Hi all, newbie here. I live in Randburg with all of the associated power interruptions. What started as a battery backup solution has grown. I replaced the 1kva inverter/charger pair with an Axpert 3kVa-48 plus unit with 2.4Kw solar panels. All works fine except that I now realise that this unit switches between mains and PV inputs so all the energy available when Eskom is available is lost.

How do I add a grid tie or hybrid to this setup so I can use the solar to reduce my electricity bill? Advertising blurb for most inverters use terms I am unfamiliar with. I don't want to spend money on kit that won't make full use if the PV energy.

Looking forward to your inputs

12 hours ago, Madscot said:

How do I add a grid tie or hybrid to this setup so I can use the solar to reduce my electricity bill?

I guess your best option will be to replace rather than add to the Axpert. I don't think that Axpert has the capability to interface with PV inverters like some of the other inverters for example Victron. 

The downside of a PV inverter connected to the input of any other inverter is that you will loose its functionality during a power outage. 

I would rather replace the inverter with a Hybrid that will "blend" your power supplies, rather than switch between them, with the added benefit of battery backup.  

Your options for a real hybrid inverter is : Victron or Goodwe.

Enjoy all the reading, your about to do a lot of it

@PJJ don't forget MLT in the list  

Instead of swapping out inverter - Work out how much energy you are losing and add battery capacity to capture the energy - you now have 48V inverter which is compatible with Solar MD Lithium Ion batteries amongst others. It will never make 100% use of PV power unless you match/oversize batteries but it's the better alternative in my opinion as it gives more off-grid resilience and a grid-tie inverter will also spill power unless you have access to feed-in facility.

I'm not sure I agree with the @PeterP on adding more batteries. Well. maybe... but what you should do is the one that will cost the least in the long run. So basically work out how much will it cost per kWh to store that energy and use it later, vs buying a different inverter, or even an additional PV inverter (aka grid-tied inverter).

The rule of thumb is that if you want to use the power during the day, then AC-tie it with a grid-tied PV inverter (like an SMA, Fronius, ABB). If the bulk of your energy is needed after hours, then DC-tie the PV, and then depending on your peak loads and so forth, you decide whether you need a hybrid inverter or not.

To me it sounds like that Axpert is incorrectly set up. They have this voltage-based thing where they automatically switch to battery mode when the voltage goes high enough, thereby getting you a crude kind of self-consumption. In other words, you use the PV for loads by disconnecting the grid automatically when the battery is full enough.

I'm not saying this is a good way of doing it. The default Axpert way is actually horrible, using voltage for SOC is inaccurate, and it remains all or nothing. It's pretty much only good for smaller loads, you can't really use the excess for a geyser for example, and so on. All arguments for getting a proper hybrid. But let nobody say I wasn't honest about your options just to sell you something! 😉

(I think it is quite funny when people avoid the higher cost of another inverter by installing two parallel Axperts, thereby doubling the risk of a failure, massively increasing the cost of the battery bank, and so forth.... but hey, I got 10kw worth of inverter for the "same price" 🙂 ).

So basically, decide when you need the power. Then pick an inverter. As @PJJ said, the options are Victron or Goodwe.

With the Solar MD battery AI settings you overcome some of the limitations of the Axpert inverters as it lets the BMS control the switching based on accurate SOC and it allows user to set the % trigger points.

Furthermore they allow for relays to be set for geysers or similar which will trigger when excess PV is available so you will be able use your own preferred settings (SOC vs Load vs PV) to determine trigger. 

Unless you have very favourable feed-in tariff (which we don't) or only want to off-set a very small % of your Eskom usage the off-grid battery option is improving in price and useability.

But ultimately it depends on a cost benefit analysis of the desired functionality as Plonkster says. 

2 hours ago, plonkster said:

(I think it is quite funny when people avoid the higher cost of another inverter by installing two parallel Axperts, thereby doubling the risk of a failure, massively increasing the cost of the battery bank, and so forth.... but hey, I got 10kw worth of inverter for the "same price" 🙂 ).

I was one of the biggest supporters of the last part of this statement, and no one could convince me otherwise. I lost a lot of money and time and had to buy the more expensive equipment in any case at the end.  😠

3 hours ago, Jaco de Jongh said:

I was one of the biggest supporters of the last part of this statement, and no one could convince me otherwise. I lost a lot of money and time and had to buy the more expensive equipment in any case at the end.  😠

Jip, same story this side. Had to pay school fees to learn the hard way. Rather save and buy the better option. 

I have to agree with Plonkster here. It sounds as if you need to fiddle with the settings of that Axpert to get the most out of it.

 

When it comes to solar components, I believe in separate components, not the “all in one” solution of Axpert. If my one charge controller or solar array dies, my system still runs (perhaps only at 50%), but it still runs. If an Axpert dies, the whole system dies. Sorry, just my personal opinion... 

Thanks for all the feedback, Lots of reading and playing to do.

On 2019/07/26 at 9:55 AM, PeterP said:

Unless you have very favourable feed-in tariff (which we don't) ...

May I suggest a small clarification and throw a lot of ideas in to boot?
No in SA we don't have favourable feed in tariffs AND it is costly to get all in place to be able to feed back.
So no, we don't do that in SA. 

What we do do is we get a hybrid grid tied inverter that feeds into the entire house whilst feeding nothing back to the grid.

Like so on a 3.5kw array and 2.4kw continuous power limiting 3kva inverter - grid setting at 20w to keep it lean and mean:

 

And then when there are bigger loads - with lots of spare still available from MPPT for a bigger battery bank as the MPPT can still do a lot more:
1) The "Always on DB" loads
2) Plus the entire house main DB loads
= +- 4.261kw
3) Minus the max the inverter can continuously generate - by design - from the 3.5kw array
4) = the difference drawn from the grid

And that, boys and girls, is how we roll now. Maximum savings with no regrets. 🙂 

 

Note: Batts above are kept "Fully Charged" because:
1) they are EOL and  I need to buy time
2) whilst I generate the most savings by covering as much of the entire homes loads as possible
Titbit: And the "Always on DB" loads are set to meet the batts and not the batts to meet the loads.
 

FYI - the next level with the EOL battery bank: Soon I will have 4 more 2nd hand T105 batts and will start to fix the EOL current T105RE bank problem by doing this hack:
1) The existing T105RE bank has one batt that is problematic right. I will replace it with one of these: http://www.dixonbatteries.co.za/dc-golf-cart-6v-210ah-lwh-260x180x290
2) Then I will connect them all up for a 450ah 24v bank mixing T105 and T105RE's BECAUSE they all are "old" with one new Dixon batt.
3) Once in place I can then open the tappets with the 3.5kw array and use more of the ESS featured "savings".

If this hack can last 1-3 years more I will be happy because I have learnt that 4000 cycles at 20% DOD, only happens in marketing material because in real life, temperature really has a huge impact on claimed cycles, whilst I wait for a 24 Pylontech bank to arrive in SA, at a good price with the lead price on 8 x +-32kg batts carrying a wee bit towards the new 24v lithium bank.

Because as I have again experienced, matching the loads to the batts and not the batts to the loads on a 24v system, you can get away with murder ito battery costs. 🙂 

So I make a case for having a smaller lower cost 24v bank OR double it for longer run times (same as a48v bank) for I hate spending money on batts yet we need batts for evening failures.

Titbit to note: If Eskom fails daytime and the sun shines, a hybrid system will first use all the power the panels can produce, whilst not touching the batteries, until it has to. 
 

On 2019/07/26 at 8:51 AM, plonkster said:

As @PJJ said, the options are Victron or Goodwe.

You can add Infinisolar to that list.

2 hours ago, The Terrible Triplett said:

1) The existing T105RE bank has one batt that is problematic right. I will replace it with one of these: http://www.dixonbatteries.co.za/dc-golf-cart-6v-210ah-lwh-260x180x290

@The Terrible Triplett ek het nie eers geweet Dixon maak golf cart batterye nie. Die prys lyk nogals baie goed ook. 

36 minutes ago, Gerlach said:

Die prys lyk nogals baie goed ook. 

Jip, hang ook af met wie jy praat daaroor. 🙂 

Hulle Royals is ook nogal nie te sleg.

1 hour ago, Chris Hobson said:

You can add Infinisolar to that list.

He's back ... nope, Victron GoodWE ABB. And that's that! 😜

10 minutes ago, The Terrible Triplett said:

ip, hang ook af met wie jy praat daaroor. 🙂 

Hulle Royals is ook nogal nie te sleg.

Ek het daai Royals gespot ook. Klaar begin uit werk wat n 48v bank gaan kos op daai GROOT outjies!!! sal love vir so set. 

12 minutes ago, The Terrible Triplett said:

Hulle Royals is ook nogal nie te sleg

so 24 van die outjies sal my baie happy maak. http://www.dixonbatteries.co.za/s-1660-2-volt-battery

I have found someone that can source a Solis 4.6kW hybrid  at a price that appears to be reasonable. 

Hopefully someone here can help with some questions I have:

Any experience with Solis inverters? Quality? Service?

What function does the DC Switch serve?

Hi I got a infini solar 10 Kv and need some help pls 

when I run the unit on the batteries it works all fine then when grid power comes on it gives me a error code 16 and says BATTERY UNDER VOLTAGE WHEN GRID IS OK

Then runs for a while on the grid and then the whole house shuts down. It then re boots and runs on battery for a while with the utility flashing for a while and then finally kicks back into running on the grid. My setting is ‘off grid lll ‘ 

This is happening when no PV is around also noticed the batteries only charge at 7-9 amps and my setting is 40 amps. Got 2 hauwei 48 volt lithium 

When I had PV I see the batteries get to 100% but on utility it’s around 70%

pls help I’m lost