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Caring, Feeding and Enhancing UPS Battery Systems? 50

Posted by Cliff from the energizer-bunny-can't-top-these dept.
cdn-programmer asks: "I've got a couple UPS's that are now about 5 years old. They are MGE EL4 units - rated at about 450VA /280W. These originally came with a battery rated for 2x6V - 7.2Ah I've found an inexpensive replacement battery: SBS60 rated at over 50Ah and I've done a little mod so the unit 'fit' together. I've also done as much reading as I can on float currents and ripple currents and so forth basically covering the care and feeding of your UPS battery system. People can find some good information in the SBS web site and the specific data sheets are here. Look under the SBS section for the manuals. If people find alternative batteries there seems to be some excellent tech specs here. Having read these it seems to me that there should be no reason that I cannot 'redesign' the UPS to give it a significantly increased power reserve. The load is the same... the only difference is that a larger battery is used so this means that the recharge times will potentially be much much longer. So what? We are not interested in cycling the battery. Indeed the power here is quite stable and we get very few outages per year."

"Now - the SBS people have been very professional and have provided good technical engineering data. I haven't been able to find much data on the MGE EL4 and I wonder if this cheap little UPS has the proper smarts to take good care of my new battery? If it does not - then why not and what models/manufacturers should we be considering?

For instance, what is the ripple characteristics of the EL4 and how can I measure it? Since the SBS60 is HUGE in comparison to the original batteries (Panasonics - 7.2Ah - 2x6V) is ripple even something to worry about?

Does the EL4 charging system 'cycle' in a harmful way? I tested the float voltage levels and found that they varied from 13.89 to 13.42 over the course of a day. But this battery has only been hooked up for a day so maybe its stabilizing. The nominal float should be 2.27 per cell according to SBS so that works out to 13.62 for the battery.

Does the EL4 have a temperature sensor? This is something else that the charging system should do according to the SBS people because optimal float voltage varies with temperature.

Finally, I'm interested in doing a load test to determine how healthy by batteries are. I'm thinking that a very simple test can be a couple lamps - say 100 watt - that can be plugged into the UPS. Since I've never done anything like this before the thoughts in my mind are that all I would need to do is take a voltage reading say every 5 minutes over the next few hours and if I can find the proper curves this should yield enough data to determine the life expectancy of my battery.

If anyone has actually done tests like this it would be wonderful if they could tell us how to do this."
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Caring, Feeding and Enhancing UPS Battery Systems? More

Caring, Feeding and Enhancing UPS Battery Systems?

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  • First of all, you need to know how batteries work [howstuffworks.com]. The main thing to take away is the ion transfer from anode to cathode. This is vital in understanding what temperature sensor you need.

    After you've read that, you'll need to get additional information on rechargeable batteries [sciencenet.org.uk]. Note that that page talks about nickel oxide batteries but the information applies to lead acid batteries such as you find in a typical UPS (and cars, for that matter).

    It is also crucial to understand that the battery is an el

    • Physics genius is a known troll...i'm inclined to agree with those who call his post irrelevant
    • Note that that page talks about nickel oxide batteries but the information applies to lead acid batteries such as you find in a typical UPS (and cars, for that matter).

      Rechargable batteries of different types have different characteristics. Beyond the most general platitudes, Nicad-type batteries are very different than led acid. and even the two families can variy between themselves. I managed to find a number of good books in the library about rechargable batteries that described the differences well

      • I remember my chemistry teacher shorting the two terminals of a car battery with a coat hanger. After a few seconds the coat hanger was glowing bright read, before 15 seconds were up the metal was burning and throwing off sparks. He pulled it off when it started to melt (<40 seconds).

        Car batteries are designed to source a kilowatt or more for the starter motor (moving all that metal takes a fair bit of energy), so this shouldn't be too suprising.
        • They usually measure starter horsepower in kilowatts. If I remember right, a starter in my Honda was rated at 2100 watts, or about 3 horsepower (746 watts per horsepower by definition.) You should get several hundred amps from a good charged car battery when shorted. The speed of the chemical reaction is the limiting factor. High amperage batteries tend to have the plates thinner to pack more in the same place for more amperage generating surface area. Duty cycle is limited due to heat that can make th

  • Larger batteries = more charging current/voltage (Score:4, Informative)

    by RobKow ( 1787 ) on Friday June 20, 2003 @10:17AM (#6253377)
    Larger batteries draw more charging current at a given voltage than smaller ones. Depending upon the charger configuration in the UPS you could either end up undercharging the battery or shortening the life of the charger by increasing power dissipation in it.

    I've seen car batteries work connected to small UPSes for years until the power went out for an extended time, the battery was significantly drained, and the charger failed when the power came back on. Just something to be aware of.
    • A clarification:

      A proper "universal" charger design (which I wouldn't expect to see in a UPS that doesn't accept add-on batteries) would charge properly, but more slowly.
    • UPSs are usually designed with base electronics that would work across a range of capacities (i.e. battery sizes). if you have a UPS of a given size, you should be able to use batteries a good bit larger than what you've got and still get good results.

      Car batteries, on the other hand are probably getting into a completely different scale of size. I'm not terribly surprised that the charger would fail going to that capacity size. It's It's like the difference between putting a small U-Hall trailer on yo

  • A couple of problems... (Score:5, Informative)

    by stienman ( 51024 ) <adavis&ubasics,com> on Friday June 20, 2003 @10:28AM (#6253500) Homepage Journal
    The only issues you'll have to deal with are

    Smaller chargers are not meant to charge larger batteries - you may well be overstressing your UPS charger by expecting it to charge your new, larger battery for so long.

    Lead Acid batteries and their variants (gell-cell, deep cycle, etc) do NOT like to be discharged more than 50%, yes, that includes so-called deep cycle batteries. Deep cycle means that deep discharges won't hurt the battery as much as it would hurt a regular gell cell, but it'll still be damaged.

    Most consumer and low end UPS systems do NOT monitor battery temperature. They simply charge the battery so slowly that there is little risk of overheating, boiling, or overcharging.

    Cycling the battery with light bulbs may not be a good idea, because many UPS systems allow more than 50% battery discharge. You'd have to monitor the voltage, then shut it off when it drops below 11 or 12v.

    Light bulbs will not pull power the same way your computer will, so the best load test is the real load you intend to use. a 400W powersupply doesn't draw 400W. Depending on how you measure it, it may pull more or less from the AC line (read about Power Factor and power factor correction). This is one of the reasons these supplies are rated in VA and not Watts. Of course, the real question is, Why? When you have few power outages, what is the reason to use such a large capacity battery, but more important, why do you even need to characterize it?

    Lastly, make certian you aren't pulling more current than the supply is regulated for. As you suggest a larger battery does not make it more able to handle larger loads. You'll be tempted in the future to add more stuff because 'it should handle it', but it'll only make it fail faster.

    -Adam

    • Re:A couple of problems... (Score:1)

      by Anonymous Coward
      Is there any way to take a reading of the power drawn by an electric device ? For example, plug the device between the power outlet and the electric appliance you want to rate and then take the reading ?

      • Is there any way to take a reading of the power drawn by an electric device? For example, plug the device between the power outlet and the electric appliance you want to rate and then take the reading?

        If devices like this [realgoods.com] are being marketed to (albeit a niche of) homeowners, I wouldn't think it'd be too difficult to find something similar that has a more informative readout.

      • You can get both in-line and clamp-type meters. Clamp-type meters are designed to go around one (only one) of the power-lead wires to your appliance. They measure the current indirectly. to use it, you will probably need to build a special purpose extension cord (i.e. strip the outside shielding to expose the 3 separate cables. You can get either purpose made meters, or add-ons for your general purpose multimeter (they're designed to provide a straight-forward translation between resistance (I think) and a
      • A multimeter?
    • Lead-acid batteries have a really nice charging curve, so you don't need to do anything special to charge them. If you hook them up to a power supply that supplies their rated voltage, they will charge automagically. Once they are charged, their voltage will rise and the current will stop flowing. How do you think your car battery gets charged? Hint: there is no special charging circuit in cars.

      Also, having few power outages has nothing to do with having a large battery. With a large battery, your com

  • Stay close to the same battery (Score:3, Informative)

    by kawika ( 87069 ) on Friday June 20, 2003 @10:37AM (#6253587)
    If the batteries are that old, they most likely are not holding a good charge. I would replace them.

    I would stick with batteries that have similar specs.The charging and inverter circuitry on the UPS expects something in that neighborhood. Those are probably gel-cells which are very common for UPS and other applications like alarm systems. Sounds like the two 6V batteries are connected in series, you could go with a 12V battery which may be easier to find. It depends on the physical dimensions.

    I changed the batteries in my APC UPS for $50 using two batteries from batteries.com; APC wouldn't even sell me replacement batteries. They wanted to offer a small tradein allowance on a new unit that would have cost me $400.

  • Overheating on long use is the issue. (Score:4, Informative)

    by Futurepower(R) ( 558542 ) on Friday June 20, 2003 @10:50AM (#6253743) Homepage
    UPS units are often cheaply and poorly designed, especially the older ones. The ONLY issue is whether the unit would overheat with the longer time of use that is possible with a more powerful battery.

    Earlier posters mentioned that a bigger battery would draw more current at a particular charging voltage. This is true, but irrelevant. The chargers are designed to be constant-current, or close to it. The current drain does not depend on voltage.

    I've powered a telephone answering computer from an 18 volt UPS using a 6 volt and 12 volt car battery in series, with no problems. However, the unit was arranged that there would be much more air flow for cooling than it would normally get.
    • We have a winner. :)

      I agree, the main thing is that the designers of the UPS were expecting a certain length of operation, given the normal battery of the unit, and therefore lie about specs.

      An example:
      A 500VA UPS is rarely able to handle 500VA continuous and sustained for long periods of time. The battery it comes with might give only 5 minutes of usage at full load, so the designers usually cut corners and just made sure it wouldn't overheat in 5-10 minutes at 500VA, but that's about it. Run the unit
    • Earlier posters mentioned that a bigger battery would draw more current at a particular charging voltage. This is true, but irrelevant. The chargers are designed to be constant-current, or close to it. The current drain does not depend on voltage.

      It depends on the charger. constant-voltage is generally considered to be better for the battery (good chargers will provide different voltages at different stages of the charge cycle). Constant-current chargers can be easy to build and won't burn out with lar

  • My two cents (Score:4, Informative)

    by fruity_pebbles ( 568822 ) on Friday June 20, 2003 @11:11AM (#6254004)
    UPS batteries usually don't last more than two or three years. Test on a regular basis, or just buy new batteries every two years. Heat kills UPS batteries. A lot of UPS's connected to desktop PC's are sitting on a carpeted floor under the desk. That carpet makes wonderful insulation that helps keep the batteries nice and warm. Put the UPS somewhere that has good airflow all around the UPS's case. I simply laid a couple large pens under either end of the UPS to get it an inch or so off the carpet, and that works fine.
  • My quick translation of your question is:

    I put this huge-ass battery in my tiny UPS. How do I prove to myself that it still works right?

    Answering that question is difficult. I realize that you probably got a good deal on your new battery, but you could've gotten a good deal on a correctly-sized replacement battery too and avoided the problem.

    You also write:

    Indeed the power here is quite stable and we get very few outages per year.

    The big battery *will* help with longer outages, as

    • My quick translation is:

      I have a few old UPS units to which are attached a handful of dual-power-supply servers and a laserjet printer. For some reason the UPS would beep whenever I printed a report, which is annoying, and it has now gotten to the point that one of the servers bounces midway through any longer print jobs. I've decided that adding batteries and modding the unit is the most cost effective solution for my employer.

      Move the printer. Do not test with lightbulbs.

      If your server gets fried --

  • What exactly is the question ? (Score:2, Funny)

    by Anonymous Coward
    It sounds to me like you did it. You took a battery of roughly the same capability and stuck it in the UPS.

    You should test it a bit with computer, not just a lamp. I plug in a "test" system and my biggest monitor, check to see that the system hasn't rebooted a couple of days later, yank the plug and see that it stays up long enough for me, and maybe repeat the process once. I sniff for burning wire insulation as I do it.

    I get small UPS's for $5 at the Goodwill Computer Works in Austin, and they usually

    • Re:What exactly is the question ? (Score:1, Informative)

      by Anonymous Coward
      I'll add one thing. When you connect the new battery in, be sure to use BIG wires. Lamp wires or even thin entension cord wires will get hot and melt the insulation off them. Get the thick multi-strand copper wire used as grounding wires, you can get it in auto parts stores and hardware places. Insulated of course, there are grounding wires that aren't. The connections at each end must be very good to handle the current; get the little copper tabs you can wrap around the battery posts and clamp down wi
  • I have been asked to fix a number of UPS's and set up hugh battery banks for telcom. carriers with very large UPS's, and I've observed a couple things.

    FuturePower (above) was right, every UPS I've seen has current limited charge circuitry. Not because they are anticipating larger battery packs, but because that is the easiest way to do it.

    The cheap systems just had a current limiter on the float charger. They tried to bring the battery to some float voltage (let's assume a 12V system) like 13.6 and li
    • The problem with this, is that if the power goes off while you're away for a couple days, the fan will drain the batteries flat (bad for the batteries, but not dangerous).

      If he's like me and leaves the computer on while away (and doesn't connect the serial cable from the UPS to the computer), doesn't really matter :)

      This brings me to a question... and I'll admit I haven't researched it much... what UPS-monitoring software have people been successful in using under Linux, and which UPS's did it work with?
      • > what UPS-monitoring software have people been successful in using under Linux, and which UPS's did it work with?

        --Belkin UPS that I bought from Circuit City comes with Linux software but I'm not sure if recommending it is a good idea... Their Xwin monitor comes with a memory leak. :( I did notify them by email but that was like a year ago and I highly doubt they've done anything about it.
      • NUT!

        Network UPS Tools.

        I use it with my APC SU1400RM, and couldn't love it more. client / server design, nice looking CGI front end, easily extensible. Its great.

        --
        lds
    • Your article reminded me to test the 68Ah worth of batteries I added to my SmartUPS 1400 five years ago.


      I have a similar set-up (SmartUPS 1400 Rackmount) but I'm having trouble getting more than 5 minutes of run time at 50% load. Front-panel calibration doesn't fix this. Was there any undocumented calibrating you had to do?
      • Just don't rely on the APC sizer online. They claim something like 7 hours runtime for the APC 1000XL with a UX24BP(the monster battery pack). Actual runtime at the load specified is just over 3 hours.

        APC claimed it was because of the APC power bars plugged into the unit.
      • Compwizards point is a good one. These things do not size like they're supposed to.

        It think part of it is the fact that the batteries are rated to a much lower drain than the UPS can use them (like rated for a drain down to 9 volts when the UPS kicks off at 11) and that the UPS step-up powersupply has significant inefficiencies.

        When I first got it. With that weaselly little battery that comes in side it, I got ~35% load (which is only 350w) for about 9 minutes. So, you're not far off the mark here.
        • I live in a rural area and we usually have around one 1-hour+ outage per year.

          Regarding the why: My ISP's POP for the local phone exchange is located in my basement. In return for providing power and rack space, I get T1 access. <Really Big Grin> (Their equipment on my UPS is a "temporary" situation, but I'm not complaining.)

          The extended run time is necessary because there are usually customers who aren't affected and want to be on-line. (Even in the middle of a lightning storm.)

          The UPS is repor
          • Then it looks like it's definitely misbehaving. If the voltage just before shutdown is 26-27 volts then you definitely need to adjust the shutdown threshold. The voltage just after shutdown should actually pop up to this range if the batteries aren't discharged (which they don't seem to be), but the voltage output of an unloaded battery is a poor indicator of it's state of charge.

            On a typical 12V battery under medium load (say one that would take an hour to drain it of it's rated amp hours), 10.8 volts
  • These originally came with a battery rated for 2x6V - 7.2Ah I've found an inexpensive replacement battery: SBS60 rated at over 50Ah and I've done a little mod so the unit 'fit' together.

    I can see two problems with this setup. One is the oft-mentioned capacity of the unit to handle a long-term outage and/or the resulting charge cycle (possibly fixable with bigger heatsinks).

    The other is that you're talking about a 7-1 capacity ratio for the replacement battery. I'm guessing that the UPS may not recogniz

  • a friend gave me an old tripplite BC500LAN that was dead.
    Or so he thought. I opened it up and discovered that the SLA batteries were swollen and some had split open.

    I watched ebay carefully and found direct replacements for about $7 each plus shipping. So, for under $30 I got a killer UPS. just get the model numbers from the internal batteries and find them on ebay..

    mailto:spammesilly@gt.rr.com [mailto]
  • APC will politely tell you to not even think about it.

    Had an older unit that used something like 15 AH battery, and asked them about using the panasonic replacement which was something like 17ah. they wouldn't talk to me at all beyond saying no it can't be done.

    But then again, considering they don't care about the security holes in their powerchute plus 5.02 software either, I'm not all that surprised

  • oh yeah (Score:3, Interesting)

    by pair-a-noyd ( 594371 ) on Friday June 20, 2003 @02:51PM (#6256323)
    one other thing.

    Take an OLD PC case and fill it with whatever size batteries you want, wire them in parallel and run the cables into your UPS. Wire the external battery pack into the UPS in parallel.
    The voltage must remain the same but you get more amp hours this way. You can also use batteries that are physically larger that normally won't fit inside the UPS.
    You can get LOTS of run time this way, hours and hours of run time..

    mailto:spammesilly@gt.rr.com [mailto]
  • As has been alluded to by others, these little UPS systems are generally not on-line systems, meaning that the inverter is not normally supplying power to the load. When you operate the inverter for longer than 15 minutes, you will likely over-heat it.

    One thing people fail to mention, though, is the expected life of the batteries. Usually, you will only see these batteries last 5 years if you never use them. If you deep-cycle them, don't expect more than 10-20 uses! Short (...unless it catches fire.

  • Depends on the UPS (Score:3, Informative)

    by Andy Dodd ( 701 ) <atd7NO@SPAMcornell.edu> on Friday June 20, 2003 @03:50PM (#6256986) Homepage
    Lead-acid batteries are generally not too finicky about charging. The worst thing for lead-acid batteries, as others mentioned, is deep cycling. A 50AH battery will last for MANY more charge/recharge cycles than a 7 AH battery if the outage frequency/length remains the same, as the battery will be discharged to a much smaller portion of its capacity.

    If anything, with almost any battery chemistry, charging a battery with a charger designed for a lower-capacity version of the battery at the same voltage will rarely be a problem. It will, of course, take MUCH longer to charge.

    Typical lead-acid charging schema: Constant current with a max of 14.5 volts or so. The charger will somehow detect end-of-charge and switch to "float" mode, which is typically 13.8 volts constant voltage for a 12V battery. Constant voltage at 13.8 with a current limit is perfectly safe. Note that if the charger is REALLY dumb and doesn't have a current limiting circuit (almost all do, even if it's as simple as a resistor), a 50AH battery could overload it.

    NiCd and NiMH batteries require the most sophisticated end-of-charge detection. This entails reading the battery voltage during brief pauses in charging - NiCds and NiMHs will actually start DROPPING in voltage if charged past their max capacity. No end-of-charge detection is needed if you charge them slowly though. (C/16 or slower. i.e. if it's a 1600 mAh battery, if you charge it at 100 mA, you can leave it on for hours past full charge, but you want to take it off eventually.)

    Li-Ion: These aren't really that hard to charge. Constant-voltage at 4.1 or 4.2V/cell with a current limit is all you need. I know people who charge Li-Ions with benchtop lab power supplies (current/voltage limits adjustable). The real trick with Li-Ion is that pack protection circuitry is an absolute must. Short-circuit = BOOM. Overdischarge = Dead and useless pack. Charging beyond 4.1 or 4.2v/cell = Dead and useless pack.
  • I took a 1250va APC UPS with dead bateries, stuck 2 "lesiure" batteries (caravan style, so more likely to be ok with deep cycle) underneath it, and the thing runs like a dream.

    I get at least a good 4 hours battery life out of it, and I think more if I left the monitors off of it.

    The charger seems to cope ok, although it does take a long time to fill these batteries.

    BTW, the original batteries were something like 20ah and I replaced them with 85ah batteries. They also have a nice design where any gas is e

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