I will just put my 2 cents in here. Not looking for any argument and don't shoot me this is based on my own experience.
Just last week I had to replace my 2 batteries because of 2 reasons. (only 6 months old and paid R6000 for the AGM batteries)
1.) I had it run down twice until the alarm from the inverter came on to alert me of low voltage. This is because my area where I stay was without power for 2 days at a time twice over 2 months. (Cable theft and transformer vandalism) Huge blow to the batteries.
2.) I had 2 batteries (105Ah on my 3KW inverter) charging at 30A. This is exceeding the golden rule of 10% charging rate of the Ah rating on the batteries. Now people can debate this, I spoke to 2 different Companies and both stated the same principles that even if the batteries state they have 30 or 50A max charging rate, you try to never exceed the 10% rule for the longevity of the batteries.
10% x 100Ah = 10A charging and not 20 or 30A. Yes it will charge much faster at higher amps, but WILL impact the life span of the batteries.
Then I started asking more questions to understand inverters, solar, batteries and the operating of the equipment etc.
As mentioned, I have a 3KW inverter and both companies advised me to run 2 banks of 2x 100Ah batteries each for the size of my inverter simply because, my lowest charging on my inverter is 20A and running 2x banks of 100Ah will give me 200Ah and this is spot on with the 10% rule. Some people will argu against this, each to their own. I like to save where I can if I can.
So I had to pay the school fees and price and now I have 4x 105Ah batteries (2 banks) and boy can I see the difference and my inverter is also smiling.
This should probably last me at least 2 years if not longer with the current load shedding of 2 hours twice a day. The stage 6 is a smasher, because I need at least 5 hours to charge the 4 batteries with a load of 200-250 watts on the system.
For 2 hours of load shedding they take about 1-2 hours to charge depending on the load. During the day I only run about 130 watts of load and after 2 hours of load shedding it takes about 40min of charge till full.
What do I normally run: (Weekends only)
2 Pc's
Wifi router
some lights (12V 3 watt down lighters on 5 amp PSU)
Occasionally cellphone chargers
And some desk top fans
I try to max my load on the inverter to 25% ( 750 watts and this is my personal preference) so that I can get the most life out of the batteries, but I generally put a little less on the inverter during load shedding as per the above list I think is about 500 watts max.
During daytime during the week I only run my office PC and some small thingies and this runs a load of about +- 130 watts total.
Here comes the part people normally don't explain and as a lot of people that recommend Li-ion / Life-Po is correct in suggesting this.
IF you run your batteries down by 10% every load shedding, you can get a maximum of about 2000 cycles regardless.
Running the batteries down to 50% will give you about +- 300 cycles life out of them.
With Li-ion you can get up to 10 000 cycles of life while running them down all the way to 50%.
Now lets do my math.
I paid R8500 for the 4 new 105AH deep cycle batteries last week. They will probably last me 2 years with this dam load shedding we have at the moment and having to charge the batteries average twice a day. Every charge count as a charging cycle on the battery's life and the deeper they drain the harder they work and less life you get from them adding it up.
If I had the money and I paid R17 000 for 2x 100AH Li-ion batteries, I could save at least R35 000 minimum over the next 10 years that I can get from the Li-ion batteries instead having to pay R8500 min. every 2 years for 4 new batteries.
My OPINION if someone wants to run a gaming PC, TV, wifi and few lights you are good to go with a minimum of 1800watts inverter and 2x 100Ah Li-ion batteries saving you hefty costs over the long run. This is just for individuals and limited load. For a family house you need deep pockets.
Again, this is my opinion, each to their own and what can fit your budget.
PS: Li-ion batteries can also handle the higher charging rates and will charge faster than the Lead Acid batteries which is a great bonus to have.
