using a power supply to charge a battery.

Discussion in 'General Technical Questions and Answers' started by KC9NEQ, Oct 28, 2008.

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    From textbooks...and cloned into Wikipedia now I see:

    "Some chargers use pulse technology in which a pulse is fed to the battery. This DC pulse has a strictly controlled rise time, pulse width, pulse repetition rate (frequency) and amplitude. This technology is said to work with any size, voltage, capacity or chemistry of batteries, including automotive and valve-regulated batteries.[2][3] With pulse charging, high instantaneous voltages can be applied without overheating the battery. In a Lead-acid battery, this breaks-down stubborn lead-sulfate crystals, thus greatly extending the battery service life.[4]"

    I think the distinction here is that pulse charging actually heals sulfation, and helps prevent it from ever occurring.

    I've found CO batteries aren't much like automotive batteries, and I've never actually seen "regulated DC" chargers used, unless there's a PWM circuit between the DC source and the battery bank.

    Since the control system for a "smart" charger costs almost nothing and can be used to charge 100mA or 1000A batteries exactly the same, I cannot imagine why anyone wouldn't use it. And it works fine with completely unregulated, unfiltered supplies.

    WB2WIK/6
     
  2. K7JEM

    K7JEM Ham Member QRZ Page

    Do you currently work in the telecom field?

    Personally, I have NEVER seen a telecom charger that isn't a "regulated DC" power supply, of one sort or another. I also have never seen a PWM charger (as described) used in such an application, for many reasons.

    It wouldn't be advantageous to have a PWM charger in an application where what you actually need is a pure DC voltage, at a somewhat constant current.

    I think people here are confusing "charging" a battery with "floating" a battery. If the battery was discharged, and not being used, the PWM might be a good way to go. If the battery is powering sensitive electronic devices, like radios, computers, multiplex, etc, then a regulated and filtered DC is the proper way to go.

    Can you point to any source that sells a charger for float application that puts out something other than a regulated, filtered DC component?

    Joe
     
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    >Do you currently work in the telecom field?<

    ::Nope, not for about 20 years. I was on the authoring committee for NEBS, which was drafted by Bellcore (Red Bank, NJ -- now Telcordia), and all standards relating to equipment sites were part of that document and I believe still are.

    >Personally, I have NEVER seen a telecom charger that isn't a "regulated DC" power supply, of one sort or another. I also have never seen a PWM charger (as described) used in such an application, for many reasons.<

    ::What are the many reasons? We designed DC chargers, and the switchmode DC:DC converters that powered everything at COs and I can't think of a single reason why the equipment racks would require regulated power input: They're all rated -36 to -72Vdc input, which obviously requires just about zero regulation. The input needn't really be filtered, either, since the power converters re-create pure DC at their outputs. No equipment is directly powered by the -48V except for the converters, which couldn't care less what their input signals look like...

    -WB2WIK/6
     
  4. K7JEM

    K7JEM Ham Member QRZ Page

    There are lots of things powered by the 24 or 48 volt bank. Again, if you think someone is selling an unregulated, unfiltered charger for telecom float use, provide a link to the specs.

    I have never seen one. I have been to hundreds of sites with float chargers and batteries. NONE of them are unregulated, or unfiltered. The sites are all designed so that the batteries can be totally removed from the system, and it will continue to perform with no changes in output voltage or additional noise. This is necessary to be able to do proper battery maint, where straps between the batteries need to be occasionally removed, or when the bank needs to be replaced.

    Telecom people are very picky about the power supplies being used to charge the batteries. An unfiltered, unregulated supply just wouldn't be acceptable, whether or not it could run the equipment.

    Joe
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    >There are lots of things powered by the 24 or 48 volt bank.<

    ::What are those? If any circuitry is directly powered by 24 or 48V, things have certainly changed. And I'd be really surprised, since everything today is solid state and most of that stuff should be running at 5V or lower, which of course requires the use of secondary DC converters between the battery bank and the actual circuitry. What, exactly, is directly powered by the 24 or 48V?

    >Again, if you think someone is selling an unregulated, unfiltered charger for telecom float use, provide a link to the specs.<

    ::I have no idea if they are, or not. I can call one of my old Bellcore buddies to try to find out -- he's still with the company.

    >I have never seen one. I have been to hundreds of sites with float chargers and batteries. NONE of them are unregulated, or unfiltered. The sites are all designed so that the batteries can be totally removed from the system, and it will continue to perform with no changes in output voltage or additional noise. This is necessary to be able to do proper battery maint, where straps between the batteries need to be occasionally removed, or when the bank needs to be replaced.

    Telecom people are very picky about the power supplies being used to charge the batteries. An unfiltered, unregulated supply just wouldn't be acceptable, whether or not it could run the equipment.<

    ::They can be as picky as they wish, but AFAIK (and if someone here has other information, let's hear it), Bellcore GR-63-CORE still governs all requirements for Telco gear in the United States and that document, parts of which I authored myself, have absolutely zero requirement for using anything regulated before the actual equipment installed DC power converters. The NEBS document does call out a lot of standards for equipment protection from lightning and transients, EMP, RFI, etc; as well as standards for equipment grounding, avoidance of grounding loops and induced AC currents; radiated and conducted emissions for electromagnetic compatibility; and lots of stuff, but those are all generic and you can use whatever methods you wish to assure you meet them. Simple "rectifier" supplies without filtering or regulation actually meets most of these requirements much easier than complex regulated supplies would, due to simplicity. That's one of the reasons they were used almost exclusively back in the 60s when the standards were being drafted for conformity.

    73

    Steve WB2WIK/6
     
  6. K7JEM

    K7JEM Ham Member QRZ Page

    Don't know anything about those standards, or if they even apply. The standard that is used is what the battery manufacturers and equipment manufacturers specify. I have never seen any sort of "charger" for these batteries that was not regulated and filtered. How would a technician be able to take the batteries offline?

    I was a kid in the 60's, so I don't know much about that. I started working in the telecom industry in the late 70's, but a lot of the chargers were 60's vintage.

    A lot of telecom equipment is made to operate over a specific voltage range, with specific filtering requirements. I'll guarantee you that all of our sites have very well filtered, low ripple, DC busses. You won't see much of anything on them if you look at a scope that is AC coupled.

    Joe
     
  7. K7JEM

    K7JEM Ham Member QRZ Page

  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    >K7JEM;1382165]Don't know anything about those standards, or if they even apply.<

    ::They do, I just looked it up. NEBS is the Network Equipment Building System standard and governs all hardware specifications for CO equipment. It's still effective, and all connected hardware must meet the standard. If you manage a CO and are not familiar with the standard, that's a little bit surprising, but maybe not because many Telcos are big enough that they would have Compliance Engineering departments handling equipment selection, installation, compatibility and compliance issues -- all of which must be in accordance with the standard.

    >The standard that is used is what the battery manufacturers and equipment manufacturers specify. I have never seen any sort of "charger" for these batteries that was not regulated and filtered. How would a technician be able to take the batteries offline?<

    ::We did that all the time, works fine. Again, since the 48v bank never directly powers any system electronics at all -- and all power supplied to the electronic circuits comes from DC-to-DC converters which regulate the 48v down to 12v, 5v, and 3.3v bus rails to actually power the circuitry -- it doesn't matter if the batteries are present or not. The converters present in all NEBS equipment (the racks themselves) will accept unregulated and even unfiltered DC at any rail voltage from -36v to -72v, by the standard. They convert that to pure, very smooth DC at the bus voltages required. I cannot figure why either 24v or 48v would ever need to directly power any circuitry.

    >A lot of telecom equipment is made to operate over a specific voltage range, with specific filtering requirements. I'll guarantee you that all of our sites have very well filtered, low ripple, DC busses. You won't see much of anything on them if you look at a scope that is AC coupled.<

    ::You wouldn't see any even if the chargers weren't filtered because the x2, x3, x4 etc. input filters in the DC converters smooth everything down to a noise and ripple free rail. And of course if the battery bank is actually present, it's a bigger filter than any amount of capacitance would be!

    WB2WIK/6
     
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Typical medium/high powered NEBS power supply:

    http://www.cisco.com/en/US/products/hw/routers/ps368/products_data_sheet09186a008020ab4b.html

    This takes -48v nominal input to deliver a bunch of filtered, regulated outputs. Even includes a 42v output which can be used to source other power converters downstream.

    Because it handles the task of regulating whatever's thrown at it on the input rails, it's not picky about the signal quality of those rails. I have the whole manual on this supply...it can withstand +/-5v input ripple and still meet its specifications.

    WB2WIK/6
     
  10. K7JEM

    K7JEM Ham Member QRZ Page

    I don't manage a CO. I mange lots of remote microwave and radio sites. Maybe what you're talking about is only applicable to certain types of telephone exchanges. It seems these things apply to RBOC's mainly, and have to do with physical and environmental issues. Regardless, I don't think any telecom provider would have a battery plant that was not fed by a good, regulated, filtered charger (as linked above).
    We have lots of stuff powered by the 24 volt system. Some of it doesn't want to see raw, unfiltered voltage, or large swings in voltage. But again, we don't fall under NEBS. The fact that you can't provide a link to anyone that actually makes a charger for telecom like you describe is telling.
    Again, what happens when the batteries are taken off line? I would really like to see some of these specs on the type of charger you're describing, and that it is specifically designed for telecom use. I haven't been able to find one, but several manufacturers make similar items to the one I linked to.

    Joe
     
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