how to attach to roof tiles

[dennis]

Its a vacuum tube panel. Its much heavier than a solar PV panel. PV panels weigh about 12 kg for a 250W one. They are easily managed by one person, the thermal panel needs two.

[Dave Liquorice]

Er the manifold of vacuum tube panel is a bit of a lump but large rather than heavy. A tube weighs not alot at all? Perhaps you don't realise that the tubes plug into the manifold, you don't handle the whole assembly as a single unit.

PV will need stronger fixings as the panels are solid and have a higer windage than thermal tubes where the wind can pass betwen them.

[dennis]

There is no where for wind to pass through my panel, the multi-parabolic reflector is pressed metal and the thing arrives pre-assembled.

[Dave Liquorice]

Not seen that type, have you a link for it?

[dennis]

[Andrew Gabriel]

Sounds like it. As it was useless, I pulled it apart to look inside. I don't seem to have it anymore, so I suspect I chucked out out. I only bought it after they'd been significantly reduced, and didn't expect much, but it failed to live up to even that.

Yep - exactly same with mine.

ISTR the circuit was embedded in a lump of silicone, or some such.

[Dave Liquorice]

Wouldn't be surprised but just bunging in a schotty diode to stop the leakage would be an improvement. I doubt it'll ever generate enough umpf, even in direct sunlight, to damage a wet lead acid battery.

[Andrew Gabriel]

Don't know about current technology wet batteries, but charging them really slowly use to cause the generation of large crystals on the plates, which were much more prone to fall off (losing their storage capacity), and build up a sediment at the bottom of the cell, where they eventually short the plates out.

[Johny B Good]

Which explanation rather neatly accounts for why a bank of 4 12v 36AH car batteries used in place of the originally specified 17AH SLAs on my SmartUPS 2000 only lasted 6 months or so at a time before they started going 'leaky'!

Sadly, I did this 'experiment' _twice_ before realising the futility of such an 'economic' solution' to the lack of the battery box that normally would have come with my 'Bargain Purchase' at a radioham rally a decade or so back.

The worst of this was this wasn't the first time I'd experienced this problem a decade or so earlier. However, it was a 'one off' which I put down to it being a defective battery I'd used with a 13.8v 4A CB power pack to endow my PSU with low duty cycle high current output. A common solution for the majority of the CBers running "100W Burners".

I've run out of suitable SLAs for the UPS and don't care too much for the extortionate pricing of replacements so it's sat in the basement in bypass. The "Protected Sockets" are no longer 'protected'.

However, I suppose I could use a very low output voltage mains transformer to impose a 50Hz half volt peak to peak ripple on the charging supply and try another set of 'cheap car batteries' but I suspect I'd need something a little more sophisticated to maximise battery life without confusing the UPS's original 'charging circuit'.

Luckily, I've downloaded several dozen APC UPS manuals and circuit diagrams, including the all important SmartUPS 2000 one so I do have some chance of being able to achieve this happy state of affairs.

The UPS manufacturers could have so easily addressed this issue but it simply wasn't in their interest to do so (UPS supplied SLA batteries are their equivilent to the inkjet printer manufacturer's cash cow of inkjet refill cartridges).

[tony sayer]

I've noticed on all the APC ones they seem to cook their SLA batteries after a while ....

[Johny B Good]

Well, after I posted that, I took a look at the charging circuit for the 2000 and it seems incredibly complex for its function. The whole circuit diagram for the UPS is spread over 6 sheets (the charger is sheet6 BTW). In this case, the power comes from transformer terminals

1 and 2 on sheet 3 and following the trail takes you to the inverter powerfet stack circuit (a full bridge cct attached to the very same terminals that are used to feed the 5A rectifier diodes on sheet 6 - the inverter transformer does double duty as a charging transformer).

I gave up pondering the problem any further and decided to google to the wiki on Lead Acid battery technology with regard to best charging regimes where it all became ever so complex over the issue of choosing a charging voltage that's high enough to avoid sulphation yet low enough to minimise corrosion.

Interestingly there are three different float charge volts per cell figures for Gel, AGM and flooded cell types (2.23, 2.25 and 2.32 to within a figure of +/- 0.05v[1] respectively) for 20 deg C temperature with a temperature compensation figure of -.0235v per deg C rise per 6 cell battery).

Reading the article suggests it might not entirely be the UPS designer's fault but more the terrible limitations of Lead Acid battery technology (but that doesn't explain the 6 month life under the benign management scheme of a UPS versus the 5 to 10 years life in the harsher conditions of starter battery use).

I have considered the use of deep discharge flooded cell batteries (there is a trimpot to adjust the float charging voltage) but that's an even greater financial risk than buying a set of four cheap 36AH SLI batteries (probably still cheaper per AH's worth of the APC recommended SLA types though).

[1] The +/- 0.05v seems to make a mockery of the specific cell type voltages and temperature compensation coefficient figures quoted which leaves me wondering whether or not it is a per cell tolerance or, as in the case of the temp comp figure, per 6 cell's worth.

You can see what I mean here:

[Dave Liquorice]

batteries

Aye, my small APC Smart UPS iNet 750 kills a set of SLA's in 3 to 4 years.

Recently been through this loop as well. In the case of my APC UPS the killer seems to be the temperature. I reckon that the batteries where normally at the upper 30's to 40 C, when you apply the derating the voltage from the UPS is really rather high. Measured charge voltage 27.7 V, calculated charge voltage at 40 C 26.58 V, 1.12 V to high

No tweaky pot in my UPS. But digging about on the web found a mod to add one and how to enter setup mode and adjust the settings so it thinks the charge voltage is correct. I also removed the SNMP card slot housing and fitted a PC expansion slot exhaust fan with thermal speed control (using the MIC502 chip). Before the UPS used to run decidedly warm to the touch, now it is cool.

Time will tell how much longer the batteries last (or not!).

[Andrew Gabriel]

Their argument for high charge rate is that the UPS needs to be ready for use again within a short time.

That isn't a valid excuse to carry on cooking the batteries once they are charged, which is what used to happen in one we had at work.

We used to get 3 years viable life from an APC SmartUPS UPS, or 4 years life to completely dead.

OTOH, in another datacentre, we had a central 80kW UPS (Chloride Gaedor?) with separate batteries which were 10+ years old and still as good as new.

Car batteries are not normally run down at all. Starting the engine requires only a tiny proportion of their capacity, and they're normally recharged from this within a minute or two even on tickover. They are excellent at providing high current, but running them flat kills them very quickly. Their capacity drops fairly linearly over their life, but as you only need a tiny fraction of their capacity to start the car, you normally won't notice until they are will under

10% left.

[Johny B Good]

I agree with that assessment but I think there was more to it than just that. Despite the trickle charge tailing off to miliamps (when new), this did eventually lead to high self discharge rates and cell voltage imbalance which, in turn, led to higher trickle charging current, accelerating the process of deterioration to the point where the battery became a liability after a mere 6 months or so.

Considering the much higher float charge voltage used by alternators (typically 14.0 to 14.2 volts) and the 150 odd amps discharge when cranking the starter (and even higher current draw in wintertime conditions), it's a rather surprising finding.

I've learnt the hard way (or, if you prefer, the easy way) that car batteries aren't suited for such usage. Testing the batteries when new to determine the endurance time to exhaustion 2 or 3 times in the first week didn't suggest the relatively deep discharge was causing any noticable loss of capacity.

The UPS would start charging the batteries within minutes of completing each test which should have avoided the sulphation issue. Admittedly, it needed a good 16 hours or more to complete the charging process (normally a matter of 8 hours for the originally specified

17AH SLAs) but I don't think this was a material factor.

The normal advice over totally discharged Lead Acid batteries is to not leave them longer than 24 hours in this state before putting them back on charge. Perhaps I've misinterpreted this advice and it was meant to say they should be fully recharged within 24 hours. Even on the basis of this interpretation, the batteries were being fully charged within this 24 hour period.

The problem seems to be exclusively down to the float charging conditions since they'd deteriorate without being called upon to power the inverter during a blackout.

One thing's for certain, I won't be entertaining the use of car batteries as a substitute for SLA batteries. It's either SLA or Deep discharge depending on how cheaply I can get my hands on a set of four.

[Dave Liquorice]

Which is valid. If the thing switches off with flat batteries they have to be suffciently recharged to enable any attached kit to shut down gracefully should the power disappear again.

Quite agree it's a poor design but common across APC UPS's. As some one else said, replacement batteries to APC are like ink cartridges to printer makers. Last set of batteries I bought (Mar 14) where £29.99 delivered from Value Power Systems, their "own brand" replacement pack, cheaper than 2 x Yusa NP batteries from them, the pack used Yusa... APC wanted getting on for £50.00...

Like once can be enough ... Thats why you can get deep discharge wet lead acid batteries, sometimes termed caravan batteries.

[Johny B Good]

According to wikipedia, there are two varients of these Deep Discharge batteries, the true deep dischrge type and the 'leisure' ones to which you allude which are a compromise between high discharge duty and deep discharge durability, i.e neither one thing or the other although obviously a useful compromise for 'leisure' activities.

[Martin Brown]

Keep an eye out for suitable replacements from RapidOnline when they are doing a good deal or one of the other non ripoff merchants.

Avoid any that say "wheelchair" battery as they are typically cunningly rebadged heavy duty deep discharge cells sold at 3x the normal price!

If you can match voltage, dimensions and Ah capacity you should be OK.

[Johny B Good]

Deep cycle is what I'm after but not at 3x the 'normal' price (not even at 'normal' prices after taking a gander at the Rapidonline website).

No problems on size or AH capacities other than finding a matched set of four 12v batteries. Since I didn't get the battery case half with this UPS, I've used externally connected batteries. Initially a set of

36AH car batteries I blagged for 60 quid the lot which I stood on the lower shelf of the angle iron shelving unit in the basement upon which the UPS is perched.

I've supplemented this with sets of four 12v7AH SLAs and even a set of four 12v 25AH SLAs mounted on a sheet of MDF hanging from bolts underneath the top shelf and over the car batteries below.

As I said, the car batteries were the first to go bad and were weighed in when I tried yet another set of car batteries which are now sat there disconnected. The 25AH, along with the 7AH batteries eventually went bad a few years later and the UPS is disconnected until I can find another set of 25AH SLAs for 40 to 60 quid the set at a major Radioham rally or flea market.

My best bet may be to set my sights a little lower and use the 7 or 8 AH batteries. It can be rather galling to think that whatever capacity of SLA battery you choose, you'd be doing well to get 4 or 5 years life out of the investment before you have to 'splash the cash' once more.

The maintence costs in battery replacements alone, never mind the 35W maintainance consumption of a SmartUPS2000, is rather high to achieve autonomy periods measured in hours rather than minutes.

The obvious solution to hours long autonomy by using a petrol genset is only workable with the more expensive inverter type of genset. An ordinary 2.8KVA generator will grossly overvolt if it sees even a modest leading current load. A 4.7uF PF correction cap was enough to send the nominal 230v north of 270 volts and there's nearly 9uF's worth in the mains input circuit of the SmartUPS2000 alone, before we even consider that due to the protected loads themselves - no wonder the poor UPS kept cycling endlessly between mains and battery power when it was supplied by the genset!

[tony sayer]

Yes I've seen just that happening but the generator voltage measured on a true RMS Fluke meter was indicated at 230 volts;!..

Just out of interest, reproduced below an excerpt of an RAIB report issued today were a railway level crossing gate system didn't work. Fortunately nothing was going thru the crossing at the time from the road vehicle direction..

A bit of malarkey with the power it seems and the UPS system. All originally caused be a RCD tripping which wasn't needed as there were multiple earth's, so it sez;!....

1. Network Rail issues guidance about UPS systems. The guidance acknowledges that the batteries of a UPS system ?are the most critical component? and are ?perishable? in that their performance will degrade over time. The guidance also states that ?manufacturers will provide batteries with a design life which will often not be achieved. For example an 8-10 year battery will probably need replacing after 7 years provided that maintenance and good temperature control has been maintained?. The batteries of the UPS system in use at Butterswood level crossing had not been replaced since the system was installed around 20 years before the incident.
2. The signalling department whose responsibilities included Butterswood level crossing had no plans to replace the UPS system batteries during the life of the system. In fact, Network Rails knowledge about the condition of the UPS system at Butterswood, including the age of its batteries, was incomplete until after the incident on 25 June 2013.

The data logger

1. The data logger fitted at Butterswood level crossing had its own internal UPS system, separate from the level crossing?s main UPS system. Normally the data logger is powered from the main incoming network power supply and uses its own internal batteries to provide back-up power in the event of a main power failure for a maximum of 6 hours. The data logger is tested annually by signalling technicians. The test involves pulling the main network power lead out of the unit, and checking that the indications are still showing that the data logger is operating correctly. Network Rail requires that the batteries in the UPS systems of its data loggers are renewed at no more than 10 yearly intervals.

For level crossing UPS systems, Network Rail required them to operate for 20% of their expected performance.

The UPS system at Butterswood level crossing was believed to be capable to operate for up to 12 hours, therefore the permitted performance time was 2.4 hours.

1. Records indicate that the batteries were replaced in 2012. This means the batteries only lasted around a year before they failed. Information from the data logger manufacturer suggested that the batteries may only last 5 years, depending on how many channels the data logger is monitoring. It was the belief of the local signalling and electrification and plant teams, that it was often the case that new batteries can spend significant periods of time ?on the shelf? in store rooms, and could thus be several years old before they are used, sometimes leading to premature failure.

[Johny B Good]

That's a pretty accurate view regarding backup batteries. However, a

12AH 12v SLA I picked up in my local fleamarket for a fiver about two years ago has proved to be a rather remarkable example of SLA technology. It showed 13 point something volts on a borrowed digital meter at the time of purchase but actually showed only about 12v when I tested it at home (clearly the borrowed meter's battery was low).

I left it connected to one of those car battery maintainance solar panels for nearly 6 months to fully charge it up last year, which it did. It's basically been sat on my office windowsill for nearly a year without being recharged because every time I checked its voltage, it was showing 12.78 or so volts, even after using it for brief periods testing 55W halogen capsule lamps for a minute or two at a time and to use it as a test supply voltage for other kit every so often.

The total lack of care doesn't appear to have done it any harm and when I checked it again today, it still showed a healthy 12.76 volts and still fully lit up a 55W test lamp. I put it on charge from a pair of those panels mid afternoon today (100mA) and the voltage peaked at

13.25v before settling back to 13.02v after sundown. A test just now shows a voltage of 12.99v (1:30 am).

Mindful of the comments I'd seen recently about these solar panels having high reverse leakage sufficient to undo the benefit, I checked and measured a mere 2 micro-amps (using both a digital meter and an analogue one on its 30 micro-amp range as a sanity check).

This was for two units in parallel in total darkness (the 33 microvolts open circuit reading probably being due to sodium street lighting spillover) so whatever others experience might be in this regard, this is certainly not true for the two units in my possession.

As far as charge retention performance goes, the difference between a wet cell 12v motorcycle battery bought brand new last year and this SLA is like night and day. The motorcycle battery (removed from the T120v) only took a month or three to self discharge from full down to a mere 6 or 7 volts!

I'm not sure if this is typical of a decent quality of SLA but if it is, it would seem best _NOT_ to keep them on a float charge long term. Just a refreshing charge once a year might prove to be the best bet. Perhaps a float voltage of 13,2v with a brief monthly top up to

13.8v might turn out to be a better solution to achieving longevity in standby service.

For anyone interested in a 12AH 12v SLA that can be left a whole year between refreshing charges, the battery is a Chines made 'Maplin' branded battery also marked as "AINO MICRO" underneath which it has the following: "AM12-12 (12Volt 12AH)".

I can't spot any obvious date code except possibly one encoded on the made in China sticker bar code - "5 026686 823035" for the benefit of anyone who may know how to interpret it. The only other sequence of digits visible is "0908051" embossed into the top cover plate.