Slashdot Mirror
Caring, Feeding and Enhancing UPS Battery Systems?
"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."
After you've read that, you'll need to get additional information on rechargeable batteries. 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 electric, not an electronic, device. So there's no way for the battery itself to report to your server that it is getting low on power. You'll need some after-market monitoring electronics hooked on there that will sense how the battery is doing and will function as a middle man to your PC.
Another important issue is sinewave capability. If your UPS can't put out a sinewave voltage, you should probably avoid it.
Can anyone add anything to that?
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.
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
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.
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.
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.
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.
Where's a link to YOUR clear and concise answer to the question? Oh, you don't have one? Then STFU.
doesn't fool me.
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 your car and trying to pull something that would normally take an 18-wheeler.
Free Software: Like love, it grows best when given away.
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:
The big battery *will* help with longer outages, assuming it (ever) gets fully charged and your UPS will stay up that long without overheating. Lots of UPS's are pretty sadly designed for only intermittent use.
It sounds to me like you did it. You took a battery of roughly the same capability and stuck it in the UPS.
;) . If you are really stingy the bad ones can sometimes be resusitated by charging them on trickle charge for several days, then draining the acid (pour it on ant hills) and replacing the acid. I think what you are doing is dissoving some of the impurities that plated the internal plates into the acid, and then pouring it off.
;)
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 have a bad battery. I recycle the battery (they pay you like 25 cents) and get a car battery for the big systems and a lawn tractor battery for the smaller ones. Walmart has as good prices as any; you can also steal old batteries from the place where people return them at Walmart or an auto parts store, these batteries are often good enough to back up a computer even if they won't crank over a high compression V-8
With these methods, you don't really need to worry about melting the circuitry by pumping more current through it for longer than it was designed for. Just get more $5 backups and $20 lawn tractor batteries. Much cheaper than what they try to sell you new.
I generally don't put the case back on the battery backup because it doesn't fit. Instead I just put the UPS and battery sitting next to it in a retangular plastic tub, the kinds of things that look like giant tupperware containers. I get those from the dumpsters of restaurants. I put two slats of wood (the wooden stake from those junky plastic road signs, you know the $1500-$3000 mo. FT/PT kind, works great) in the bottom so if acid does leak I will notice before everything has been sitting in it for a while.
P.S. Since I mentioned that I am in Austin, I'd just like to say that I don't work at any of the big co-lo places here, this is all for my own use and a few small businessmen for whom I do monthly computer janitor type stuff. Just in case any of the twitchy types start worrying that their precious servers aren't on a backup that's "white" enough
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.
:) ) and see how it performs.
/. so we can buy them up off of ebay.
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 limited the current to an amp, and that was it. This of course is a lousy way to charge the battery, that will take forever to get it to a full charge, but it's cheap and easy.
The better systems were dual mode. They would set a higher target charge voltage like 14.5 until and limit the current to something like 6 amps until the current dropped down to a couple amps, and then kicked over to their float mode for the last bit of charge. These systems recover properly and well.
If the voltages match, I would try it out, with the actual equipment (you are using the ext3 file system right
The only two things that you might want to tweak are float voltage and cooling.
You'll be very lucky if there is a POT (varible resistor with a screwdriver or thumbwheel adjustment) that lets you adjust the float voltage. If there is, please post the make and model to
If not, you'll probably have to have someone who knows his electronics look at the charger stage and tell you where the adjustment resistor is. It may be the only 1% (always five striped, often blue) resistor in the charging circuity. If you can spot it, my favorite trick would be to use two of the pin-cups from a machine pinned socket and solder them in where the resistor was, then you can try several resistors just by forming their leads and jamming them in.
The whole "float voltage varies by temperature" issue is important for a remote mountaintop installation, but if this is going on your home, do the calcs for 70 degrees and leave it. The variance between 60 degree nights and 80 degree days isn't going to have any measurable effect on your battery life.
The other issue is cooling. As others have pointed out, the engineers that were selling a UPS to operate for five minutes at a particular load can safely choose (cheaper) components that will overheat in 10 minutes. The quick and dirty fix for these is a fan. Easiest way to hook it up would be to use a double pole relay with a 120V coil and contacts rated for at least 12V (they will probably be rated for much more, but that's ok). You choose the connections such that when the relay is energized it opens the circuit. If you use a 12V battery, then the circuit is a 12V fan connected to the 12V battery with the relay in between. When power is on, the circuit is open, the fan is off, when power is off the relay closes the fan comes on. 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).
The slightly more complicated solution uses the relay plus a 5V 100ma. fan (found everywhere) and a 6.2V 1Watt zener diode (found lots of places but worst case Digikey 1N4735AMSCT-ND 25cents (min. order required; good excuse to buy cables and connectors)). You hook it up as before, but with the diode reverse biased so it drops ~6.2V in the circuit with the fan running. This won't move as much air, so you'll have to figure out what gets hot and get the fan positioned to blow on it and get some good ventilation holes in the case. The good part is, it will stop conducting at 6.2V (probably 7V in a practical circuit), and won't drain your batteries dry.
Your article reminded me to test the 68Ah worth of batteries I added to my SmartUPS 1400 five years ago.
This article typed to you on battery power. Good luck.
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 recognize when your new batteries have reached charged state (at which time it's supposed to go to tricle-charge state). Most chargers recognize when this is happening by the current that the battery draws at a given voltage (or vice versa). It's quite possible that a fully charged 50AH battery is going to act (and be treated like) like an uncharged 7AH battery.
Free Software: Like love, it grows best when given away.
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
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
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
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.
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.
retrorocket.o not found, launch anyway?
I've enhanced UPSes multiple times with extra batteries, and it works fine, but watch out for overheating!
Other people have mentioned the charger, but the part that really gets hot is the inverter, when the UPS is sucking its battery dry in 5 minutes to feed the computer.
Cheap UPSes often don't have a fan and can't sustain full power output for very long without melting something. With the built-in battery, they only need to last a few minutes, but if you give it the Monster Battery Pack Of Doom, it will be able to keep running until it's thoroughly cooked.
Other than that, the only thing you might want to watch is the float voltage. There are three different ways to make lead-acid batteries: the ordinary style that needs distilled water occasionally (flooded), and two valve-regulated "maintenance free" versions that are sealed unless you charge them too fast: gel cell and absorbed glass mat (AGM).
They have slightly different optimal charging voltages, which you might want to adjust for.
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 expelled through a tube, so I can point it away from the bits that might get hot.
I've got a spare 900va here that I'm going to do the same to when I move house, then I can probably run everything I need from battery power!
-- You ain't seen me, right?