Hey Guys, 

 

I just want to make sure im not being stupid here before i place my order.

I currently have a household usage around the 10kw mark.

Im planning on installing a 8kw Sunsynk paired with a Sunsynk 100AH 5.12kWh 51.2V Battery.

 

Does this mean i should be able to run at normal load for a total of 0.512 days (5.12kWh/10kW) so a smidge over 12 hours?

 

Thanks

It's difficult to do it this way... what  you really need to look at is what is your consumption during loadshedding, assuming this is what you want to cater for, or during the night time, when solar production is 0, if this is you goal.

10kW sounds a bit skraal, but no impossible, do you have a hot water cylinder? or a solar hot water system? basically here we run, during the day, washing machine, dishwasher and do most of the cooking that requires electricity, during hours when solar production can cater for this, most things have to be sequenced, though, the dishwasher only draws, probably 400 to 500W, except when the heating element is on, which is twice during the cycle for app. 20minutes each time, then the power draw is 2-odd kW.

So, your 10kW consumption would be for many things during the 24 hour period, some of which you'd hopefully not do, whilst running off battery...

Thanks for the quick response.

 

Indeed i have a gas geyser which resulted in a huge drop in usage.

In winter its around 12kw, and summer around 8, hence the 10kw average.

This is as per the prepaid meter i run.

 

Im currently planning for purely a backup system, so no solar at all, that will come next year.

 

Ideally im looking for an estimate of battery usage under average use. With the inverter, the maid for instance wouldnt know loadshedding is ongoing, so wouldnt know not to use the vacuum or the washing machine. Thats also why i went for a larger inverter than needed, to hopefully cover for these occurances.

Ideally you would want to use an energy meter to measure your total usage from about an hour before sunset to an hour after sunrise. That usage will determine the energy required to be supplied by the battery.
As Meerkat also mentioned, you would want to schedule all your high usage activities during the day. It involves a "lifestyle change" if you will. Manage your usage, sequentially if needed.
I only have a single 5,5kW battery and it serves me throughout the night. My early morning SOC is normally between 30 and 40% before recharging starts from Solar.
As soon as I see 1,5kW Solar I start the washing machine or the Dishwasher. 
 

The inverter is very good at converting solar PV to 220V AC but charging the battery from mains and discharging to power the house you will likely lose about 10-15% in the process.

Random thoughts. Consider at own risk, and get a professional opinion. Maybe ask whether an 8kW inverter is not overkill. Many folks seem to prefer the bigger size for reasons you mentioned, for overhead, but your daily consumption is really low.

That 8kW inverter can in theory deliver around 70%-100% of your daily consumption in a single hour. How often will you need that type of output with your daily usage of 8-10kWh?

Are you planning to expand your battery backup as well anytime in the near future? Because consider that the battery's standard discharging current is 50A, so basically it's a 0.5C battery that should mostly be delivering around 2.4W of power only, and 4.8kW as a max continuous discharge, so if you're not taking a different 1C battery or doubling up on a second battery, the 8kW inverter's capacity will be mostly wasted.

Why then not consider a 5kW inverter, and put the savings towards your panels, or maybe towards another battery, although I think that's not your first priority. Depending on where you shop that's around R15,000 saved on the inverter that could be good for maybe around 2kW worth of panels, and on your daily consumption that's more or less all you really need. Add in some sundries, and the job's done.

@GreenFields

My 1st thought was also is 10kwh is used per day and you fit a 8kw inverter then the guys in the know says you must have 15kwh of battery power. That comes in at R75th.

The proper way is as @zsde

suggested to know what power in kwh is used say from 16h to 08h in the morning. This you want to cover with about 70% of the battery size. Also one need to know what is the peak power you intend using when there is LS or do you want to continue using power is if the grid was on.

Another way of approaching the question is determining how much excess production capacity you have. For eg, if you generate 25kWh per day, and use 20kWh during the daytime, having a 10kWh battery is pretty pointless as it'll never be fully utilised. 

45 minutes ago, Speedster said:

Another way of approaching the question is determining how much excess production capacity you have. For eg, if you generate 25kWh per day, and use 20kWh during the daytime, having a 10kWh battery is pretty pointless as it'll never be fully utilised. 

During the 12hrs that the grid is on and a 63A circuit breaker Eskom can supply about 173kwh per day. That is if all power is used charging batteries and what will be available. While using 10kwh a day 163kwh is available.

The OP will only be charging from the grid.

Edited July 13, 20223 yr by Scorp007

I guess if you're charging from the grid my point is moot 

4 hours ago, Sparkz0629 said:

Ideally im looking for an estimate of battery usage under average use. With the inverter, the maid for instance wouldnt know loadshedding is ongoing, so wouldnt know not to use the vacuum or the washing machine. Thats also why i went for a larger inverter than needed, to hopefully cover for these occurances.

8KW Deye inverter does not blink when the vacuum cleaner, iron, washing machine, kettle, coffee machine or dishwasher are used. Note the *or*, it would be a bit mental to be running all of those at the exact same time.

Your battery may be the limiting factor for your inverter. A 100Ah battery at 1C is 100A multiplied by 51.2V yields 5kW. At 0.5C the current drops to 50A * 51.2V yielding 2.5kW.

Your baseline usage should to be well under 1kW. My daily is around 8kWh and the baseline usage with lights, music, computer and a fridge kicking on is about 350W, fridge stops and it'll drop back to 250W, without the desktop talking more like 150W. There are spikes up to about 2KW from the appliances mentioned above.

17 hours ago, Sparkz0629 said:

Thanks for the quick response.

Indeed i have a gas geyser which resulted in a huge drop in usage.

In winter its around 12kw, and summer around 8, hence the 10kw average.

This is as per the prepaid meter i run.

Im currently planning for purely a backup system, so no solar at all, that will come next year.

Ideally im looking for an estimate of battery usage under average use. With the inverter, the maid for instance wouldnt know loadshedding is ongoing, so wouldnt know not to use the vacuum or the washing machine. Thats also why i went for a larger inverter than needed, to hopefully cover for these occurances.

Firstly distinguish between kW and kWh

Vacuum maybe 0.75kW and used for say 30min 0.75 x 0.5 = 0.375kWh
Washing machine on cold cycle?
Then what else do you use during the day? Dishwasher? Iron? Kettle?

Then you will have two scenarios in my opinion. 
- Daytime with base load (fridges, wifi etc) and high kW short time items
- Night time with base load with maybe some added stuff like lights, tv, phones charging or whatever your profile is.
(night time load also drops after bedtime)

For argument lets say you use 2.8kWh during the day for intermittent / higher load appliances and an average base load or 300W (0.3kW x 24h = 7.2kWh) to make up the 10kWh used.

Your battery is 5.12 x 90% = 4.6kWh usable
Day: 4.6-2.8=1.8/0.3= 6hours
Night 4.6/0.3= 15hours

Just for illustration on a best guess and your figures might differ depending on your load profile.

19 hours ago, Sparkz0629 said:

Hey Guys, 

I just want to make sure im not being stupid here before i place my order.

I currently have a household usage around the 10kw mark.

Im planning on installing a 8kw Sunsynk paired with a Sunsynk 100AH 5.12kWh 51.2V Battery.

Does this mean i should be able to run at normal load for a total of 0.512 days (5.12kWh/10kW) so a smidge over 12 hours?

Thanks

You only save money if you have PV panels.
Without PV you have a UPS.
The only recommended  & economic use of a UPS is for load shedding.
There are some losses in charge/discharge the battery from the grid which cost you money.
For UPS mode you should use the grid directly when it's available.

Adding PV (during sun hours) will charge the battery and also run the house.
Since the PV charged the battery you can then use it for both load shedding and night usage and save money.
With some planning and timers you can move loads (eg pool motor, electric geyser, washing, dryer) to sun hours.

According to https://www.sunsynk.org/lithium-batteries
The battery has 5.12kWh usable capacity, 0.5C (50A) rating, and 100% DoD.
I would limit this to 90%-95%
Usable = 5.12kWh * 90% = 4.6kWh every cycle
Load = 50A * 48V = 2.4kW (for comparison a kettle uses ~1.8kW) - if the grid is on, then the load is based on the inverter pass thru capability
My whole house on the "essential load" of the inverter and not had a trip yet.

Due to the 0.5C rating, you probably need more batteries to cater for peak load.

On 2022/07/14 at 10:17 AM, system32 said:

You only save money if you have PV panels.
Without PV you have a UPS.
The only recommended  & economic use of a UPS is for load shedding.
There are some losses in charge/discharge the battery from the grid which cost you money.
For UPS mode you should use the grid directly when it's available.

Adding PV (during sun hours) will charge the battery and also run the house.
Since the PV charged the battery you can then use it for both load shedding and night usage and save money.
With some planning and timers you can move loads (eg pool motor, electric geyser, washing, dryer) to sun hours.

According to https://www.sunsynk.org/lithium-batteries
The battery has 5.12kWh usable capacity, 0.5C (50A) rating, and 100% DoD.
I would limit this to 90%-95%
Usable = 5.12kWh * 90% = 4.6kWh every cycle
Load = 50A * 48V = 2.4kW (for comparison a kettle uses ~1.8kW) - if the grid is on, then the load is based on the inverter pass thru capability
My whole house on the "essential load" of the inverter and not had a trip yet.

Due to the 0.5C rating, you probably need more batteries to cater for peak load.

On the website that you posted it says maximum continuous discharge is 100a and maximum pulse discharge at 200a for 30s. Which should give off 4.6kw at 1c rating. 

Remember when wiring the inverter into your house you can select essential and non essential loads. 

Your average discharge is about 420w if you take 10kw per day and divide by 24h. But because this is an average you will have higher discharge at times during the day then at night so at night the batter should last just over 10 hours but vacuuming during the day with a 1800w vacuum the battery should last 2 hours. 

2 of those batteries in parallel because of current sharing would be the minimum I would run the 8kv inverter from but best would be 3 but being expandable you can do these at a later stage. 

This should get you through loadshedding most days. Without noticing if the power is even off.

Then get panels as you can but atleast you are starting in the right direction 

Just my 2c from what I understand and what we have running at home

On 2022/07/13 at 2:48 PM, Sparkz0629 said:

Ideally im looking for an estimate of battery usage under average use. With the inverter, the maid for instance wouldnt know loadshedding is ongoing, so wouldnt know not to use the vacuum or the washing machine. Thats also why i went for a larger inverter than needed, to hopefully cover for these occurances.

ok, can't really help you there, since we run off the solar panels during the day + they charge the battery at the same time... washing machine is a low consumer here, its a tub without heater, thus it probably only uses 200 to 300Wh for its cycle, I'd think... this is no problem for the battery if needed, the vacuum cleaner is more of an energy hog, depending, anywhere from 600W to 1k2W whilst in operation, again, not a huge issue, but don't run it for 2 hours if its at the 1kW+ end of the spectrum... Ideally if you have solar + battery and the grid is down, the solar, if its not cloudy, would provide a fair chunk if not all of your consumption, maybe you should consider adding 2 to 4kW's worth of panels as part of this setup, with more panels at a later date... this is what I'd recommend, just running with a battery, looking at a UPS for all intents and purposes is probably a bad idea, specially considering that you really don't know your real usage, Im not sure if the battery is specced at 1C or C/2, if its C/2, then it can only provide 2.5kW of power peak, this may not be sufficient, our house here with a chest freezer and 2 other fridges and some odds and ends runs at an average of 450W overnight at the moment (its winter and the refrigeration end is not running like they would in summer). So during the day, you'd look at this base load + whatever else you're doing... you'd need to figure out your base load and then calculate what else you'd need or want to cater for and see how viable this is, based on the setup suggested...

Interesting that at least one answer indicated some vacuum cleaners at 1800W. This would be the typical wet and dry type. This has been the type we have been using for decades as it doubles up sucking saw dust when doing woodwork as well as cleaning up which is quite a dusty affair 😊😊1 hour and a big chunk of the battery could be gone if during LS.

On 2022/07/17 at 2:31 PM, Scorp007 said:

Interesting that at least one answer indicated some vacuum cleaners at 1800W. This would be the typical wet and dry type. This has been the type we have been using for decades as it doubles up sucking saw dust when doing woodwork as well as cleaning up which is quite a dusty affair 😊😊1 hour and a big chunk of the battery could be gone if during LS.

Now that is just plain rude to brag about your vacuum and solar system by vacuuming at night during loadshedding when everyone else is sitting in the dark.  😜

On the odd occasion that the vacuum is used during loadshedding it would most likely be when there is enough solar power to cover the load and not drain the batteries.
Actually, depending on the system, does it matter if it is during or outside loadshedding?

37 minutes ago, Pietpower said:

Now that is just plain rude to brag about your vacuum and solar system by vacuuming at night during loadshedding when everyone else is sitting in the dark.  😜

On the odd occasion that the vacuum is used during loadshedding it would most likely be when there is enough solar power to cover the load and not drain the batteries.
Actually, depending on the system, does it matter if it is during or outside loadshedding?

No this is the cheapie. Others are 2200W.

Hahaha most of the times a person drops a glass they don't 1st check is it during the sun period or is there LS.

😜😜😜😜😜😜😜

Edited July 18, 20223 yr by Scorp007

18 hours ago, Scorp007 said:

No this is the cheapie. Others are 2200W.

Hahaha most of the times a person drops a glass they don't 1st check is it during the sun period or is there LS.

😜😜😜😜😜😜😜

So you use a 1800-2200W vacuum to vacuum glass shards at night and it takes you an hour...  😜

2 hours ago, Pietpower said:

So you use a 1800-2200W vacuum to vacuum glass shards at night and it takes you an hour...  😜

No my reference point was using it for an hour during LS like we are having the last few weeks. 😬😬😬

And perhaps tomorrow with very little sun.

Edited July 19, 20223 yr by Scorp007

1 hour ago, Scorp007 said:

No my reference point was using it for an hour during LS like we are having the last few weeks. 😬😬😬

And perhaps tomorrow with very little sun.

Was my reference point too but then you deviated to people dropping glasses after hours? 😜

But my question still stands:  Does it matter if it is loadshedding or not?  On most inverters when there is little sun you will draw power from the battery whether LS or not?

Edited July 19, 20223 yr by Pietpower

6 hours ago, Pietpower said:

Was my reference point too but then you deviated to people dropping glasses after hours?

But my question still stands:  Does it matter if it is loadshedding or not?  On most inverters when there is little sun you will draw power from the battery whether LS or not?

OK. Point taken.  Guilty. Sun has no affect as there are no panels. LS and loads are important to have an idea on the battery size as requested by the OP.

Edited July 19, 20223 yr by Scorp007

On 2022/07/13 at 2:49 PM, zsde said:

Ideally you would want to use an energy meter to measure your total usage from about an hour before sunset to an hour after sunrise. That usage will determine the energy required to be supplied by the battery.
As Meerkat also mentioned, you would want to schedule all your high usage activities during the day. It involves a "lifestyle change" if you will. Manage your usage, sequentially if needed.
I only have a single 5,5kW battery and it serves me throughout the night. My early morning SOC is normally between 30 and 40% before recharging starts from Solar.
As soon as I see 1,5kW Solar I start the washing machine or the Dishwasher.