Dimi

This is exactly why I refuse to buy Apple and Samsung products. El Cheapo phones and TVs from China, where everything is made, have served me well. 

This is exactly why I refuse to buy Apple and Samsung products. El Cheapo phones and TVs from China, where everything is made, have served me well. 

@Modina thank you so much for taking the time to highlight the potential issues with the solution. These are issues I have thought of beforehand, and hope my answers provide some clarity.

1. An inverter costs money :
The inverter module costs R70, not an issue. 

2. If you are extremely lucky, your inverter will waste 10% of your battery power :
It turns out to be very efficient. Ran a test yesterday with minimal loss, under 10%, I was surprised as well. 

3. You would need to remember to switch your inverter off :
The inverter is switched on by the relay, only used when there is no ac power. No battery drain, no standby mode. Lights go off for a second during switch over. 
4. 230VAC can be dangerous :
Not if enclosed in the plastic enclosure and not at such low current. Had myself a tiny tingly shock, wasn't bad. 

5. The safety aspect here is even more important :
Safety was first priority in the design. No external wires, everything enclosed safely.
 
6. Even the best pure sinewave inverters produce HF switching noise :
Not an issue given it's on a single circuit, powering only lights. 
 
I hope I have addressed the concerns here. Let me know if I should expand on any of these points. 
 
Note:
Why am I doing this? 
They say that necessity is the mother of inventions, and it's true in this case. Loadshedding is a huge problem, and there are really good solutions for all needs, except for lightning, which is the most important, especially to the poor. The idea is to build a low cost solution for those who don't have 10s of thousands to invest in a full inverter/battery system tied to the db board. 
I intend to complete this project and adhere to all safety regulations. If this is materializes with the off the shelf components, I intend to design a single board pcb with the complete circuit, no individual components. I'm a Software engineer by trade, so final designs will be done by qualified electronics engineers. This will bring costs down even further. 
I don't believe that the government will solve the problem, it's up to us to come up with solutions. 

Got the batteries yesterday, started tests on my desk. Will wire up to an actual light switch in a day or two. 
 

They threw some inverters with some batteries in a container connected to a solar array to power 30 "low cost" homes. I wonder what was paid for this remarkable innovation? (sarcasm) 

@GMAC yes, that's the whole idea. I want to build a solution that is accessible to anyone. The solution works, and is cheap.
This is what it looks like on my desk, I'm waiting on a 3s2p battery will and put it up on the wall and take better pics. 
Another extension box with a blank plate would house 18650's. 

Who thinks that this is a good idea? 
I have built a battery backup for my lights. It is connected to my regular light switch via an extension box. When the mains are on it charges 6 x 18650 cells, storing about 50wh of power. When the power is out it switches to battery and a mini inverter. This will power a single 5w light bulb for 10 hours, a 10w for 5 hours etc. This is at full brightness, no dimming as with the rechargeable bulbs. 
The cost for the entire system is about R600 using off the shelf parts, making it really affordable, even for multiple units around the house. 
This is a solution for those who can't afford a full on lithium battery / inverter setup but want to keep the lights on. 
Thoughts?