Loadshedding affordable battery setup?

[wingnut771]

@wingnut771 I am still a bit confused about the implications of this.

Does this mean that if you draw 600w for 1 hour it would have used 1000W from the battery?

Can we take the power factor and multiply it with the Wh of the battery to get to the capacity that you can get from it?

So when looking at their trolley with this inverter: https://www.geewiz.co.za/long-run-u...life-kit-600w-with-lithium-battery-640wh.html

and you take the power factor of .6 x 640Wh = 384Wh. (not sure if it works this way)

Why does Geewiz then claim that you can get 3 hours of use with a 150W load? (450Wh)

Probably because 3 hours rolls off the tongue better than 2.56 hours? Rounding up?

 

[Stokstert]

Probably because 3 hours rolls off the tongue better than 2.56 hours? Rounding up?

I might be completely wrong, but this is how I see it.



It should actually be 12V X50Ah battery = 600Wh. Now with the 0,6 power factor, 600Wh multiplied by 0.6 gives 360Wh, then 360Wh divided by 150W load will give a 2.4 Hours usage time. This implies one completely drains the battery.(Wrong assumption, battery is 12,8V)

Or the power factor is not used by Geewiz and one actually gets 12Vx50Ah/150W = 4 hours and the battery is not completely drained, and the Geewiz statement is thus very conservative. (Wrong assumption, battery is 12,8V)


I don't know where Geewiz gets their 640W with a 12V 50Ah battery to start off with.(Wrong assumption, battery is 12,8V)

Edit: All my calculations are based on the wrong assumption of LFP being 12V when they are actually 12.8V.

 

[wingnut771]

I might be completely wrong, but this is how I see it.

It should actually be 12V X50Ah battery = 600Wh. Now with the 0,6 power factor, 600Wh multiplied by 0.6 gives 360Wh, then 360Wh divided by 150W load will give a 2.4 Hours usage time. This implies one completely drains the battery.

Or the power factor is not used by Geewiz and one actually gets 12Vx50Ah/150W = 4 hours and the battery is not completely drained, and the Geewiz statement is thus very conservative.

I don't know where Geewiz gets their 640W with a 12V 50Ah battery to start off with.

LFP is 12.8V

 

[Stokstert]

LFP is 12.8V

Thank you for your correction.

 

[Schmatix]

I might be completely wrong, but this is how I see it.



It should actually be 12V X50Ah battery = 600Wh. Now with the 0,6 power factor, 600Wh multiplied by 0.6 gives 360Wh, then 360Wh divided by 150W load will give a 2.4 Hours usage time. This implies one completely drains the battery.(Wrong assumption, battery is 12,8V)

Or the power factor is not used by Geewiz and one actually gets 12Vx50Ah/150W = 4 hours and the battery is not completely drained, and the Geewiz statement is thus very conservative. (Wrong assumption, battery is 12,8V)


I don't know where Geewiz gets their 640W with a 12V 50Ah battery to start off with.(Wrong assumption, battery is 12,8V)

Edit: All my calculations are based on the wrong assumption of LFP being 12V when they are actually 12.8V.

May I ask what is power factor? I'm trying to figure some of this stuff out so I can make an informed choice on what to buy c:

I read the above replies about what it is but I am still so confused. As I have not been taking power factor into account yet. I also noticed on my watt meter it has a display of power factor when measuring my PC. Do I take this into account as well?

 

[Stokstert]

May I ask what is power factor? I'm trying to figure some of this stuff out so I can make an informed choice on what to buy c:

I read the above replies about what it is but I am still so confused. As I have not been taking power factor into account yet. I also noticed on my watt meter it has a display of power factor when measuring my PC. Do I take this into account as well?

Just read on from post #156 of this thread. Power factor = efficiency
A Google search will most probably give a better understanding of the definition.

 

[wingnut771]

May I ask what is power factor? I'm trying to figure some of this stuff out so I can make an informed choice on what to buy c:

I read the above replies about what it is but I am still so confused. As I have not been taking power factor into account yet. I also noticed on my watt meter it has a display of power factor when measuring my PC. Do I take this into account as well?

I don't blame you. It is higher grade stuff. You can ignore the one on the killawatt afaik. Just take the Wh you see on the killawatt and divide by 0.6 (or whatever the ratio (W/VA) is of your inverter, 0.6 or 0.83 or 1), then divide by 0.8 again for 80% DOD so you have 20% capacity left.

example: killawatt reads 300Wh for the session
300 / 0.6 = 500Wh
500Wh / 0.8 = 625Wh battery required.

I would double it again to factor in substations blowing up and whatnot so 625 x 2 = 1250Wh.

so pretty much a 100Ah LFP which is 1280Wh.

 

[Park@82]

ll

I read the above replies about what it is but I am still so confused. As I have not been taking power factor into account yet. I also noticed on my watt meter it has a display of power factor when measuring my PC. Do I take this into account as well?

Most of the power station tests I've seen indicates that that they have around 70 - 90% efficiency.

I just got done testing with my kill a watt meter on the EcoFlow Delta Max and I only got 1517Wh with mixed loads (form 40 to 2300w). To work out efficency take the amount of wh that you got out of the unit and devide it by the rated capacity x 100. (I think this is correct.)

In my case: 1517 / 2016 =.75 x 100 = 75% efficiency. This is on the low side for this unit. Another reviewer got 90% but I think he pulled a smaller load form it.

Made a post about sizing power stations here if you are interested: https://southafricanconsumer.co.za/2023/02/20/sizing-a-power-station-inverter-trolleys-solutions/

 

[leon.davibe]

Most of the power station tests I've seen indicates that that they have around 70 - 90% efficiency.

I just got done testing with my kill a watt meter on the EcoFlow Delta Max and I only got 1517Wh with mixed loads (form 40 to 2300w). To work out efficency take the amount of wh that you got out of the unit and devide it by the rated capacity x 100. (I think this is correct.)

In my case: 1517 / 2016 =.75 x 100 = 75% efficiency. This is on the low side for this unit. Another reviewer got 90% but I think he pulled a smaller load form it.

Made a post about sizing power stations here if you are interested: https://southafricanconsumer.co.za/2023/02/20/sizing-a-power-station-inverter-trolleys-solutions/

The efficiency is how much do you get out vs what you have or put in not how much they say it should have

If your battery happens to have 95% of rated capacity

And you base your math on rated capacity then it's wrong

Or if you have a battery that exceeds capacity same applies

Lithium has its efficiency
The inverter has its

Depends what you want to measure

For most if they say efficiency
I assume they mean combined efficiency

ie how many kwh units will i have to use to replace the kwh i used

 

[Park@82]

The efficiency is how much do you get out vs what you put in not how much they say it should have

Not sure about the correct term but it's commonly referred to as efficiency by many highly rated reviewers on YouTube.

I've even heard one of the best known power station reviewers on YouTube "Hobotech" refer to it as efficiency.

Let's just call it real world battery capacity vs rated capacity.

 

[leon.davibe]

But this has a caveat though

It is only applicable to your test scenario ie hardware

a person with better quality hardware setup can get a different ratio

Saying real world capacity, makes it sound like a battery capacity test

While this is actually
inverter efficiency half cycle (discharge)

But not really because you use rated not actual capacity

You assume you have rated capacity, which you may have as it is a new device (just devils advocate)

In my opinion a battery capacity test should not include inverter efficiency

Ie decide what you are testing inverter efficiency or
battery capacity

 

[wingnut771]

But this has a caveat though

It is only applicable to your test scenario ie hardware

a person with better quality hardware setup can get a different ratio

Saying real world capacity, makes it sound like a battery capacity test

While this is actually
inverter efficiency half cycle (discharge)

But not really because you use rated not actual capacity

You assume you have rated capacity, which you may have as it is a new device (just devils advocate)

In my opinion a battery capacity test should not include inverter efficiency

Ie decide what you are testing inverter efficiency or
battery capacity

what if you're not testing anything and you just want to know if you have specced the inverter/battery properly from Wh your devices uses?

 

[leon.davibe]

what if you're not testing anything and you just want to know if you have specced the inverter/battery properly from Wh your devices uses?

Just offering perspective

On what he is doing and saying

Somebody just stumbling into this may not be able to interpret what the data is saying

If they read battery capacity test they use that as what to expect from batteries

While lifep04 efficiency is most likely between 96-99%

This should not mention battery capacity test at all actually

It should say this inverters coversion efficiency

but for that also you want to do a full cycle measurement, ie run it flat charge it up measuring how much you put in then measure how much you took out

ie you can't use assumed values

For battery capacity test you would
Need to measure how much you take out of the battery
Preferably with measuring device between battery and inverter ie a shunt

 

[wingnut771]

Just offering perspective

On what he is doing and saying

Somebody just stumbling into this may not be able to interpret what the data is saying

If they read battery capacity test they use that as what to expect from batteries

While lifep04 efficiency is most likely between 96-99%

This should not mention battery capacity test at all actually

It should say this inverters coversion efficiency

but for that also you want to do a full cycle measurement, ie run it flat charge it up measuring how much you put in then measure how much you took out


For battery capacity test you would
Need to measure how much you take out of the battery
Preferably with measuring device between battery and inverter ie a shunt

I'm going to assume the battery tests with 100% capacity or else it's faulty, so all we're talking about here is "inverter efficiency" which is the "power factor" afaik but using the former is easier to understand than the latter imho.

 

[leon.davibe]

I'm going to assume the battery tests with 100% capacity or else it's faulty, so all we're talking about here is "inverter efficiency" which is the "power factor" afaik but using the former is easier to understand than the latter imho.

Power factor isn't inverter efficiency thing per se

it is a device efficiency thing

ie like a fridge motors pc fans pool pumps

Now yes the inverter can also be an inefficient device

So if you measure the capacity with an inefficient device it can make the inverter look worse than it is

Edit :some misconceptions here , only reading up on pf now

So not an efficiency thing at all

 

[wingnut771]

Power factor isn't inverter efficiency thing per se

it is a device efficiency thing

ie like a fridge motors pc fans pool pumps

Now yes the inverter can also be an inefficient device

So if you measure the capacity with an inefficient device it can make the inverter look worse than it is

hopefully we're not running these kind of things on a loadshedding affordable battery setup but to play safe, divide by 0.8 again.

 

[wingnut771]

I've got LS tomorrow at 10am. I'll use my killawatt and see what power factor my pc and fan is.

 

[leon.davibe]

As a laymen this is how i get it
So far ,ie i don't know what i don't know


The PF does affect what you pull from the battery

Running at non 1 PF you can pull less from the battery , it does put more strain on the inverter because it has to deal with reactive and and apparent power differences

So you have to keep this in mind when selecting inverters , for specific devices

The difference in VA and watts isn't an indication of a inverters efficiency, it indicates how high this can go in PF scenarios so the apparent load will look like 1000va while only pulling lets say 600watt from the battery ,with the whole reactive and apparent power thing which is PF

This is related to induction devices ie fridges pool pumps and any motor that does not use brushes or any device where you read induction
ie induction stove plates so not just motors

If you pull from eskom they still bill you the full amount as the lower PF puts strain on their network

From the battery power backup your inverter handles the strain and you see reduction of power pulled from battery during loadshedding from devices running at lower PF

So PF may increase the time you actually get on battery

Or this is how it will look ie power meter says you pulled 800w but since lower PF you only pulled 600w from battery

With normal resistive loads this does not come into play

ie your kettle pulls at PF 1 all the time

If i misunderstand it do correct me

 

[leon.davibe]

Power factor isn't inverter efficiency thing per se

it is a device efficiency thing

ie like a fridge motors pc fans pool pumps

Now yes the inverter can also be an inefficient device

So if you measure the capacity with an inefficient device it can make the inverter look worse than it is

Edit :some misconceptions here , only reading up on pf now

PF isn't an efficiency thing at all
Gets complicated with reactive and apparent power

never knew this

All i did know is with induction the load can go higher at startup

Always thought capacitor is like a jump starter for induction motors , which is technically what it does just delayed in the wave

Which i should have realised because i knew that is what it does on pc motherboards it smooths out the power

 

[leon.davibe]

I've got LS tomorrow at 10am. I'll use my killawatt and see what power factor my pc and fan is.

Read with a clamp meter what you pull from battery at the same time to see the difference

At lower PF there should be a difference ie lower on battery side if i understand it correctly