Solar Car Battery Charger

I own a small 1.1L car, Kia Picanto. I replaced my previous battery 6 months ago when it was about 2 year old and occasionally having difficulty in cranking up the engine. My car was then slightly more than 2 years to go before my COE expires in Feb 2016. I hope the new battery can last me more than 2 years so I do not have to get another one before Feb 2016.

Therefore topping up the battery charges to it's optimum and fullest potential becomes very important for me. I bought a 4.5W solar car battery charger (picture on the right) from DealExtreme to try out and regretted about it because it was under power and would take weeks to top up my battery to its fullest.

It comes with a cigarette lighter adapter with an LED indicator when there is enough sunlight to charge the battery. But I discovered that the circuitry to power the LED pulls down the voltage so much that it left with not enough voltage (below 12V) to charge the battery.

I ended up connecting it directly to the battery terminals and later on added a PWM charge controller because I was worrying of over voltage as I measured 19+V open circuit from the solar panel.




As I mentioned, 4.5W is too small that it will take weeks to top up my battery. The battery status of my 10A PWM solar charge controller always shows red in the morning before I crank up my car engine. I ended up purchasing a few 10W semi-flexible poly-crystalline solar panels from eBay and here's a short video of the 10W panel with 10A PWM charge controller.

With this Solar car battery charger, I now have the peace of mind that my car battery will always be top up to its fullest potential and will prevent lead sulfate from building up on the battery plates which will shorten the life span of the battery.

I have also added 2 10W panels to bring the total wattage to 30W so that it can top up the battery everyday.

Automatic Lighting

I have installed 2 sets of automatic LED lighting. One in my balcony and another in my common toilet..

They are programmed (using the charge controller) to turn on when it is dark - around 7.30pm and turn off after 3 hours - around 10.30pm.

Each set consists of a 30W mono-crystalline panel, a 10A solar charge controller, a 2nd hand car battery and a 1 meter LED strip.

The one at the balcony is also powering the solar fan occasionally. The LED lights in the balcony will shine into my living room, so eliminating the need to switch on my living room lights while we are watching the TV.

The one at the common toilet also lights up most part of the kitchen so we don't have to switch on the lights when we go into the kitchen to wash our cups, clothing, etc.

My wife and I are quite happy with the LED lighting as it brings us lots of conveniences.
I managed to keep the cost down (less than $100 per set) by using 2nd hand car battery from scrap yard.

Actually, I can simply use 1 set of this system to light up 2 places, but the wire will be very long and unsightly.

My Solar Energy Harvesting Begins to Bear Fruits

After a few months of Solar harvesting, my electricity usage has began to come down for the past 3 months. I recon that I am able to save about 100 kWh of electricity per month (Refer to my own record of actual electricity usage).
Based on current tariff of S$0.28 or 28 cents (inclusive of 7% GST), I estimate that I would be able to save S$28 per month which means I am able to recover my cost within 4 years.

But part of the reason for the electricity usage to come down could be because of the cold weather we experienced in Singapore these 2 months. The cold weather has resulted in lower usage of air conditioning. I would have to monitor the usage during hotter months, but for now I am quite happy with the result.

The higher gas and water usage shows that I am not on holiday during this period. I still wonder why my gas usage shoots up so high ??

Month	Amount	Est (*)	Own record	Electricity (kWh)	Gas (kWh)	Water (Cu M)
Jul-13	$152.85	*		372	49	13.3
Aug-13	$202.92			515	65	17.3
Sep-13	$180.03	*	413	451	58	15.6
Oct-13	$145.71		399	347	50	13.5
Nov-13	$151.29	*	349	367	50	13.4
Dec-13	$141.01		306	280	80	17.1

Update:
My electricity consumption has dropped to 73kWh in Feb, believe it or not?
Of course not. The actual reading is 170kWh, they had over estimated in Jan and made adjustment in Feb. I think it will stabilized to around 200kWh. That's a saving of 200kWh per month or $56 per month or $672 per year, which is 100% more saving than I expected.