Haha, it's only a hop skip and a jump from Durbanville to Paarl. 

I will still take the Victron Battery Inverter over the Axpert (if within budget) as it will take better care of your expensive battery bank investment. (Eg. Accurate voltage measurements, temperature compensation on the charging voltage etc.) 

Bushman's Grid Tie Inverter's will be churning out power at about a 97% efficiency and then you can either consume those high efficiency watts or charge your batteries (if you cycle batteries to increase self consumption) or send it to the Utility as the last resort. Every last watt will be utilized. 

Bushman probably has the most efficient system you can get.

1 hour ago, Camel said:

What would happen if morning and afternoon panels were on the same mppt? Is running more then one mppt safe? Would the mppt have to be the same specs?

Conventional wisdom says not to do it (different orientations on the same mppt). I've read reports saying that having east/west panels on the same mppt actually works okay. In theory, the mppt finds the voltage that gives the best overall power, and since half your panels aren't making anything, they don't make much of a difference as the mppt plays with the voltage, while the other half make a huge difference as the voltage approaches the mpp... with the result that the panels that are getting sun basically drive the decision as to what voltage it runs them at. So the panels on the low end end up operating at a voltage where they can't really do anything... which is fine. The argument was that overall the little bit you gain from having two controllers might not be worth it. But then... I believe that was many years ago. MPPTs are much cheaper now, and I think it's a good idea to have several small ones rather than one large unit anyway.

The mppts don't have to be the same spec. They only need to be large enough for whatever you have on the roof on that side ;-)

I must agree, you have a good point there ito the grid tied inverters Carl. And if you use the batteries daily, yes, good investment with the Victron. No need then for charge controllers.

But, if you don't use your batteries daily, i.e. purely for Eskom failures, then that Victron (INVERTER with a built in charger), is a overkill. The 10 000VA one is like around about 70k, the smaller 5000VA something like 50k. 

The UPS'es I am referring to are not the ones we all see and use most. It is these little monsters: http://www.cpsww.co.za/Product/Product/GetProduct?id=74&mid=72#.VuHR55x95aQ , DB board connected, for they have to be on their own breaker due to the amps it can use to re-charge them batteries, of which you can add a LOT. And they changeover in 10ms, for the average of 20ms, is too slow nowadays for most LED TV's due to smaller power supply units.

UPS'es are tried and tested technology, sometimes more reliable than solar inverters, and they have a host more protection in place than any and all solar inverters, including Victrons. 

As matter of fact, at one stage I was considered getting a CyberPower, for they can run 24/7/365, with all its protection and features, and charge the batteries only using solar panels and charge controller, only using the CyberPower's charger if I want to. 

Any case, I just mentioned this for any and all who may not be aware you can now get long running large UPS'es that can take a LOT OF BIG batteries, that is connected to your DB board.

 

 

Hey TTT, even if the batteries aren't cycled he may still need a bi-directional inverter to export excess power back to the grid. (assuming his grid tie inverters are downstream of the Victron)

R70 000 is a huge investment though and thats just for the Victron 10KVA inverter!

That CyberPower 7500, long run UPS i see has a built in 45 Amp charger so max battery size of about 450 Ah at 48 Volts - which as you mentioned is very good for a UPS.

The CyberPower 7500 VA unit is only rated for 5250 watts so best to compare watt ratings on inverter's when shopping around. Last time i looked they were retailing for about R20 000. 

I think the CyberPower and the Axpert can be classed as a "Line Interactive" UPS which is very different to the expensive "On Line Double Conversion" UPS  

Don't you think the Axpert is better value for money? 

	Axpert 5 KVA / 4 KW	CyberPwr 7.5KVA / 5.25 KW
Approximate Cost	R10 000	R20 000
Solar Compatible	Yes	No
Transfer time	10ms (UPS mode)	< 10ms
Charger Capability	3Kwatt Solar, 30 Amps Utility	45 Amps
Efficiency	< 90%	Not stated

 

 

 

The CyberPower with 4 batts is more like +-50k. 

Must admit, I forgot that just the unit, is rather pricey. When I was looking, I could get one at about 13k.

Reluctantly I may have to give a wee bit and say that the Axpert, being a glorified UPS with MPPT ability, could maybe, probably be a alternative, at that price. 

My reasoning for considering the CyberPower was because of the Automatic Voltage Regulator(AVR), Brownout and Over Voltage Protector, that the Axpert, and ALL other solar inverters, do not have. Because when Eskom has a wee bit of drama on their lines, that drama goes through the inverters to your equipment, if you are using Eskom at that time.

I still keep my ups's (both with AVR) in running order although under hybrid inverter. It sounds like a waste and it was supposed to be temporarily while I was testing the inverter but by now I have decided to keep them there for good: grid frequency is wild and a few minutes ago tripped all my earth leakages (out and under inverter). I now wish my hybrid inverter had AVR

You have a point there TTT. 

However, my MLT Powerstar Inverter has a built in AVR but looks like the Victron doesn't.

Just a note on these expensive rack mounted UPS's. 

My one and only job so far in this industry was to spec a UPS / Inverter System for a room full of computers, printers, PABX and all the equipment in the file server room.

As i have a good quality Power Quality meter available, I decided to measure all the loads accurately. (Kw, KVa, KVa Reactive, Power Factor, Harmonics etc.)  

When i got to the file server room i noticed that the equipment was supplied by a Proline 3KVA on line UPS

So to install my meter i had to switch off the AC power at the supply socket outlet. So guess what happened next?

I flicked the switch and then heard a small ontploffing inside the UPS and then all the file servers, routers etc. shut down. It was not a good feeling.

Anyway the UPS had blown a Mosfet so even these expensive pieces of equipment doesn't always guarantee continuity in supply.   

Luckily the File Server survived the crash and R20 000 later the company was back up and running on a new UPS and i scored the old one.

Anyone looking to buy this second hand UPS?

 

 

 

11 hours ago, plonkster said:

I've read reports saying that having east/west panels on the same mppt actually works okay.

I was thinking last night... someone is going to try this and blame me. There is the little matter of bypass diodes in solar panels. In some old BP panels my father had some years ago there was even a series diode in each panel, but it had two connection points so you could choose to wire in the diode or not. You were supposed to wire in the diode on one of the panels on each string. This was to prevent backflow at night. Modern MPPT controllers have a MOSFET that disconnects at night (well, the microcare I disassembled had one), so the panels don't always have it.

In any case, what concerns me, and what I haven't fully considered, is that having two strings in parallel, with one running way higher than the other, might very well cause reverse flow through the other, and then the bypass diodes come into play. If I ever even attempted such a thing, I'd have a diode in each string to prevent such a thing. It would probably be a schottky diode... :-)

Good point Plonkster!

Maybe it is then a good idea to have 2 MPPT's, one per East / West string?

 

Carl, I also had a 3000VA Proline that was between my equipment and power sources being either Eskom or solar inverter.

One day electrician did something in the DB board that made it trip like 4 times in a row before they found the problem. They tried to explain using VERY vague words along the lines with cryptic sentences with the word earth and neutral in it.

Now, at the time Eskom was supplying the Proline with power. Little while later the Proline beeped persistently, like really trying to get my attention ... woeps, everything is off the next moment. The batts where flat.

After checking we found that whatever happened in the DB board, damaged the charger board in the Proline.

If it was not for that ONLINE ups between Eskom and important equipment, I would have lost a LOT of devices that day. A LOT!

I tried to get the Proline repaired, no chance from Pinnacle and a UPS whisperer. So I stripped it for fun ... no, to get to the batts, only THEN to realise it was an Insurance claim.

Too late! (facepalm)

I am 100% for online UPS'es.

You know plonkster, I was thinking of trying it,  lying in bed last night planning how I could set it up, even took out my spare mppt this morning

Hi Bushman, are your grid tie inverters installed before or after your Victron inverter?

Hi Carl. At the moment the Victron is a really expensive battery charger. The Schneider inverters are before the Victron. As I understand it the reason is because of my 3 Phase electricity house.

Not sure if this makes sense. I am still a bit ignorant to know what clever questions to ask.

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Tell me Bushman, if Eskom is off, how will the house be powered, being  3 Phase?

Tell me Bushman, if Eskom is off, how will the house be powered, being  3 Phase?

One phase at a time. Busy rewiring DB to get all lights, plugs,and some aircons to run on the phase the Victron is on. What I am doing now is the start of a process and it kicks off with the best equipment that I can afford to allow me over time to get to an ideal state which in my opinion will be completely off grid. Lots of things will change over time such as getting rid of 3 phase aircons and replacing them with single phase and then getting off 3 phase muni etc.

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So i.e just the lights powered using the Victron?

5 hours ago, The Terrible Triplett said:

Tell me Bushman, if Eskom is off, how will the house be powered, being  3 Phase?

Well... one phase is going to have power and the rest will be dead. So you put all the important stuff on that one phase. Pretty much what many of us (myself included) have done. I was lucky, didn't have to split the DB. Already had most of the important stuff on the same circuit anyway, freezer right next to the inverter, short extension going to the fridge. Done.

All plugs and lights and two aircons in the bedrooms and heat pump are all supported. Big old 3 phase Aircon plus two other non essential aircons plus small geyser in flat and stove and swimming pool pump not supported by 10kW Victron.

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How big are the two bedroom aircons? Are they modern inverter units, or older type?

We have a 12000btu aircon which I wasn't not able to run off my 8kW inverters and batteries. The initial load when it switched on would drop the volts so dramatically that it tripped the inverters.

I haven't tried with the new batteries yet.

They are both 12000btu Inverter units.

Inverter unit should be fine. Non-inverter units have a startup spike of around 5-times the nominal. The non-inverter 12kbtu unit in my main bedroom has a running consumption of around 1.2kw (not continuously, when the compressor is actually running), so it will have a 5kw or 6kw startup spike.

Inverter-units are supposed to slowly ramp up the motor, so it should not have the spike, and should even out at a little over a kilowatt, I would expect it to have a somewhat inductive power factor too, so in terms of VA, probably around 1.5. Should be able to run it on a sufficiently powerful inverter.

I am going to try a online UPS (secondhand, obtained for free) between inverter and the aircon, to absorb the spike.

Much cheaper than replacing the aircons ... IF it works.

On 3/30/2016 at 1:15 PM, The Terrible Triplett said:

I am going to try a online UPS (secondhand, obtained for free) between inverter and the aircon, to absorb the spike.

Much cheaper than replacing the aircons ... IF it works.

I don't see how this will make any difference, unless the UPS can handle larger surges than your inverter.

An online UPS is just one with an inverter running all the time - no switching over when the grid/mains fails. If the aircon compressor kicks in and the UPS cannot handle the surge, it will either trip or fail, exactly what the inverter will also do if connected directly to the aircon. The UPS does not contain something magically that will work like a capacitor on DC, which might help to supply the source if demands peaks momentarily. We are talking about AC here, nothing magically available to "store" power in case of a surge.

4 minutes ago, superdiy said:

I don't see how this will make any difference, unless the UPS can handle larger surges than your inverter.

An online UPS is just one with an inverter running all the time - no switching over when the grid/mains fails. If the aircon compressor kicks in and the UPS cannot handle the surge, it will either trip or fail, exactly what the inverter will also do if connected directly to the aircon. The UPS does not contain something magically that will work like a capacitor on DC, which might help to supply the source if demands peaks momentarily. We are talking about AC here, nothing magically available to "store" power in case of a surge.

Agreed.

So therefor I want to try a 3kva online UPS, powered by a 1600va inverter to power a 9000btu aircon. 

UPS must handle the spike, not the 1600va solar inverter.

1 minute ago, The Terrible Triplett said:

Agreed.

So therefor I want to try a 3kva online UPS, powered by a 1600va inverter to power a 9000btu aircon. 

Yes, that might work.