Do I replace my Axpert 5k





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  1. #1
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    Default Do I replace my Axpert 5k

    Hi

    Busy placing my order for 12 x Canadian 410W high efficiency panels and 2 x LifePO4 6Kwh battery banks. My 12 panels will be strung in the following configuration:
    String 1: 4 panels on the North-east roof section (200V)
    String 2: 8 panels on the North-west section (400V). I might bring 2 strings (4 panels, 200V ) into a combiner box before the MPPT
    String location is based on available roof space, optimizing panel performance for winter and the fact that we are in the Swartland (WC)


    Biggest issue is my existing RCT-Axpert 5k inverter's inability to deal with the solar strings (each panel VOC = 50v). The inverter max VOC is only 145V DC, effectively rendering it "unusable" with my panels.


    Are there any grid-tied/hybrid inverters that will link parallel to my Axpert with 2 x MPPT controllers (400V/10A min) such as the KODAK i4.6

    If this is not an option, what would you recommend as a grid-tied/hybrid inverter (5 or 8KW) that could drive my 12 panels (2 x MPPT controllers (400V/10A min)).

    Note: If I have to replace the Axpert, budget becomes an issue thus rendering the likes of Victron out of the picture

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    Default Re: Do I replace my Axpert 5k

    You can do two panels series per string, then parallel the strings to get 100V open circuit.

    But ideally each string pointing in another direction need its own MPPT to make the most out of the panels.

    Just get one additional MPPT directly to batteries?

    On my Axpert I just string enough panels together to stay within spec and then parallel the strings.
    Last edited by faniedup; 2020/06/03 at 01:16 PM.

  3. #3
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    Default Re: Do I replace my Axpert 5k

    Or get a Solis Dual MPPT grid tied inverter.

    Axpert stays in play, become a UPS, a very good UPS at that.

    Next level:
    And when loadshedding hits again daytime seeing that Axperts do require some manual intervention, have an option, by being clever in the wiring of the panels, that one can disconnect the panels from the Solis back onto the Axpert's MPPT, keeping in mind the max volts from the panels.




    Ps. I will deny I ever suggested the above.
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    Default Re: Do I replace my Axpert 5k

    At least 1 guy that sees value in using a Solis 4G grid tied and a Axpert for back up. Up to now I was a lone wolf on the forum.

    Fanie has provided a good setup. Due to the high voltage on the west side with 8 x 50V panels one could also sell the Axpert. Replace with a Solis Hybrid 3.6K or 4.6K 48ES which can accept up to 600V PV input in any of the 2 MPPT controllers. It can have up to 6000W DC input. Only 2 strings allowed if one had to use parallel strings. The only drawback is only Pylontec and 1 other make of Li-Ion is currently compatable.

    4.6K model Solis Hybrid sells for R27 500 so Axpert might have to be sold.
    Last edited by ekkekan; 2020/06/03 at 08:34 PM.

  5. #5
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    Default Re: Do I replace my Axpert 5k

    Quote Originally Posted by ekkekan View Post
    At least 1 guy that sees value in using a Solis 4G grid tied and a Axpert for back up. Up to now I was a lone wolf on the forum.
    When Solis 1st came onto the market a while ago I looked very seriously at them, not only to buy but also to potential to integrate one with a Victron setup instead of Victron MPPT's.
    Solis was then cheaper than some models Victron MPPT's.
    Since then their prices have jumped quite a bit.

    At that time, on another forum, because of the idea of Victron/Solis, I suggested Solis/Axpert combination. I still deny that.

    For newbies, very important caveat to note: If Eskom goes off daytime for hours:
    Unless you get a hybrid grid tied inverter, your grid tied inverter will switch off with Eskom.


    Quote Originally Posted by ekkekan View Post
    4.6K model Solis Hybrid sells for R27 500
    Pricing seems to be comparing with GoodWE's ... interesting.


    Quote Originally Posted by ekkekan View Post
    The only drawback is only Pylontec and 1 other make of Li-Ion is currently compatible.
    Jip, there is that with a few inverters. Good idea if you sell to a non-DIY market. It makes support so much simpler and easier, safer.

    Me, I am not in that market. I want to buy batts I want what I want.

    To this effect I got 16 x 150ah lithium separate cells recently, with a Daly BMS, to replace my Trojan bank at a price that beats the pants off any lithium bank out there.
    7.6kWH bank - 150ah x 16 with parts and BMS - at R26k delivered.

    "You can with a Nissan" ... Victron ... mix and match to your hearts content if you follow the bare bones rule: Don't under size the bank, unless you are prepared to throttle the system.
    Worst thing that can happen if you don't: BMS will switch off the bank, leaving you ion the dark.

    Now I patiently wait for BMS manufacturer to integrate with Victron where the BMS does not cost another kidney. Not a need, but a want.
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    Default Re: Do I replace my Axpert 5k

    Solis have been awarded a number of prizes for it's design in Europe. Not so popular in SA where there are about 210 systems that shared their live stats at some stage. In Aus there are 3450.
    I just think to have your system spread between 2 different inverters gives a better use of PV. Should one fail the 2nd one can still work.
    Yes building ur own Li-Ion bat bank with loose cells and BMS makes it far cheaper. Did you buy from lithium batteriessa.co.za?
    It took 2 years before we saw any Solis installed in SA. The 1st units in Aus were done in 2014 AFAIK.
    Last edited by ekkekan; 2020/06/03 at 10:59 PM.

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    Default Re: Do I replace my Axpert 5k

    Quote Originally Posted by ekkekan View Post
    I just think to have your system spread between 2 different inverters gives a better use of PV. Should one fail the 2nd one can still work.
    That is why I like my kit, MPPT is separate from the inverter.

    It is all about the batteries in my view:
    If MPPT goes inverter can continue to charge the batteries whilst I get a new one.
    And if the inverter goes, the MPPT keeps on charging batteries whilst I use a 48v UPS to "overcome" the inconvenience.

    Quote Originally Posted by ekkekan View Post
    Yes building ur own Li-Ion bat bank with loose cells and BMS makes it far cheaper. Did you buy from lithium batteriessa.co.za?
    Jip, from them thanks to Gerlach.

    It is quite a learning curve to get the settings settled for optimum use but that also means one is getting an very thorough understanding of how it all works, which limits can be pushed, and which ones not.



    Now I patiently wait for a BMS to come onto the market that is plug and play with a VenusGX.
    There are ones available already, but the price!!!
    One I like is like 3/4 of the price of my batteries!

    Some may snicker saying "He buys Victron and then complains about price!"
    If the inverter is +-R25k, how can it be that a BMS that interfaces, cost +-R15k, when most BMS are under <+-R4k that don't yet interface?
    It "feels like" - O, you buy Victron, then we can charge you R15k for a BMS that interfaces with the VenusGX.
    That is after Victron made the Venus BMS ready, easy software interface, done and dusted.
    Price just does not "feel right" in my gut. Still making up my mind.
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    Default Re: Do I replace my Axpert 5k

    Thanks for all the input

    Batteries coming from https://lithiumbatteriessa.co.za/

    Quick question,
    1. is there value in keeping the existing 4 x 100Ah FLB's that is currently connected to the Axpert?
    2. what it not be better to just add another Axpert and do any grid requirement through a manual change over switch?

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    Default Re: Do I replace my Axpert 5k

    Quote Originally Posted by the_terrible_triplett View Post
    That is why I like my kit, MPPT is separate from the inverter.

    It is all about the batteries in my view:
    If MPPT goes inverter can continue to charge the batteries whilst I get a new one.
    And if the inverter goes, the MPPT keeps on charging batteries whilst I use a 48v UPS to "overcome" the inconvenience.



    My question now is which dual MPPT (400V+ / 80A+) should I look at

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    Default Re: Do I replace my Axpert 5k

    Quote Originally Posted by wims_za View Post
    Quick question,
    1. is there value in keeping the existing 4 x 100Ah FLB's that is currently connected to the Axpert?
    2. what it not be better to just add another Axpert and do any grid requirement through a manual change over switch?
    1. If you have lithiums batts, nope. The two types cannot work on the same inverter.
    2. Manual changeover switch is a must, if you want to comply to SANS/NRS. Adding a 2nd Axpert is an option if you want to go off-grid yes.

    But adding a 2nd Axpert requires more batteries. Cost increases.

    In cities, where one has Eskom, it makes much more financial sense to go grid tied than off-grid.
    On farms/plots where there is a huge connection fee before usage, then it makes more sense to go off-grid.


    Quote Originally Posted by wims_za View Post
    My question now is which dual MPPT (400V+ / 80A+) should I look at
    Depends on what KW you want to push into the house.

    NRS/SANS says 3.5kw max inverter on a 60amp breaker, if that helps.
    Of if you have a 5kva inverter, then the panels must be limited to 3.5kw.
    Last edited by the_terrible_triplett; 2020/06/04 at 04:50 PM.
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  11. #11
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    Default Re: Do I replace my Axpert 5k

    So I can have my existing Axpert still charging my FLBs and the new Axpert doing the Li?

    According to Rectron I cannot parallel and RCT-Axpert 5k with an RCT-Axpert 5K MKII. Any comment on this?

    Or, I can keep the existing Axpert. add an MPPT dual to drive my strings and charge my LifePO4 (second life) 2 x 6.1Kwh battery packs. If that is true, what is the recommended MPPT for this (Victron is too expensive)

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    Default Re: Do I replace my Axpert 5k

    Quote Originally Posted by wims_za View Post
    So I can have my existing Axpert still charging my FLBs and the new Axpert doing the Li?
    You can, if they are operating completely separate i.e. because if you parallel them, they need to share a battery bank.
    That you cannot do if you mix lead acid and lithium banks.


    Quote Originally Posted by wims_za View Post
    Or, I can keep the existing Axpert. add an MPPT dual to drive my strings and charge my LifePO4 (second life) 2 x 6.1Kwh battery packs. If that is true, what is the recommended MPPT for this (Victron is too expensive)
    Whatever MPPT you get, make sure it can charge lithium batteries, as the charge volts are vastly different from lead acid.
    Also, you don't want to skimp on a MPPT. It is charging your batteries, which are even more expensive than the MPPT's.
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    Default Re: Do I replace my Axpert 5k

    I succesfully run 2x5kW Axpert with a mix of lead acid and lithium batteries. I have set the charge parameters for lead acid, which is a bit higher than lithium require. The BMS in the lithiums just disconnect when it's charged and the voltage goes higher than they would like.

    You cannot have seperate batteries on each Axpert if they run in parallel, the battery bank needs to be common.
    Last edited by faniedup; 2020/06/04 at 06:55 PM.

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    Default Re: Do I replace my Axpert 5k

    Quote Originally Posted by faniedup View Post
    I succesfully run 2x5kW Axpert with a mix of lead acid and lithium batteries. I have set the charge parameters for lead acid, which is a bit higher than lithium require. The BMS in the lithiums just disconnect when it's charged and the voltage goes higher than they would like.
    Well blow me down.
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    Default Re: Do I replace my Axpert 5k

    Quote Originally Posted by the_terrible_triplett View Post
    Well blow me down.
    https://community.victronenergy.com/...d-lithium.html

    I decided to give it a go when I read an article where the lead acid batteries in large PV systems in the USA was supplemented succesfully with Lithium Ion batteries when they needed to expand capacity.

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    Default Re: Do I replace my Axpert 5k

    Thanks, I saw that. I used to run a Trojan bank coupled - as one bank - with a AGM bank for a few months.
    Both banks where old.
    Set the charge settings to the AGM's and every few weeks I equalized the Trojans.

    Although it seems that the charge settings I current use, and float voltages, are same for AGM / lithium, I can connect the Trojans back up again ... but I am a wee bit reluctant to do that with a brand new lithium bank.

    Still tweaking the settings on the system to work with the Daly BMS.

    Having said that ...
    Quote Originally Posted by faniedup View Post
    I decided to give it a go when I read an article where the lead acid batteries in large PV systems in the USA was supplemented succesfully with Lithium Ion batteries when they needed to expand capacity.
    Do you have a link to that article maybe?
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    Default Re: Do I replace my Axpert 5k

    Will try to find it again

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    Default Re: Do I replace my Axpert 5k

    I'm now thinking very hard on this.
    The lithium volts I use are spot on for floating Trojans (54v), just a wee bit low for the bulk charge of Trojans i.e. 57.6v vs 59.28v.
    But that matters not too much on a old bank IF you can equalize.

    My system is setup for a BMS that does not communicate with the system. I use a BMV to manage the SOC.

    So now I'm thinking:
    1) Set system back to lead acid profile - for the absorb time parameter.
    2) Keep the volts the same as is currently for lithiums ito bulk and float, set absorb time for 4 hours for the Trojans.
    3) Keep the 50-70amps charge on, because the lithiums will take the brunt first, in and out, the lead acid's following the curve.

    What am I missing, anyone?

    I can easily switch between the two banks in order to isolate the Trojans for equalization. Needs 64.8v to do that for a little while, can do that manually with a click of a button.
    So that is sorted.

    If I had AGM's, even easier, as it appears that lithum and AGM's are as close as damn already.
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    Default Re: Do I replace my Axpert 5k

    I have an Axpert MKS11 for a year now with 2 strings of 7 x 350W panels and 4 x 3.5kW Pylontechs. Charge about 250 - 300V with 9 amps per string. Works like a charm. I would recommend you buy MKS11 5kW.

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    Default Re: Do I replace my Axpert 5k

    Quote Originally Posted by wims_za View Post
    Hi

    Busy placing my order for 12 x Canadian 410W high efficiency panels and 2 x LifePO4 6Kwh battery banks. My 12 panels will be strung in the following configuration:
    String 1: 4 panels on the North-east roof section (200V)
    String 2: 8 panels on the North-west section (400V). I might bring 2 strings (4 panels, 200V ) into a combiner box before the MPPT
    String location is based on available roof space, optimizing panel performance for winter and the fact that we are in the Swartland (WC)


    Biggest issue is my existing RCT-Axpert 5k inverter's inability to deal with the solar strings (each panel VOC = 50v). The inverter max VOC is only 145V DC, effectively rendering it "unusable" with my panels.


    Are there any grid-tied/hybrid inverters that will link parallel to my Axpert with 2 x MPPT controllers (400V/10A min) such as the KODAK i4.6

    If this is not an option, what would you recommend as a grid-tied/hybrid inverter (5 or 8KW) that could drive my 12 panels (2 x MPPT controllers (400V/10A min)).

    Note: If I have to replace the Axpert, budget becomes an issue thus rendering the likes of Victron out of the picture

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