EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: mlx on February 14, 2016, 01:48:52 pm
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Hello all,
New joiner though I have been visiting the site for some time to learn from the wealth of knowledge available. As a first post I was hoping for some guidance on the following:
My UPS (APS Back-UPS RS 1500, beige with no LED panel) is not providing power through its battery outlets after having been switched off. The surge outlets are OK, so is the fuse. As the unit is positively prehistoric (circa 2000 ) I though as a first trouble shooting step I will replace all the capacitors. The caps involved comprises of regular electrolytics and SMD V-chips. Its the specs of these SMD V-chip electrolytic caps which I am having a problem with.
They are only marked on the top, over 3 lines.
Examples are:
4.7
25S
B13
22
16S
H92
10
35S
H23
47
16S
CN2
My guess is the first line denotes the capacitance, the second the voltage and the third the batch. So for the first example above, it would be 4.7uF, 25 Volts (no idea what the S is for, manufacturer perhaps), batch B13. The alternative is these markings needs to be referenced to some sort of conversion table for the actual specs. I have searched the web extensively for more info but with no joy and would much appreciate any light that can be thrown on the issue.
Thanks
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Not sure why you're replacing the caps.
When was the last time the batteries/cells were checked/replaced?
UPS lead acid cells are usually replaced ~every 3 years.
If nothing was done since 2000, I'd pretty much guarantee you that the cells are toast.
Have you done a load test on the individual cells?
Thought I was given a deal on a free UPS..unfortunately replacing the cells was more expensive than a new UPS.
Also, newer UPS units are probably more efficient than the older units.
G' luck!
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I've scored plenty of low cost UPS units because of bad batteries - on eBay as long as the seller will ship without the battery since that's what drives up the cost, and local because a lot of companies just toss them rather than replace the batteries. For the smaller ones I often can find the batteries locally, no expensive shipping, but even for the bigger ones there is a battery seller, who has pretty much any battery you've ever heard of, and 10 kinds you haven't, who is within the 2 day delivery window for UPS ground, which is good because, like I said, shipping batteries is expensive. They are a fraction of the price APC charges for their "genuine" batteries but are the exact same thing, often the same OEM. Since the cheapest shipping method gets them to me in 2 days, I have no need to spring for higher cost shipping options.
If you don't have such an option, or a local shop that might stock the needed battery (the ones I get locally come from an electrical supply house - NOT an electronics shop, we don't have any of those around, sadly), it's probably not worth it as you will run into the same problem Teledog has, the batteries cost more than a new UPS.
I would definitely suspect the batteries before I went nuts and started tearing out the caps. Hell, I scored a free UPS once that I thought I was going to have to buy a new battery for - it did the same thing, powered on, got AC out the outlets, but if I pulled the plug it dies immediately. I opened it up to get the battery type and found the problem - they usually ship with the positive lead disconnected from the battery and no one ever connected it, despite the big sticker on the front that notifies you to do so! Connected it up - perfectly working, brand new UPS!
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The ups had been in storage for quite a little while. When I decided to recommission it, the replace battery light came on, as expected. The batteries were replaced with new generics (at a fraction of the branded prices) both on this unit and another identical one.
After the replacement of the batteries this particular unit will power the load for about 10 -15 minutes before shutting down. Thinking it was an undercharged battery I left it on to charge for a couple of days, then reconnected the appliances and it worked fine until I switched it off overnight. On switching it on the next day, it no longer supply power from the battery outlets. The other unit is working fine. The surge sockets are fine.
To me there could be a number of possible causes - these new set of batteries are faulty, the batteries are not be charged or no longer making proper contact, the inverter or caps have gone. Getting the specs of the caps sorted seems like a good place to start trouble shooting. Considering the age of the unit it would not be a bad idea to replace them anyway.
I spoke to APS and since the unit is out of warranty they very kindly offered me a replacement at reduced cost but from what I have heard and read, the consensus of opinion appears to be that their new line up are not as reliable and well build as their older models.
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Monitor the battery voltage when it tries to power something, see if it holds up. SLA batteries aren't universal, and ebay and Amazon is full of garbage. Listed as "equivalent" and "compatible with"If you can't get a datasheet on the battery, don't buy it. Since a ups is a very high rate load (5 minute discharge with a full load and no battery expansion, 15 minute rate for if you have the expansion, or a relatively light load) you need special high rate batteries with low esr.
Check out the bb-battery hr9-12 as an example of the type of battery you want. The datasheet gives constant power discharges for 5 and 15 minute intervals of 472 and 207w down to 1.6v/cell. Compare the cells you got to that.
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ConKbot, thanks for suggestion. Unfortunately it wasn't the battery. To eliminate that possibility I swapped them around with the set from the working UPS. Same problem with this UPS, the other works as normal.
It is clear the issue lies elsewhere. Back to trying to decipher the V chip specs.