Angelfish Posted August 9 Share Posted August 9 No Load output is 11.5 volts. It was abandoned on a job site where I was a laborer in 1997. New clamps and an AC plug and I’ve used it ever since, until about a year ago when it didn’t seem to charge very well. Just one of those old things I’d like to keep in service. Link to comment Share on other sites More sharing options...
Larry Schramm Posted August 9 Share Posted August 9 What is the input and output voltage of the transformer? That will determine if it is worth fixing. 1 Link to comment Share on other sites More sharing options...
TerryB Posted August 9 Share Posted August 9 Do you get 6v on the 6v setting? Link to comment Share on other sites More sharing options...
TerryB Posted August 9 Share Posted August 9 39 minutes ago, Larry Schramm said: What is the input and output voltage of the transformer? That will determine if it is worth fixing. Those values will be in AC volts. The diodes which are used to rectify the AC to DC I believe are mounted to that aluminum plate. 2 Link to comment Share on other sites More sharing options...
Rusty_OToole Posted August 9 Share Posted August 9 (edited) It's ok with me. Usually the only thing that goes bad is the selenium rectifier. Can be replaced with diodes but diodes are far more efficient, doubling the output of the charger. Both volts and amps. One solution is to only use one side of the transformer. It's nice if you can have the gauge and the lights working too. You can laugh at these little home chargers but they are all most of us need, and they minimize the chance of overcharging and damaging a battery. Edited August 9 by Rusty_OToole (see edit history) 1 Link to comment Share on other sites More sharing options...
ABear Posted August 9 Share Posted August 9 7 minutes ago, TerryB said: Do you get 6v on the 6v setting? Output voltages of this type of charger are unfiltered DC, reading the unfiltered DC with no battery will result in a lower than anticipated DC voltage reading so I would not expect the 6V to have 6V or more, should be half of what the 12V unloaded and unfiltered voltage measurement is. When a battery is connected the battery acts as a "filter" and the rectified DC voltage will be higher due to the battery acting as a filter. These are really simple "power supplies", basically a transformer, with full wave rectifier, ammeter and auto resetting breaker. The front voltage switch simply switches primary voltage taps to change the output voltage of the transformer. The back plate is where the two rectifiers diodes are (red wires), the output of the rectifier plate is the connector in the center of the plate and that goes to the output charging lead, the secondary center tap (green) goes to a auto reset breaker and that goes to the ammeter and from the ammeter to your charging output wire. Typical points of failure on this unit is the the auto reset breaker and the rectifying diodes, transformer unless it has been dunked in water will outlast everything else. You could try using a fuse temporarily in place of the breaker to see if you improve the charging.. If that works then buy a new breaker and call it a day. Diodes are a bit trickier but they to can be replaced. Those are good units to have around, smart chargers will not start up unless they see a 10V min voltage so sometimes you have to trick them by using a old school charger to jump them into working. Attached is a basic power supply diagram. In that diagram, they use a 4 diode full wave rectification, the charger the OP uses a two diode full wave (two half wave rectification) with a center tap on the secondary which results in a lower unfiltered DC voltage. The charger in question does not have any filtering capacitors or voltage regulation.. 2 Link to comment Share on other sites More sharing options...
TerryB Posted August 9 Share Posted August 9 Electrical connections like clean mating surfaces with each other so that would be one thing to check on the inside. Do you get any current flow indication on the front meter when you hook it up to a battery? 1 Link to comment Share on other sites More sharing options...
Angelfish Posted August 9 Author Share Posted August 9 (edited) 1 hour ago, Larry Schramm said: What is the input and output voltage of the transformer? That will determine if it is worth fixing. If I did this right, I have 12.7 VAC into the rectifier and 11.7 VDC on the way out. I don’t know what the input should be but that seems low. Edited August 9 by Angelfish (see edit history) Link to comment Share on other sites More sharing options...
Angelfish Posted August 9 Author Share Posted August 9 58 minutes ago, TerryB said: Do you get 6v on the 6v setting? 7 volts output. 1 Link to comment Share on other sites More sharing options...
ABear Posted August 9 Share Posted August 9 Just now, Angelfish said: If I did this right, I have 12.7 VAC into the rectifier and 11.6 VDC on the way out. I don’t know what the input should be but that seems low. Depending on the meter calibration you have, that is pretty much spot on to being correct AC voltage on the secondary. To understand the difference between rectified filtered and rectifier unfiltered DC would require basic electronics theory. In a nutshell, when you recitify AC to DC, you lop of half of the AC wave form, so now you have half of a sinewave in one direction. So, you get one peak per hertz, overall slightly less than half of the AC voltage. Two diode Full wave with center tap gives you two peaks per hertz which now gives you a little higher DC voltage. Add in a filter capacitor that "smooths" out the DC and the result is a bit higher DC voltage than with no filter cap.. When you add a battery into the mix, the battery it's self acts like a filter capacitor and the resultant voltage will be greater than the unfiltered voltage. To test the charger, it needs to be connected to a known good 12V battery that is charged, measure the battery voltage before connecting and after connecting the charger. Compare the two voltages, resting voltage of a fully charged 12V battery should be 12.6V-12.8V. You should get a reading of 13.0V-14.0V easily and perhaps a bit higher when the charger is connected to a fully charged 12V battery. There may be nothing wrong with the charger and the problem may be your batteries you are trying are just done with life and need replaced. 1 Link to comment Share on other sites More sharing options...
TerryB Posted August 9 Share Posted August 9 12 minutes ago, Angelfish said: 7 volts output. On the DC battery leads? Just want to verify it’s DC. Link to comment Share on other sites More sharing options...
TerryB Posted August 9 Share Posted August 9 Putting the charger on a battery and observing it output is a good thing to try. You can leave the lid off for poking around with your meter if necessary. Link to comment Share on other sites More sharing options...
Angelfish Posted August 9 Author Share Posted August 9 3 minutes ago, TerryB said: Putting the charger on a battery and observing it output is a good thing to try. You can leave the lid off for poking around with your meter if necessary. 7 VDC. What’s the correct to measure output on a battery? Across the battery terminals? Link to comment Share on other sites More sharing options...
Angelfish Posted August 9 Author Share Posted August 9 9 minutes ago, ABear said: Depending on the meter calibration you have, that is pretty much spot on to being correct AC voltage on the secondary... Thank you for another good explanation, learn something new everyday around here. Link to comment Share on other sites More sharing options...
Angelfish Posted August 9 Author Share Posted August 9 Well what the heck. Connected a fully charged battery and now I get this. Maybe I just didn’t have it connected properly all those months ago. 4 1 Link to comment Share on other sites More sharing options...
ABear Posted August 9 Share Posted August 9 Looks like results to me! Battery condition and state of charge plays a lot with the actual measured voltage as you have shown. Fully charged battery will draw very little current from the charger, resulting in a higher DC voltage. Connecting a partially discharged battery to the charger can result with sub 12V DC reading and the current being drawn by the Ammeter will be high. As the battery charges, the battery voltage will rise, the current drawn through the Ammeter will taper down automatically and as the amperage drops the voltage rises. Because of this voltage/amperage relationship these chargers are not recommended to be left connected and powered 24/7/365 as end charge voltages above 13.2V will result in excess electrolyte boiling and loss in most batteries. So they are not recommended for long term battery storage maintenance, but they are sure nice to have, reliable and dependable and plain just get the job done unless you have a truly bad battery with a bad cell. For long term battery storage maintenance solutions I do recommend more modern "multi stage" chargers for vehicles that are not driven often enough to keep the battery in top condition. There is a lot of multi stage chargers on the market, but those can be put into two classes. First "class" is the same idea as the transformer based versions, these are intended to replace the portable transformer type chargers and add in multistage charging. They do work well but they do have a few issues. Number one issue with this class is they do not apply charging voltage to the leads unless they see at least 9V-10V DC. You cannot connect a dead battery (less than 9V-10V) and get it to charge. Number two issue with this class is they do not "auto start" charge and do not "auto restart" after end of charge or power failure and if left connected 24/7 can drain your target battery as a result. These have a manual "Start" button that you must push to start the charge. Second "class" is continuous multistage chargers, these are designed to be connected 24/7/365, they will automatically start and restart and will automatically cycle through the different charging stages from bulk charging (14.4V-14.6V) down to long term storage (13.2V-13.4V). The drop to storage voltage at end of charge reduces electrolyte loss and the charger will at predetermined periods increase the voltage for short bursts to stir the electrolyte to reduce sulfination that can happen in long term storage. I have a couple of these 5A multistage chargers in use for $35 each from Amazon.. https://www.amazon.com/BMK-Maintainer-Detachable-Alligator-Waterproof/dp/B06XK7PM9F/ref=sr_1_7?crid=2Y28Z5SQKHMII&dib=eyJ2IjoiMSJ9.Fx7UNMck00mtb_4aVL01Zk0XPsCH52JP0ZwItqlJjw_hUlqXUjtuLyQxDDxM-K6Nhm52po8kwV4xyw1nsHTPlZSNnSuZGuCCyBR2PRfuvhPX3xEujQC0jNmtZkV1L8rA8pJ9C2bq_ZS3qFxcJDONOMDMWjdQNM-0Jg8rn99tiK7y--55vxGdyX0yiVyUDwMrrAPTR5SIyveq28koCcgWxF6lSe7N3jQ2oTNhLE9GFWHS43_r4DzOy3AuTsB5_qqKRa9aDY14SOy7Wjh09zNu4ACyXRCV9V439gZnhT7Djr8.x176DTj3tmvuGBVDWOy9D26xCaInVXpRYRYvAbaGUs0&dib_tag=se&keywords=5amp+multistage+12v+battery+charger&qid=1723238778&sprefix=5amp+multistage+12v+battery+charger%2Caps%2C97&sr=8-7 You get a wire set with rings (permanent connection) and a set a gator clips. so you can mount the charger in the vehicle or not. Now, I do not know if the one I have listed will work with 6V, never tried that, so for 6V applications you will need to do some research and verify if you can find one compatible with 6V.. 2 1 Link to comment Share on other sites More sharing options...
Oz Dodge 4 Posted August 9 Share Posted August 9 That's one of the things I like about this site, you get to learn a lot about things you know nothing about, but would like to know more of ! "Thanks Guys" 👍 2 Link to comment Share on other sites More sharing options...
Frank DuVal Posted August 10 Share Posted August 10 In fiddling around you may have just reseated the spring metal fit to the diodes!👍 I was going to mention put the red meter lead on the other side of the circuit breaker too, as they sometimes go bad, so checking both ways is good. If one diode gets a bad connection then it is a half wave (one rectifier) circuit so the voltage will be down slightly, and the current will be down by maybe half. These are the best chargers for our old cars, as they will charge a dead or weak battery. Newer chargers are so safety minded they will not charge unless the battery has some voltage. Also these seem to last forever. Minor issues can be fixed. I have not seen a bad transformer yet. Also, on the newer Schlumberger chargers with the circuit cards riveted to the heatsink (aluminum plate) I have fixed several just by drilling out the rivet, cleaning the area and screwing it back in place. Just corrosion under the rivet.😉 2 Link to comment Share on other sites More sharing options...
dodge28 Posted August 12 Share Posted August 12 I have noticed most times the problem lies at the wire connection to the clamp. Corroded,, loose or both. 2 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now