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Hi All,

 

how I wish I knew about this forum before last night :D

 

I am fairly new to solar. Have some knowledge but not as much as the pool on here. I have an existing setup but wan tto change the batteries.

 

12x330w Canadian solar

Growatt SPF5000 (off grid)

Batteries - lets not go there...

 

So I proceeded to want to put a  few lithium batteries on the system. However everyone I speak to says to me that pylontech batteries ( I was looking at 3x 3.4KW) are not compatible with the inverter and cannot be used.. I dont agree but dont want to buy a battery that wont be waranteed. I assume the issue is actually that I cannot current limit the Growatt and that this may cause premature failure t the battery it continues current is higher than what they want you to draw to keep the proposed battery life. They all say it is because of the communications protocol. Which should not be an issue as the battery charges itself right? The Pylontech have a BMS built in which handles the charging as long as it has voltage and current? Or am I missing something?

 

Anyways. Long story short. I am deciding to rather then get an Axpert Infini  48v4k. I know from reading that Axperts are not the rolls of inverters but I dont have the rolls money at this point after I what I will be paying for batteries... btw I still have an old disk based power meter. My thought thus is to place some of my load between my inverter and eskom(geyser) and some behind the inverter (everything else - kettle on the stove which is gas). Grid tie it  the inverter like that? That way the inverter can feed the geyser and Eskom can feed what the inverter lacks? Is this a good idea? Reason for this is that I dont want to hang the geyser off the battery bank/inverter but still want to get benefit of the panels for the geyser. Will this work? And if I am lucky perhaps the meter will play along as well for the reverse feed excess netting off in the end? 

Proposed setup then..

1. ultimately 18panels

2. Axpert 4k

3. 3 x pylontech 3.4k's

Do if you guys think my setup is a good idea? Any other suggestions that would be cost effective?

Thanks in advance for the feedback!

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I changed my batteries recently and weighed up the pros and cons of lithium versus lead acid. Eventually I went for Trojan SAGM 375 batteries which were the same  price, capacity and almost the same lifespan  as the lithiums. My inverter is also not compatible with the Pylon warrantee which was a concern. 

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16 minutes ago, DeepBass9 said:

I changed my batteries recently and weighed up the pros and cons of lithium versus lead acid. Eventually I went for Trojan SAGM 375 batteries which were the same  price, capacity and almost the same lifespan  as the lithiums. My inverter is also not compatible with the Pylon warrantee which was a concern. 

My issue is constant international travel. I dont want to saddle the wife with having to keep an eye on the batteries. Hence the idea to go to Lithium. 

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3 minutes ago, plonkster said:

I'm going to tell you to go with the Growatt. Well... I want to tell you to buy the Rolls, because neither the Axpert nor the Growatt has paperwork for grid connection (which might not matter right now unless you are in Cape Town)... BUT... the Growatt has at least some proper paperwork beyond a "CE" mark.

My Growatt is a off the grid box and cant be tied (unless there is a way I dont know about?) So I do end up losing a lot... Question is if anyone will sell me a lithium battery which will keep its warantee if I stick with my growatt?

 

How much realistically would the Rolls set me back? the infini 4k can be had for around 14k now?

Edited by JTK
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2 minutes ago, JTK said:

My issue is constant international travel. I dont want to saddle the wife with having to keep an eye on the batteries. Hence the idea to go to Lithium. 

I'm not sure if they require less monitoring, there have been a number of problems reported.

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Just now, DeepBass9 said:

I'm not sure if they require less monitoring, there have been a number of problems reported.

thats no good!

I pull around 8kwh through the night by the looks of it..  So economies of scale suggest that 3 pylontech 3000's will be cheaper than a lead acid bank as well?

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1 minute ago, JTK said:

a off the grid box and cant be tied

The trouble is that it has an AC-input, a transfer switch, and it can charge from AC. At least if I am looking at the right documentation. In places like Cape Town, such an inverter is deemed grid-connected even if it cannot tie with the grid. A while ago some of us went on a bit of a documentation dive trying to see if the Axpert has any sort of paperwork at all, and found out that it only has a CE certificate (which is a self-certification thing). My point is that at least in the safety and quality/testing department (not to mention the double MPPT feature) the Growatt is a better inverter. At least on paper. I think you'd be making a mistake to buy down.

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Just now, DeepBass9 said:

Depends if you have to buy a new inverter as well!

true. but my 3kw geyser, microwave and iron run off mains at the moment. Probably costing me around R1k-1.2k  a month. So the inverter should pay for itself in 12 months.. And I will get half the spend back from the growatt

 

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41 minutes ago, JTK said:

I assume the issue is actually that I cannot current limit the Growatt

Fwiw, you cannot current-limit the Axpert either. You cannot current-limit anything that isn't a hybrid inverter (where it will take the difference from the grid). However, Pylontech has recently started to allow off-grid use of their batteries. In @DeepBass9's case he was also dealing with an inverter (Microcare) that doesn't have a lithium charging profile, or to really get down to the details: Typical lead-acid chargers require a 4V drop from float voltage before they will go back into bulk charging... and this won't work well with a pylontech.

I don't know what you've been quoted, and if you are dead-set on a 5KVA unit, but if you want something that you can be sure of (paperwork, battery support), get a Victron Multiplus-II. That's only available in 3KVA though, and of course in terms of price it's about a 5-series BMW to a Rolls... 🙂

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7 minutes ago, DeepBass9 said:

You would get a better ROI from a solar geyser, because most of the mains will be powering the geyser.

agreed. but if I could push back into the grid I will cover that portion right? Lets say my grid can push out around 2.2kwh for say 6 hours every day... Then I should cache the 3kwh it takes to heat the geyser once? Or am I missing something?

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4 minutes ago, JTK said:

heat the geyser once

How much you need depends on your water use. It takes 1.16Wh per liter per °C, so heating 150 liters from ambient to 55 takes more like 8kwh (depends on ambient water and how much you have to heat). Plus you have a standing loss of around 2kwh (ie if you use no water, it still takes 2kwh to keep it warm).

6 minutes ago, JTK said:

cache the 3kwh

Are you thinking of spinning the meter backwards and bringing it in again later? Yeah that is possible... not really legal... but possible :)

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27 minutes ago, plonkster said:

How much you need depends on your water use. It takes 1.16Wh per liter per °C, so heating 150 liters from ambient to 55 takes more like 8kwh (depends on ambient water and how much you have to heat). Plus you have a standing loss of around 2kwh (ie if you use no water, it still takes 2kwh to keep it warm).

Are you thinking of spinning the meter backwards and bringing it in again later? Yeah that is possible... not really legal... but possible :)

I agree on the 2kwh loss but I usually run it on a timer for an hour at a time. Which would negate the loss. One hour heating is enough to heat the 55l geyser.. Sure the mathc dont make sense but it works..

yes. spinning the meter backwards...  :D

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41 minutes ago, plonkster said:

Fwiw, you cannot current-limit the Axpert either. You cannot current-limit anything that isn't a hybrid inverter (where it will take the difference from the grid). However, Pylontech has recently started to allow off-grid use of their batteries. In @DeepBass9's case he was also dealing with an inverter (Microcare) that doesn't have a lithium charging profile, or to really get down to the details: Typical lead-acid chargers require a 4V drop from float voltage before they will go back into bulk charging... and this won't work well with a pylontech.

I don't know what you've been quoted, and if you are dead-set on a 5KVA unit, but if you want something that you can be sure of (paperwork, battery support), get a Victron Multiplus-II. That's only available in 3KVA though, and of course in terms of price it's about a 5-series BMW to a Rolls... 🙂

The growatt has a lithium profile but I cant get into it. It has a 3 digit password. I have asked the local growatt support for help but that is not forth coming. Just "you cant use the growatt with lithium". Which is bollocks, to be honest. The profile is there it just has a password preventing accidental access and I cant get to china support if I am not a dealer. So if anyone can assist with the password :D. Also a firmware update might solve the issue... I do believe they have a better later firmware but again I am stuck. ps: 3kw may be too little unless I can run the meter backwards...

Edited by JTK
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2 minutes ago, JTK said:

I agree on the 2kwh loss but I usually run it on a timer for an hour at a time. Which would negate the loss. One hour heating is enough to heat the 55l geyser.. Sure the mathc dont make sense but it works..

T = ce^(kt), where T is the temperature after t seconds, and c is the starting temperature (usually 55°C for energy conscious people). k you usually have to derive backwards by plugging in the standing loss and doing a natural logarithm. Essentially, k is a constant that indicates how good the insulation of the geyser is. And t is essentially the time period you're looking at, usually 24 hours as you are concerned with consumption in a day, which means the only factor that influences energy consumption is c, the average temperature you hold the tank at.

Loosely based, that means you only save power if you allow the tank to spend substantial amounts of time at lower temperatures, ie if you turn it off BEFORE the morning shower and only turn it on an hour before the evening bathtime-slot. All other methods save no energy. Guaranteed. Unless someone found a hole in the laws of physics 🙂

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19 minutes ago, plonkster said:

T = ce^(kt), where T is the temperature after t seconds, and c is the starting temperature (usually 55°C for energy conscious people). k you usually have to derive backwards by plugging in the standing loss and doing a natural logarithm. Essentially, k is a constant that indicates how good the insulation of the geyser is. And t is essentially the time period you're looking at, usually 24 hours as you are concerned with consumption in a day, which means the only factor that influences energy consumption is c, the average temperature you hold the tank at.

Loosely based, that means you only save power if you allow the tank to spend substantial amounts of time at lower temperatures, ie if you turn it off BEFORE the morning shower and only turn it on an hour before the evening bathtime-slot. All other methods save no energy. Guaranteed. Unless someone found a hole in the laws of physics 🙂

This is exactly that. It is turned on for an hour before we use the water. then stays off until next cycle. I do understand a bit of temperature dynamics :D

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1 minute ago, JTK said:

This is exactly that. It is turned on for an hour before we use the water. then stays off until next cycle. I do understand a bit of temperature dynamics :D

Fair enough. But you'd be amazed how often I run into people who save thousands with a R200 geyser timer... 🙂

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3 minutes ago, plonkster said:

Fair enough. But you'd be amazed how often I run into people who save thousands with a R200 geyser timer... 🙂

lol! yes agree on that one. Trick is not to warm up the water long before you use it. That way you have to warm it up again and again.. Warm it up once. then dont warm any new water that flows into the geyser whiles you use it. Then warm it again before you need it turning off before you use..  It does save. But I agree. it isnt thousands. Mine was little to start off with :d

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2 minutes ago, DeepBass9 said:

A 3 digit password? You don't have a 10 year old child handy to crack it for you? LOL.

Even a 4-digit password is easy enough to crack manually as long as it has no lock-out features, eg some will lock you out for some minutes if you get it wrong too many times.

But 3 digits? If you try 5 times a day you should be in by November... 🙂

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13 minutes ago, DeepBass9 said:

A 3 digit password? You don't have a 10 year old child handy to crack it for you? LOL.

My inverter has one of those, it is 234.

lol

 

up and down arrows... 3 digits will take while to run through 999 options. will try some obvious ones

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