Hi 

I was thinking of getting an 8kw Sunsynk inverter with 2x 5.32kwh Sunsynk batteries and 12 panels JA solar bifacial  (545w) until I came across another battery choice- Dyness 14.3kwh power brick.

Some of the things I found attractive were

1) This battery has higher storage than 2 batteries - yes I understand 0.5c charge and discharge but if inverter is 8kw and you are discharging at say 7.1kw - I don't think you are losing out much. not to mention it can discharge at 10kw if need be as per website

2) this battery is cheaper than 2 sunsynk batteries and comes with unlimited cycles 10y warranty 

why would someone not go for this and go for less storage with sunsynk batteries - only reason could think of was more warranty on inverter as you use sunsynk batteries 

Another thing I wanted to clarify was monofacial vs bifacial panels - given a choice would it better to have bifacial even though they would be on the roof as they have glass coverage on both sides

Just looking for opinions from the Solar people who are pro at this 

 

 

Hey Vik...welcome.

Decently spec'd system you have thought of there, have you spec'd that based on your actual kWh usage per day and month also taking into account current appliances/devices you have running? Will everything run through the system?

1. I think it would really come down to the application of what you looking to do with it? Will you be pulling that much of a load for that long to warranty a 1C discharge rated battery when you dont have grid or PV available? In most cases if you are running on battery its because there's an outage or its load shedding so you would likely want to use only what is absolutely needed so the battery will last longer.
2. I only just got the Dyness batteries in November, so far so good no issues to report. Yes it is cheaper than the SS too, so easier on the pocket.

More capacity on the Dyness Powerbrick at 14.3kWh, I guess the one downfall will be that if you ever want add another battery you would need to buy another 14.3kWh battery - this was my issue I faced before. Whereas with the 5kWh battery you paying for another 5kWh if you want to add to it later. In the end its also going to be your preference...I mean your budgets preference 🤣

Many thanks for the reply Carl

So the system was thought to reduce the dependency on COJ - I.e I use around 40units of electricity a day and if I can generate say around 25-30 of those with a system then my electricity bill should go down (in addition move to prepaid as well so as to lower running expenditure). The payback I calculated was around 5 to 5.5 years if I am able to halve my electricity bill (esp as costs have come down)

Also the idea was to change behavior and use sun energy when available- use dishwasher, washing machine, pool pumps during the day - if there is any excess I could use it to run my Aircons or put it towards my geysers. My geysers are retrofitted to solar tubes already and on timer so don't need to run geysers as an essential load as such. Also there is a gas burner so don't need electricity for stove.

There is a koi pond in my house which requires a 24hes pump but I thought with solar and battery it shld be ok (700w odd).

I would use batteries at night when sun goes away so as to supplement the stored energy for grid and reduce my electricity bill

i doubt if I use judiciously (change behavior to use more solar energy when a available) I would use more than 14.3kw (that's almost closer to 3 5kw batteries). I get your point on additional battery but I doubt I would need it (touch wood and never say never😂) 

Also would love your view on monofacial vs bifacial panels 

 

That's very similar to what my usage use to be, I think I was around 45 a day...but the system runs 2 x households so everything is doubled; fridges, TV's, washing machines, irons, network equipment, borehole pump, booster pump and other electronic devices. I also use to run 2 x geysers a 3kW and 4kW elements. But since gone the gas geyser route so no need to run the 4kW geyser anymore. My PV generation use to be on average 35kWh a day...some days closer to 40kWh...that's servicing the load and charging the battery. Also a slight behavioral change from everyone to do more during the day, but I feel like its a losing battle at times 🤣 .

My battery is set to deplete to 50%...which now during summer means I hit 50% by 2am-3am and then it uses grid again.
Currently for the summer days my average grid usage is down to 8units. I'm also on prepaid.

I guess the nice thing about the SS inverter is that it can still provide PV to your non-essential circuit...only downfall is that Grid will have to be available for it to do that. So that means even you have great PV during the day if the grid is down so is your non-essential circuit...and if you have timers already maybe just consider putting everything on essential and just manage the loads. Also maybe consider like 2 x 5kW inverters or 1 x 10kW just for that extra bit to compensate...given you have aircons, pool pump etc.

Your koi pond pump 700w over lets call it 12hrs from sunset to sunrise now will already use 8400w...so depending how you going to setup your battery take that into account when deciding on going the 14.3kWh Dyness or with the 5kWh SS's to allow for easier future expansion.

Panels...I'll leave that to the real experts on the forum to give you an answer 🙃

3 hours ago, Vik said:

There is a koi pond in my house which requires a 24hes pump but I thought with solar and battery it shld be ok (700w odd).

What happens if that doesn't run for 2 hrs? 4 hrs? How many hours can it be off before bad things happen to the koi?

If it HAS to be on all the time, then make sure it's on the backed up loads. Depending on how it's connected to the main DB this may be challenging.

700W for an hour is 0.7 kWh. Times 10 is 7kWh. So overnight that is going to consume half your battery all by itself. Over a day that's 16.8 of your 40 kWh.

OK... so actually about the same as my pool pump, except I don't run that 24 hours a day.

6 hours ago, Vik said:

I was thinking of getting an 8kw Sunsynk inverter with 2x 5.32kwh Sunsynk batteries and 12 panels JA solar bifacial  (545w) until I came across another battery choice- Dyness 14.3kwh power brick.

Somebody has been advertising a not very used FreedomWon 15/12 on this forum. That's a good battery. 1.0C as well (so you can charge fast and sustain a heavy load).

1 hour ago, Bobster. said:

Somebody has been advertising a not very used FreedomWon 15/12 on this forum. That's a good battery. 1.0C as well (so you can charge fast and sustain a heavy load).

 

Me personally, I would prefer 2 batteries for redundancy.Your 1 big battery goes down and you have no back up for the night time if needed.

 

27 minutes ago, Nicholas Strachan said:

Me personally, I would prefer 2 batteries for redundancy.Your 1 big battery goes down and you have no back up for the night time if needed.

 

Yes. There is that. 1 big is generally a bit cheaper than 2 small, but the latter gives you that redundancy.

hi Bobster 

thanks for the reply to your point on that koi pond pump - point taken that it needs to be on a timer and can't chow half my batteries at night (I mean I wouldn't want it to) - so those koi have been without electricity for a day many a times so I believe they can stay without filteration for 12 hours and use the pump via solar during the day (little bit of grid spillover maybe but nothing that breaks the bank in terms of units consumed).

to your point of 1C battery (and thanks for the lookout of ads) - what is the downside of a 0.5c battery here in this configuration- 14.3kwh can be drained at 10kwh (probably only for a brief while I guess) and even if it is 0.5c you get discharge at 7kw for 2 hours - my inverter is 8kw and with some efficiency loss here and there might be able to handle only 7.5kw - so to me I like the bigger backup with not too bad of a bottleneck

Nicholas - totally get your point on redundancy- one goes off and other one can still work - 15kw in 5kw batteries is around 60k and for 70k one can get two 14.3kw batteries - that's like 28kw backup - I mean even if i were to think of redundancy I would add 14.3 and have backup for days - almost like be off grid (very hypothetical indeed) - but get your point absolutely - many thanks for pointing it out 

I see no one has a view on mono bs bifacial panels 

 

 

 

1 hour ago, Vik said:

thanks for the reply to your point on that koi pond pump - point taken that it needs to be on a timer and can't chow half my batteries at night (I mean I wouldn't want it to) - so those koi have been without electricity for a day many a times so I believe they can stay without filteration for 12 hours and use the pump via solar during the day (little bit of grid spillover maybe but nothing that breaks the bank in terms of units consumed).

OK... so if you run it 12 hours a day, you will drop your 40 units per day to 32, just like that.

 

1 hour ago, Vik said:

to your point of 1C battery (and thanks for the lookout of ads) - what is the downside of a 0.5c battery here in this configuration- 14.3kwh can be drained at 10kwh (probably only for a brief while I guess) and even if it is 0.5c you get discharge at 7kw for 2 hours - my inverter is 8kw and with some efficiency loss here and there might be able to handle only 7.5kw - so to me I like the bigger backup with not too bad of a bottleneck

It may be theoretical. a true 1c battery can be expended in an hour. IE if it's a 10kWh battery, you can draw 1kW for 10 hours, or 10kw for 1 hour. It's unlikely that you would want to do the latter, but it also goes to the momentary peaks that the battery can handle.

Like so many other things in Solar, folks play games with these terms. Some "1C" batteries allow the full discharge for 1 minute each hour, or variations on that theme. FreedomWon LiTE you can run it at the peak rate for as long as you like. And charge it that fast too if your inverter is capable. 

In my case, it's never going to happen. My inverter can charge at 100A, and it's rated at 4.6kW. It take short bursts to 6.9. So I will never get close to using the 1C either way.

But for me it's also better to have the battery rating exceed the inverter rating. That's because if there is an overload, the inverter will reboot itself if there is grid or PV. I don't have to do anything - and there is nothing I can to do hurry the inverter up. It takes about 45 seconds. If the battery gets overloaded but not the inverter then I may not even know because the inverter will just resort to mains.

So for me, I like the inverter to trip before the battery.
 

2 hours ago, Vik said:

I see no one has a view on mono bs bifacial panels 

You said you wanted answers from a pro who works with these things. If you're happy with an ordinary oke's reading of general theory, if you're planning to put it flat on a standard roof, don't bother with bi-facial panels. Just get more standard panels.

Hahahah thanks for the response Greenfield - I didn't mean to discourage any response - may bad

the whole shpeel that some people sell around panels being double sided glassed is better and more durable even when you put it on a tiled roof

i wanted to confirm the durability part as it does seem like there is no use of bifacial on a normal tiled roof 

Sorry Bobster I don't know how to respond to each part like you 😀

I get your point on how gimmick marketing has been used by the companies to push products. But when it is advertised and you know then I think it's a decision thing for me.

as for your spec of battery being higher spec than inverter I think it is the case with this Dyness battery as well - top charge rate is 200amps while 8kw SS can only do 190amps top so that gives me some inbuilt failsafe as you have mentioned 

Thanks for the calc on 12hr use of koi pond and drop in used units - I reckon then potentially I could be grid free for certain hot days actually if my consumption drops to 32-35 - I think it's totally worth it then - many thanks 

1 hour ago, Vik said:

double sided glassed is better and more durable

Some Aussie University tested them and apparently the normal ones is stronger, especially in hail storms?  The bifacial is 2mm glass front and back - normal mono is 3.2mm

4 hours ago, Vik said:

I see no one has a view on mono bs bifacial panels 

Hi Vic.

My setup is almost similar to yours. I have a 10kW SS with 4 x Dyness DX51000 (1C) batteries (had only 2 until early January), 6 x JA Solar 550W Bifacials on MPPT1, 6 x Trina 545W mono on MPPT3 (MPPT 2 will be connected soon, once roof has been completed). Flat roof painted white, all panels facing directly north. Everything is on essentials (1 x 3kW Solar geyser, 1 x 2kw normal geyser, gas stove, pool pump, electric fence, LED lights, 3 x AC units etc). Solar geyser is set to heat from 12 (if not on temp), smaller geyser and pool pump on CBI Astute with timers for time of day and remote access). Both geysers are on during day while the sun is out, pool pump runs in the afternoon from 1 to 5. Batteries are set to charge from PV only, once below 40%SOC, use grid. No export to grid. I have been monitoring usage, PV production, etc closely since install was done in June 2024 and these are my findings:

Before the Sunsynk, there was a Synaps 5kW with 6 x360W Canadian solar panels on the roof and 12 x lead acid batteries in the garage (we bought the house with this on site). Eskom usage was around 20 units per day. Late in May 2024 I took the plunge and replaced it with the SS, 2 x Dyness batteries and bigger panels.

With the SS and 2 batteries I used to start using grid from around 3AM until the panels start producing again. On a nice and sunny day, the batteries would be at 100% SOC around 11am (we try to run the big stuff when the PV's are producing). On these days we would consume around 4 Eskom prepaid units/ day (down from 20).

Since January this year, with the 2 additional batteries and the charge rate set @ 0.2C (80A), all the batteries are now at 100% SOC around 10:30 (on nice sunny days). Around 6 AM the 4 batteries are now at 65% SOC, when PV start producing again. My grid usage (according to the the SS app) are now right down to 0.3kW/day = happy days.

What I have found, is that the mono panels are better/ more efficient in low light conditions, but on nice and sunny days, the bifacials will produce around 400-600w more at the same time (even though they are effectively 30W more powerful)

I hope this helps in making a decision.

Many thanks Teltech - really appreciate the detailed response