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Hi Guys

Been following the forum for quite some time and at a stage (no pun intended) where I want to install an inverter system with a phase 1 being battery only to combat load shedding and stage 2 being adding solar panels to reduce grid consumption.

Our household uses an average of 40kWh per day with the big culprits are the 2 geysers (we have 3 in total but 3rd is a gas geyser) and pool pump which runs for around 6-8 hours per day.

There are a plethora of invertors and systems on the market, too many to choose from, after careful consideration I think I’m going to opt for either Victron (very likely) or Goodwe (a little less likely) mainly because they’re quite well know and well supported brands I’d rather spend more and know that I’m getting a product with good support. I would also like to later integrate the Victron with Home Assistant.

I’d imagine based on our consumption that we’d need around a 5KW inverter? I probably wouldn’t run things like the pool pump and geysers on it until we’ve added the solar.

In terms of batteries I’m thinking Pylontech US3000B’s x 2 maybe 3? What sort of run time could I expect?

Would really appreciate some feedback from the helpful community and hopefully a push in the right direction from the clever folk around here.

I’m currently got all of my networking gear which is exclusively Mikrotik and Nokia ONU running off 2 x 35Ah batteries with Victron charger so that our internet hungry home has connectivity through load shedding, given that I’ve already got this in place I’d probably put it on a circuit that’s isolated from the inverter setup, no point in adding this draw albeit low to the inverter.

Thanks in advance I really do appreciate any advise and people in the know taking time to answer questions like this on a forum. 

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18 minutes ago, pauljatho said:

Our household uses an average of 40kWh per day

 

18 minutes ago, pauljatho said:

I’d imagine based on our consumption that we’d need around a 5KW inverter?

Hard to say, because the inverter has to be sized for the peak load, but based off a total of 40kwh a day (my own combined consumption is between 25 and 40) and two geysers, you are probably right with this estimate.

19 minutes ago, pauljatho said:

In terms of batteries I’m thinking Pylontech US3000B’s x 2 maybe 3? What sort of run time could I expect?

That's like asking how far can I go on a tank of fuel. It depends both on the size of the tank and the rate of fuel consumption. We only know the size of the tank... 🙂

Theoretically you have 6kwh in two of those US3000s, so a 1kw load can run for 6 hours, a 500W load can run for 12 hours, and so forth. The max discharge rate for the Pylontechs are C/2 (discharge from full to empty in two hours) so the maximum allowed continuous discharge will be 3kw over 2 hours.

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Hi,

You can run basically anything from solar/solar system. It just have a trick to it. 5KW inverter can only handle max loads of 5KW at a time, with a boost of couple of seconds.

You need to figure out how that 40kWh is distributed during the day.

You also need to figure out how much you are using maximum at a time. If you push more than 5kWh with a couple things on, a 5kW will not be enough.

Your battery bank need to be sized to be able to handle the kW usage (inrush) until something like the PV can generate enough to take over the load.

In your scenario where you will use it as a back-up system for load shedding, 2x US3000's should be enough (as you only need to handle 2.5hrs of darkness currently), but you have to limit loads at that same time to lenghten the time, as well as to compensate for what the batteries can handle as Plonkster pointed out.

Typically a new US3000 will each give you around 3.2kWh, meaning you can use 3.2kW per hour, if you draw a constant of 3kW it will only last one hour. If you draw 1000W per hour it should last 3 hours, etc. 

As I was typing this @plonkster posted :)

 

Edited by Wilfred
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Hi Guys

 

Thanks for the replies.

Disregard my battery production question, I realise in hindsight it is a question that cannot really be answered as it depends entirely on the draw.

Regarding the 40kWh daily draw, I realise that its not a consistent draw over a 24 hour cycle and is most like using most of this between say 7am and 8pm so I'm guessing a fair estimate for this period would be around 3-4kWh but that includes the geysers and pool pump, if these are omitted from the installation I think I'd have more than enough headroom with the 5kWh inverters and once installed and have a better understanding of my draw I could then possibly look to add a geyser and possibly pool pump and just ensure they're both running at different times.

I think my question really is, which inverter should I go with Goodwe or Victron, are the Pylon's a good (best) combination with these inverters or are there better options?

 

 

 

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4 minutes ago, pauljatho said:

Hi Guys

 

Thanks for the replies.

Disregard my battery production question, I realise in hindsight it is a question that cannot really be answered as it depends entirely on the draw.

Regarding the 40kWh daily draw, I realise that its not a consistent draw over a 24 hour cycle and is most like using most of this between say 7am and 8pm so I'm guessing a fair estimate for this period would be around 3-4kWh but that includes the geysers and pool pump, if these are omitted from the installation I think I'd have more than enough headroom with the 5kWh inverters and once installed and have a better understanding of my draw I could then possibly look to add a geyser and possibly pool pump and just ensure they're both running at different times.

I think my question really is, which inverter should I go with Goodwe or Victron, are the Pylon's a good (best) combination with these inverters or are there better options?

 

 

 

Out of those three, I only know the Pylon's, in my opinion they are working well. I am sure that they are compatible with Victron and Goodwe.

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1 hour ago, pauljatho said:

Hi Ploknster, silly question what is C/2?

Capacity of the battery divided by 2. So a US3000 battery is a 70Ah battery (amp hour, which is essentially the Wh figure divided by the nominal voltage, Ah is a more common measure of battery capacity).

Depending on battery chemistry a battery does not want to be charged or discharged beyond certain limits. This is one of the advantages of the Lithium chemistries, they can charge/discharge faster, so while a lead acid battery should really not be worked harder than C/10, or C/5 at a squeeze, a lithium battery can work as hard as 4C (four times capacity, or full to empty in 15 minutes if you were to sustain this level), but usually only for short periods, as in seconds.

The battery maker provides certain parameters that they want you to stay within... and it is usually a good idea to do it for warranty purposes. For pylontech that figure is 35A for a US3000, which happens to be approximately C/2. So roughly 30 amps at 50V... that is 1500W per module. Nice rule of thumb to size the batteries to your loads.

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15 minutes ago, plonkster said:

Capacity of the battery divided by 2. So a US3000 battery is a 70Ah battery (amp hour, which is essentially the Wh figure divided by the nominal voltage, Ah is a more common measure of battery capacity).

Depending on battery chemistry a battery does not want to be charged or discharged beyond certain limits. This is one of the advantages of the Lithium chemistries, they can charge/discharge faster, so while a lead acid battery should really not be worked harder than C/10, or C/5 at a squeeze, a lithium battery can work as hard as 4C (four times capacity, or full to empty in 15 minutes if you were to sustain this level), but usually only for short periods, as in seconds.

The battery maker provides certain parameters that they want you to stay within... and it is usually a good idea to do it for warranty purposes. For pylontech that figure is 35A for a US3000, which happens to be approximately C/2. So roughly 30 amps at 50V... that is 1500W per module. Nice rule of thumb to size the batteries to your loads.

Thanks Plonkster, appreciate the detailed explanation, seems I'd need to increase the number of Pylons for my load although I suppose it would then rather make sense to introduce solar panels.

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Plenty information on the data sheet, to understand it all is another story.

Yes, @plonkster have a very good understanding of batteries, I am still learning. Luckily my power usage at night time will barely go over 1500W, but with 4x of those batteries I don't even worry about it. Most times my batteries end up without PV @100% SoC, the lowest it went down to was around 22% then the PV kicks in, I only had one instance when the AC kicked in in the last 44 days of use. I have pushed the system to 6000W around three times and never had an issue thus far, no alarms, no shut down, system works perfect with these batteries. 

I like that I am learning a lot in a field outside of my expertise and I like to play around with these things to see what happens and when it happens.

 

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41 minutes ago, pauljatho said:

Thanks Plonkster, appreciate the detailed explanation, seems I'd need to increase the number of Pylons for my load although I suppose it would then rather make sense to introduce solar panels.

Just keep in mind that you must sort-of keep things in proportion. There is a group of people I call the "small battery crowd", that's the people who put in ridiculously small batteries with large solar arrays because they want to use the solar power for loads during the day and only have a small amount of backup during an outage. Then they run into issues with overvoltage on the battery (because a highly charged LFP battery spikes up at ridiculously low currents) and then they want the support people to solve it.

Please don't join that crowd 🙂

 

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42 minutes ago, plonkster said:

Just keep in mind that you must sort-of keep things in proportion. There is a group of people I call the "small battery crowd", that's the people who put in ridiculously small batteries with large solar arrays because they want to use the solar power for loads during the day and only have a small amount of backup during an outage. Then they run into issues with overvoltage on the battery (because a highly charged LFP battery spikes up at ridiculously low currents) and then they want the support people to solve it.

Please don't join that crowd 🙂

 

@plonkster, Could you give us an example of how these "small battery villains" operate? What is the solar array to battery bank ratio that would make us part of this insidious group?

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10 minutes ago, VisN said:

@plonkster, Could you give us an example of how these "small battery villains" operate? What is the solar array to battery bank ratio that would make us part of this insidious group?

Well, that would be people with a single Pylontech US2000 and a 3kw of PV, so the charging capability is more than double what the battery wants. But more often you get people who do the same thing with lead acid (over 2kWp of PV... 100Ah battery bank), ESS mode set to KeepBatteriesCharged, feeding the excess PV to the load... leaving those poor batteries to take the brunt of every large load change.

Edited by plonkster
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@pauljatho - Some very large loads, so need to consider what you can do without during load shedding, or can reduce drastically.

There is no doubt in my mind that if you can afford the capital outlay of a good Victron installation then you should go that route first, It may hurt the pocket, but you will never regret going that way if properly installed and advised. (PS: I don't sell or can afford Victron myself - It is a goal I aspire to:D)

Next, as almost beaten into you by the guys above, a 40kW load per day is actually quite large for a house, you need to try reduce this with other strategies first.

I seriously think that before you invest in solar electricity, you need to invest in Solar Water heating. Solar Water heating is a far better return on your investment, and the correct (not even that hugely expensive) solar tubes, would probably drop 5+ kW or even 15 kW off your power draw per day (depending on settings). The biggest draw I found when I started was the Geyser heating. Fix that and you might find that you power draw can even reduce a battery bank or inverter needed.

In your large draw environment, consider having a changeover switch that isolates the solar install from just a municipal install. Keep a municipal power changeover switch (in emergencies, use municipal or Eskom power), this has saved me from SWAMBO on at least 2 occasions when the Solar stuff has let us down temporarily.

With the size of your current power draw, I personally would still keep a Municipal/Eskom link, even though it's tempting to go completely off grid. A generator backup to supply your current load would be expensive to purchase, and a large cost to keep maintained properly.

Try keep in mind - as a target - that even a large household, with a pool, should be able to get to under 25kW per day. So treat that as your first goal before you spend a lot of money on Solar Electricity.

* SWAMBO - She Who Always Must Be Obeyed

 

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14 minutes ago, VisN said:

@plonkster, Is there a rule of thumb regarding PV array vs battery bank size?

Not really... just don't be an idiot about it 🙂

Victron does not recommend running with just one Pylontech rack (either US2000 or US3000). For a UPS it is okay, but the moment you have PV in the system (AC or DC tied) you are simply better off with two. I'm of course talking about using a 3KVA Multi and above. I'd say the rule of thumb is that old nugget your teacher drilled into you: If it feels like it might be a bad idea, it probably is. If you're turning over your R2 coins and trying to get max power savings while not spending money on batteries... you are probably doing it wrong 🙂

 

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I see the system working like an old school turbo charged car with lots of turbo lag.
Even if your inverter can do something like a 5 000w constant draw with a 10 000w spike, it would trip before it can even deliver that if your battery bank is sized too low.

The inverter need to supply the power you are asking from somewhere, it want to get it from the PV, but the PV’s and inverter has lag (turbo lag if you will), so first it will get it from the batteries, if the batteries can’t supply it, “CLICK”, self induced load shedding, reset everything, let’s try again.... rinse repeat.

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11 hours ago, Wilfred said:

turbo lag

A bit off topic... but Oone thing I really like about large turbo setups... is when you really get on it and the turbo makes that high-pitched sound as it comes up on pressure, and then as you lift the throttle you get that choo-choo sound... so I am more of a Diesel guy and as such pressure release mechanisms are not as common (no big throttle body that can flap shut, so less need)... but I still love the sound... even on a Diesel you get a bit of high-pitched blowing sound.

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My nephew used to have a non-standard Subaru. I swear that turbo sucked in all the air for a square km..... As an adrenaline junkie I never thought that it would be possible to drive me bang. I was dead wrong on that account....

The only other car that I have ever felt the "G" force in, was a Ford Mustang Mach 1.

Edited by GVC
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Since we going "off-topic":D: Mine was a non-turbo rotary engine Mazda 616, but with a faulty 2nd gear in an Automatic 3 gear box... Only way to drive the thing was to use the accelerator as an ON/OFF button. Nearly snapped a few passenger necks when trying to drive in traffic🤣

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