get carried away RE: whether it's pulsed DC, non-filtered DC (ripples within) or not.
At this stage, you should try to focus on the fact as to why your output side voltage reading is low.
Why don't you find yourself a load (a 12V automotive lightbulb,e.g. brake light or similar, with at least10Watts or more) to load test your output side and see if you get a reading of 12V DC or higher?
If you still getting low voltage reading (waaay lower than 12VDC, I mean you mentioned you got something like 1.x volts, right?!), your secondary is shot.
No need to dwell/spend time on technical perspectives like "...should I add a filtering capacitor?..."
And please! when you have a moment: please take some photo shots and upload to share. We are still playing guessing game here...
Q.
OK here is what I have:
This is my first time posting pic's, I hope this works.
I hooked the charger to a partially drained battery, the battery read 11v before connecting the charger, but I could only get a reading of 8v when on charge.
Output from the terminals alone was only .01v
I have 120v ac going into the transformer, and the best reading on the 'out' side is about 10v (but I'm not sure where probe for this)
This is my first time posting pic's, I hope this works.
I hooked the charger to a partially drained battery, the battery read 11v before connecting the charger, but I could only get a reading of 8v when on charge.
Output from the terminals alone was only .01v
I have 120v ac going into the transformer, and the best reading on the 'out' side is about 10v (but I'm not sure where probe for this)
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thank you expat.
Now we know that we are dealing with one of those not-so-dumb charger (Still transformer-based, but automatic charger). It's most likely your diode(s) or the bipolar transistor that is at fault, or something on the circuit board went bonkers.
While I don't have your mortarmeister version of schematics on hand, the automatic chargers are fairly typical design and this is something I typically referenced to:
http://freecircuitdiagram.com/2008/09/07/automatic-12v-lead-acid-battery-charger/
bottomline: you will have to find means to test the diodes, the bipolar transistor or the SCR (in my referenced schematic).
Good luck.
Q.
Now we know that we are dealing with one of those not-so-dumb charger (Still transformer-based, but automatic charger). It's most likely your diode(s) or the bipolar transistor that is at fault, or something on the circuit board went bonkers.
While I don't have your mortarmeister version of schematics on hand, the automatic chargers are fairly typical design and this is something I typically referenced to:
http://freecircuitdiagram.com/2008/09/07/automatic-12v-lead-acid-battery-charger/
bottomline: you will have to find means to test the diodes, the bipolar transistor or the SCR (in my referenced schematic).
Good luck.
Q.
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