Hi LikeMinded People,

So I have 16 panels, 7.2KW OCI inverter and 3 Shoto 5.12 batteries. I would like to add 4 more panels with 1 more battery. My installer says I need either an other inverter or an MPPT controller. Whats the best option? I need a dumb down version of what the MPPT does. I’ve googled and youtubed but explainations are very good but it assumes you know what the MPPT does.

please help? What do I do? 

20 minutes ago, Raiden2912 said:

So I have 16 panels, 7.2KW OCI inverter and 3 Shoto 5.12 batteries. I would like to add 4 more panels with 1 more battery

Do you have specs for your panels i.e. Pmax, Vmp, Imp, Voc & Isc? 

 

24 minutes ago, Raiden2912 said:

I need a dumb down version of what the MPPT does.

MPPT, short for maximum power point tracker, is electronic circuitry (DC to DC converter) that optimises power extraction from solar panels (or wind turbines) to the inverter or battery system, as weather conditions vary. A good analogy of an MPPT as a vehicle's transmission system, offering power from the engine to the wheels is explained here.

 

Edited August 9, 20232 yr by Kilowatt Power

1 hour ago, Raiden2912 said:

Hi LikeMinded People,

So I have 16 panels, 7.2KW OCI inverter and 3 Shoto 5.12 batteries. I would like to add 4 more panels with 1 more battery. My installer says I need either an other inverter or an MPPT controller. Whats the best option? I need a dumb down version of what the MPPT does. I’ve googled and youtubed but explainations are very good but it assumes you know what the MPPT does.

please help? What do I do? 

I will explain it with this picture. PWM solar controller takes the panel voltage and applies it to the battery via a on/off by modulating the on and off time to provide the correct average voltage for charging. 

A MPPT takes the voltage above the battery voltage and converts that to extra amps continuously for faster charging at higher Watts. 

The line in red is the panel amps and the green line is the amps going into the battery. DC to DC converting doing it's thing. 

Actual graph taken from my Epever MPPT charging the battery on a Axpert from a single panel. 

 

 

Thank you that’s helps a lot. 
 Pictures attached 

Question: do I only need the MPPT controller because I wanna increase my panel numbers or can I just install one to increase my current solar yield? 

39 minutes ago, Raiden2912 said:

Question: do I only need the MPPT controller because I wanna increase my panel numbers or can I just install one to increase my current solar yield? 

Place a picture of the rating plate on the inverter. 

My post was just to indicate how a MPPT works. Not meant as a solution for you. 

Edited August 9, 20232 yr by Scorp007

Thanks for the info on the solar panels, I did not knew the inverter brand so I googled it and the inverter looks like a 7.2Kw Axpert clone and the solar power input for the 7.2Kw is 8Kw across two inputs so that means that it is 4Kw per input.

According to the specifications of the solar panels that you supplied the power output is 545W and you stated that there are 16 panels so that means the power of the array is 8.72Kw if the array is receiving proper sun.
The array is already oversized so why do you want to add more panels to the array?

I have a couple of questions
A]Is the inverter connected to a utility power source (Eskom or Municipal power source)?
B]Is the inverter standalone where there is only a solar input?
C]Does the batteries charge fully?
D]Are all the solar panels facing North?
E]Do you have any means to monitor how much power you receive from the solar panels? 

23 hours ago, Raiden2912 said:

Hi LikeMinded People,

So I have 16 panels, 7.2KW OCI inverter and 3 Shoto 5.12 batteries. I would like to add 4 more panels with 1 more battery. My installer says I need either an other inverter or an MPPT controller. Whats the best option? I need a dumb down version of what the MPPT does. I’ve googled and youtubed but explainations are very good but it assumes you know what the MPPT does.

please help? What do I do? 

After all the chat around your system as well as your other chats that you feel you are using too much grid then the following. 

Having 8kW of PV and the inverter only produces 30kWh per day I suggest you try to store more PV for cycling by adding a 4th battery. Also try to use more PV during the sun period to reduce your grid use of 13kWh per day. 

The above should help to use the up to 40kWh of PV that can be produced. Area specific. 

Further I did not see that you mention if you at times have a higher peak use that exceeds the 7.2kW the inverter can produce. 

Also with 3 batteries can you not try and discharge to say 30% SOC instead of 40%. I hope I read it correctly that you only discharge to 40%.

Your installer might be right that you will need a 2nd similar inverter when you want to add more panels. 

Edited August 10, 20232 yr by Scorp007

Thanks for the responses. So I don’t have the outlay just yet for another battery so I’m trying to optimize 

which settings do I change? 

 

23 hours ago, Raiden2912 said:

Thanks for the responses. So I don’t have the outlay just yet for another battery so I’m trying to optimize 

which settings do I change? 

 

Hope someone can help. I just wonder why you want to use utility at say 48% SOC at around 14h00. Below the red line. 

Edited August 11, 20232 yr by Scorp007

So the 14:00 timer is set to heat the geyser for my misses and kids evening shower, so I’m using a bit of the sun and then also grid. 
 

any suggestions on this would be great.

Does this make sense or no? Am I confused? Really don’t mind the advice

9 minutes ago, Raiden2912 said:

Does this make sense or no? Am I confused? Really don’t mind the advice

My call would be to heat the geyser say at 11h30-13h00 time slot as at 14h00 PV power is already quite a bit lower as per my graph. This implies using more PV with less grid. 

Normally geysers are one of the high load items and one will want to use PV when at a peak. 

Edited August 13, 20232 yr by Scorp007

Thanks Scorp007

17 hours ago, Scorp007 said:

My call would be to heat the geyser say at 11h30-13h00 time slot as at 14h00 PV power is already quite a bit lower as per my graph. This implies using more PV with less grid. 

Normally geysers are one of the high load items and one will want to use PV when at a peak. 

This is what I do as well. Start heating at 11:30. Geyser is hot and switches off before 2pm. Water is still very hot in the evening. 

1 hour ago, Chris_S said:

This is what I do as well. Start heating at 11:30. Geyser is hot and switches off before 2pm. Water is still very hot in the evening. 

A lot of savings can be had a little bit at a time. 

Just this morning I suddenly found that my overnight consumption is 50% of my daily use after not checking it for about a year. 

Now the hunt is on to find the reason. 🤔🤔

 

On 2023/08/09 at 1:32 PM, Raiden2912 said:

Hi LikeMinded People,

So I have 16 panels, 7.2KW OCI inverter and 3 Shoto 5.12 batteries. I would like to add 4 more panels with 1 more battery. My installer says I need either an other inverter or an MPPT controller. Whats the best option? I need a dumb down version of what the MPPT does. I’ve googled and youtubed but explainations are very good but it assumes you know what the MPPT does.

please help? What do I do? 

@Raiden2912 all above inputs very informative and helpful but getting back to your original question. Due to the various losses in a solar system, it is common practice to oversize the solar array to enable the system to generate more power during bad weather and under various conditions, such as high temperatures where power derating can occur. The main loss factors include - poor weather (low irradiation), dust and dirt, shading, poor orientation, and cell temperature de-rating. These loss factors combined can reduce power output significantly. For example, a 300W solar panel will generally produce 240W to 270W on a hot summer day due to the high-temperature power de-rating. Depending on your location, reduced performance will also occur in winter due to low solar irradiance. For these reasons, oversizing the solar array beyond the manufacturers ‘recommended or nominal value’ will help generate more power in unfavourable conditions. Oversizing by 150% (Nominal rating x 1.5) is possible on many professional MPPT solar charge controllers and will not damage the unit. However, many cheaper MPPT charge controllers are not designed to operate at full power for a prolonged amount of time, as this can damage the controller. Therefore it is essential to check whether the manufacturer allows oversizing. Sunsynk, Deye and Victron Energy allow oversizing well beyond the nominal values listed on the datasheets as long as you don’t exceed the input voltage and current limits. Victron MPPT controllers have been successfully used with 200% solar oversizing without any issues. However, the higher the oversizing, the longer the controller will operate at full power and the more heat it will generate. Without adequate ventilation, excess heat may result in the controller overheating and derating power or, in a worst-case scenario, complete shutdown or even permanent damage. Therefore always ensure adequate clearance around the controller according to the manufacturer’s specifications, and add fan-forced ventilation if required

 

@Raiden2912That said in my post above i had a quick look at your inverter specs:

OCI-MX-7.2k 7200 watts. Mppt max charge current- 80 amps.

Inverter Surge power 15000va ( 12000 watts)

MPPT Operating Voltage-90~450vdc

Max PV Array Power 8000 watts( 2x 4000 watts).

Max PV Array Open Curcuit Voltage 500vdc.

So your existing array 2 strings series off 8 panels @ 50.18v Voc. 8 x 50.18 =401.44vdc + 7.5% = 431.55vdc/mppt all good so far. Now 10 panels 2 strings series 10 x 50.18vdc = 501.8vdc + 7.5%=539.4vdc way over your allowed max of 500vdc. So your installer is correct to say you will need an external Mppt if you want to add 4 panels to existing array. 

4 hours ago, TaliaB said:

as long as you don’t exceed the input voltage and current limits.

 

Thank you for this.

small steps for me so I’ve changed a bit of settings before outlaying again. To simplify things I’ve adjusted my geyserwise timers 

Afternoon - I’ve reset my timers on my geyserwise to use more sun hours. 11:30 - 14:00.

Early morning 3am - I have no choice but to use battery. And I’ve noticed after charging without any interruptions like loadshedding and or cable theft i have 49% of the battery left. 
 

all of this information is super helpful so I thank you all for the info. 

9 hours ago, Scorp007 said:

A lot of savings can be had a little bit at a time. 

Just this morning I suddenly found that my overnight consumption is 50% of my daily use after not checking it for about a year. 

Now the hunt is on to find the reason. 🤔🤔

 

Please let us know what was the outcome here?

14 hours ago, Raiden2912 said:

Please let us know what was the outcome here?

It seems without measuring the night time load for a long time my use after checking every load is normal. My gut was wrong. I also forgot to add the 1.5kwh used early morning to heat the geyser. Adding 9 outside lights, 2 fridges plus bar fridge and then the 11 hrs ths elec blanket is on together with the charging of 4 x lead acid batteries for the outside lights just all add up. 

Will monitor the use over a few days. Switching off the know loads I got a 1.7W reading which can be chargers and other appliances which I am not going to try and find. 

I am lost for words with you CoJ rates account while you are on prepaid power for some time. 

Edited August 15, 20232 yr by Scorp007