Estimated wattages

G

gboy

Expert Member
Joined
Dec 27, 2005
Messages
1,607
Reaction score
169
Location
in my house
hi

for all the electric guys out there.

I need some help with the following calculation

Inverter 800w pure sine wave - apparently that makes a difference.

I need to calculate the runtime of the following

400w with a 1x102 AH , 2x102AH, 3x102AH, 4x102AH battery

800w with a 1x102 AH , 2x102AH, 3x102AH, 4x102AH battery

just to double check my calculations

400w load is about equal to

TV, DSTV, 4x 11w Energy saver Lights, 2x Laptops.

or

3x 11w Energy saver Lights, 1 standard Computer.

800w Load is about equal to

TV,DSTV,4x 11w Energy Saver Lights, 2x Laptops, 1 Standard Computer

thanks this is of a big help
 
gboy said:
hi

for all the electric guys out there.

I need some help with the following calculation

Inverter 800w pure sine wave - apparently that makes a difference.

I need to calculate the runtime of the following

400w with a 1x102 AH , 2x102AH, 3x102AH, 4x102AH battery

800w with a 1x102 AH , 2x102AH, 3x102AH, 4x102AH battery

just to double check my calculations

400w load is about equal to

TV, DSTV, 4x 11w Energy saver Lights, 2x Laptops.

or

3x 11w Energy saver Lights, 1 standard Computer.

800w Load is about equal to

TV,DSTV,4x 11w Energy Saver Lights, 2x Laptops, 1 Standard Computer

thanks this is of a big help
Click to expand...

The calculations are easy.

Take your wattage that the equipment draws.
Lets assume you current draw is 1000 watts.
Divide the 1000 watts into twelve( for a 12 volt system)

This gives you 83.3 amps drawn.( all this is per hour)

Your batteries are marked in 102 Ah.

After 1 hour you would have 18.7 amps left in your battery.

With 4 x 102 AH batteries you can draw power for 4.89 hours.
(Assuming you continue to draw 1000 watts all the time.)

When the inverter converts 12 volt to 220volt there is a 5% loss of efficiency.
You also have to take that into consideration.
 
well thanks,

that makes life a bit easer.

I am trying to develop a back up power, as my area is loadshedded between 18:00 - 20:30 tuesdays, thurdays, and saterdays, all in the dark,

so 1000w / 12v = 83.3 so 204AH batteys should give me 2:40 hours of power.

but i think i can stretch it as i dont think a few lights, laptop, tv & dstv will be mutch more than 500W (give or take the loss)

so i am looking at about R7400 for a decent system to build myself
 
Don't forget about startup wattages. Light bulbs, for example, need twice the wattage to start up: 11W x2 = 22W. Same goes for things like a microwave and an electric motor. Your genny should be able to cover those startup loads as well.
 
gboy said:
well thanks,

that makes life a bit easer.

I am trying to develop a back up power, as my area is loadshedded between 18:00 - 20:30 tuesdays, thurdays, and saterdays, all in the dark,

so 1000w / 12v = 83.3 so 204AH batteys should give me 2:40 hours of power.

but i think i can stretch it as i dont think a few lights, laptop, tv & dstv will be mutch more than 500W (give or take the loss)

so i am looking at about R7400 for a decent system to build myself
Click to expand...

Rather go for a 2000 watt inverter.They cost about R1800.

The 102 AH Deep cycle batteries will cost about R 1200 each from Battery Centre. (Raylites) AC Delco is more expensive (it is Imported)

AC Delco is not available at the moment.They are all sold out.
You can get away with 2 (preferably 3)

You should be able to get away for R 5 500.(3 Batteries and inverter)

Get yourself an intelligent charger as well.
It works better with deep cycle batteries.
A Charging rate of 10 amps minimum.
With 3 batteries connected, it will charge each battery with 3,33 amps.
It should recharge the batteries in time for the next blackout.

The cost is about R 750 for the charger.
 
Last edited:
Remember the inverter is not 100% efficient. Generally the higher the input voltage to the inverter, the more efficient. Modified square wave inverters are cheaper, but can put extra loading on some devices. In addition size your batteries such that you do not discharge the batteries beyond 50 to 65%
 
Last edited:
psc said:
Remember the inverter is not 100% efficient. Generally the higher the input voltage to the inverter, the more efficient. Modified square wave inverters are cheaper, but can put extra loading on some devices. In addition size your batteries such that they do not discharge the batteries beyond 50 to 65%
Click to expand...

True.
I forgot to mention that.
The deeper you discharge a deep cycle battery,the longer it takes to recharge.

A deep cycle battery is also only capable of being charged and discharged for 500 cycles.
The deeper you discharge the shorter the lifespan.
 
hi

well i do know from experience that a modified sine wave inverter, makes lines across a TV, and a Computer CRT screen, also some UPS dont work with modified sine wave, but whats your expert opinion.
 
gboy said:
hi

well i do know from experience that a modified sine wave inverter, makes lines across a TV, and a Computer CRT screen, also some UPS dont work with modified sine wave, but whats your expert opinion.
Click to expand...

I use a modified sine wave inverter.
The trick is to move the inverter away from the TV.

The inverter is too close to the PC or TV.
 
gboy said:
oh, ok as simple as that ?
Click to expand...

Yes.
I moved mine away and it works fine.
I was not going to pay three times as much for a true sine wave inverter.

I have a 3000 watt modified sine wave inverter with UPS and charger combined.

When the power goes, i do not know about it.

When the power goes, the only way i know about it is when the street lights do not work.

Mine kicks in in 20 milliseconds.

Fully automatic.
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X