Help!

[ClintonDBN]

Okay, the subject was a little dramatic but I am needing some eyes on this system plan to advise what looks wrong, and help with a few queries. 

 

Anything that immediately jumps out as an issue? Yes, I am using a fuse holder as a busbar as it works out cheaper (strangely!). 

 

Batteries are lead acid, 200ah at 48v. Eventually they'll be replaced with lithium. 

 

Questions:

1. Given the output of the panels, do I even need fuses between the MPPT and battery busbar? My (perhaps mistaken) understanding is that the fuse protects the cable. A 6mm PV cable has a rating of 60+a, which those panel strings won't push out, even in perfect conditions (from what I can tell). 

2. The fuse holder/busbar is 250a rated which should be fine for three MPPTs of 60,85 and 35a attaching to, and then off to the 200Ah 48v battery? 

3. I've highlighted the Solarworld panels as I realised 150.4 VOC means too much for the 150/85 MPPT. It has been like that for over 5 years now, so, I know it should be rewired to parallel/series, but can I assume it is unlikely to be an issue? I want to avoid parallel. I presume over that time components had deteriorated so things would have decreased further. 

4. What is generally, and cost effectively, used as an isolator switch between the panels and the MPPT? I am considering two of these. That'll allow a 4th string if needed but it works out cheaper that 3 x 2p isolators anyway. 

 

Edited September 19 by ClintonDBN

[HendrikBigChief]

1 hour ago, ClintonDBN said:

Okay, the subject was a little dramatic but I am needing some eyes on this system plan to advise what looks wrong, and help with a few queries. 

 

Anything that immediately jumps out as an issue? Yes, I am using a fuse holder as a busbar as it works out cheaper (strangely!). 

 

Batteries are lead acid, 200ah at 48v. Eventually they'll be replaced with lithium. 

 

Questions:

1. Given the output of the panels, do I even need fuses between the MPPT and battery busbar? My (perhaps mistaken) understanding is that the fuse protects the cable. A 6mm PV cable has a rating of 60+a, which those panel strings won't push out, even in perfect conditions (from what I can tell). 

2. The fuse holder/busbar is 250a rated which should be fine for three MPPTs of 60,85 and 35a attaching to, and then off to the 200Ah 48v battery? 

3. I've highlighted the Solarworld panels as I realised 150.4 VOC means too much for the 150/85 MPPT. It has been like that for over 5 years now, so, I know it should be rewired to parallel/series, but can I assume it is unlikely to be an issue? I want to avoid parallel. I presume over that time components had deteriorated so things would have decreased further. 

4. What is generally, and cost effectively, used as an isolator switch between the panels and the MPPT? I am considering two of these. That'll allow a 4th string if needed but it works out cheaper that 3 x 2p isolators anyway. 

 

1. you are going to need two battery balancers. Whenever batteries are in series, you need to balance them. 2. You are going to need fuses on the solar panels. 3. You are going to need a COC certificate from a qualified electrician.

[Bobster.]

Best to put surge protectors on the lines from the panels, as well as between grid and inverter.

[ClintonDBN]

9 minutes ago, Bobster. said:

Best to put surge protectors on the lines from the panels, as well as between grid and inverter.

Thanks. Surge protectors? Is this an electrical requirement or a nice to have? I am near Durban so, as far as I'm aware, lightning strikes are rare. I also live in a faraday cage (ibr sheet structure), so not sure if that makes a difference.

I see they're expensive too! Solar is a bottomless money pit.

This is an offgrid system so I'm not connected to the grid? 

[ClintonDBN]

1 hour ago, HendrikBigChief said:

1. you are going to need two battery balancers. Whenever batteries are in series, you need to balance them. 2. You are going to need fuses on the solar panels. 3. You are going to need a COC certificate from a qualified electrician.

Thank you.

 

1. Yes, battery balancing is something I had pondered from the start. This system is slowly being built up. At the time I attempted to use best practice (cable lengths and connections) to assist with balancing the load. Looking to get lithium soon so want to prioritise the most important things. 

 

2. I've read that with series panels a fuse is not a priority. Explorist delved into this:

 

3. Yip, everyone needs their pound of flesh

[Bobster.]

23 minutes ago, ClintonDBN said:

Thanks. Surge protectors? Is this an electrical requirement or a nice to have? I am near Durban so, as far as I'm aware, lightning strikes are rare. I also live in a faraday cage (ibr sheet structure), so not sure if that makes a difference.

More technically skilled people than me can advise.
 

23 minutes ago, ClintonDBN said:

I see they're expensive too! Solar is a bottomless money pit.

One lightning strike could cost you more than the price of those SPDs. On my system there's an SPD, a fuse (cylindrical) and a breaker per string. You're not protecting just the cabling, you're protecting the inverter too. Also if you're trouble shooting, it's handy to be able to disconnect those inputs. 
 

29 minutes ago, ClintonDBN said:

This is an offgrid system so I'm not connected to the grid? 

Then you won't need SPDs between the non-present grid and the inverter.