24 volt regulated power supply

[aboonski]

I just came across a power supply that I have had in storage for years and decided to wire it up to see if it works. I got this back when I was assigned to the USAF Hospital Homestead, Homestead AFB Florida back in the early 80's At the time they were renovating the biomedical laboratory and new equipment came in to replace the old; this power supply ran one of piece of equipment (no idea which one) but it would up in the dumpster. I used an old power cord from a washing machine that I scrapped out which had the ground wire in the center, added some solderless connectors and hooked the thing up - it works great! Voltage output is a steady 24.2 volts. I plan to use it to test out 24 volt items (like headlight bulbs, lift pumps, tail light assemblies, etc.). I thought about using it for a 24 volt battery charger but it would not work unless it were slightly higher in voltage. It does put out 5 amps though which should provide enough power to test almost any 24 volt item - with the exception of a starter of course! I'll provide a photo of the data sticker.

 

[papakb]

aboonski,

Kepco made a pretty good power supply and for simple testing it'll work just fine. Be careful if you go to power up some radios though as they are going to need more than 5 amps.

Most battery chargers have a current regulator circuit in them that this supply doesn't have. It measures the output voltage of the supply as the battery charges and cuts back the current as it reaches full charge. 5 amps isn't a lot but if you left it on a bettery too long you could cook it.

 

[aboonski]

Thanks so much for the reply and advice regarding the use of the power supply. I recently had one of those Harbor Freight (HF) "float chargers" go bad (the transformer overheated and died). I needed a float charger right away so I cut the little in-line regulator box off of the HF charger and spliced it onto another transformer with a .05 volt deviation - I think it is a 14 volt unit and the one that HF uses is 14.5 volts. I am guessing that little device does something to taper the charge but not really sure what it does. Trying to rejuvenate a couple of Interstate 6TLs but not having a lot of luck. I have heard these were lousy batteries and now I know for sure that they are! Unfortunately I don't have any military radios or much of anything that runs on 24 volts other than bulbs and an occasional electric fuel pump. I did not see a reset button on this power supply so I will have to be really careful about maxing this thing out with high amp loads..

 

[tennmogger]

Most battery chargers, even the ones that have some 'smarts', use a 'soft' transformer as a source. The transformer is made to NOT stabilize voltage, and the voltage will sag as current increases. The result is the charger runs at rated high current (depending on battery voltage and internal resistance) until battery voltage raises to match the peak output voltage of the transformer. Then it "automatically switches" (as the advertisements say) to trickle charge. The process is actually voltage equalization between the battery and the charger.

If you measure the unloaded voltage from the charger, it'll be higher than you think it should be because it's not under load. To measure that peak voltage, however, you have to put a little capacitance across the charger to act as a peak reader for the meter. Otherwise the meter will tend to measure average voltage out of the charger because the voltage swings wildly as the 60Hz cycle varies.

A cheap charger needs nothing more than the transformer, a diode as a rectifier (but could be half wave, full wave, or bridge type) and self-protection devices like inline resistance, or a circuit breaker (thermal cutout types are common).

On the other hand, a power supply intended to provide a regulated voltage output (like the power supply being discussed) uses a transformer that has enough iron in it to stabilize the output voltage somewhat on it's own. Then the voltage is rectified and regulated. Some regulated power supplies are quite sophisticated.

To use a regulated power supply as a battery charger several things are needed. First, the voltage has to be high enough (as already pointed out) to force current through the battery. Second, a diode really should be included, in series, because the regulator in the PS might allow the current from the battery to back-feed into the PS, cooking it. Third, some series resistance. I use a 1 Ohm resistor (high Wattage) for this for low current charger.

The unloaded/regulated voltage out of the PS could be set at 13.8 v plus about 0.6 volts (drop across the series diode), for about 14.4 v, (a good long term float voltage for the battery is 13.8 v). Add half a volt to that if the PS is only used to fast charge the battery.

Hope that helps.

 

[steelandcanvas]

Nice little power supply, and a good price too! You might want to fuse the output with a 5 amp fuse, just to be safe. Look at Northern Tool for Battery Minder. Very good charger, maintainer, conditioner, desulphater. There is a thread about chargers also.

 

[aboonski]

I just typed out a nice long reply to two of the members who added comments to my thread and when I went to post the reply I had to "sign in" again which resulted in the loss of everything that I wrote. This has happened before and normally I copy the text so that I can paste it back in the quick reply area again. Does this happen to just me or what?

 

[steelandcanvas]

Try again, if was that long, it must be a good read!
Never had to sign in mid-post. Zombies.

 

[aboonski]

For several days now I have had one of my Interstate 6TLs charging with a schumaker 1.5A Battery Maintainer units that never seems to move from the charging mode to the fully charged mode. At least two of the cells in this battery are weeping electrolyte and it appears that the other cells are bubbling pretty well. Took a reading of the voltage and it was 12.41 volts which is pretty good I think; not sure if it will put out the amps needed to turn a deuce motor but probably would. The other 6TL is about the same now - I alternate between the two with the Schumaker after they have been charging for a couple of days then use the float charger to maintain the charge accordingly. Like I said, these are Interstate 6TLs and I rarely hear positive feedback about these batteries from other SS members. Right now I am using the batteries out of my MEP002A genset in the battery box of the deuce and they crank the truck without hesitation - these are Royal batteries by the way.

The technical detail that one of you went into was jut amazing and I plan to copy and paste that info to put into one of my reference books that I have to keep around because my memory is starting to fade anymore. When I owned a lot of Triumph Motorcycles years ago all of them came with a Zener Diode which basically was the voltage regulator for the charging system; supposedly it burnt up the power over 12 volts but that was not always the case when these things went bad. I have a lot of take-out parts (capacitors, diodes and rectifiers) from old military equipment to experiment with in order to fabricate a homemade battery charger but lack the basics of electronics to do so. I'll have to post a photo of some of the industrial grade diodes (or are they rectifiers?) that have what appears to be battery cables coming out of the base of them. I'm keeping this stuff for some reason and hope someday to learn that I have the parts necessary to assemble a "flux capacitor" like they had in that movie "Back to the Future" (just joking).

I will go by Northern Tools (right close to where I live) and will check out that Battery Minder because I do need another desulphator to use with the dual battery systems that are used on all of my military equipment. The solargizer worked on deuce for a while then, for some reason, went bad on me. I don't drive the deuce a whole lot anymore so I was really disappointed when my investment in those Interstate 6TLs went south way before I expected!

 

[aboonski]

Diodes or Rectifiers?

Here are a couple of photos of the parts I was referring to. They came out of a huge military power supply.

 

[steelandcanvas]

I will go by Northern Tools (right close to where I live) and will check out that Battery Minder because I do need another desulphator to use with the dual battery systems that are used on all of my military equipment.

Aboonski, I have had excellent luck with the Battery Minder. I bought the large 24 V unit Model: 24041 to charge, and then a few of their small desulphater/maintainers Model: 12117. Before you go to Northern Tool, check out VDC's website, if you are not familiar with those paticular units. Shop around, Northern doesn't always have the best price. Hope this helps.
Battery Chargers by BatteryMINDers.com

 

[Speddmon]

Here are a couple of photos of the parts I was referring to. They came out of a huge military power supply.

This is unrelated to your post, but the diodes you have a picture of can be useful for other things, If you have an old Lincoln "buzzbox" AC welder like I do. I made some heat-sinks and used some large amperage diodes similar to those to make a bridge rectifier for the welders AC output to convert it to DC. Now my AC welder can be either AC or DC. I'll grab a picture of it down the road sometime and post it up.

 

[aboonski]

SPEDDMON!!!! Actually it IS related because I have been trying to find a use for these things and just happen to have an old Sears buzz box in my garage. Show me whatever you have in regards to converting AC to DC! Do you still have your Lube Trailer?

 

[aboonski]

Steelandcanvas, I'll definitely look into the model 12117 units next time I am over at Northern. Not sure if my 6TLs have sufphated plates but they probably do. Most battery failures are because of that problem. Thanks for the info!

 

[cbvet]

aboonski,
That power supply will be handy to have for light loads.

Keep in mind, that you can always wire two 12 volt power supplies in series if you need more amperage. If they are different amperages, you will get the output amps of the lower rated unit.
A good source for 12 volt power supplies is an RV repair service. Many campers use a power supply with 2 load circuits.
One circuit puts out "pure" 12 volts for running radios, etc. The other circuit puts out 13.5 - 14 volts for battery charging.
Typically, just one of the circuits will "burn out", & the RV owner wants the unit replaced. Especially if it's an insurance job.
The other circuit is still good.
I use a 35 amp & a 40 amp in series, & get 35 amps at 24 volt for testing fuel-burning heaters & such.
Just remember to isolate the two units so the chassis don't touch!