Re: UPS

I replaced two RBC7s this year, and got them for a good deal less than the 170 pounds quoted by APC. I paid 123.00 delivered, although as you say they might well fail the same way anyway.

My supplier is doing RBC6 for 111.96 delivered, all inclusive.

Sorry, didn't make it clear. These are the actual APC products.

That seems a bit much for an RBC6 (not much less than APC who want

I bought Yuasa at a 1/3 of the price APC charged for their cells. When I opened up my UPS to fit them, guess what APC had fitted at the factory. Yep - the exact same Yuasa cells, the only difference being the letters APC stamped on the grey plastic (along with all the regular Yuasa branding/markings).

Excellent. Thanks for the info, guys. I notice my UPS does a load run for about 10 seconds once a week but this has had no effect on the quoted runtime figure and the runtime has only changed (reduced) since we had a 15 minutes powercut. I really should do a complete run-to-flat operation to see how mich capacity the batteries really have.

True, SLA batteries are common commodity items, there is no reason to buy from APC unless it was a rare, proprietary cell.

They used to fit the next size up connectors to their SLA's, from what you'll standardly find on the same size/capacity commodity SLA. Not sure if that's still the case.

I had a strange symptom of a UPS problem - the Carbon Monoxide detector in my living room started indicating low levels (about 17ppm I think) when it usually reads zero and there were no sources of it in the room

- the gas fire wasn't being used.

Then I noticed I was getting high temperatures inside the UPS, to a pattern. It would run at its usual level (around +32C) for some hours, then start rising over about half an hour, getting to about +50C, then falling back again. I opened it up and found that the batteries were bulging, and I had to lever them out with a crowbar!

I contacted APC who said that obviously the batteries were knackered, but because of the swelling I should get a whole new UPS (yeah, right! :-) I went to MDS (on the North Circular near Edmonton, I think) and bought the new batteries there for about a third of the APC price. I had to do a bit of work to fit the old bits to the new batteries - they have some plastic plates and a set of leads and connectors that presumably would come with them from APC, and the two batteries are stuck together to form one unit. A bit of prising and resticking of the plates and some gaffa tape to hold the batteries together did the job, and they've been working fine since.

This is a Smart-UPS 1400 iNet by the way, and the original batteries lasted 5 years (APC reckon 3 years is their design life). The batteries I fitted were the same type of Yuasa that APC use, incidentally.

The UPS top-up charges the battery from time to time, but also does some "maintenance" of the battery if you are using the Powerchute software - you can schedule self-tests and "calibration" runs, and I had the latter being done monthly, which runs it down to the "low battery" condition then recharges it, noting the energy needed to discharge it, so it can calculate run-time remaining.

I think the failure mode was this: The batteries were worn out, and the top-up charge was overcharging their (reduced) capacity and the excess energy went to heat, raising the temperature and pressure, causing the casing to soften and bulge. Then the pressure-limiting vents let out some of the gasses (Hydrogen and Oxygen) and that's what my CO detector was reading. This reduced the battery capacity even more, and lead to a downward spiral. As more electrolyte was lost, the peak temperature during the top-up charge would have risen further and further, but I got to it before it reached the stage of thermal shutdown, as David's did.

If David's unit is still overheating even with new batteries, there is obviously another problem, and maybe a case for a new unit, but if only the old batteries overheated, new ones should solve it. Mine has been running with the MDS-supplied batteries for about 16 months now, with no problems (so much for APC's suggestion to replace it! :-)

Oh, and the battery voltage has been showing 27.74V for some time according to the logs, so I think the reading given above is perfectly normal!

Cheers,

Howard

Why would you think that a CO detector would be triggered by other gases? Isn't it more likely that someing in the UPS was actually combusting?

Suppose the problem is in the control electronics? Putting in new batteries will just get them wrecked.

Personally I'd buy the more standard battery and swap the connectors on the APC's battery leads (with appropriate aftermarket ones).

Jeremy C B Nicoll wrote: [...]

It depends on the technology used to detect CO. Some actually use an artificial haemoglobin which darkens when it binds to CO, and this is picked up with a light sensor.

Others use tin dioxide on a ceramic base with wires running through. This causes it to be electrically charged and attracts both O2 and CO which both affect the resistance - a low resistance corresponds to a high level of CO. Other molecules can be attracted and cause false readings, but typically these don't normally appear in high enough concentrations to make any difference so it's a reasonable test. Besides, if it does pick up an unusual gas in the atmosphere, wouldn't you rather be safe than sorry?

Yes, but I didn't think O was that rare, though maybe H is.

See

Summary: Oxygen is extremely plentiful, hydrogen is pretty rare.