read below your posts and finally understood when you typed 6w. you corroborate my findings. the AC-DC converter that the LED lights are using have pretty low efficiency. surprising really, because yours are from CREE themselves.
ROI using the default led driver is just too long for me. i never believe electronics will last more than a couple of years, especially switching circuits. 5-6 years is just too long.

tho LEDs have a few important advantages that CFL could never provide. most important for me is:
1) heat dissipation to the backside of the case, which is to the ceiling.
2) can be powered by DC power using backup battery in case power failure.

best setup IMO is to isolate the DC conversion and current limit (led driver). use a high efficiency SMPS to convert to DC, then use a separate current limiter to drive the LED. you could use multiple LED per driver but there's a few downside.
upside:
- should provide higher efficiency as the current limiter is rated for ~97% efficiency, SMPS rating above 85%.
- cheaper maintenance cost since the smps and current limiter is isolated. replace just the problematic item.
- easily retrofitted to run from battery power for backup lights.
downside:
- switches will be handling DC. arching could destroy the switches in the long term.
- multiple equipment to maintain.

another easier setup is as you explained. using multiple LEDs wired in series to a single driver.
upside:
- cheaper initial cost. cheaper to modify existing wiring.
- easier to maintain. driver could be placed in easy to access area and since the LED itself are hard to spoil it's shorter downtime.
downside:
- higher replacement cost. single high power driver will cost more compared to either smps or current limiter.
- most led driver (integrated driver with smps and current limiter) have higher efficiency if nearly fully loaded. so it's gonna be hard to maintain high efficiency throughout the entire house.

have you considered building your own LED downlights?
i can't seem to find any supplier in ebay or aliexpress selling just the LED downlight case/housing. epistar 1w and 0.5w SMD LEDs are selling quite cheaply on the net. it's gonna be easy to hit 100 lumen/DC watt (or more) if we build the LED ourselves.
pair it with some cheap, high efficiency driver and string a couple of them together, it's gonna hit 90 lumens/watt or more on AC.

anyway for my garden lights, wall lights and flood lights, i'm gonna feed them DC directly (with or without current limiter) and build my own LED string. i've already bought the cases for the garden and wall lights so it's do or die.

mind to explain what is 3P? 91% efficiency is quite high.

For the fun and mother nature is really good to use the method you mention. But for pocket and practicality is another story. I doubt it will generate any good ROI.

Have you consider Solar -> Battery and Let the battery power the LED in series. This way you have minimal wastage in conversion, and "free" energy from solar. Than again, you have to spend money investing on Battery. I been researching lithium ion battery after Xiaomi selling a good and cheap Powerbank. It actually don't cost much to buy the similar battery Xiaomi using LGABB41865 (universal 18650), maybe RM 5 / unit for low quantity order. 
If you can get the same or higher mAh batter capacity like Xiaomi powerbank using (2600mAh), you get 9.6watt hour per battery. That enough to power one 9watt Led for 45mins (assuming 75% efficiency).

Long I have not work on the power supply, I maybe wrong but I think the 97% efficiency can't be achieve in real world environment with the heat, and component  quality.

For the fun and mother nature is really good to use the method you mention. But for pocket and practicality is another story. I doubt it will generate any good ROI.

Have you consider Solar -> Battery and Let the battery power the LED in series. This way you have minimal wastage in conversion, and "free" energy from solar. Than again, you have to spend money investing on Battery. I been researching lithium ion battery after Xiaomi selling a good and cheap Powerbank. It actually don't cost much to buy the similar battery Xiaomi using LGABB41865 (universal 18650), maybe RM 5 / unit for low quantity order. 
If you can get the same or higher mAh batter capacity like Xiaomi powerbank using (2600mAh), you get 9.6watt hour per battery. That enough to power one 9watt Led for 45mins (assuming 75% efficiency).

Long I have not work on the power supply, I maybe wrong but I think the 97% efficiency can't be achieve in real world environment with the heat, and component  quality.

It is a 3phase 415vac/240vac SMPS. You can check their SMPS and efficiency at here --> http://www.omron-ap.com.my/products/catego...lies/index.html

SMPS like this Japan product surprising in not expensive. A 24vdc 50watt SMPS efficiency over 80% cost only rm45. Thanks to the crap china product driving their price down. But actual it manufacturing from china also.

For the reliable, 5 yrs is not a problem. Some I see running more than 8yrs. Just don't get their low end product.

My those outdoor solar light, modify solar decor light are still surprising function well after 2yrs. Some using nicad battery and some is lithium ion. I put it at outdoor with rain and sun abuse. Some run in ON till drain the battery (about 6-7hr) and morning charge again. Some run on motion sensor and morning charge.

But the solar garden light all kong liau.    the cheapest 1.

I think can consider using solar with battery for non critical light usage. You won't get back your ROI. But it won't burden you monthly bill.

you mean this right?

i've bought some for sampling. another project for another day. a viable source of energy pack for embedded systems.
yes i agree they're worth more than what xiaomi is asking for them. so good that i've bought more than i need and given as gifts to family members.

have considered solar charging. but the costs are not justifiable. as least for me.
got a friend using them tho, with a 1kw panel powering his led downlights.

he's using your normal lead acid battery. a car battery to be exact. and i'm with him on this. lithium ion cells are expensive and require extensive protection circuit. even charging circuit is quite complicated. the advantage is only for size and energy density where lithium cells stores more energy for the size.

it's better to use lead acid in this case as we have no size and weight constraints. it's reliable, have no problem supplying huge amount of current, robust, no problem with heat, less risk, doesn't require complex monitoring circuit, able to work with unstable charging voltage, and it's cheap. and it doesn't have memory effect.
having previously worked with NiCad & NiMH cell, LiOn and lead acid i really think lead acid is the best for this situation.

the reason why i won't implement it is because of the adoption costs.
it should cost about RM10k for a 1kW panel.
and if my memory serves me right, that 1kw panel should give you around 3kW per day average. 4kw at most. i'm realistic so we're gonna go with 3kw.

N70 battery at RM250 a piece. 12v x 75A = 900W per battery. 3 years working life.
say you're using all 3kW to power all the lights inside the house. realistic as it's gonna cost RM0.90 per night, ~RM30/month to power just the lights.

adoption cost at RM10k (panel) + RM750 for the battery + ~RM250 for the charging circuits, wiring, etc etc.
total RM11k, for a saving of RM30 a month for the lights.
that RM11k / RM30 per month saving = 366 month just to break even.

that's 30 years. just to break even.
not worth it IMO.

Haha, as to date, I brought 10 units of Xiaomi power bank

Walau, brought so many for what? Pasar malam sell? 

But this power bank is only 5V only wor. What you want to do with 5Vdc?

Haha, add another 2 more units, just bought today

I referring battery inside,, is 3.6v or was it 3.7v exactly good for led light.

Depend the length size. The max length can go 3.7v, 3400mah. That can fired up a 1w led for 10hr+.

Those in my solar deco are 3.6v 2200mah. Can run about 6hr+ for a 1w led.

Next to get is solar panel and charger.

Yeah, and is cheap if buy in bulk. Saw in Alibaba can go down to less than 1USD each. Imagine buy 200 units

The killing is the panel and inverter.

Can use or not so cheap? The price is abit suspicious.

I brought this last yrs if not mistaken. Cost RM55/pcs from subang jaya.


The panel (12v/10w) and charger cost less than RM200 from local. Not that expensive anymore nowaday. Maybe even more cheaper from ebay or aliexpress.

Lets use Xiaomi Powerbank as a base to calculate, is selling at RM 36 with circuit + 4 battery 2600mah inside. If i take everything as zero cost except the battery, that make it RM 9 per battery. I don't think Xiaomi selling at lost right? Think they maybe getting it at RM 3-4 per unit.

Xiaomi buying crazy qty stock. We consumer can't get that price. A simple check at  Aliexpress already cost over RM10/pcs.

But getting indirectly from Xiaomi also very good price already.

Think can get lower, need to buy more lo. Think we are oot already

Car battery are not mean for solar usage way. It charatistic is to supply high burst amp in short time. But it need to be charge back immediately. It usage cannot be more than 50-60%. Otherwise will be shortlife.  Solar do have lead acid battery called deep cycle battery. It design to be use in steady amp supply with more than 50% can be drain. Last 2 yrs asking the GP deep cycle battery price. Cost RM750-850 for a 100A.   

Lead acid require maintenance to top up and place outside. Seal lead acid , lithium, NiMH etc don't require maintenance. All this require dedicate charger to maintain the charging. So the battery life can be last longer. Lithium ion is getting popular for solar usage. Probably the price is coming down.

This is the solar battery charger which I brought from state. It have efficiency about 90% more if not mistaken. It program to charge few type battery, maintain and monitoring usage.

to make battery to last, need battery optimizer like hybrid (nvr go below 30% & charge up to 70% nvr full) & automated process top-up dehydrated lead acid

with 10000mAh, usable is 3000-4000mAh

base on NiMH can last abt 18months- charge full n drain 10% (battery power flashlight)

maybe consider this Iron Edison

Think we are oot already