Jump to content

24v and 48v install


 Share

Recommended Posts

Install 1. 48v 5Kva 6 by 315watts panels and 8 by J305 6v 310amp. 2 by 80amp fuses. BMV 702

Install 2. 24v 3Kva 5 by 315watts panels and 8 by J305 6v (2 banks) 610amp 4 by 80amp fuses. BMV 702

Still have a lot of cleaning up to do, so please excuse the dirt ^_^

Hoping to have both to 48v 5Kva and 10 by 315watt pants each by the end of the year.

Very new to solar and only started playing around 6 months ago, before that I knew nothing! Hope all is in order. Been running very well so far. Just not sure if my panels are in the right place! I am a more of a try and error person.........:wacko:

20160303_072118_resized.jpg

20160303_185119_resized.jpg

20160303_185107_resized.jpg

20160303_071904_resized.jpg

20160303_072004_resized.jpg

20160303_072043_resized-2.jpg

20160303_071904_resized-1.jpg

Edited by Camel
Link to comment
Share on other sites

Camel, that You magazine must go. :D It detracts from the batteries.

If those batts where mine, I would have shortened the cables and used lugs instead of the car battery type connections.

I used to use to do same, but they are not as tight as crimped lugs.

Hellerman-Tyton have crimpers and lugs. Their lugs are better quality than the ones at ACDC, who's are quite thin compared to Hellermans, although ACDC is +-half the price. :D

Link to comment
Share on other sites

16mm is a bit thin for batteries, try looking at 25 to 50mm even if you are willing to spend a little more

 

edit: also do you have a disconnect\isolator on the batteries to the inverter

Edited by viper_za
Link to comment
Share on other sites

1 hour ago, viper_za said:

edit: also do you have a disconnect\isolator on the batteries to the inverter

Question viper: If the cable is made to be the shortest distance between poles like under 300mm, why go bigger?

Link to comment
Share on other sites

1 hour ago, The Terrible Triplett said:

Question viper: If the cable is made to be the shortest distance between poles like under 300mm, why go bigger?

The distance from the batts to the inverter is surely not going to be just 300mm?

edit: Also the one bank is in parallel

Edited by viper_za
Link to comment
Share on other sites

I was referring to between the batts i.e.  " ... distance between poles ... ".

For I am wondering, based on amps that a wire can handle in direct relation to its length, is why you cannot have say 250mm 16mm2 cable between the battery poles and only 25mm2 or bigger to inverter?

Link to comment
Share on other sites

Then why not since you have to do the run to the inverter with thicker cables not do all at once and future proof this a little for upgrades.

Yes it can work with 16mm2 over short distances.

I see this the same as buying computer hardware at minimum spec

 

Link to comment
Share on other sites

I always tend to use 25mm2 cables myself minimum ...
BUT!!!
... I feel uncomfortable to tell each new person here to replace cables, especially if they are on 48v, when there are no maths to support it.

How many of us have started with i.e. 16mm2, or hardware at minimum spec as you say, to later upgrade when we have learned a bit more, replacing a battery bank or inverter or getting a new computer? :D

The cable only becomes a very real problem if you go to low batt voltages and inverter at continuous maximum output. So it is not any more or less dangerous, on 48v using 16mm2 if the cable lengths are very short between the battery poles, is all I am saying.

If it was all up to me get 50mm2 cable with the right fuses and be done with it ... but to use a computer analogy: Why get a i7, 1tb SSD drive and 64Gigs of memory if you are not going to push the memory to its limits, store at least 800gigs of frequently accessed data on said drive with the processor hovering regularly at 100%?

The dealer who sold you that setup smiled all the way to the bank where you could have used a small laptop, based on your needs to access FB, open a few emails and use Excel on occasion. :D

Needs and wants again ... does Camel NEED 25mm2 between batts? Yes, then replace. If not, why replace?

Link to comment
Share on other sites

You see you yourself use 25mm2 as a minimum why then recommend less :P

He was asking about the 16mm2 and we are recommending still is up to him to use this recommendation or not.

 

His 48v system is capable of producing 4000w and this can pull 83A  from the batts (please Camel don't do this :)

What if this happens even worse it can surge to 8000w  :o not so nice on a 16mm2 cable (by then I would have wanted the fuse to blow already)

If I remember correctly 16mm2 is rated 75A at 30C 

 

What if I NEED to play a game on my small laptop, sometimes the needs just have to make space for some wants and then I don't need to spend double later (remember the AC man) :D

Link to comment
Share on other sites

I have actually pulled 8500W through a 5kva Axpert before as a test.

It immediately switched to bypass mode and screamed very loudly at me, so he should be able to get away with his current battery cabling, but I totally agree on going with thicker cable. As thick as he can afford is best. Just to cover himself.

Link to comment
Share on other sites

This is how I am looking at it, please correct me where I am wrong:
48v bank is flat flat flat @ 46v right?
Lets say at the time you draw 8000w continuously - not a very clever thing to do if you ask me.
You could be drawing 256amps with inefficiencies taken into account.

But, you are not going be be drawing 8000w continuous.
You could be, in dire straits, draw 4000w continuously from flat batteries (46v), with inefficiency factors, which is 128amps - still not very clever at all.

So, lets use the total length of cable, from inverter to bank, between batteries, bank back to inverter: 4.5m
46v
128amps
http://www.bulkwire.com/wireresistance.asp says, with up to 4% voltage losses: AWG 8
I like, on that calculator, add 2 more levels, as was suggested to me: AWG 6

AWG 6 is about 13mm2, so 16mm2 is more than enough.

If you where on a 12v system, same specs as above, THEN you need min AVG 2, 35mm2 cable.

Link to comment
Share on other sites

18 minutes ago, viceroy said:

And his 24V system?

Surely if the 16mm2 is more than enough for the 48V system, it wont be enough for his 24V system?

3kVa = 2400w, Min 23v, 4.5m length cable = 153amps at full power, on flat batts.
AWG 6 = 13mm2, two lower is AWG 2 = 33mm2 over cautious.

If you are NOT going to run it continuously at full power, use AWG 5 = 16mm2, for it is better than AWG 6

Just make sure the fuses are in place, in both scenarios.

And THIS is where one decides with mixed systems like mine, to strip jou dinges, and take the shortcut and go 25mm2. 
But, 16mm2 is still fine, fused and all that.
 

Link to comment
Share on other sites

6 hours ago, The Terrible Triplett said:

This is how I am looking at it, please correct me where I am wrong:
48v bank is flat flat flat @ 46v right?
Lets say at the time you draw 8000w continuously - not a very clever thing to do if you ask me.
You could be drawing 256amps with inefficiencies taken into account.

But, you are not going be be drawing 8000w continuous.
You could be, in dire straits, draw 4000w continuously from flat batteries (46v), with inefficiency factors, which is 128amps - still not very clever at all.

So, lets use the total length of cable, from inverter to bank, between batteries, bank back to inverter: 4.5m
46v
128amps
http://www.bulkwire.com/wireresistance.asp says, with up to 4% voltage losses: AWG 8
I like, on that calculator, add 2 more levels, as was suggested to me: AWG 6

AWG 6 is about 13mm2, so 16mm2 is more than enough.

If you where on a 12v system, same specs as above, THEN you need min AVG 2, 35mm2 cable.

How accurate it that website?

 

Using your values, 46V, 256A, 4.5m, this website says you need 6 AWG / 13mmsq cable: http://www.bulkwire.com/wireresistance.asp

Another website says 0000 AWG / 120mmsq: 

Yet another says 351mmsq: http://www.energymatters.com.au/climate-data/cable-sizing-calculator.php?main_page=wire_calc&calc_action=cable_size

 

Which is correct?

Link to comment
Share on other sites

Very good point. I have seen the same on the web, the difference between sites.

I was referred to it by other experts. Back when I looked for cables, bulkwire was the closest to the cable manufactures specs in SA, at the time.

Maybe we should do some effort here and see which one is the best? For if in doubt, the cable manufactures specifications in the end, after all is said and done, is all that counts.

mmmm ... energymatters gives you 351mmsqg, for me it gives

   
System voltage 48 V
Amps entered: 128 A
Length entered: 4.5 m
   

The cable cross-section should be at least 175.68 mm2.*

 

The 4.5m, I took the cross sections between the batts plus to and from the inverter. Ideally you would want the cable length as short as possible.
Between the batts I personally prefer very short thick cable, and from batts to inverter, max 1.5m per cable lengths to match the inverters requirements.

Link to comment
Share on other sites

Thanks for all the advise and help, really  Appreciate it  , I will be going 50mm2 with lugs all round! Will get it done and over. From pole to pole will be 170mm long and batter to inverter will not be more then 1M long.

I have Traction plugs and 80Amp fuses on both neg and pos poles between the batteries and inverter.

Took some reading today on both 24 and 48 at the same time. What you guys think?

24v is 33.3Amp (This Inverter is 10m away from the panels)

48V is 18.2Amp (This inverter is 38m away from the panels)

20160305_114840_resized.jpg

20160305_122629_resized.jpg

Link to comment
Share on other sites

NICE ... the decision YOU made on going for 50mm2. :D

The fuses on them cables ... a wondering thought that is as always off the beaten track. :P
You add fuses to protect the wires from melting right?
50mm2 wire will take a huge amount of amps for a while before they melt. I think the rest will be destroyed, bar the batteries, long before they melt?

So why do we not use fuses to protect the devices attached to the batteries? They are cheaper and does the same job.

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...