I have an older 24v 3kW inverter running off a 24v 100ah lithium battery. Am thinking of getting a 5kw Sunsynk inverter, hook it up to the panels & utility & get it to feed my current inverter via the A/C input. Reason is Sunsynk is 48v so it won’t charge my 24v battery pack & discharge from it. Once my battery reaches end-of-life, hopefully by then can afford a 48v battery to match with the Sunsynk & decommission it. Anyone with advise & thoughts on this?

35 minutes ago, Moffat said:

getting a 5kw Sunsynk inverter, hook it up to the panels & utility & get it to feed my current inverter via the A/C input

Ok, just realise, when utility is AWOL, so will the Sunsynk be... it can work off solar, as long as it has either utility, or batty as backup to help with fast changing load current...

35 minutes ago, Kalahari Meerkat said:

Ok, just realise, when utility is AWOL, so will the Sunsynk be... it can work off solar, as long as it has either utility, or batty as backup to help with fast changing load current...

Yes am aware of that hence why it’ll be feeding the 3Kva system which then charges and discharges loads. So the load on Sunsynk will be the 3KVa. Just trying to figure a way to retrofit a Y-junction on panels in case Solar is low or we have cloud cover so I can turn off Pv to Sunsynk but have same low-end PV going to smaller 3Kva system. Gymnastics in my mind at the moment… oops just realised it won’t work because Pv to Sunsynk will be paired to ensure higher voltage, which lower 3Kva won’t take as it’ll create an overload🤦🏽‍♂️ 
Still it’s mind-stimulating simulations going on. 🤣😂

Other option is to look for the smallest 48v battery to handle those issues, am wondering where I could get a 50ah battery or thereabouts. Just got another thought: I have a 600va UPS, which I could also use on between the Utility and Sunsynk, wonder if that would at least handle short-term fast changing load, hopefully it may... who knows hehehehe.

Edited December 10, 20232 yr by Moffat

49 minutes ago, Moffat said:

Yes am aware of that hence why it’ll be feeding the 3Kva system which then charges and discharges loads. So the load on Sunsynk will be the 3KVa. Just trying to figure a way to retrofit a Y-junction on panels in case Solar is low or we have cloud cover so I can turn off Pv to Sunsynk but have same low-end PV going to smaller 3Kva system. Gymnastics in my mind at the moment… oops just realised it won’t work because Pv to Sunsynk will be paired to ensure higher voltage, which lower 3Kva won’t take as it’ll create an overload🤦🏽‍♂️ 
Still it’s mind-stimulating simulations going on. 🤣😂

Other option is to look for the smallest 48v battery to handle those issues, am wondering where I could get a 50ah battery or thereabouts. Just got another thought: I have a 600va UPS, which I could also use on between the Utility and Sunsynk, wonder if that would at least handle short-term fast changing load, hopefully it may... who knows hehehehe.

You connect the Sunsynk to your grid. The 3kW AC in is also connected to the grid. PV from Sunsynk then feeds the whole house when the grid is on. When the grid is off you have the 3kW than can feed the selected loads from your battery that was charged. 

Can work until the batteries are shot. 

Are you going to wire everything yourself? 

What is the maximum Voc the 3kW inverter MPPT can accept? 

Edited December 10, 20232 yr by Scorp007

19 minutes ago, Scorp007 said:

You connect the Sunsynk to your grid. The 3kW AC in is also connected to the grid. PV from Sunsynk then feeds the whole house when the grid is on. When the grid is off you have the 3kW than can feed the selected loads from your battery that was charged. 

Can work until the batteries are shot. 

Are you going to wire everything yourself? 

What is the maximum Voc the 3kW inverter MPPT can accept? 

Maximum Voc on the 3kW is 115volts, Sunsynk needs minimum 150volts. No am not wiring myself but will direct "my guy" how I want things wired and test. Your idea makes sense to wire panels to Sunsynk.

1 hour ago, Moffat said:

Maximum Voc on the 3kW is 115volts, Sunsynk needs minimum 150volts. No am not wiring myself but will direct "my guy" how I want things wired and test. Your idea makes sense to wire panels to Sunsynk.

In order for the Sunsynk to make any sense the panels must be connected to the Sunsynk. If not and you don't have a battery the Sunsynk can perform no function. 

Back to the panels. 

What size panels do you use or intent using? 

10 minutes ago, Scorp007 said:

In order for the Sunsynk to make any sense the panels must be connected to the Sunsynk. If not and you don't have a battery the Sunsynk can perform no function. 

Back to the panels. 

What size panels do you use or intent using? 

I have 12 x 250w panels. True, there's no way panels cannot be connected to the Sunsynk, otherwise I'd have to wait on hooking up the Sunsynk till am able to do that, though I know Sunsynk can work without panels and connected to AC, problem is with current loadshedding and AC drop, Sunsynk also switches off.

20 minutes ago, Moffat said:

I have 12 x 250w panels. True, there's no way panels cannot be connected to the Sunsynk, otherwise I'd have to wait on hooking up the Sunsynk till am able to do that, though I know Sunsynk can work without panels and connected to AC, problem is with current loadshedding and AC drop, Sunsynk also switches off.

Yes as you know you need to have at least 2 of the items. Although it can work with grid and no panels you need a battery and the 24V does not help. 

Then as you asked would be in grid tied mode with panels and grid as I suggested earlier. 

What you can do is to connect 3S(guess) panels to the 3kW to charge battery and at least provide some power from PV even when the grid is off and the other 9S to the Sunsynk is idle. 

When grid is on the Sunsynk can self power a number of loads during day time and provide some savings. 

When batteries shot you can use the 12 panels in series on  MPPT1 and MORE new panels on MPPT2 with battery. 

Edited December 10, 20232 yr by Scorp007

2 hours ago, Moffat said:

Other option is to look for the smallest 48v battery to handle those issues, am wondering where I could get a 50ah battery or thereabouts. Just got another thought: I have a 600va UPS, which I could also use on between the Utility and Sunsynk, wonder if that would at least handle short-term fast changing load, hopefully it may... who knows hehehehe.

I would highly recommend you get a battery, even if it is very small like this pylontech:

https://www.sustainable.co.za/collections/lithium-batteries/products/pylontech-us2000c-2-4kwh-48v-li-ion-battery-1

It will smoothen out power delivery to your house as solar can jump up and down like crazy if a small cloud comes over or the cat walks over the corner of one of your panels.

Just remember you cannot mix and match old and new batteries, lithium internal resistance goes up over time, which causes issues.

17 minutes ago, HendrikBigChief said:

I would highly recommend you get a battery, even if it is very small like this pylontech:

https://www.sustainable.co.za/collections/lithium-batteries/products/pylontech-us2000c-2-4kwh-48v-li-ion-battery-1

It will smoothen out power delivery to your house as solar can jump up and down like crazy if a small cloud comes over or the cat walks over the corner of one of your panels.

Just remember you cannot mix and match old and new batteries, lithium internal resistance goes up over time, which causes issues.

You're right there, only downside to this battery is that if I use my induction cooktop which pulls 1800w, the immediate draw on the battery will be quite high. Currently my "knock-off" Chinese inverter delivers maximum 2400w at 1800w it's quite strained and fans go off like crazy and am almost maxing it out so I have to reduce my power to 1600w which then measures about 80% on the inverter side. Was looking for a datasheet for this battery you've recommended so I can see the C-rating, didn't find it.

7 minutes ago, Moffat said:

You're right there, only downside to this battery is that if I use my induction cooktop which pulls 1800w, the immediate draw on the battery will be quite high. Currently my "knock-off" Chinese inverter delivers maximum 2400w at 1800w it's quite strained and fans go off like crazy and am almost maxing it out so I have to reduce my power to 1600w which then measures about 80% on the inverter side. Was looking for a datasheet for this battery you've recommended so I can see the C-rating, didn't find it.

Just now, HendrikBigChief said:

You should be able to run the induction plate as the max is around 2500W, especially if you have solar as well. However with this smaller battery you are not fully using the inverters 5000W capacity.

26 minutes ago, HendrikBigChief said:

You should be able to run the induction plate as the max is around 2500W, especially if you have solar as well. However with this smaller battery you are not fully using the inverters 5000W capacity.

True, it does mean I still have some headroom to play around with and am well under 50%. It's the maximum achieved value of 1.2kw was concerned about as per screenshot (battery side).

Edited December 10, 20232 yr by Moffat
Added info.

2 hours ago, Moffat said:

True, it does mean I still have some headroom to play around with and am well under 50%. It's the maximum achieved value of 1.2kw was concerned about as per screenshot (battery side).

Thanks for that idea of starting with the small Pylontech us2000c, because it then means effectively with my 24v 100ah older battery I have 2400w + may 2400w (-about 10-25% of that older battery pack) seeing as it is some "Chinese knock off" which has been with for almost a year now.