A little story and a few questions.

[Anonymous user]

My rack mount UPS (SU700RM2U) failed one day, along with some beeping and odd flashing of lights. So I unplugged everything, switched over to a backup UPS, and let the unit sit charging for a day, hoping it would recharge the batteries. I came back and was greeted by the same beeping and failure to power anything. Pulled out the DVM and the batteries were reading 13.10V, not quite the 24V to be expected. I realized I would now have to take out the batteries, a task that proved harder than ever imagined. As I was pulling out the tray it nearly immediately got stuck, and I noticed the batteries were swollen. Clearly they had been overcharged.

I was able to force the first battery out, but the second, not a chance. I've seen this happen to a few SLAs, but never anything as bad as the second battery. I now had to remove the rack, take of the top, bend a bunch of steel, and finally it came out. Finally I thought I was done, but no. The combination of the pressure on the sidewall and retaining plate from the expansion and the tape on the batteries forced me to pry the batteries out with a chisel and a hammer.

Some photos:
http://i.imgur.com/4sS1H.jpg
http://i.imgur.com/H0m6Q.jpg

Now the questions. I obviously understand I need new batteries, but how can I test the charging circuit to ensure it won't just overcharge them again? Was it a fluke, or a full failure?
Second, I notice the unit has space for 4x 12VSLAs, any downside to wiring two more in?

Thanks!

[Anonymous user]

How long had those batteries been in service in the UPS? Under ideal conditions (reasonable temperature, not discharged often or deeply), service life can run from 3 to 5 years or so.

Regardless of manufacturer, the smaller (< 5KVA or so) UPS market is extremely price-sensitive, and charging and monitoring circuits are not as elegant as they might possibly be.

Even in a battery system with very sophisticated monitoring (thermal sensors on one terminal on every battery in the string, current and voltage monitoring) and in a non-cost-sensive market (I'm specifically talking about telco remote battery plants), there are failure modes that will not be detected until a tech arrives for an unrelated reason and discovers the smell of burnt batteries.

I assume your UPS is out of warranty? You should consider the cost of replacement batteries vs. moving to a new UPS (possibly larger capacity if warranted, more features, etc.). I've gotten good deals from APC in the past (mostly on larger units - Matrix and Symmetra). There are (or at least there were, I'm not really up-to-date on this), 3 different APC programs. First was simply buying a replacement battery pack (RBC). Next was the Charge-UPS® program which provided the battery pack and an additional 2 years of warranty (subject to eligibility). Top was Trade-UPS® which provided a whole new UPS with factory warranty.

If you decide to just replace the batteries, I'd suggest checking the manufacturing date of the batteries (normally thermally embedded into the battery case, as shown in your photo). That's not the assembly date (which will be on the APC barcode sticker if genuine APC, or in random other places if aftermarket). Some resellers have these batteries sitting around in inventory, discharging. In one particularly bad case, "new" batteries I purchased (for a non-APC application) actually had a date code from two years prior.

[BillP]

Even if there are space for four(4) batteries, the UPS/charging circuit is designed for only up to 2 batteries on it. Also, we are no longer offering the Charge-UPS. Considering on what happened to your unit, I would suggest getting a new UPS via the TradeUPS program.

[Anonymous user]

The float voltage of these units is set too high, thus killing the batteries..
I guess APC was hoping to get some extra revenue (they sell the battery packs, too), but people went to other vendors after that.

And with most of those old units it cannot be set easily, unless you solder some resistors.

But I wouldn't go throught the hassle for such an old unit.

See my other thread, and search for "APC float voltage".

[Anonymous user · Accepted solution]

What was the ambient temperature?