APC UPS battery design seriously flawed?

D

Drunkard #1

Expert Member
Joined
Aug 15, 2007
Messages
3,668
Reaction score
18
Long story short: MY APC SURT UPS batteries failed and melted. In an effort to save the office from being burned to the ground when this happens again, we're completely changing the battery design and moving them outside. To design this properly, I needed to open the UPS. All batteries are connected to two poles on the main board, which leads to my question, "Is the design of these batteries seriously flawed?"

Obviously the ideal battery care situation is to have 96 x 2V cells individually monitored and charged. This isn't possible for such a small UPS. Next best would be individually monitoring and charging 16 x 12V batteries, and third choice being charging and monitoring the entire 16 x 12V string as one, which is what the UPS does if there are no external battery cabinets.

If there are external cabinets, they're just hooked up in parallel. So now (with one cabinet) you've got 3 parallel strings of 16 series-connected batteries. This causes parallel-series string interaction, and unless every battery is perfectly matched, melting batteries. I consider that a serious flaw.

Knowing this, I can't move the now spare battery cabinet to another site and just clip it in. Then I'd have 5 parallel strings with not-even-remotely matched batteries, and a 90% of a conflagration next time the power fails.

I find this quite disappointing. From thinking that these products were well designed to knowing they're flawed. Every new installation will now need a custom built battery bank if it needs more uptime than one string can provide. This is bull****, actually.

Have I missed anything? Electrical engineers, comments?
 
Get yourself a good battery tester (no, not just a multimeter), such as this one, that measures the actual capacity of the battery.

Periodically measure all the batteries individually, then it's pretty easy to weed out the rotten apple before meltdown occurs.
 
We've had a SURTD5000XLI pop in our offices as well. After some fights APC agreed to replace it free of charge. They never even bothered to collect the old one, so I guess it's not uncommon enough to warrant an investigation.

We've also had several of the small APC UPSes melt to such an extent that we simply refuse to buy anything from APC.
 
ponder said:
http://en.wikipedia.org/wiki/Uninterruptible_power_supply#Series-parallel_battery_interactions
Click to expand...

I read that. The puddle of batteries on the floor* kind of tipped me off that there was a problem. The wiki article explains it nicely, and gives the solution:

The only way to prevent these subtle series-parallel string interactions is by not using parallel strings at all...
Click to expand...

The fact that APC still uses this system is pathetic.

kayvee said:
Get yourself a good battery tester (no, not just a multimeter), such as this one, that measures the actual capacity of the battery.

Periodically measure all the batteries individually, then it's pretty easy to weed out the rotten apple before meltdown occurs.
Click to expand...

That seems like a nice tester, but we're talking about 112 batteries overall. The new setup will reduce that, but also make the batteries more difficult to test due to M6 terminals, rather than spade terminals. I'm seriously considering putting Power Pole connectors on each battery. But the cost!

Anyway, it doesn't help the fact that APC connects the external cabinets badly. That's just not right.

*I may be exaggerating slightly.
 
Even there is individual for each battery monitoring system in place, it doesn't exclude maintenance. Let me explain this.
Manufacturers recommend periodic replacement of all betteries in the string, but what happen if one battery deteriorates earlier and needs to be replaced? We usually put a new battery. Adding a new battery to the two-years old string is not good and replacing entire string is a waste of money.
Solution is rotation. Having extra spare batteries and rotating periodically with spare ones it ensure that all batteries are in the same age. When one battery fails, it is replaced with the same age. Difference between individual monitoring system and lack of it, is that during maintenance rotation you need to additionally test individual batteries with tester (as adviced above).
Hoping this will help with anger management. :)
 
Last edited:
So correct me if I'm wrong here but they actually produce them while knowing about these flaws?
 
tortured said:
So correct me if I'm wrong here but they actually produce them while knowing about these flaws?
Click to expand...
Not exactly. They say, all batteries in the string must be replaced after certain period of time. If client obeys this requirement, design is not flawed, as probability of battery failure is low and they earn money on batteries too. This is how business works.
They don't tell client things which would reduce their profits.
 
sajunky said:
Not exactly. They say, all batteries in the string must be replaced after certain period of time. If client obeys this requirement, design is not flawed, as probability of battery failure is low and they earn money on batteries too. This is how business works.
They don't tell client things which would reduce their profits.
Click to expand...

There's a difference between making normal profits by selling quality products at fair prices, and extorting money from unsuspecting [-]customers[/-] victims after you've sold them crap. What APC is doing is borderline criminal negligence. If I buy a R 30 000 UPS, I expect it to just work, which means proper battery charging and temperature monitoring. I don't expect a severe, undocumented fire risk from adding additional [official APC] batteries.

But APC is clearly not a honest, reputable company. The replacement battery strings are R 5 000 each, or R 15 000 total. One and a half new battery cabinets would cost R 12 000 (real friendly to the environment :rolleyes:), and 48 new batteries R 5 500. Three times the price for "official" replacements. That sound more like extortion than honest business.

In any case, we can't risk using internal batteries, so for the same price as the replacement batteries, we're redesigning the whole battery. Yes, I (with no electrical engineering degree) have fixed an obvious flaw. Surely the company that makes these products, with years of experience, could have foreseen this problem.

In any case, at least this thread can serve as a caution to others.
 
Now you guys have me worried. I have a small (single battery) APC that I leave running at home 24/7. Based on your experience do you feel that this is a fire risk?
 
garyc said:
Now you guys have me worried. I have a small (single battery) APC that I leave running at home 24/7. Based on your experience do you feel that this is a fire risk?
Click to expand...

Not really, the SURT systems operate with multiple parallel strings consisting of 16, 12V batteries each, giving an output of 192V per string. One 12V battery won't experience the parallel-series string interactions causing these problems, and will also contain much less energy, so there's a lot less chance of fire if it does fail. Put it this way, my new cabinet will hold 180kg of batteries.
 
Thanks, that is comforting to hear.
 
What is the Ah rating of each battery?

Edit : Okay, I see it is those horrible 7Ah jobbies.
 
Last edited:
@Drunkard - WOW - If those are the 7-8ah batts there R100-R200 a piece...the R200 being a decent Panasonic..the R100 being a Deltec...We join 2 together to use for a 24V system & the cheaper ones even from the same batch often fail.Now moved to buying the Panasonics again.
 
At R30k you can build a nice 5kVA setup using a good sine wave inverter, a decent charge controller and some good quality 12V deep cycle batteries (either 24V or 48V strings).

Just wondering why you decided to go this route first.
 
The SURT192XLBP (battery cabinet) has 2 strings of 16 series-connected, 5Ah 12V VRLA batteries giving 192V. Vision replacements cost just over R 100 each.

The new system chucks out the string in the UPS and the two strings in the extra battery cabinet, and replaces them with one string of 16 series connected 33Ah 12V VRLA batteries. No more parallel-series interactions, it's got over twice the capacity, and it's external so there won't be nearly as much damage if it fails catastrophically. An added bonus is that they're 10 year design life batteries, not 5 year.

We choose the APC system (back when it cost R 14 000 all in) because it's got the right specs (dual conversion online, pure sine wave, 480J surge arrestor, web interface), had a good name and was a plug and play deal. Now that I know what's really required to get it to work properly, I'll look at my options, but I think I'd look at another brand of UPS before I look at a complete DIY system. Getting everything working with the sort of reliability we want could be challenging. I might even look at APC again, because there aren't many options out there matching our requirements.
 
Drunkard #1 said:
There's a difference between making normal profits by selling quality products at fair prices, and extorting money from unsuspecting [-]customers[/-] victims after you've sold them crap.
Click to expand...
I am not here to defend APC. They use their market position which is due to their excellent conversion hardware. They will rip you off as far as you allow it, many other do the same.
Now if you act emotionally. you will end up with features like sensors, but UPS is going blow your hardware (the one it supposed to protect) on the next occasion and you will learn it hard.
This is why I say, use the best hardware, but also use your brain to not get ripped off and spread word.
Drunkard #1 said:
One 12V battery won't experience the parallel-series string interactions causing these problems,
Click to expand...
Right, but it can take down entire string, it is why there is no substitute for maintenance.
 
sajunky said:
I am not here to defend APC. They use their market position which is due to their excellent conversion hardware. They will rip you off as far as you allow it, many other do the same.
Now if you act emotionally. you will end up with features like sensors, but UPS is going blow your hardware (the one it supposed to protect) on the next occasion and you will learn it hard.
This is why I say, use the best hardware, but also use your brain to not get ripped off and spread word.
Click to expand...

Yeah, you're right, the UPS has saved a lot more kit than it's killed. Especially with the lightning we get.

Like you say, it comes down to using your head when you design these systems, and telling anyone interested in setting up their own system what I wish I'd known when I bought mine.

Right, but it can take down entire string, it is why there is no substitute for maintenance.
Click to expand...

I was referring to garyc's one-battery-UPS.

My idea of maintenance is replacing the puddle of old batteries with shiny new ones, hopefully after 10 years like their brochure says. I really don't have time to strip all the batteries every 6 months and take readings.
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X