Battery charger not working, electrical guys get in here

[jeepwm69 7,611]

Have had this charger for a long time, and all of the sudden it doesn't work.  Comes on, hums, but doesn't charge. 

 

I also have my grandfather's old Schauer charger, and to test each of them, took my voltmeter, attached clamps, and turned  on. 

 

Schauer, which works, the voltmeter showed about 12.75 volts.

 

Did the same on my Schumacher, and nothing.  If I turn the switch from 2 amp to 10 amp the voltmeter shows a bump to 4-5V for a second or two, that's it.

 

Any idea on troubleshooting this thing?  Might not be worth fooling with, but I always try to fix something before going and buying a replacement, especially with all the garbage being sold now vs 20 years ago.

 

 

[56Sierra 1,844]

These older chargers are pretty simple.  Usually not much more than a step down transformer, a full wave bridge rectifier a switch an internal fuse and maybe a capacitor.  If you are getting only 12.75 VDC no load on the good one makes me think it isn't all that good either.

[jeepwm69 7,611]

3 hours ago, 56Sierra said:

These older chargers are pretty simple.  Usually not much more than a step down transformer, a full wave bridge rectifier a switch an internal fuse and maybe a capacitor.  If you are getting only 12.75 VDC no load on the good one makes me think it isn't all that good either.

Well that’s running the clips directly to the voltmeter. I have a feeling if I had a battery hook to the clips and then checked the voltage it would be higher.

 

I know it works because I recently revived a completely dead battery with it for one of the vans at work, which is why it is sitting in my office. I took the top cover off of the Schumacher after bringing it to work to charge the van battery and discovering it did not work. No loose or otherwise obviously corroded connections.

[_Wilson_™ 6,567]

12 hours ago, jeepwm69 said:

Have had this charger for a long time, and all of the sudden it doesn't work.  Comes on, hums, but doesn't charge. 

 

I also have my grandfather's old Schauer charger, and to test each of them, took my voltmeter, attached clamps, and turned  on. 

 

Schauer, which works, the voltmeter showed about 12.75 volts.

 

Did the same on my Schumacher, and nothing.  If I turn the switch from 2 amp to 10 amp the voltmeter shows a bump to 4-5V for a second or two, that's it.

 

Any idea on troubleshooting this thing?  Might not be worth fooling with, but I always try to fix something before going and buying a replacement, especially with all the garbage being sold now vs 20 years ago.

 

 

 

I have one like the Schumacher..... What mine does is kinda like yours... it drops when the switch is toggled for a few seconds.. then it's starts charging again... (sometimes) does it both ranges..(and at times) .. it won't hum or show any signs of life (no gauge needle movement) until it's clipped to the battery poles... it's seems to work better depending on the outside temp... I'm thinking maybe a week solder joint, or sketchy switch But no odd smells or nothing... I don't use it un attended.. when it's acting right it charges fine...it's one of many reasons I'm looking for one like @Wheeler has ( NOCO 3500 ) I think it's a battery charger / tender / booster ?  3 in 1 it sure beats the battery tender jr by deltran... tuned in. 

[Fishfiles 20,145]

My troubleshooting guide for a battery charger , plug it in , if it doesn't work , get a new one and immediately dispose of the old one , so you will never try and use it again ----  it is a disposable world we live in

 

[_Wilson_™ 6,567]

Ya.....its like jeep said... newer stuff isn't any good, that's why I keep this I have, but I'm reminded of someone here who had a fire due to a battery charger incident.. I don't recall who, maybe they will speek up... that's good enough reason to get shed of it... (add to the scrap load) 

[Fishfiles 20,145]

I have seen some cool devices people build from broken stuff , maybe make a perpetual motion machine or some kind of generator out the scraps ---- I like to , at least , cut off and  save power cords from stuff I am throwing away , got a pile of them , LOL

 

 

I have fixed stuff over the years that was heading for the dumpster , the amount of time usually exceeded the value of the item , then many times the fix last for a moment and the item craps out anyways --LOL >>>>> 

 

With all that being said , I have wanted to kick my self in the butt before , for throwing soething away and right afterwards could have used a part off of it 

 

 

[jeepwm69 7,611]

1 hour ago, Fishfiles said:

I have seen some cool devices people build from broken stuff , maybe make a perpetual motion machine or some kind of generator out the scraps ---- I like to , at least , cut off and  save power cords from stuff I am throwing away , got a pile of them , LOL

 

 

I have fixed stuff over the years that was heading for the dumpster , the amount of time usually exceeded the value of the item , then many times the fix last for a moment and the item craps out anyways --LOL >>>>> 

 

With all that being said , I have wanted to kick my self in the butt before , for throwing soething away and right afterwards could have used a part off of it 

 

 

i’m the same way, and that’s why when I die my kids will inherit  a giant pile of crap that they will have to sort through

 

I’d rather have one of these old analog chargers working than the new ones that are all controlled by circuit boards.  
 

Hoping this might be something simple since it still hums and puts out volts if flipping that switch

[Wheeler 2,525]

I’ve never owned an old charger. But like @_Wilson_™ said my NOCO 3500 works great. Even had a repair option, 6v, 12v large & small size. I have a cable off the quad to maintain or charge as I need. I’m no electrician so for me to try & repair like u said @jeepwm69 I would fail. Haha

[retro 4,048]

On 10/20/2023 at 1:44 PM, jeepwm69 said:

Have had this charger for a long time, and all of the sudden it doesn't work.  Comes on, hums, but doesn't charge. 

 

I also have my grandfather's old Schauer charger, and to test each of them, took my voltmeter, attached clamps, and turned  on. 

 

Schauer, which works, the voltmeter showed about 12.75 volts.

 

Did the same on my Schumacher, and nothing.  If I turn the switch from 2 amp to 10 amp the voltmeter shows a bump to 4-5V for a second or two, that's it.

 

Any idea on troubleshooting this thing?  Might not be worth fooling with, but I always try to fix something before going and buying a replacement, especially with all the garbage being sold now vs 20 years ago.

 

Sorry Jeep, I didn't see this thread yesterday or I would have jumped in right away.

First let me explain the differences in battery charger types and their components. Full manual chargers are the simplest design, they usually have just two parts in the case; a stepdown high output current capacity transformer, and either a half-wave rectifier configuration (one diode), or a full-wave bridge rectifier diodes configuration (4 diodes). 

 

The transformer used in all battery charger types just steps down the 115 volts AC input to produce an output AC voltage that is a slightly higher voltage than a fully charged battery can tolerate without destroying the battery during a normal charge cycle. For instance, my purchased in 1993 Schumacher full manual (just has a mechanical timer controlling it) charger transformer outputs 17 volts AC @115 volts AC input. Since it is a full manual type the user must monitor battery voltage while charging and stop the charging cycle when the battery has reached a fully charged condition. That lil' bugger can boil a flooded lead-acid battery dry if it is allowed to continue to charge way beyond a fully-charged condition. It is not intended to charge AGM type batteries, the output voltage is way too high, so it can destroy an AGM if the user allows the AGM to continue to be charging beyond 14.7 volts. I love manual chargers because I want to have full control over the charge cycle.... If I feel like I need to bring an aging battery up to a low boil (for cell voltage equalization and to shed sulfates from the plates) I can do that with a full manual charger. I won't buy an automatic charger (they taper and shut down the charge cycle at 14.7 volts) and I refuse to use one where I have a manual charger option.

 

The rectifier diode configuration in battery chargers converts the transformer AC output voltage into a DC voltage that the battery can accept. A half-wave rectifier consists of one diode (two diodes are used in some configurations), which converts just one half of the AC sine wave into DC. They work by not conducting any current at all while the AC sine wave cycle is in it's lower wave state (negative polarity) and begin to conduct current only while the AC sine wave is in it's upper wave state (positive polarity). Using an oscilloscope you can view an AC sine wave pattern alternating from positive polarity through negative polarity and back through positive polarity at 60 cycles per second. So a half-wave rectifier only conducts current during half of the available AC cycle, which results in the production of pulsating DC. It's common to find half-wave rectifiers mounted inside older model full manual chargers produced decades ago, because they were cheaper to produce than full-wave rectified units (1 diodes vs 4 diodes). Nowadays diodes are inexpensive, so modern chargers often times have full-wave bridge rectifiers inside the case because they're more efficient units. This is what a half-wave rectifier circuit looks like:

 

 

 

Full-wave bridge rectifiers are a requirement for automatic chargers though, because auto units have a solid state DC voltage regulator added inside the case which monitors the battery voltage during each charging cycle and tapers off the rate of charge from a high to low charge rate (as the battery approaches it's full charge condition), then usually shuts off the charging output completely once the battery reaches full charge (usually preset at 14.7 volts shutoff for a 12 volt battery) condition. The DC voltage regulator can only function if it's input supply voltage is (almost) pure DC (minimum residual AC when viewed on an oscilloscope). The regulator cannot function if there is AC voltage supplying it or if the supply is pulsating DC. So automatic chargers have a full-wave bridge rectifier inside the case which works to output (close to) pure DC by conducting current on both the positive polarity portion of the sine wave and the negative polarity portion of the sine wave output by the transformer. Modern automatic chargers usually have a filter capacitor connected into the output immediately following the full-wave bridge rectifier, which smooths out the DC supply for the voltage regulator, by absorbing the peaks of the full-wave signal (which results in a slight increase in output voltage due to the smoothing effect). This is what a full-wave bridge rectifier circuit looks like:

 

 

The Schumacher unit you have in your pic likely has a fried voltage regulator in it that was killed by the failed bridge rectifier. The transformer is still good, so the unit can be fixed by replacing the full-wave bridge rectifier with a new one (depending on the design of that unit you might need two bridge rectifiers, one for 10 amps output mode and one for 2 amps output mode -- otherwise the voltage regulator featured the 10/2 amps output options). Just leave the Auto/Manual switch in the Manual position and it will work again. You don't need the Auto feature.... just don't leave the charger unattended. Old stuff is the best stuff, don't throw that charger away!

 

Here ya go, they're cheap! You can afford to buy two or three of them (I keep them in stock) in case ya gotta fix another unit someday!

 

(eBay) Bridge Rectifier, Single Phase, 50 V, 25 A, Module, 1.1 V, 4 Pins GBPC25005+

 

If you need any help getting it going again, take the top of the case off and shoot me a few pics of the internals.

 

EDIT:

This is a better choice than the one I linked above. It is a reputable major brand, so it's not a china knockoff being marketed by a potential liar who could be selling a 10 amp part, but advertising it as a 25 amp part. This one is rated at up to 40 amps too, so it will be more durable and last longer than a 25 amp rectifier. This one costs more, but it's worth more....

 

(eBay) NTE Electronics NTE5340 BRIDGE RECTIFIER-FULL WAVE SINGLE PHASE 200V 40AMP

 

This is the link to the datasheet for the NTE5340:

https://www.nteinc.com/specs/5300to5399/NTE5340.html

[retro 4,048]

It's possible Jeep, that the voltage regulator inside your Schumacher may still be functional.... you won't know until the fried bridge rectifier is replaced. It likely got fried when the bridge rectifier failed, but it's certainty for failure depends on whether the bridge diodes shorted out or popped the circuit open. If the diodes popped open then the regulator ceased to be supplied with voltage, which means that it could not have been fried by unrectified AC voltage. Fingers crossed. :)

[jeepwm69 7,611]

I’ll get some pics tomorrow of the innards.  I’ve tried it in manual, auto, 2amp and 10amp.  Doesn’t seem to work on any settings. 
 

I’ll take a battery and voltmeter to work with me and see what kind of readings I get. 

[jeepwm69 7,611]

Well this morning I did a little testing with these chargers hooked to an ATV battery, and it looks like the Schumacher IS working, but apparently the gauge is broken.  This is interesting because when I had it hooked to that dead van battery at work, it didn't seem to charge it.

 

Hooked to this ATV battery this morning, for a baseline, I hooked up the red Schauer charger, and checked voltage at battery terminals with my voltmeter, and it was 16.6ish volts.

 

Did the same with the Schumacher I thought was broken, and got 15.75 volts at the 10amp setting with it on "manual" and 13.85V with it on the 2amp setting.  So apparently it IS charging to some degree.

 

So, jury is out on the Schumacher, but it does appear that it would charge, and that the meter is just broken on it.

 

Pics of the Schumacher innards.

 

 

[retro 4,048]

You can put your multimeter on Amps mode, move your Red multimeter lead to the Amps socket on your meter (if applicable), unplug the two wires that go to the Amp meter on the Schumacher and poke a multimeter lead into each spade connector on those two wires to measure the charge current going into your ATV battery. If you get a low amps reading (1 or 2 amps? Depends on the charge level in the battery how much current it will accept) then you can assume that the Amp meter in the Schumacher is dead. I would check that Amp gauge before going any further.

 

It looks like there is a half-wave rectifier diode mounted inside on the rear panel. It looks like there is another diode (single spade terminal, White/black wire plugged into it) mounted on the rear panel to the right (as viewed in the photo) of the half-wave rectifier. That diode is probably used for reverse-polarity (allows you to connect the charger leads up backwards on a battery, dummy-proofing) protection, although I can't tell where that White/black wire goes to, so I could have those two diodes mixed up.

 

You can use an old toothbrush and some rubbing alcohol to clean up that circuit board. 

 

You can test those two diodes too, by setting your meter to resistance mode (or diode test mode if your meter has that feature), disconnect the wires from them -- and for the diode that has two soldered terminals, measure between the two terminals on the diode with the wires disconnected. Swap your meter leads (opposite polarity) and measure again across those two terminals. If that diode conducts when measured one way, but does not conduct when measuring with opposite polarity (two meter leads swapped, then that diode tests good. If the diode conducts on both polarity's then it tests shorted and is junk. If it does not conduct on either polarity then it tests popped open and is junk.

 

Test the same way on the diode with the White/black wire plugged into it, but since that diode has only one terminal, the case provides it's ground where it is mounted. So one lead on the terminal, the other lead on case ground when measuring. Swap the meter leads to measure opposite polarity.

 

[jeepwm69 7,611]

50 minutes ago, retro said:

You can put your multimeter on Amps mode, move your Red multimeter lead to the Amps socket on your meter (if applicable), unplug the two wires that go to the Amp meter on the Schumacher and poke a multimeter lead into each spade connector on those two wires to measure the charge current going into your ATV battery. If you get a low amps reading (1 or 2 amps? Depends on the charge level in the battery how much current it will accept) then you can assume that the Amp meter in the Schumacher is dead. I would check that Amp gauge before going any further.

 

Got about .33 showing on the 2amp mode.  Put it on 10amps and meter showed around 1.00 on the voltmeter.  Jumped around a bit on the 10amp setting.

 

But the battery is showing 12.8 volts now so it's topped off.  It's been on a tender at the house.  Just a spare older (2017) battery I had laying around.

[retro 4,048]

So as you said apparently the Schumacher is working (somewhat at least), but the amp meter doesn't seem to be working since you can't get the needle to wiggle off of zero. That Amp meter is easy to replace and you can probably find them On eBay for cheap. But first lets learn a bit more about which type of charge controller you're working with.

 

There are two basic types of charge controllers in use in Automatic battery chargers. The most simple and inexpensive charge controller just monitors the battery voltage while charging and shuts off the output when the battery reaches a certain voltage threshold. The simple type provides charge voltage and current to the battery clamps at all times, even when the battery clamps are not connected to a battery.

 

The more complex and more expensive type Automatic charge controller does not provide any output to the battery clamps until the clamps are connected to a battery, because the controller must sense a low (below fully charged battery voltage threshold) battery voltage before the controller will kick on.

 

You can learn which type of controller you're working with by quickly sparking the red and black battery clamps together (shorting them together quickly as you can - don't hold them together) while they're not connected to a battery. If sparks fly from the clamps then you're working with the simple and inexpensive type controller, and sparks flying indicates that the charger is working. Try this test on 10 Amps Manual mode, then again on Automatic mode. Let me know what happens. 

 

If you see sparks fly but the Amps meter doesn't jump toward max scale then the Amps meter is definitely junk. Then measure DC volts across the  battery clamps with your meter while the clamps are not connected to a battery. Then switch your meter to AC volts mode and measure again. Let me know what those two measurements are.

[Fishfiles 20,145]

I have seen new chargers , where   if the battery is lower than a certain low voltage  threshold , the  charger  won't start charging until you jump the battery a few voltages

 

Last few years I also seen another freaky thing happen a few times now ,  batteries going  " reverse polarity " 

[jeepwm69 7,611]

41 minutes ago, retro said:

So as you said apparently the Schumacher is working (somewhat at least), but the amp meter doesn't seem to be working since you can't get the needle to wiggle off of zero. That Amp meter is easy to replace and you can probably find them On eBay for cheap. But first lets learn a bit more about which type of charge controller you're working with.

 

There are two basic types of charge controllers in use in Automatic battery chargers. The most simple and inexpensive charge controller just monitors the battery voltage while charging and shuts off the output when the battery reaches a certain voltage threshold. The simple type provides charge voltage and current to the battery clamps at all times, even when the battery clamps are not connected to a battery.

 

The more complex and more expensive type Automatic charge controller does not provide any output to the battery clamps until the clamps are connected to a battery, because the controller must sense a low (below fully charged battery voltage threshold) battery voltage before the controller will kick on.

 

You can learn which type of controller you're working with by quickly sparking the red and black battery clamps together (shorting them together quickly as you can - don't hold them together) while they're not connected to a battery. If sparks fly from the clamps then you're working with the simple and inexpensive type controller, and sparks flying indicates that the charger is working. Try this test on 10 Amps Manual mode, then again on Automatic mode. Let me know what happens. 

 

If you see sparks fly but the Amps meter doesn't jump toward max scale then the Amps meter is definitely junk. Then measure DC volts across the  battery clamps with your meter while the clamps are not connected to a battery. Then switch your meter to AC volts mode and measure again. Let me know what those two measurements are.

 

Manual mode, no sparks, no movement on the amp meter

 

No measurement across the clamps in either AC or DC mode with the clamps not connected to a battery.

 

Tried it connected to the battery, got @ 16V in manual mode on DC, and sparks and a 1 on the voltmeter (like maxxed out range on the meter 1) on the amp setting.

You gotta remember, electrical stuff is voodoo magic to me.  LOL

 

Looks like I need to replace the amp meter on this thing and it probably works ok.  @Fishfiles made a good point that with a completely dead battery, it might not have started charging if it couldn't sense a battery. 

 

I got this charger when I was 12-13 years old to use to charge my trolling motor battery.  I remember that if I left it on the automatic function, once the battery was charged, it would then cut on for a second, then off for a few seconds, then blip on, then off for a few seconds.  It would do that as long as it was left hooked up, again once the battery was charged..

[retro 4,048]

Yeah, the controller design that senses low battery voltage before they'll kick on are poorly thought out designs. They won't kick on unless the battery is partially charged. They ignore a completely dead one. I see the same designs on some AA NiMh battery chargers and on many LiPo battery chargers too. They suck because the main design criteria for component selection is to be as cheap to manufacture as possible. Old stuff is usually better stuff because function was valued more than production cost prior to the repugnicans teardown (moved everything to the far east countries where slave/child labor costs are almost free) of USA manufacturing.

 

I've only seen a battery go to reverse polarity once. It happened to my Kawasaki dirt bike battery when I was kid. I blew both ends off of that battery when it exploded after I jumper cabled it to a car battery, trying to flip the polarity back. :)

[jeepwm69 7,611]

1 minute ago, retro said:

Yeah, the controller design that senses low battery voltage before they'll kick on are poorly thought out designs. They won't kick on unless the battery is partially charged. They ignore a completely dead one. I see the same designs on some AA NiMh battery chargers and on many LiPo battery chargers too. They suck because the main design criteria for component selection is to be as cheap to manufacture as possible. Old stuff is usually better stuff because function was valued more than production cost prior to the repugnicans teardown (moved everything to the far east countries where slave/child labor costs are almost free) of USA manufacturing.

 

I've only seen a battery go to reverse polarity once. It happened to my Kawasaki dirt bike battery when I was kid. I blew both ends off of that battery when it exploded after I jumper cabled it to a car battery, trying to flip the polarity back. 🙂

 

This charger should have been circa 1987-88.  Somewhere in that general time frame.

 

I was talking to a friend the other day about how the "free trade" garbage that I thought was great at the time, actually did nothing but gut our manufacturing and send it all overseas.   Now we have cheap crap, and it's just that; CRAP.

 

We were discussing the area and how all of industry is gone. leaving nothing but .gov and farm jobs, along with all of those living on welfare.  

 

Tyrants like dependents.  Keeps them in control.

[retro 4,048]

YUP! Truth on all the points you made!!! We gotta put all corporate gubmints into disappeared mode. Along with money too.

 

Well you think that electrical stuff is voodoo to you, but I think that's a pretty humble take. You're good at fixing everything you are challenged by once you understand it. You'll soon be an electrical wizard me thinks.

 

Hope you can find an AMPS meter that snaps right in to that case.

[LedFTed 1,127]

the US was once a place of quality manufacturing, well, better than most. the masses wanted something CHEAPer, and so they got it.

[56Sierra 1,844]

8 hours ago, LedFTed said:

the US was once a place of quality manufacturing, well, better than most. the masses wanted something CHEAPer, and so they got it.

Often we are sold inferior quality at the same price of something made in America.  I once saw two Christmas tree stands, very similar in design but the one made in America was actually cheaper than the one made in China.

[jeepwm69 7,611]

On 10/23/2023 at 3:18 PM, retro said:

YUP! Truth on all the points you made!!! We gotta put all corporate gubmints into disappeared mode. Along with money too.

 

Well you think that electrical stuff is voodoo to you, but I think that's a pretty humble take. You're good at fixing everything you are challenged by once you understand it. You'll soon be an electrical wizard me thinks.

 

Hope you can find an AMPS meter that snaps right in to that case.

 

 

Found one and ordered it.  Same company still makes them in Cleveland.  "Prime"

 

Interestingly enough, took the original out and it has APR 04 1992 on the back, so I guess I was older than I thought when I bought it.  I would have been 16

[jeepwm69 7,611]

Got my new meter installed on this charger, I had another dead battery on a different vehicle at work so I figured I would try it out.

 

with the charger on the 10 amp setting, the negative clamp on the charger got too hot to touch.  From what I can find this appears to be indicative of a poor connection or a bad battery.

 

I’m pretty sure the battery is shot, but I also think these terminals likely need to be cleaned up, with the wire trimmed back and re-clamped.