First post with some questions

[Vaaljapie]

Good day,

I am new to Power forum and only became aware of it over the weekend.

I have done some solar work on my farm in Northern Cape and have paid a lot of school fees so far (and hope to limit it in  the future), so I am extremely glad that I found a forum that can share experience.

I am about to build a system for to small guest units that will only be solar powered with generator as backup. So far I have two 310W Enersol panels, considering a WRND 30A controller, Axpert 3Kva Plus and 8 Dixon 105 batteries for the system to feed both units from. Now keep in mind that I have a tight budget.

The consumption per unit will be a small 90w fridge, 40w of lights (max) and a wall socket to charge cellphone and laptops with a 3 amp circuit breaker on it. I have seen very little comment on WRND units but I have one in use and favor the ability to set Bulk, float and equalization charge values on it.

The concern was however the high voltage of the panels so I figured that I will connect them in parallel for the odd chance that I will use the charger of the Inverter.

I have my hardhat on , please advice as to mistakes or better ways of doing.

Glad to be on this forum.

Thanks

Pieter 

 

 

[Guest]

Welcome Vaaljapie.

Just a quick note. The Dixon 105ah batteries are ok for starting to lean about solar, but they are not true solar batteries. They are better than all the other 105Ah batteries in that you can fill them and that they have a higher cycle rate.

 

[PaulF007]

I for one would consider getting a even smaller bracer than the 3a. 3 x 220 = 600 w and that is 600/48 = 12a on the batts. If you have a 200 ah bank and you would it only to be drawn to a max of 60% soc that will give you 200*60% = 80 amps for the night and at 12a will give you 6 hours. As this is a guest unit people will not be sensitive to the perks of solar so rather let the breaker trip than the batts die. 

Also 620 w seems a bit small unless it is a weekend place and the batts will have the whole week to get charge then I can see any harm

 

[pilotfish]

Hi Vaaljapie,

Make sure that you have a chin strap on your hard hat!!!

• The Axpert 3kVA Plus has a 1500w MPPT charge controller whereas the WRND 30A is only 750w at 24v - so you would be wasting your money on the WRND in my opinion, just use the Axpert charger.
• Your battery bank is 8kWh at 100% DoD, but your PV array will only provide 310x2x5/1000 = 6.3kWh per day ( on a GOOD day, using the customary 5 sun hours per day which accounts for all sorts of loses).

Save the R3k that you where planning to spend on the WRND30 and rather buy 2 additional Enersol 310 panels, that will give you a much better balance.

[Vaaljapie]

Hi all,

@ TTT, You are right, they are not but it is merely bying some time as the cash flow is a bit strained at the moment. Hopefully they will make 2-3 years. I also managed to get them through a fiend at a very good price 

@ Paulf007, it is small but the expected occupancy will be less than 80 days each per year. We are in Northern Cape so it is not like Knysna. The only time that we might have back to back bookings is in August and generally there are days in between that the units are not occupied and people are only using it as overnight facility. Anything between 3-5 hours utilization per day is what we have found with the existing unit. I am considering a 2a breaker but will test it once done to make sure that it will be sufficient.

@ pilotfish, are you a pilot by any chance (your avatar)? The reasoning behind the WRND is because as far as I know on the Axpert one can only set bulk and float charge voltages. With the dixeons we have to do an equilization charge of 15.2v which is pretty high. The other charge rates are also very high and for longevity it is impaotant to be able to achieve the settings as per battery requirements. The WRND allow me to set all three modes. I also know that some controllers does not allow some settings to go that high.

The PV array was decided upon based on lowish utilization (as per reply to Paulf007). It might be worth looking into more panels but then I need to make sure the charge volts for the 3 modes can be achieved to sacrifice the WRND.

If you look at the battery spec sheet on www.dixonbatteries.co.za (pdf document if you look on the 105dt battry page) you will find the requirements.

Who is the most knowledgable supplier of Axpert (Mecer ....) inverters? Some guys have lost me when I tried to find out about it.

So far so good no incoming artillary  ......

Thanks guys for the info and advice.

Pieter

 

[SilverNodashi]

5 hours ago, pilotfish said:

Hi Vaaljapie,

Make sure that you have a chin strap on your hard hat!!!

• The Axpert 3kVA Plus has a 1500w MPPT charge controller whereas the WRND 30A is only 750w at 24v - so you would be wasting your money on the WRND in my opinion, just use the Axpert charger.
• Your battery bank is 8kWh at 100% DoD, but your PV array will only provide 310x2x5/1000 = 6.3kWh per day ( on a GOOD day, using the customary 5 sun hours per day which accounts for all sorts of loses).

Save the R3k that you where planning to spend on the WRND30 and rather buy 2 additional Enersol 310 panels, that will give you a much better balance.

well said

 

[pilotfish]

1 hour ago, Vaaljapie said:

@ pilotfish, are you a pilot by any chance (your avatar)?

I used the name when I played a bit of online poker a few years back - it refers to feeding off the sharks and nothing to do with flying.

[Vaaljapie]

I went through the manual for the axpert 2k an 3k Plus again but by the looks of it there is no parameter to set for equilization charge, am I missing it or is it a set value?

[___]

19 hours ago, Vaaljapie said:

considering a WRND 30A controller

I reviewed a 120A unit some months ago. Someone was kind enough to send me one that blew up. Let me just pause here and put on the armour and throw out the disclaimer: This was an old unit. It is possible that the quality improved. They do actually look a little different on gumtree nowadays. This unit was also repaired before it blew up a second time, so some of the issues might have been introduced in repair -- even if I don't think that was the case.

With that out of the way....

Frankly, I was unimpressed. The assembly was extremely shoddy and after-sales service (according to the guy who sent it to me) is extremely poor. I think the items that cement this observation was this: 1) spring/locking washers was used directly on the pc-boards in places, which actually damaged the copper cladding as it was tightened down, 2) the screws that were holding up the LCD were counter-sunk screws but the case wasn't, so all the screws stood up in the air like a crowd singing YMCA, 3) I have my reservations whether the rails used to tie the 4 buck converters together were rated high enough for the current, 4) the only thing separating the connectors (normal galvanised steel bolts) from the steel case were slivers of double-sided tape, and 5) there was no mica insulators between the MOSFETs and the heatsink, which if you understand how a synchronous buck converter works means it relied solely on the heat-transfer paste for insulation. If you use this thing, make sure you have a properly rated fuse between it and the battery!

If you need to use an external MPPT, buy a Victron BlueSolar. I don't say this just because I am a fan of their hardware, there is really no longer enough of a price difference between this controller and other quality controllers to justify wasting time trying to find one. Just get the smallest one (the 150/35) and never look back.

[Vaaljapie]

Plonkster,

Thanks for this inside view (pun intended) of the WRND unit. i would love to have a Victron but the prices swung me away from them and I know there is a premium on quality.

Who can I contact to get prices and specs on the unit? 

Other requirements above the normal is that it must be able to set bulk, float and equilization charge volts (29.6, 26.4 and 30.4 for a 24 volt system).

I will search now to see if there is a manaul available.

 

 

[___]

5 hours ago, Vaaljapie said:

Who can I contact to get prices and specs on the unit? 

Which unit? The BlueSolar? The PDFs are on Victron's website, and prices vary widely, depends on where you are and who is closest to you. Usually what I do to get an idea of the price is look at sustainable.co.za, and subtract 20% :-)

The reason I say to go directly for the blue controller is because you really have to consider the lineup. The cheapest MPPTs are the low-end Microcare units, but those typically have a maximum open circuit voltage of only 50V, they are meant for smaller 24V systems. If you move up from that, your small BlueSolar units are next (100/15 and 75/15, 24V max, around the 2k mark), and then you're pretty much in the 4k+ domain after that that has everything else. The Microcare units used to be a good option, it was cheaper than some other units, but those are over 5k now. You can however buy the Victron BlueSolar 150/35 for around 4.5k, sometimes even less. All the other makes (Outback, MorningStar)... they will cost more.

I did qualify my post with "If you have to use an external MPPT...". Perhaps you don't have to, as @pilotfish said.

[Vaaljapie]

It will be great if I dont have to buy an external charger. However, the external charge controller is used only because as far as I know the Axpert cannot set bulk (29.6v on 24v system) to the level Dixon requires and it does not have a parameter for Equilization charge which is specified as e.g. 30.4v on 24v system. See attached file.

This is important as test were done by a friend of mine on these batteries and if these charge levels are not achieved then they dont get the expected nr of cycles. 

[Chris Hobson]

@Vaaljapie if you decide to go for external SCC you would do well to visit this forum's sister site (Powerforum Store) here.

[pilotfish]

Note that I made a c***-up in my original response regarding your panels,

On 2017/06/19 at 3:40 PM, pilotfish said:

310x2x5/1000 = 6.3kWh per day

the above is incorrect and should read as follows;

• 2 panels - 320x2x8/1000 = 3.1kWh per day
• 4 panel = 6.2kWh/day

Your consumption with both units occupied will be something like the following;

• fridge = 90W x 12h = 1080Wh x2 = 2.16kWh
  • might be more because guests will probably stock up with warm beer and hot meat, and then open the fridge every 5minutes for another dop!
• lights = 40W x 6h = 240Wh x2 = 0.48kWh
• Total about 2.5kWh per day.

This means that after a cloudy day the 2 panel system will have very little overhead available to charge 4 strings of batteries. I therefore suggest a minimum of 4 panels (1.2kW which is within Axpert capabilities but exceeds WRND30 750W panel capability).

If you are uncomfortable with the Axpert charge capability then you should go for an external SCC, but not the WRND-30 which will limit you to 2 panels forever. If you go for the WRND-80 (12/24v) it has a 2kW panel capability and is cheaper than the WRND-60 which is is 1500Wp but at 12/24/36/48v.

To be perfectly honest if I was in your shoes I would change the entire system design

• Axpert MKS 5k or MKS 3K-48+
  • Both the above give you 3000Wp and 48v system
• Minimum of 4 x 310W panels
  • Gives enough power to supply load and charge batteries,
• Single string of 4 x 200Ah AGM battery
  • Allows for single battery string matching the energy of the 4 strings on previous system, this will do MUCH more for battery longevity than fancy chargers,
  • Axpert charging algorithm suits most AGM requirements very well.
• Battery balancer to prevent individual battery voltages going out of whack
  • does the similar job for AGM battery life as equalizing does for flooded cells.

If all you have bought at the moment is 2x panels then the above will probably cost about the same as your previous design.

 

 

 

[___]

8 hours ago, Vaaljapie said:

29.6v on 24v system

Oh, 24V system!? Well that makes things a lot simpler, because the cheaper 100/whatever controllers cost less money. A 100/30 is less than 3k. You could get two 100/15 controllers for around 3k, run two strings and have independent tracking and some redundancy.

[Vaaljapie]

@pilotfish, I will try and put figures to your suggestion to see what the total cost is going to be and also find out about the products itself. Thanks for the advice. Any suppliers that will have competitve pricing? Bear in mind that I am in Northern Cape.

@plonkster, the 24v was used as an example only. I will try and set it up as a 48v system for the various advantages. This unit will only work if I change batteries with lower charge settings or that is not sensitive to specific charge requirements?

[Vaaljapie]

@pilotfish, is the Sonx RA12 200A battery, as an example, what you are referring to?

[Vaaljapie]

@chris hobson, thanks, I have had a look there already 

[___]

6 hours ago, Vaaljapie said:

This unit will only work if I change batteries with lower charge settings or that is not sensitive to specific charge requirements?

We've discussed that before, in fact we've beaten that horse to death and then some more... :-P The topic of the high absorption voltage as well as the high equalisation voltage of the Trojan batteries come up time and again. I think the last consensus was that these batteries are designed for use in golf carts, scrubbers, and fork lifts (sometimes) where you preferably want them to charge quickly. A higher absorption voltage means you can charge faster... BUT it doesn't mean you won't get the batteries full with a lower voltage... it will just take longer. You can recharge a battery using nothing higher than the spec'ed float voltage, it will just take the whole week! So you can compensate for the inverter's lower abilities by making sure your batteries hang around at the highest voltage the charge controller/inverter is capable of for longer periods of time. You can empirically determine how long that is by using a BMV and seeing how long you have to hold them there before the tail current drops below 1% of the capacity.

But it is also true that batteries really should be recharged as quickly as possible for long life, and I would rather look at a better battery match if I already made up my mind about using that particular charger/inverter.

[pilotfish]

6 hours ago, Vaaljapie said:

is the Sonx RA12 200A battery, as an example, what you are referring to?

Yes that will do the job if you decide to go the AGM route, just make sure that you are getting the RA-12-200D which is optimized for cyclic life rather than standby - the more common RA12-200Ah is a standby battery better for UPS etc

"RA12-200D is an AGM deep cycle battery with 10 years floating design life,specially designed for frequent cyclic discharge use. By using thick grid & specific paste plates the battery has 30% more cyclic life time than standby batteries. Applications include solar & wind energy systems, golf carts, electric wheelchairs, etc."