Jump to content

solar to axpert 3kva


charl
 Share

Recommended Posts

Hi guys

I have my inverter all connected and wired into my db. I did the entire installation myself and all is working well.

It's now time to add some solar panels. I plan to eventually add 5 300watt panels. But have orders 2 for now. And should have them by Friday. I'm planning on installing them over the weekend.

I have the axpert mks3 plus allowing for 1500 watts of sloar and the valts can range from 30 to 115 vdc at 60a

My panels are 300 watts 36,7v 8,17a

My question is what is the best way to connect them. All the panels in parallel.

What is the best for the 2 panels now and for the future of all 5 panesl

I'll accept any suggestions

Link to comment
Share on other sites

I'll accept any suggestions

 

Connect the initial 2 panels in series and eventually have 6 (rather than 5) panels as 3 strings of 2. You can exceed the 1500W in terms of panels. The unit will just not draw more than 1500W from your panels. For the most part you would get 2/3 to 3/4 of your rated 1500W so having 1800W you would be closer to your 1500W most of the time. the figures to watch and not exceed is the 115V and 60A.

Link to comment
Share on other sites

Thanx for the advice.

So Id wire the two panels in series down to my dc disconnect box. And then in my box. I can then connect the 3 strings in parallel and then go into the inverter.

Seems like a easy option. I like the idea of getting the most power out of the system.

Link to comment
Share on other sites

You will need to fuse your panels. So either a combiner box with fuses. One can get ready made ones from solar suppliers or 4X fused MC4 Y connectors and then on to you DC disconnect. Make sure your cabling is rated to carry the maximum current you will see (Isc x n where n is the number of strings. This for the cabling  after the combiner box or Y connectors) and rate your solar ceramic fuses at 1.25 of Isc).

 

You can determine your cabling requirements here

http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

 

Chris

 

P.S. Read up about earthing there has been a fair amount of discussion on this forum and mybroadband. If you have the bandwidth watch MIke Holt's video (1 hour long)

 

Link to comment
Share on other sites

I agree with 3 strings of 2 in series = 73.4V @ 24.51A

but wouldn't it be better initially with 2 in parallel = 36.7V @ 16.34A than in series 73.4V @ 8.17A for charging purposes, or does it not matter as far as the MPPT controller is concerned ?.

 

Two panels in parallel could drop below the 30VDC minimum for the MPPT and the idea of the MPPT is to maximise W and then match that to the batteries' requirement.

Link to comment
Share on other sites

Here are some pics of my instalation today. Got the 2 panels up and connected in series. I only completed it at about 3pm. Was generating around 350watts from the 600. I'm intrested to see what they generate tomorrow in peek sun.

The panels are facing more north East than true north. So don't think I'll get the best full days power from them

post-1106-0-69181100-1446936522_thumb.jp

post-1106-0-75520800-1446936444_thumb.jp

post-1106-0-42904800-1446936305_thumb.jp

post-1106-0-17812200-1446936374_thumb.jp

Link to comment
Share on other sites

  • 3 weeks later...

Could anyone offer some assistance with the battery settings. I have a 24v system and don't know what voltages to set in watchpower.

post-1106-144882616261_thumb.png

It seems though I have my back to grid voltage to low. Theoretically I should have 1.2kwh of power once the sun goes down. 24v X 100ah X 50%

It seems like it cuts over way to quick.

Does anyone know what the settings should be for the batteries

Thanx

Sent from my C6833 using Tapatalk

Link to comment
Share on other sites

I see what you mean. I guess my average draw in my house once I'm home in the evening is 350watts.

Bellow is a table of what I have been keeping track of my usage since I added kw meters to the input and output of the inverter.

40ce99169fb738235868adac1ac4f219.jpg

So I know I need more batteries and better batteries for my back up. By looking at the table. On average I am 1.9kwh short and most is 2.5kwh per day. So when sizing my new batteries is should add the 1.2kwh from my existing batteries. Any suggestions on what batteries I should get and size to see me through the night

Sent from my C6833 using Tapatalk

Link to comment
Share on other sites

You don't say what batteries you have, but your story sounds similar to mine.

 

I have 2 x 200Ah batteries in a 24V bank, so 200*24*0.5 = 2.4kwh. Solar makes between 4kwh and 5kwh a day, and most of the stuff just runs directly from there until about 4PM when shading sets in and we slowly start to dig into the batteries. By 10PM I'm back to the grid, and by then I've taken around 2kwh from the batteries. So from that basic observation, I need around 200Ah for every 5 hours in my setup, perhaps a little less as we do go to bed, and then the load comes down somewhat. So I'm thinking I need 600Ah (at 24V).

 

Most cost-effective way to get that would be to buy a bank of 2V cells at 550Ah-600Ah (Eternity batteries makes a nice C10 rated one). Buuuut, that's going to set me back around 35k :-)

 

Since yours is a 48V system... just halve the Ah figures.

 

So what can you get that's around 300Ah? There's the Trojan T105RE at 225Ah. That has decent cycle life (1600 cycles to 50%). But it's going to cost about 21k for that, and the storage cost in one of those is strictly speaking still R2.37 a unit, which is above the cost of buying it from the grid.

Link to comment
Share on other sites

Oh those FMF things are bloddy horrible. Their cycle life is atrocious. An acquantance of mine was selling his 230Ah batteries (9 months old), which is basically the same thing. I was interested initially, but he wanted R2000 per battery, which was about half of what he paid, and STILL not really worth it to me. They have around 600 Cycles, maybe 750 to 50%. The cost per kwh storage is something like R3.20 to R3.50 per kwh.

 

My advice would be to cut off at 20% DoD and just use Eskom. That would be cheaper. Shop around for cheap second hand UPS batteries. Sure, their cycle life is still pretty terrible, but if you get them cheap enough that's a much better deal :-)

 

For cycling, I would recommend at least the Trojans. One of these days I'm going to make lots of money and get a nice 2V setup :-)

Link to comment
Share on other sites

Let me tell you about the terrible batteries I'm presently using. It's two Victron AGM batteries. UPS batteries, pretty terrible cycle numbers (the gell battery is marginally better). But... and this is the thing, I got them dirt-cheap at 1.5k a piece. At that price... I don't care if I kill them by next Christmas.

Link to comment
Share on other sites

102/105ah maintenance FREE batts are bad news for solar systems, been there, done that.

Good for UPS'es IF IF IF IF you never drain them below 50% ... o wait, UPS'es cannot stop until the batts are nearly 100% drained ... 20-30 cycles and you buy more batts.

 

So IF you have them and cannot sell them, keep them above 20% DOD, 80% or even better, 5% DOD with 95% spare all the time, they will give you MAYBE 2-4 years.

You keep the 95% spare for if Eskom starts their woes again.

 

But if you go below 50%, you kill them quick.

Go to 100% DOD daily, few weeks on a solar system and they are dead.

Link to comment
Share on other sites

TTT that is me neighbours house. I know it's close but it's a small complex

I was not expecting them to last long. I was using it as back up during load shedding. And then it stopped soon as my system was up and running.

I then added the solar and realised how terrible the batteries actually are. I was planning to use them until they are finished. And then replace them. I'm thinking they will need to go very early next year. This is why I'm calculating mu usage to see what size batteries I should buy

Sent from my C6833 using Tapatalk

Link to comment
Share on other sites

1.2 kW/hr seems a lot of power but unfortunately it is not. 400W which is an average draw (couple of lights PC etc) your batteries are going to last 3 hours until your SOC is 50%. You will have to be judicious in your use to get the batteries to last.

Rather opt for a SOC of 80% if you want to get some useful life out of the SF100 batteries. 50% is possible, but at a price.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...