Great AA Alkaline Battery Test – Addendum: 25mA Constant Current Tests

For those following along, they’d probably realize by now that I have left the country and are officially on holiday in the slightly-warmer-than-average-for-this-time-of-year Hong Kong. I had originally planned to make this post before I left home, but things got in the way, so now it’s happening remotely.

A while back, out of my own curiosity and armed with a DC electronic load, I decided to test a vast selection of alkaline AA batteries. This resulted in the four-part “Great AA Alkaline Battery Test” series (Part 1, Part 2, Part 3, Part 4) where over 100 individual cells were tested, taking around 22 days of test time. The tests were done at Constant Power (CW/CP) mode at a load of 0.48W, a compromise “higher level” load which I justified as being more relevant to the modern switching-converter based electronics in use today. This test protocol also had the advantage of being fast to administer, allowing a sample size up to 4 cells per type, and reducing any discrepancies that may arise due to cell storage.

However, I also did make a few assertions which, upon closer examination, felt a little concerning to me. This included:

  • the fact that lower drain devices are less likely to see as large of a capacity difference between different brands of cells as it is less demanding on the cell.
  • that better performing cells at high loads are likely to correlate well with good performance at a low-level current drain.
  • that ultimately, high level current drain performance is more important as you go through more cells, more quickly, and combined with the first point, means it has the bigger financial impact.
  • and that Ni-MH cells outdo alkaline cells (in general) just extrapolating from the high-load data.

Because I felt the shortcomings of my original study were significant enough to warrant a follow-up investigation, I’ve worked hard, spending approximately 950 hours of test time to do some additional testing to see whether my assertions were correct. This addendum proved to be an even longer experiment than the original CW test.


The test methodology follows the use of the same equipment and protocols as that of other “Great AA Alkaline Battery Test” articles, so I won’t bother fully describing it here. However, there are variations.

For one, the test regime is a CC 25mA discharge, instead of CW 0.48W. Secondly, only one sample was tested for each candidate cell type. The cells all came from the same batch (namely, the “extra cells” in the pack not used in the previous test). A selection of cells across a range of performance levels were chosen based on the previous results, taking care to choose cells where the tested population showed low variance (to hopefully improve the quality of the data from the single tested cell). In some cases, cells of similar performance were chosen as well, to allow for comparison between similar high-rate performances. These were referenced to a single Ni-MH cell and carbon-zinc cell. A total of nine cells were tested, including these reference cells.

Due to this, drawing firm conclusions is made slightly difficult by the infinitesimal sample size of one, but even just one result could be enough to cast doubt upon the assertions I had previously made, so it is worth doing. As tests do take around 5 days of continuous discharging per cell, some small variations in temperature were unavoidable, as the air conditioning was struggling to keep up with Sydney heat-wave conditions (which are still persisting as we speak), however, the impact appears to be minor (slight variations in voltage with a diurnal pattern).

Results and Analysis

The results are summarized in the table below, with a downloadable PDF file here. Please note that this information is compiled based on experiments run by a hobbyist at home, on a single sample of cell, and not a standards institution. The standard disclaimer applies – I cannot guarantee this information will be correct under your load conditions or even with your batch of cells. The information is provided in good faith with no warranties whatsoever. I cannot be held liable for any damages howsoever incurred.

Apologies, as the table is a bit small and presents poorly, so do click on it to get a larger view. The statistical calculations are made across the alkaline population only, excluding the reference cells.

Already, we can conclude a few general results:

  • The lower rate discharge at CC 25mA allowed the cells to deliver about 200% (+/- 50% approximately, for 95% confidence) the capacity as at CW 0.48W.
  • The average cell voltage was 1.253V for a 0.8V cut-off. This is still below the sticker-label 1.5V nominal voltage claimed.
  • The range between the highest cell and lowest cell is roughly 25% in capacity in both discharge cases, however, the worst performing cell in the high-drain test was not the worst performer at low-drain.
  • The capacity of the Ni-MH cell was largely rate-independent, and thus delivered less than all tested alkaline candidates at the 25mA rate.

We can examine the results a little more closely.

Looking at the voltage curves, the alkaline cells showed a relatively-typical curve, with some bumpiness towards the end. Cell voltage initially drops relatively steeply, flattening out, before then dropping more steeply again after reaching 1.2v. By comparison, the Ni-MH cell was only slightly more stable for voltage, however, remaining well below that of the alkaline. However, since the fall-off in the Ni-MH curve is quite steep, the average discharge voltage is still comparable to the alkalines, which spend a lot of time “slowly” falling in voltage. This seems to suggest that even at low rate, there isn’t much evidence to support Ni-MH voltage as being a major issue in any way. When combined with what was previously established at high rate, I don’t feel that the 1.2v “nominal” rating actually compares poorly with alkaline cells in practice, making higher-voltage rechargeables like Ni-Zn a “moot point” when it comes to matching alkalines. The carbon-zinc cell was more competitive for capacity, but still far behind that of its alkaline peers.

In terms of mAh capacity, the cells are ranked based on their CW 0.48W average results, plotted in the pink bars. The mAh capacity established under the CC 25mA regime is plotted in the green bars. The Ni-MH cell showed marginal improvement, whereas the rest of the cells showed significant gains implying internal-resistance/chemical-diffusion related difficulties at high currents which Ni-MH does not suffer from. From the height of the green bars, it’s clear that some high-performers at high current do not translate to equally good low current performance. The Eunicell, IKEA Alkalisk, Industrial by Duracell and Winmax Extra Alkaline are all vaguely similar performers with a tight tolerance, however, their low-current draw results differ markedly. The Eunicell proved to be a big disappointment in comparison, producing the lowest result in this test. This may or may not be an outlier, as the sample size of one does not give us any firm data. However, even amongst the remaining cells, the best performing Winmax Extra Alkaline cells came third, with IKEA Alkalisk coming second and Industrial by Duracell edging it out for first. The differences are not too big, but the change of relative ordering may indicate the bigger intricacies of battery design – namely having enough active material (to produce the necessary capacity), and making sure it is in a form that is usable with a low-enough internal resistance (for high current).

More information that seems to support this stance was the significantly poorer-performing Pairdeer cells, while still being relatively poor compared to the remainder, delivered the biggest gains from going to low-rate discharge.

A similar result is given for the mWh graph, with the gains somewhat boosted by the higher average voltage, especially in the case of the carbon zinc reference cell.

The average voltages were compared on a graph – there appears no real correlation between CP and CC average voltage trends, although the range of values is relatively small.

Looking at the ratio of CC results vs CW results, the largest gains were for the carbon zinc, and in general, as the capacity at CW increases, the gains from moving to CC low-rate discharge diminish somewhat, which may indicate ultimate capacity limitations due to how much usable active material you can fit into the cell. The greater increases for poorer-performing cells may point to a poorer cell design, or active material which isn’t usable due to poor diffusion to electrodes. The Eunicell result is notably atypical.

Finally, taking the difference of the mWh percentage from the mAh percentage above gives us the amount of percentage gain of mWh between the CW and CC tests that is due to increased terminal voltage alone. This seems to decline as the cell capacity increases.


In all, it turns out that this exercise was indeed worthwhile. Even though the sample size is very small, at one cell per type and only seven alkaline types tested, it is still illustrative. My own thoughts are seemingly contradicted by the data I have collected, and I am happy to have learnt something. It seems that the percentage difference in capacity across the tested (smaller) population at low-rate is of a similar magnitude to that at the high-rate, and that high-rate performance is not a great predictor of low-rate performance for some of the tested cells. At the CC 25mA load condition which is frequently used by manufacturers to make raw capacity claims, the approximate capacity for alkaline batteries is twice to three times as much as that reported by the CW 0.48W due to the reduction in influence of internal resistance (which results in increased average voltage under load) and increased time for chemical diffusion to occur within the cell. Such gains were even greater for the carbon-zinc which was overstressed at the CW regime. Such gains were not realized for the Ni-MH cell which presented a much more “load-independent” capacity which was less than the alkaline cells at CC 25mA, thus proving that alkaline cells can exceed the performance of Ni-MH cells but only at light loads.

The odd result from the Eunicell was based on a random-pick of cells from the same batch. It could be an outlier in the sense it may have been a faulty cell, however, this is not certain. Due to the long test regime, and lack of time (as this test finished two days before I was due to fly), I am not able to confirm this.

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Review: Logitech Bluetooth Wireless Keyboard & Mouse (K380 & M337)

Some of my readers have noted that it’s been a while since I last made a blog posting. This is mainly because I’ve been extremely busy trying to prepare everything for my upcoming holiday. As I mentioned previously in this posting, this year will be a “year off” for me, so I will be spending a lot of time away from the house. This means spending time away from my “bedroom lab” of test equipment, the stable internet connection at home and my desktop computer equipped with a nice mechanical keyboard. Instead, I will be “making do” on the road with a laptop, a Windows tablet, and an Android phone.

As I’m not someone who likes to invest in thin-and-light ultrabooks, as I find them overpriced and underpowered for the types of experiment I often like to run, I resort to living with a “fatbook”. This is very limiting in terms of battery life and convenience – it’s pretty heavy and takes up a chunk of space in the backpack.

The lighter and longer-battery-life Windows tablet would be great for some basic tasks (like writing a blog post of my thoughts), but the main limitation is that editing text on a touchscreen is pretty awkward, and the on-screen keyboard is just atrocious for doing anything long and involved. The remedy, of course, is to get some proper input peripherals

I had, at one stage, purchased a generic Bluetooth Keyboard and found it to be lacking. While I do own a Logitech M325, K400r and F710, they are all part of the “unifying” architecture which requires the use of a USB 2.4Ghz receiver. On a tablet, needing to use the only USB OTG port for that is both a waste and a big risk in case it gets karate chopped by accident. Bluetooth is the only option – the radio hardware is inbuilt.

Searching the market, the number of Bluetooth options are still somewhat limited and the price is still somewhat at a premium. However, it is the price of productivity, and sub-standard input devices just will not do. I decided that the Logitech K380 and M337 best fit my needs and plonked down the AU$95 or so to buy both of them.

Unboxing and Features

The K380 comes in a colour cardboard box, which is mostly teal-green in colour. The product itself is an unusual dark blue colour (mostly) with white/grey letter printing, which makes it distinctive, but probably a little toy-like.

The major drawcard of this unit is the ability to support three devices and switch between them, as well as the multi-OS compatibility that allows you to “type on anything”. The package claims a two year battery life, running on two AAA batteries.

The spine features the full specifications, with support for Apple iOS 5 or later, Android 3.2 or later, Windows 7 or later, Mac OSX 10.10 or later, ChromeOS and Apple TV. It also is covered by a one year warranty.

The keyboard comes wrapped inside a plastic wrap for protection. A small leaflet serves as the documentation, with the full guide available online for those who need it.

Otherwise, you are guided by a pictorial illustration similar to those used in IKEA furniture on how to set it up.

Batteries are included, and to keep their freshness, an insulating plastic tab is inserted at the factory. The tab is left hanging out for the user to pull, but I found pulling it awkward and instead caused the whole battery cover and batteries to dislodge anyway.

The two batteries included are GP branded AAAs, and the approvals information is printed inside the battery bay.

While the colour makes it look a little bit like a toy, the keyboard itself looks a little more like an old-fashioned type-writer with its circular rounded keys. The new Logitech logo adorns the top, which looks a little minimalist, as well as three white LED indicators above each of the quick-switch buttons.

To conserve power, a slide-switch with coloured insert is used to turn power on and off. An LED is provided next to it to indicate low-battery status.

The unit is a little on the heavy side, tipping the scales at 421g.

Unlike the keyboard, the M337 mouse comes in one of those “frustration” type plastic bubble packages. It has the same sort of colour scheme, and they did try to reduce the frustration by having the rear perforated for pull-open convenience, but instead, I found the plastic was too brittle and like to snap instead. The mouse claims a 10-month battery life, laser-grade tracking (which means it is an optical system), and compatibility with Windows 7 or later, Mac OSX 10.5 or later, Chrome OS and Linux Kernel 2.6 or later.

The documentation is again pictorial in nature with a leaflet including the other information. The full guide is available online.

The mouse features both click buttons, a scroll wheel with a centre, left and right click and a middle button (defaults to task switcher). The profile is similar to other Logitech wireless mice, with a rubberized band surrounding the mouse. The top also has a light-pipe for a blue LED indicator which shows the Bluetooth connection status.

One difference is the raised section in the rear, which can feel a little less comfortable as the lower end of the palm isn’t really supported. It is more conventional than some other more crazy looking mice from rival companies.

This time, the battery is isolated with a white pull tab, but again, it doesn’t work well and instead needs to be removed by opening the battery door rather than just pulling on the tab.

The unit is powered by a single GP AA cell, which fits a little more loosely than I expect (as is common to the M325 as well). The unit has a slide switch at the bottom to turn off the mouse, and a Bluetooth pairing button to initiate pairing.

It weighs in at a modest 81g.

Pairing and Software

As both devices are “classic” Bluetooth, pairing proved to be simple and straightforward. The mouse paired without any need to authenticate, and the keyboard paired after a the generated on-screen code was entered on the keyboard (i.e. passcode). Thereafter, both peripherals functioned perfectly fine.

Optionally, to change the behaviour of keys and read the battery status of the peripherals, the Logitech Options software can be used. Installation is straightforward, and just requires following the instructions.

After installation, it detects any supported attached Logitech peripherals and displays their battery status.

Clicking on a peripheral brings up the options specific to the peripheral. Note that I have changed some settings from their default to suit my needs.

Some of the things you will find include the names and OSes of the paired devices, the ability to customize some keys with mapping to other buttons or macros, the ability to control how the Fn buttons work, and the ability to see the firmware revision of the connected device.

The customization features for the mouse are fewer, as expected, as there are fewer buttons to map. On the whole, unless you don’t like the defaults, there isn’t a good reason to install Options. On the contrary, if you are using an operating system which is not supported, you’re not really missing out on much.

Subjective Opinion

In normal use, I saw no issues with compatibility or signal range, with both keyboard and mouse working with my Windows tablet and Android phone across the whole room. The keyboard also worked fine on an iOS tablet as well, confirming its automatic OS detection abilities to automatically select the most appropriate key mapping.

I found some pleasant surprises too, in the sense that the keyboard appears to have some internal buffer memory. If you’re sitting at the login screen and the Bluetooth connection has not established yet, you can still go ahead and key in your password and “enter”, and the keyboard will try to make the connection and dump the buffer to the host, logging you in without any frustrating “waiting” for connection or invalid password on the first attempt.

The three-device capability of the keyboard works well with power-users such as myself, who might want to swap from writing a document on the Windows tablet, to writing an SMS on the Android phone. This is accomplished using the light-blue keys and LED indications above them show you the pairing/connection status on changing from one to another. I experienced no issues hopping between devices. Sadly, it doesn’t seem the mouse has the same feature, which seems a little mismatched given the two devices visually look like they should go together.

The keyboard travel is fairly short, although not much shorter than an average chiclet laptop keyboard. The keyboard features a reduced key-count, and the style of the keys are circular similar to an old-fashioned typewriter, with large gaps between the keys. This takes some getting used to initially, as the wider spacing between keys means that key-strike accuracy is a little more important, otherwise your fingers might land in the empty space between keys. However, after a while, it’s quite comfortable to use, and the cupped shape of each key also helps. The keys are quite consistent and feel solidly attached to the keyboard, and the rounded profile might help in case it is carelessly shoved into and taken out of a bag, as they might be less likely to snag on something.

The keyboard is also impressive in the sense it has very little flex. It is possible to hold it in one hand and type with the other, without worrying about the board being damaged. However, this does come at a slight cost – namely that the keyboard itself is a little on the heavy side being about 400g. Definitely a consideration for those looking to take it in their carry-on luggage.

The mouse has a shape that’s quite similar to other Logitech wireless mice, with a rubberized band around the middle. The mouse does lose a little bit of its profile towards the rear, which leaves the lower part of the palm hanging, and unlike the M325 I formerly used, the scroll-wheel is not weighted, so it doesn’t “glide”. Aside from that, it feels solid enough. The mouse claims to have laser-grade tracking, although from my experience, it is more akin to optical with occasional lag from idle. The light from the mouse is not visible to the eye, so I’m guessing it is probably infrared as it does come up a dim purple under a mobile phone camera.

Both keyboard and mouse latency was found to be noticeable in some cases, although this probably is due to the processing overhead in the mobile device itself (e.g. it could be underpowered). But it is something to be aware of, as this latency may not be as apparent with a USB HID solution. Because Bluetooth uses 2.4Ghz, tablets such as the Iconia W3 which only have 2.4Ghz Wi-Fi will see reduced Wi-Fi performance while the Bluetooth peripherals are in use. This is common to all Bluetooth devices.

Battery life was not assessed as this is a relatively fresh acquisition, however, the claimed battery life of around 10 months (mouse) to 2 years (keyboard) seems to be quite exceptional. One downside is that the keyboard takes two AAA’s, whereas the mouse takes a single AA, meaning you still need to carry around two different types of cells. The battery cover on both is not captive, and the one on the keyboard seemed to be a little on the flimsier side. It’s nice to see the batteries are included, as is traditional for Logitech devices.


While a little on the pricey side, the Logitech K380 and M337 are a good match for the road warrior that likes to use touch devices for more productive purposes. The keyboard is a little on the heavy side, but it is very sturdy and worked flawlessly after getting used to the circular-shaped keys and wide-spacing between keys. The OS auto-detection features are one of its biggest selling points, as it ensures the function keys behave as expected. The mouse is as sturdy as required, and not too weighty, performing as expected although without three-device capability like the keyboard, with a slightly less smooth scroll wheel and less comfortable profile compared to their other wireless mice. The colour may not appeal to all, but it does make it quite unique, and the claimed battery life is quite impressive.

The proof is in the pudding – this whole review was written up on my Iconia W3 using both peripherals. It’s a mile better than working on the touch screen, and turns the tablet into a laptop-like experience. I’m glad I bit the bullet … otherwise I probably wouldn’t be doing any writing while I’m travelling.

Posted in Computing, Tablet | Tagged , , , , | 3 Comments

Experiment: Sylvania Lynx CFTE 42W Cool White Deluxe CFL Tubes

Every so-often, I drop into my local thrift shop because I just so happen to be passing by on another errand and have some time to spare. It’s often a good experience to sift through the random items for sale, and while the pricing is the least competitive it’s been in a long time, at least any money spent would be used in part for a good cause.

Among the things that catch my eye are the vintage electronics. This time, I came across a box of compact fluorescent tubes which were rather interesting to me. Priced at an attractive $5 for the box, I made the purchase and gave them a little more time before they reached their final destination (i.e. landfill).

A little CFL discussion and a Look at the Goods

At the moment, we are in the midst of a lighting revolution, and fluorescent tube lighting is on borrowed time. Regulations regarding energy efficiency are pursuing luminous efficacies unattainable with traditional fluorescent tubes, and hazardous material reduction legislation also looks unfavourably upon the mercury content within these tubes. As of last year, GE had already committed to shutting down its fluorescent tube manufacturing altogether. As a result, this is a timely find, especially when considering I did some reminiscing about fluorescent fixtures in an earlier post.

If you talk about compact fluorescent lamps (CFLs), the first thing that pops into most people’s minds (including the collective population of the internet) is that of the retrofit globes which screw/click into existing fittings, consisting of an electronic ballast and tube in a compact form.

But in reality, the term compact fluorescent lamp is broader than that. Technically speaking, the CFLs that are used in retrofit are better known as CFLi – the i standing for “integrated ballast/control gear”, but this term seems to have fallen out of popular usage. Instead, CFL merely means a fluorescent tube that is not in the traditional linear form, and is instead bent in a myriad of ways to reduce its size. Instead, now, such CFL tubes are often marketed as “Compact Fluorescent – Non Integrated” to avoid confusion.

The advent of CFLs were an important part of the history of the fluorescent lamp, as it made the high-efficiency technology more appealing to different use cases. This included higher power densities in smaller spaces to realize can-style downlights, as well as architectural “square” shapes enabled by 2D style tubes. In fact, there is a large array of CFL types and bases. The humble CFLi was a direct beneficiary of these developments, with some earlier CFLi bulbs carrying names such as PL (e.g. Philips PL) which reference the prismatic linear CFL tubes used to build them. I remember the earlier CFL bulbs also came in “separable” halves, where the electronic ballast had a PL base to accept a PL CFL tube and the standard Edison Screw/Bayonet Cap fixture at the other end to fit into a traditional fitting. Later bulbs integrated the two together for space savings, (likely) cost savings and reliability improvement (as the electronic ballasts had a limited lifetime as well).

While non-integrated CFLs have never been really popular in the majority of consumer fittings, they do see a certain amount of use in commercial fittings. I did see a good number of them even around the university I attended, it seems that the technology may still have a few years left. However, with the myriad of types, I suspect they will eventually be removed and replaced entirely as the tubes become harder to source and more costly, or the fittings begin to fail.

The tubes in question are Sylvania Lynx CFTE 42W 840 Long Life (278450LL) compact fluorescent tubes with a 4000K colour temperature, 3200 lumen output, 80-89 CRI and a GX24q-4 base. The luminous efficacy is about 76 lumens/watt, which is fairly impressive for fluorescent technology, but easily eclipsed by the best LEDs which reach 120-130lm/W. The units claim a 20,000 hour lifetime based on an 11 hours on/1 hour off cycle and are designed to be used on electronic ballasts only. The tubes are made in the UAE, although are an older tube, as presently available versions claim a 24,000 hour lifetime and use a blue base to distinguish the long life type.

The tubes use amalgam technology, where the mercury in the tube is made into a compound to regulate mercury vapour pressure and improve the high-temperature operating temperature characteristics of the tube, but as a consequence, the tubes have a significant warm-up time. This is necessary due to the high power density, as well as the significant bends in the tube.

The haul was a whole carton of 10, with a little water damage around the bottom, suggesting this was probably kept in a stock room somewhere and forgotten about. Then, possibly, the business closed and all the assets were sold, and this was part of the lot.

The reason I suspect this is because on the top of the package is a label for Mc Grath’s Hill Auctions, in Mulgrave. This suggests the whole package was probably auctioned, but didn’t find a bidder, and was then donated to the thrift shop by some commercial arrangement. Being in your average consumer thrift shop is probably one of the worst places for this sort of lamp – most consumers just wouldn’t have the fittings or know what to do with them! Eventually, after sitting on the shelf, it would have probably gone into the bin if it were not for me!

Each unit is packaged in its own colour cardboard box, in a mostly-green colour. The globe reaches a B-level efficiency in the EU’s energy efficiency scale. Its UPC is 9316236163701.

The EU energy efficiency scale and the icon with two dolphins on the front, suggests this globe is really not that old – possibly mid-2000’s by my reckoning. I suspect the dolphin logo is an indication of reduced mercury content, due to various requirements in different parts of the world with mercury doses reduced to no more than 5-6mg per tube.

The globe itself looks very similar to the picture on the box, featuring three interconnected U-shaped tubes in a delta shape, and a plastic base with four pin connections (to be suitable for electronic ballasts).

Markings are made on the body of the plastic base in blue print, with the ratings on one side, and the “LONG LIFE” indication marked on the opposite side. The rectangular base post has protrusions which allow for the socket to retain a “grip” on the lamp once seated.

The tubes are physically fairly long due to the 42W rating, so the tube seems to advertise a “crush protection” in the form of a silicone spacer which is pre-installed towards the end. This is in contrast to the consumer globes which often have glass hollows glued to the ends to maintain spacing, and may be a sign of high temperatures being a design issue.

Let there be Light? Maybe. Maybe not?

What good is having some tubes if we can’t make light with them? Well, rather sadly, these seem to have a base which wasn’t really that common, and generally speaking, a matching ballast is required to run them. Such fittings aren’t easy to come by at all. But there’s nothing wrong with a little improvising …

A while back, I salvaged a Vossloh Schwabe ELXe 236.523 T8/TC-L Electronic Ballast from the university and found it to be perfectly operational. Might this be a close enough match? Lets do some thinking.

The ballast is rated to supply:

  • 60w to 2 x 30w linear tubes
  • 64w to 2 x 36w linear tubes
  • 68w to 2 x 38w linear tubes
  • 62w to 2 x 36w bent tubes
  • 80w to 2 x 40w bent tubes

While it’s not got any rating for a 42W “bent” lamp, it seems to give the full 40W to a 40W TC-L tube, so it is at least capable of a similar power. Unlike some other ballasts, this one seems to have some tube-voltage dependent power delivery – notice only the 40W bent tubes get the full rated power delivery.

Doing a little more digging, it seems 40w TC-L tubes operate around 126V so have a current of around 317mA which is practically where we need it (i.e. 320mA). But the 42W CFTE is expected to have a higher operating voltage of about 131V. It’s a minor difference, which the ballast should be able to handle (after all, as tubes age, the voltage drop increases), but we need to test to see just how much power will be delivered.

Even though it claims not to be useable on inductive control-gear, trying it with a common 4-foot 36W choke could be unwise because it may regulate the current somewhere near the 430mA nominal current which is about 34% above the 320mA tube rating. This might reduce slightly because the operating voltage of 131V is higher than that of the 4-foot 36W tube which operates around 106V, but how the ballast might react depends on its design. If I crudely assume an inductive ballast to be a resistor, at 230V it has an effective impedance of ~288.372 ohms. Thus the calculated run current of the 42W tube on the ballast is about 343mA or a slight overdrive of 7.2% which it could probably handle. This is likely also to affect the performance of any power-factor compensation as well. I could probably try it … but then again, I don’t feel like needlessly modifying an existing fitting of mine with potential destruction of the tubes. The electronic ballast was “free”.

The reasoning behind not supporting inductive control-gear despite the four pin base is likely to be that the filaments aren’t particularly robust against a starter-based ignition which is more variable in the pre-heating of the filaments. They might be over-heated quicker due to their more compact size, or fail much sooner as they aren’t designed for frequent cycling as each starter-based start-up is like having 5-or-so on/off cycles on the lamp. But that’s really just a guess on my part. Some of the issues can be easily mitigated by swapping over to an electronic starter instead, but these aren’t that easy to obtain. One thing that’s for sure is that you won’t get as much brightness for the same energy input on an inductive ballast because of the gas re-ionization losses due to the low operating frequency resulting in more “dead time” where the tube is not conducting.

That being said, my choice of ballast isn’t particularly suitable either as the ballast appears to be an instant start type. The ballast chirps and starts the lamps quickly, with no noticeable pre-heating. The connection to one filament is just a single wire, suggesting it does not do any pre-heating current, thus it’s not a programmed-start unit with pre-heating that would be gentle on the filaments. It will shorten the life of the lamps, but I’m just happy if I get them to light even a few times.

No base? No problem. A few terminal blocks, a few random-coloured wires of mains rating or higher, a knife to cut off a little of the shroud, and judicious use of a screwdriver and the connection to the lamps is sorted.

As I had already wired the ballast up prior for test purposes, I thought I’d “bling” it up by adding an in-line switch to the cord, and give the input terminals some strain relief using a cable tie to grab the cable near the earthing eye. This particular ballast doesn’t seem to require an earthed reflector to start reliably according to the data I’ve been able to obtain – unlike some other rapid start ballasts.

The moment of truth was to flip the switch and see what happens.

The ballast chirped as it does, and the arc was struck successfully. The filament area can be seen to be slightly darkened, probably because of the harshness of instant starting them. The low brightness, including the complete lack of light from the areas away from the filament, is a normal behaviour for amalgam lamps.

After four or so minutes of operation, the brightness was even amongst the tubes and a lot of light was being produced. Rather alarmingly, the temperature around the filament area seemed quite hot, so I checked the power on the Tektronix PA1000 (which was in-line at all times to detect anomalous power usage) which indicated that the whole unit was consuming 83W, or just about the right amount. After three hours of continuous burn time, no failure occurred, although the IR thermometer was claiming the filament area was above 100 degrees C. This might not be unusual, given the high power density of the tube.

Not satisfied with just a few loose tubes and wires on a table, a small drill bit, a few bulldog clips, a few cable ties and an IKEA storage container later – I have something that’s a little neater.

Because of the random inspiration, I’m also in the process of grabbing a few electronic ballasts to add to my collection. Maybe I’ll end up converting one preheat fixture into an electronic programmed-start fixture just for the sake of it.

Bonus: My First Fluorescent Fixture

Since I did mention my first fluorescent fixture (which was a salvage) in a previous posting, but didn’t have the chance to show much of it, I’ll add it as a “bonus” part here.

This fitting was quite an old one, and it came with a Philips PowerMiser 18W T8 tube which was somewhat aged. Because I wanted an even older look, I actually went to Kmart and purchased a Mirabella branded T10 20W tube. At the time, the T10 tubes were actually pretty limited in number, so I thought I’d buy it because it was “special”.

I’m kind of glad that I did that, because the T10 tubes are even harder to come by nowadays. They really are visibly “fatter” than the energy saving T8’s that replaced them. They are less efficient, but the nostalgia gets the better of me. Nowadays, walking into one of the stores, it’s quite likely that you can’t even buy fluorescent tubes anymore.

It seems that the cost of the phosphor coating may be the reason why they didn’t coat the phosphor right to the ends of the tube. This particular tube has significant gaps in coverage at both ends which poses a slight risk in terms of increased UV emission from the tube. Rather interestingly, the light emission is influenced at the end by the filament position.

The fitting itself has an Atco EC20 20W inductive ballast, although the marking that says 600×38 suggests to me that it was probably designed for a T12 tube originally. I’ve never actually held or knowingly seen a T12 tube first-hand.

This is where the PFC capacitor that failed was. Because the neutral was looped into the PFC capacitor terminal and then onto the terminal block, I joined the ends of the wire with a small terminal block. The unit seems to be made by SUIV lighting industries, of which I cannot find a trace of anymore.


It’s amazing to think that I grew up watching the educational campaigns pushing home users to move from incandescent to fluorescent lighting, and now, we’re witnessing the death of fluorescent lighting in preference for LED technology. It feels sad to see it go, but as far as ‘fitness for purpose’ goes, the LED lights have many technical advantages which cannot be denied.

Despite this, having stumbled across a random batch of CFL tubes, I decided to save them from eventual scrappage and then improvise a system to get them to light successfully using a ballast that was not rated to drive the lamps in the first place. It did an acceptable job, although the instant start is hard on the filaments.

I also had a chance to show you what the insides of the first fluorescent fitting I salvaged looked like, and the T10 tube I purchased to go with it. Good memories.

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