Photo Voltaic Array – unbelievable efficiency from Chinese sellers

A friend recently purchased one of the many PV arrays advertised on eBay only to be disappointed.

A common metric used to evaluate cell technologies is conversion efficiency with 1000W/m^2 insolation. Most popular products are monocrystalline silicon technology which achieves 18-25% efficiency on an assumed 1000W/m^2 insolation.

If we look carefully at the above panel advertised as 200W, the active PV area is less than the frame size, probably \(A=0.93 \cdot 0.63=0.59 m^2\). We can calculate efficiency \(\eta=\frac{p_{out}}{1000 A}=\frac{200}{1000 \cdot 0.59}=34\%\), nearly double expected efficiency for monocrystalline cells. Continue reading Photo Voltaic Array – unbelievable efficiency from Chinese sellers

Oyster conversion – #2 – 24W

Conversion of oyster luminaire to LED discussed a first conversion effort. This article describes a conversion of a oyster that used a T8 32W flourescent tube.

First step was to strip the magnetic ballast, power factor correction capacitor (if fitted), clips for the tube, labels that are misleading, and to check / provide the needed protective earth connection.

The LED plate used is that reviewed at LED plate analysis – 24W round plate with driver but with a new driver that delivers 260mA (though rated at 300mA).

Above is the 24W LED plate. The plate has 48 0.5W 5730 LEDs in a 24×2 configuration. If we allow that the 24W rating is total input power, driver loss is typically around 2W so the LEDs themselves will draw 22W. We expect that the voltage at 22W will be around 80-85V, and will require ~275mA current. The original LED driver supplied (180mA) is not capable of that current and was discarded. A nominally 300mA LED driver was procured for about $10 for five, and they fall short, delivering 260mA but that is good enough for this implementation. Continue reading Oyster conversion – #2 – 24W

LED plate analysis – 24W round plate with driver

This article reviews a 24W LED plate and driver commonly sold on eBay and Aliexpress for around $12.

Above is the 24W LED plate from the sellers pics. The plate has 48 0.5W 5730 LEDs in a 24×2 configuration. If we allow that the 24W rating is total input power, driver loss is typically around 2W so the LEDs themselves will draw 22W. We expect that the voltage at 22W will be around 80-85V, and will require ~275mA current. It is shown here with a 220mA LED driver or 80% of what is required for 22W. Continue reading LED plate analysis – 24W round plate with driver

LED Driver measurement – #2

In the quest for drivers for some 18W LED plates, I have placed 6 orders for non dimming nominally 300mA drivers for 18-24W LED plates.

The LED drivers originally supplied with the LED plates were rated at 180mA (10.8W) and measured 150mA (9.0W)

The tests here use an 18W LED plate, wired as 18 pairs of 0.5W LEDs in series for a total voltage of around 60V and 300mA for 18W.

Most orders have not arrived after several months, it appears some Chinese sellers are not shipping even though they have said they did. One shipment contained a single bare board with no details, it wasn’t ordered and without ratings was consigned to the trash.

Above is a test of one type of LED driver rated at 300mA ±5%. It supplies 237mA which is 21% less than 300mA, hopelessly low on specification. The other four purchased were within 1% of the same current. Continue reading LED Driver measurement – #2

LED plate analysis – D44-22P-01

The D44-22P-01 is a Chinese LED plate rated at 15W and operates directly from 230VAC with an integrated driver.

It was purchased to explore the configuration of LEDs with integrated driver, and this driver looks deceptively simple.

The chips are JZ1009AE, a LED current driver. The 22 2835 LEDs are 9V LEDs for a string voltage of 200V. Continue reading LED plate analysis – D44-22P-01

LED lamp failure analysis – GU10 230VAC 7W

This article is about an inexpensive GU10 230V 7W LED lamp.

Like so much inexpensive Chinese lamp product, it has not markings on the exterior or the lamp (eg voltage, current, power), but the product was sold as 7W and the box had that printed on it.

The lamp failed after less than 100h service, switching on and off intermittently symptomatic of a heat related problem.

Above is the dismantled lamp. Interestingly the LED driver PCB has “Q-3-5*1W” etched into the board, so presumably it is actually a driver for 5 series 1W white LEDs. So much for the claimed 7W, LED product performance claims are often a fraud, more so when the Chinese are involved. Continue reading LED lamp failure analysis – GU10 230VAC 7W

Chinese LED ratings – LED plate drivers

I have recently purchased or attempted purchase of several nominally 18W LED circular plates and associated 230VAC drivers.

The circular LED plates all had 36 x 5730 nominally half watt white LEDs arranged as 18 parallel pairs in series.

It is difficult to find datasheets from reputable manufacturers of 5730 LED. Cree makes 5630 which are similar size (though different footprint) and also rated at nominally 0.5W.

Above is the V/I characteristic from Cree’s J series datasheet with an approximation of the 0.5W line superimposed in red. The V/I combination for 0.5W is at the intersection of the two lines, about 162mA and 3.08V. Continue reading Chinese LED ratings – LED plate drivers

Chinese T8 LED 4′ tube teardown

This article describes the internals and basic test of a no-name Chinese 4′ T8 LED replacement.

The lamp is a Type B DEP (double ended power) configuration, cool white, it requires rewiring of a traditional magnetic ballast fitting or e-ballast fitting. Don’t attempt this unless you have the needed competencies.

It has no rating label, no information about its configuration on the lamp, no warnings about compatibility… so very Chinese.

The lamp is rated at 18W 1750lm, claimed life is 50,000h but you should take that with a grain of salt. The lamps cost $6.40 ea in a pack of 10, including delivery. They were well packed and the pins had a small plastic protector.

Above, the powered end of the LED strip and the LED driver partially withdrawn from the hollow aluminium extrusion. Continue reading Chinese T8 LED 4′ tube teardown