Hi

Need advice on a  backup system  for home.  Db board split into essential and non essential loads each with an earth leakage. Essential load runs at max 8kwh per day average of around 270rwatt during the day.

Was looking at using a Mecer axpert 5kva with a Changhong 48v 100ah battery with built in bms. Anything else which anyone can recommend without making me bankrupt?

/in before axpert bashing 😛

but seriously you should read up on both sides, imo the axperts are great value but they do have some known issues.

I personally would say if you are spending the money pay a little bit more and get the king series. Also I have never heard of that battery but who knows, I would suggest pylontech or you can go with the revov's, they are second life batteries but offer good value?

You may start off with the idea of a backup system only (for now) but leave space to change your mind. I started off this way but am pondering the expansion of my system now.

Do a proper analysis of your power consumption by actual measurement of amps.

Many people have found it is cheaper to invest in energy saving appliances (depending on their age) and then go for a smaller system.

The db board which is split into two parts is a bonus provided it is compliant. A lot is published on the forum regarding that.

Get to know the different types of inverters so you don’t get stuck with a technology some time into the future.

Dealers will sell you anything you want. The difference will be your research so you can make wise buys. Experience is expensive 🙂

Edited September 8, 20196 yr by Johandup

One thing I found is that a lot of folks start off with the idea that the solar system will be for backup purposes....   and the Batteries for carrying the night time load.

However once you find how well solar works, one typically wants to grow the system, so that you can use as much solar as possible and reduce your Eskom spend and also have the backup functionality, with limited batteries for night time use, as batteries are very expensive, and typically need replacement, after a few years depending on use starting from 16 months to maybe 8 years?

My own ideal would be to have solar with the ability to blend in Eskom as needed during the day to cover excess requirements on occasion, or when it's cloudy, so ideally the panels are giving their maximum output all the time and Eskom adds to what you need, and to have a small fail-over battery backup as an option, which one could install when you have the funds for it, and a System that would run during daylights hours without batteries or Eskom? This way you maximize your savings

For this reason I started to consider the Infini Inverters, but have not yet migrated this way yet. And it seems that the Inifini has also had a few reliability issues as per comments seen on the forum? I would also be interested to get some recommendations on other brands / systems that could achieve the blended approach and have found to reliable, possibly including the Victron kit, and i have no interest in feeding back to the grid either at this point.

Currently I have 2 x 5KVA RCT Axpert inverters and just over 6kw of panels connected, with Trojan Batteries 245ah (c20) that are currently going on for 3 years old.  And am considering add a Third one mostly for the MPPT aspect, not so much for the inverting ability, so I can add more panels to mitigate bad weather and winter days.

The only problem I Have with the Axpert is trying to get them to follow the maximum power curve, automatically - in other words loads turn on when there is enough solar to run them, and on the other side if there is not enough solar, the ability to add in the missing power from eskom, rather than using the batteries and then switching completely over to Eskom, and then a while later switching back to solar.

My thinking would be to definitely invest in the correct inverter / Charge Controller etc, that has room to add batteries and Panels as you have the budget.

In your scenario above things to consider from a sizing perspective would be

• You mention peak loads of 8KW? You will need around 2 but probably 3 Axperts in parallel to run this type of load? The Peak Solar output of the RCT Axperts is 3000w 60a MPPT (For the silver and Black units) and for the newer RCT Axperts (Green and Black units) 4400w 80a MPPT.
• Allow for the losses of the panels, and conversions from dc-ac-dc, as well as inverter Self consumption - I allow for about 100w self consumption per axpert   as I find the system needs to typically generate from solar, at least 200-400w more than I am using, dependent on load,  otherwise the batteries start to discharge.
• Winter months where the days are shorter, and cloudy days, less time to recharge the battery's for night use, and less power due to the suns position.
• Consider if you have to run on batteries overnight and then have to charge the batteries and run your 270w load, ensure that you have enough panels.
• The Axperts battery management is voltage based and not accurate at all, so with smaller battery packs the voltage will drop when a large load is added, and then the solar will catch-up to the load, or on cloudy days the solar will dip severely and the battery's need to carry the load for about 2-3 minutes, before the MPPT's kick in and start trying to track again, this typically causes the system to switch to eskom, especially when running 2Kw upwards and we have a cloud pass.
• To solve the DOD issue with the axperts many folks on the forum have added a BMW702 to monitor battery discharge, and the ICCSOFTWARE (https://iccsoftware.co.za/) to montior the system, which seems to work fairly well?
• Consider a larger ah rating for your battery pack.

In my RCT Axpert (2016) manual they recommended a Minimum 200ah battery for the 5kva units? So the 100ah may take more punishment and perish sooner, depending on battery type? My own feeling is that if my own battery pack was 400-500ah, it would endure better and I would get less switching between Solar and Eskom during the day, on Cloudy days.

Good Luck and enjoy the solar journey.

 

12 hours ago, Dex_ said:

/in before axpert bashing 😛

It's a good starter inverter. When you're ready to get serious, talk to me

 

On 2019/09/07 at 7:24 PM, Shockin said:

Hi

Need advice on a  backup system  for home.  Db board split into essential and non essential loads each with an earth leakage. Essential load runs at max 8kwh per day average of around 270rwatt during the day.

Was looking at using a Mecer axpert 5kva with a Changhong 48v 100ah battery with built in bms. Anything else which anyone can recommend without making me bankrupt?

In my opinion you will not get better value for your money than the Axpert. For the price and as a back-up system it is an absolute no brainer.

To be honest it is not the best inverter on the market but it does the job just fine. 

39 minutes ago, plonkster said:

It's a good starter inverter. When you're ready to get serious, talk to me

 

Hi Plonkster,  what would you suggest as a back up system ? Not planning to use panels at all  

46 minutes ago, GVC said:

To be honest it is not the best inverter on the market but it does the job just fine. 

It has half the warranty that the others have, and from what I can deduce, it lasts about half as long as the others. It costs about half of the next one up. So it's on par... except for the total lack of firmware support and things like that 🙂

I think it's fine for a UPS, where such things are not going to bother you.

49 minutes ago, Shockin said:

Hi Plonkster,  what would you suggest as a back up system ? Not planning to use panels at all  

It was more of a joke, in line with @Dex_'s bashing comment.

12 hours ago, Shockin said:

... what would you suggest as a back up system ? Not planning to use panels at all  

With NO panels - Axpert UPS.

But IF YOU EVER change your mind and do get panels, then go a hybrid grid tied inverter from day one as in the end that is where the most savings are.

So IF you ever do get panels the a 3000va hybrid grid tied inverter that runs as a UPS until you add a MPPT and a VenusGX, i.e. you bought the panels and now are going to grid tie, that is the most cost effective way to go in my opinion. Build the system block for block up.