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Backup system and lithium batteries


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I am looking at options for a standard backup system with the option of adding solar panels later.

It is probably a very common scenario and questions which the solar experts are often asked by novices like myself

My house has a 3-phase board and the intention is to isolate the essential circuits and wire to a separate DB board which will be supplied by a Victron Multiplus II 3kVa or 5kVA inverter and compatible lithium batteries. My predicament is:

  • which inverter to start with 
  • which quality brand of lithium batteries offer the best value for money and are reliable

If I opt for the 5kVA inverter, I can back up more circuits on the essential load, but if I want to expand the sytem for all phases, it becomes very costly and too large for my requirements. 

Another disadvantage of only 1 inverter is that if I add solar panels later it will only provide a saving on one phase.

My thinking is to start with a 3kVa Victron Multiplus II inverter with the maximum compatible and recommended lithium batteries to provide the backup for essential loads.

The next step can be to add 3 kVA Victron inverters and batteries to the other 2 phases of my DB board. The one problem is that I have limited roof space for solar panels will probably not get the full savings benefit. 

There are so many different lithium batteries on the market, but it seems that there is currently limited availability. One is almost forced to take what available to have a system in place before Escom switches off the lights again. Since the batteries are such a large cost component of the system, this is a very unsatisfactory situation. For an inexperienced customer like myself, it is difficult to decide which quality brand of lithium batteries offer the best value for money and are reliable.

I would appreciate it if one of the forum solar experts can offer me some guidance as to which way to go or point me to a link where this topic has been discussed. 

 

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On 2020/05/26 at 7:35 PM, Andre@office said:

Victron Multiplus II 3kVa or 5kVA inverter and compatible lithium batteries. My predicament is:

  • which inverter to start with 

First proviso...I am no expert but the post seems to get many drivebys and no one stopping..

Your decision on inverter size is important for more than the size of load you can power  -  as far as I know if you want to add/combine units they must be of the same type/size (so if you start with 3kVA, the other 2 will also need to be 3kVA. There are also requirements in terms of processor/firmware similarity - so you will need to look at that in detail to make sure what you start with will be compatible with later additions. (the resident victron genie is @plonkster ... maybe he will swing by and smack me on the nose for invoking his name and spreading falsehoods about victron...)

On 2020/05/26 at 7:35 PM, Andre@office said:

 For an inexperienced customer like myself, it is difficult to decide which quality brand of lithium batteries offer the best value for money and are reliable.

Like most forums the "which one is best?" type question often leads to very little fruitful conversation and mostly ends with at least one member banned..

Since you going the Victron route I will start with selecting at least what is part of their confirmed supported batteries (https://www.victronenergy.com/live/battery_compatibility:start)

I will venture the following: it is too early to really know which brands are most reliable. The technology is not exactly new but we do not yet know whether these batteries really will for argument sake give the claimed 5000 or however many cycles. Maybe more importantly we do not yet know which company/companies will even be around to honour a warranty 10 years down the road (anyone can bring in a container of batteries from China, they can even be extremely good quality but 3 years later there could be a "glitch" where the bms starts giving intermittent problems - if the supplier is no longer around you may end up trying to get support from someone in China which can be good or non-existent. ). So with that said if I were to look at letting go of my money i will personally look at who at least appears to have a local foot print - even if just in terms of what most people are using so that there is a knowledge base and possible spares market to tap. My annecdotal observations of online forum discussions (for South Africa as market) and local online store stock carried will therefore steer me towards the pylontechs, BYD, and to have even more local support I will look at Freedomwon and Bluenova..

On 2020/05/26 at 7:35 PM, Andre@office said:

 Since the batteries are such a large cost component of the system,

I am a big fan of lithium for backup power use in the Eskom load shedding scenarios but i also think at times the more traditional batteries have a place - especially when looking at costs. Being independent from eskom and saving money do not necessarily mix easily according to me so you may also need to more clearly identify your main goal.

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1 hour ago, introverter said:

make sure what you start with will be compatible with later additions

Haha no that is quite correct. There is always a bit of a time limit on how long that precise model will be on sale, should you need a second one, and that's not limited to any particular brand, though it should be noted that some brands are more finicky than others. Certainly with Victron, the model has to be exactly the same, so you should be careful of earler 3kVA Multiplus-II models that may be harder to find now. The 2629 variant is widely used and should be a safe bet right now... but there is no telling what will happen in 3 years or 5 years or whatever. By then there will almost definitely be something newer and more exciting (in fact... there almost certainly will be... all the manufacturers have exciting stuff in the line-up...).

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