Hi Aki, Excellent assessment - and ascii art ;) Just one small point: - it's not a good idea to put batteries in parallel. You will run into problems with charging, and the imbalance between batteries will lead to one battery discharging through another. That's why the cells of a battery are in series, and why larger ups have many batteries in series - hence working on very high DC bus. I saw one case of batteries in parallel where one of the batteries boiled off all the sulphuric acid, producing clouds of corrosive gas! - and the battery melted! There *are* systems which use batteries in parallel - but these systems have complex control systems to selectively connect or disconnect individual batteries from the common DC bus. The best way to get larger capacity is to use big individual (2V) cells - as telcos do for their 48V DC bus. Tony 2009/7/17 aki <aki275@googlemail.com>:
While the rationing is forecast, It reminds me of the last time we had this. At that time, I designed a 2KVA invertor system from scratch with power MOSFETS which ran on 2 lead acid batteries with an external charger ( 100ah ). This thing ran for 7 hours continuos powering a 30amp load. This time around, no need for that as many things are cheaply available.
noise free minimum requirements, power delivery at least 8 hrs at 40% load :
- Power 2 energy saving bulbs. These are the AC philips 8watt ( 40 watt output ). DC load on good quality cable : 0.5amps max each
- Laptop and charger. DC load on good quality cable : 2 amps max
- Printer ( inkjet, not laser ) . DC load on good quality cable : 4amps max
- Wifi Router. DC load on good quality cable : 0.1 amp max
cheap options available :
- For lighting, I can use DC flourecent tube 8Watt. These run on 12 VDC. run a separate DC line from the batteries @ 0.2amp each.
- Use an invertor or modify a 650VA UPS for AC supply. split the DC and AC circuits while good ventilation is important
- Purchase 2 batteries ( 100ah each stacked in parallel, total 200ah ) sealed maintainence free type ( must be in ventilated area )
- purchase a single solar panel with line charger or incase of UPS, increase charging transformer size. Or AC charger upto 10amps.
sketch :
!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!! ! charging !------------! Invertor/ !-----------------AC Output ( fused protection) !system+batt ! ! UPS ! !!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!! ! !-------------------------------------------------------------DC Output ( fused protection )
( correct as necessary )
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