Assistance on inverter requirement

TheChamp

Honorary Master
Joined
Feb 26, 2011
Messages
57,360
The Synapse inverter plus two 180Ah omnipower batteries, all for under R16500.
 

Dairyfarmer

Executive Member
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Apr 17, 2016
Messages
6,213
any idea of what size inverter we’d need to see us through minimum 4hrs of load shedding ?
I have a whole thread on setting up my inverter. https://mybroadband.co.za/forum/threads/inverter-and-batteries.997062/

You just need the following formula:
volts x Ah / watts / 2 x pf = hours

Volts is your batter voltage 12, 24 or 48
Ah is the Ah of the battery 7, 9, 100, 200 , ....
watts is your load
2 is there to stop your depth of discharge below 50%
pf is your power factor or how efficient your inverter is. 85% or 95%

So if you have a 12v 102Ah battery, your load is 500w and you have a pure sine inverter:
12 x 102 / 500 / 2 x 0.95 = 1 hour 9 minutes
So for 4 hours you would need 4 batteries connected in parallel.

You need to physically measure what the appliances use. You need to know the maximum load, so use a Kill-A-Watt type device to measure the usage over a few days. It is important that you plan that ALL the devices are running all the time at full draw.
 

Steamy Tom

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Jan 23, 2019
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8,368
yeah, wattage requirement is purely based on what i found on the actual supplier website (eg. Samsung Q80 65" uses 200 watts.....) etc.... and that extract per product is what i found everywhere

those numbers are seriously wrong dude, you are setting yourself up for failure. there should be a sticker somewhere on all of the appliances, look for it, on the fridges they are often inside rather than on the back or side. i would expect the fridges to be more like 400W(peak) with a higher start up draw and the freezers also.

the tv is about right i would say though.
 

Speedster

Honorary Master
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May 2, 2006
Messages
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those numbers are seriously wrong dude, you are setting yourself up for failure. there should be a sticker somewhere on all of the appliances, look for it, on the fridges they are often inside rather than on the back or side. i would expect the fridges to be more like 400W(peak) with a higher start up draw and the freezers also.

the tv is about right i would say though.
Best option is to make the effort to measure the appliances with a kill a watt / effergy.
 

johndoe1983

Senior Member
Joined
Jul 16, 2008
Messages
953
yeah. go
Even so, a good idea would be to not connect them to the inverter because it takes more than a day for a freezer to defrost

good point.... they told us when we bought the fridges/freezers they will last some time before defrosting during load shedding (especially the bosch ones), unsure of the Samsung... but i'll rework it. 1 moment
 

Academic

Well-Known Member
Joined
Feb 3, 2006
Messages
215
3000 kva 48v victron inverter and 5kwh lithium iron battery for R70k in February. Hope that helps as bench mark.
 

Speedster

Honorary Master
Joined
May 2, 2006
Messages
21,685
yeah. go


good point.... they told us when we bought the fridges/freezers they will last some time before defrosting during load shedding (especially the bosch ones), unsure of the Samsung... but i'll rework it. 1 moment
If you knock off the fridges and freezers you're at under 500W. That puts you in Mecer 720W game, and you'll need 0.5kwh of usable battery per hour. At 12V that's 42Ah per hour (remember that lead acid batteries only give 50% of their rated capacity).
 
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