Battery charger investigations and repair, rectifier test, meter shunt problems
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- čas přidán 24. 04. 2017
- Looking at a modern 30 amp battery charger from the scrapyard. Why was it scrapped? Only some minor faults. Checking through things and testing the output.
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Well worth watching. Throughly informative and entertaining. I serve in Africa where maintenance is under-appreciated and repair often improper. We have neither the availability of repair parts or the range of replacements such as in the UK or States. One must learn to make do and improvise. Trash elsewhere is treasure here although we tend to be a dumping ground for the world's excess "treasure."
HI, Don, thanks for the positive comment and interest, so few people take the time to fix stuff and as a result do not improve their self reliance. Cheers, Andy
Andy thank you for all your videos I'm a new subscriber and an avid salvage yard admirer and self reliance proponent from CA, USA
Ron, thanks for the message and appreciation, cheers, Andy
Very well played Andy. I enjoy learning even retired. Yes, 4 diodes would provide a proper full wave rectifier, but companies put profit before performance, like the tiny ceramic capacitor. An 600 volt electrolytic capacitor rated for 40-50 volts would be smoothing the ripple A/C syne wave. But, you would not of found it in the scrape, if built well. The nuts on the shunt would have an epoxy dab if properly torqued. Nice find, need a little extra light for those inside one for the first time. Great voice and accent that is easy to understand with my $3 midwest USA ears after decades in dealerships and shops. I tease the younger generation with a question after not using ear protection...I ask “Do you know what we called sun-screen in 1970?” They have no response. I then tell them “Dirt”. Have a wonderful day. Enjoyed what you showed us! Liked & Subscribed.
Dean, thanks for the stories, always great to hear and for your ideas and comments, cheers
you sir need to be a teacher. such a simple device explained in great detail.
Hi, thanks for the appreciation. I occasionally teach and run courses around my books and I also instruct chainsaw. Cheers
keep it up mate. you have gained massive respect from myself and lots of other guy's on the tools.
Great video, thanks Andy.
Thanks, videoing investigation is quite difficult without a camera person, but the ideas are passed on in some form, cheers
That's a nice charger to find free Andy. The recifier stack doesn't look very rigidly mounted, but otherwise it looks well built. Just a thought - the +12v o/p wire back to the transformer may go to a secondary centre tap, in which case it may be that on 24v all 4 diodes are used as a "bridge rectifier", and on 12v only 2 diodes are used plus the centre tap to give "full wave" rectification - both outputs will look similar, ie pulsating dc, but the 12v output will be only half the amplitude (approximately!). I've seen this method for getting 2 voltages a few times. I can't explain the different clamp meter readings on the +ve and -ve cables, that is something else going on I suspect :o) Cheers, Dave
Dave. The centre tap makes sense as there are 2 thick wires going to the 12v postive. The way I see it is the negative is provided through the rectifier and although it is ac at the 12v positive only the positive side of the wave can flow. The negatice will not flow as there is no where for it to go. With the clamp meters there is always a difference in reading, but this is due to the orientation of the clamp to the wire. It would be slightly different if the meter was clamped the other way round. Thanks for the interest, cheers, Andy
Ok - I have not used a dc clamp meter enough to know their foibles ! Re the other thing - have a look on the web for "centre tapped full wave rectification" - the output is a full set of dc pulses, not half a set as in half-wave rectification - so the +12v o/p would look pretty similar in shape to the +24v o/p on a 'scope, but lower in voltage of course. You can think of the centre tap as a zero reference, and the ends of the winding swing positive and negative with respect to this zero alternately, and 180 degrees out of phase with each other - www.electronicshub.org/wp-content/uploads/2014/08/Center-Tapped-Full-Wave-Rectifier-Circuit-Diagram.jpg Cheers, Dave
Hello Andy
I believe that the 12 Volt output is full wave rectified. It comes from the centre tap of the transformer.
We are arbitarily considering the negative terminal of the battery as 0 volts, it is easier to understand if we consider the positive terminal (transformer centre tap) as 0 Volts. and the negative terminal as -12 Volts ( and the 24 Volt output as +12 Volts)
So, when one end of the secondary goes to +12 Volts the other end goes to - 12 Volts and vice versa, so a diode from each end of the secondary to the negative terminal (two sections of the bridge rectifier) will give -12 Volts to the negative output on both half cycles of the ac, hence full wave rectification.
Just for fun ac voltage is measured as the RMS (root mean squared) value of the voltage over 1 cycle of the supply.
When rectified and smoothed with a capacitor the dc voltage is greater than the ac voltage as the capacitor stores the peak value of the ac voltage, (this is 1.4142 times the ac voltage (square root of 2). When a load is applied then the measured dc voltage drops because the capacitor discharges somewhat between each half cycle peak.
I did enjoy the video and liked your comments about the use of tools, there is however something worse than an adjustable spanner, a mole wrench (otherwise known as a nut destroyer).
Regards
Peter Bell
Peter, thanks for the in depth thoughts, a slightly different way of thinking about this situation, pleased you enjoyed the video, cheers
Thanks Andy. Before i retired I designed electronic equipment.
Peter Bell i would enjoy it if you made more videos. I have a very basic understanding of what your describing here but you sound like a good teacher. Thanks for your explanation
@@ryanburbridge Hello Ryan I have 3 videos on youtube Rectifier investigation, Removing a relay from an Aurora inverter and Aurora relay failure investigation.
Thank you so much my Maypole is having issues...take care. 🇬🇧🚗🏍
Cheers
The reason the 12 VDC is only half wave rectified is probably because they were using it to only charge 24 VDC systems. I have a 1A 12 VDC charger that has a bad top hat diode and it is only half wave rectified. You really need a good filtration system on half wave rectification to get ripple free dc. The reason the wire to the 12 VDC lead is coiled is that is the coil part of the filter. There should be a capacitor in the circuit, somewhere to provide the LC filtering.
Most of these folks on Uribe are not masters at anything but BS. I was trained by journeyman, who knew what they were doing and talking about. You are right about files and in which direction they are used. What makes me the hardest is when folks on Uribe call something by the wrong name or just refer to it as as whatchamacallit.
John, thanks for your comment, pulling files backwards, I see so called engineers doing it, just no finesse, cheers
Thanks for the video. Very helpful. Been repairing few of these chargers, yet the experience differs case to case.
Recently I've got one abnormal unit. The voltage is very much higher at the output ranging from 60-80 Volts although the rated output is just 6 - 48 volts.
Any idea why? I've checked all the diodes, fuses, breakers,.. I'm not sure how to check the coil tho. Is it bcoz of the coil?
What does it do with a load connected? Cheers
Couldn't agree more Andy, use the correct spanner unless there is no alternative!
Exactly, we have to be pragmatic, cheers
Hi, disassembling the rectifier bridge I noticed that these 8 diodes are all in parallel 4 positive on one plate and 4 negative on the other plate by setting 12 volts only the plate with 4 negative diodes works and the other one too at 24v but it seems to me both of which work in half wave
having that kind of setup and you hear the classic 50hz hum
They are indeed strange setups, however identical looking diodes can have different bias. These are built down to a price, not up to a standard, cheers
Hello good morning do you know where I can find the insulating shims that are inside the rectifier bridges the ones that were there were in ceramic they broke into 1000 pieces now I know they make them in pvc or teflon
Thank you
Are you sure that's a capacitor across the rectifier Andy? In the video it looks more like an MOV transient suppressor to me. A capacitor that small would have no significant smoothing effects at the currents involved.
Alex, thanks for the comment, I think you are right, far too small to be a capacitor of any significance, live and learn, Cheers
I have exactly the same charger. So if the 12v side of it is half wave rectified and only the 24v side is fully rectified, what would I gain by disconnecting the 24v side to the rectifier, (I don't need the 24v output) and connect the 12v side to the rectifier so that the 12v side is fully rectified? Any advantages?
That rectifier looks like it's a selenium stack rather than solid state diodes! If that's the case, I'm astounded - didn't know they made equipment with those in them any more?
The advantage of selenium rectifiers are they are much more robust and can withstand shorts that would destroy a SSR in microseconds. The main disadvantage is they have a much higher voltage drop across them.
Maybe your 12 volt output is half wave because one of the diodes has actually gone fut? I'm sure even selenium rectifiers have their limits.
Hi. Diodes most aften go short circuit and they all check out as fine. I think the half wave was as Dave said, the centre tap was used which is why there are 2 wires going to the 12v positive terminal. Cheers
Andy, if any of the diodes have gone short circuit it'll be half wave rectifying by *shorting out* every other half cycle! If that's the case it'll be putting a huge load on the transformer and things will get rather warm. Might pay to check that...
Hi. I think the 12v output is half wave due to only the negative being rectified, the positive comes staight from the transformer. This is not an uncommon set-up. Seems to work fine with no heating. Cheers
Measure between the 12 volt & 24 volt outputs with your meter. It should be the same voltage as between the -ve terminal and the +12 volt output.
Yeah, those are definitely selenium rectifiers. I’ve got two very old chargers, a Lucas and a Bosch charger which were owned by my grandfather. The selenium rectifier in the Bosch charger went bad last year. The only problem is getting these selenium rectifiers can be pretty difficult. Most of the ones you find online are meant to be used in tube audio or tube power supplies with current ratings in few mA to under 5A mostly. The ones rated 8A and above for battery charger are quite expensive above $40 to 60 a lot of times. And as mentioned above become of the higher voltage drop of selenium rectifiers the transformers used in these chargers have much higher outputs. The transformer in the Bosch charger outputs 14VAC and 9VAC.
Wait. Do Aussies really call alligator clips, crocodile clips?
I love that. It makes too much sense!
They all have big, sharp, pointy teeth, cheers
Hi Andy . i am in the proccess of repairing a stater/charger unit similar to the one in this video,is there any way I could contact you for some advice please?
Hi, the CZcams message service has been lost, so ask away here, cheers
@@TheInfoworks Thanks Andy-I have a gunson starter /charger which has "button "
diodes(2),so half wave I assume,virtually impossible to source in the uk and wondered if there was an alternative such as a full wave selenium ,or similar,these buttons are rated quite high 50amps ,600 v p.i.v..Any suggestions would be gratefully received ,cheers. Meirion
As you have seen I just used a bolt in diode and these are easly enought to find. I was about proof of concept to make sure I had found the fault and there were no others, cheers
My maypole is showing Inaccurate reading after lending to a friend 🤦♂️ I suspect he tried starting his car with the crocodile clips attached 😡
It's difficult lending stuff out, and sometimes getting it back, cheers
Sir, I have similar charger, problem is when I switch on the charger the out put I get is 40 to 70 v dc, plz help me how to solve the problem
Hi, sounds like a transformer or meter problem. Try another meter and see what the open circuit out voltage is from the transformer, cheers
@@TheInfoworks thank you sir.
The blue component you are calling a capacitor is actually a a varistor and has nothing to do with ripple.
Were not concerned with ripple in an automotive battery charger.
Also there is no need for anything more then half rectified current.Its a charger not an audio power supply.
Thanks for your comment, someone else pointed out my mistake and called the item a transient suppressor, cheers
@@TheInfoworks Varistors serve the same purpose but they also are not the same as transient suppressors.This component appears to have been added to your charger and I see no need or purpose for it in this circuit. I would suspect it was added to attempt fixing an inheritant problem somewhere else in the charger.You should find a fuse is in the output circuit as this varistor when conductive will cause a short,which I assume was it's intention
Ever seen a filing machine work? Hint: It don't lift the file, they last just as long. That's an ol myth
Steve just Steve
Pay him no mind just another arrogant prick...No one else knows how to use a file or a spanner!
When you pull a file backwards over a sharp edge then it damages the teeth, such as on cutting teeth where the steel is tempered. This is not noticeable on flat mild steel hence the confusion and the reference to a filing machine. Cheers
@@TheInfoworks "where the steel is tempered" Are you saying that a files teeth are tempered to a different amount from front to back? Or saying when you're using the file to sharpen the cutting teeth of something else? I think anytime you use a file on something harder than the file itself it's going to damage it, regardless of which way you're going.