My girlfriend is currently doing her masters degree and requires backup power during load shedding to work on her laptop, keep the internet going, keep a light on and run a fan.

I have a 1440w Mecer trolley inverter system which currently has two deep cycle batteries. With the current load shedding, I can see the batteries deteriorating every day, so I would like to make use of the trolley and upgrade the whole system and give it to her and do so as affordable as possible. It would be a plug and play system - connected to a plug point in the house and charge through Eskom, and a multiplug output for her to connect her laptop/fan/router etc.

I was looking at the below components:

• Inverter: https://www.solarwaysuppliers.co.za/product/must-3kw-60amp-mppt-solar-hybrid-inverter/
• Battery: https://www.solarwaysuppliers.co.za/product/must-2-56kwh-lithium-ion-battery/

I have attached the inverter spec sheet as reference

• What else do I need for the complete build? In the manual it states I need a 125A DC over-current protector or breaker between the inverter and battery, and a 32A AC breaker in between the inverter and AC input. Is this required with a plug and play solution?
• What gauge wires do I need to run between the inverter and battery - Can I use the existing battery cables?
• Can I use a normal household multiplug for output or does it need to be heavy duty?
• Are there any other wires required and which gauge?

 

16-PV1800-VPM.pdf

Edited February 25, 20233 yr by Wimmas

If the total loads are as you stated, a 3kw inverter and 2.56kWh battery are overkill. the reason that most load shedding trolley type inverters and their batteries are taking strain is because they cannot recharge quick enough with our current stage 4 and stage 6 schedules.

A decent small inverter that provides sufficient  charge current coupled with a lithium battery will be more than adequate.

21 minutes ago, Wimmas said:

Can I use a normal household multiplug for output or does it need to be heavy duty?

Yes, standard multiplug serves its purpose during normal power, it will be fine with a backup solution.

Below a diagram based on the manufacturers' installation instructions. Please advise if I am correct or if something is wrong/missing:

The battery will be inside the cabinet.

Can I buy any 125A DC breaker and 32A AC breaker or are the specific ones required?

Sorry but I am still new and learning.

Edited February 25, 20233 yr by Wimmas

I agree with @jacksdadlaptop 50 to 100w if using fibre ONT 10-20w router 10-20w light if not led 50w fan 30-50w total consumtion call it 250 watts why 3kva inverter?

2 minutes ago, TaliaB said:

I agree with @jacksdadlaptop 50 to 100w if using fibre ONT 10-20w router 10-20w light if not led 50w fan 30-50w total consumtion call it 250 watts why 3kva inverter?

I want something long lasting, and with the possibility of being able to charge via panels or a generator. Wasting R10k - R15k on a smaller solution not worth it for me. In our area we have prolonged periods of load shedding at times because of power not coming back on. At least with pure sine wave she could power her fridge and a fan if need be.

Edited February 25, 20233 yr by Wimmas

10 minutes ago, Wimmas said:

Below a diagram based on the manufacturers' installation instructions. Please advise if I am correct or if something is wrong/missing:

The battery will be inside the cabinet.

Can I buy any 125A DC breaker and 32A AC breaker or are the specific ones required?

Sorry but I am still new and learning.

All ac wiring 2.5mm² battery to breaker to inverter 25mm² welding cable or multistrand flexicore Fly25

23 minutes ago, Superfly said:

Your AC cables will be 2.5mm to the inverter and 4.0mm to the 32A breaker - I have given the DC size.

@Wimmaswants to run inverter from socket outlet so you need to use 20amp curcuit breaker with 2.5 mm² wire. If you want to supply the inverter(Ac input) from the db board with 32A curcuit breaker you will use 4mm² wire. Just remember if you run it from the db you will need to get a new COC as you will have changed the curcuit configuration and you will need a accredited electrical contractor to do it.

7 minutes ago, Superfly said:

LOL seems we posted concurrently...

👍😂

6 minutes ago, Superfly said:

The 32A is AC output AFAIK

The inverter can only deliver 13 amps output i will use a RCD between the inverter output and the multiplug

Will Prowse does a pretty good guide to building your own portable Solar System using a 12V battery & inverter 

 

Edited February 26, 20233 yr by Sc00bs

If I run the 32A AC breaker, would I still need RCD between inverter output and multiplug?

On both breakers, do I go single or dual pole?

 Herewith a new diagram based on recommendations and manufacturers' specs with wire sizes. Please advise if I am on the right path:

Edited February 26, 20233 yr by Wimmas

19 minutes ago, Wimmas said:

 Herewith a new diagram based on recommendations and manufacturers' specs with wire sizes. Please advise if I am on the right path:

Cannot comment on cables as I have not used AWG in over 40 years and in stores one only sees the metric sizes. 

Locally we have been using the metric system since some time in the 1970's. Some conversions I can still remember from the imperial system but not this one. 😀😀

Edited February 26, 20233 yr by Scorp007

1 hour ago, Scorp007 said:

Cannot comment on cables as I have not used AWG in over 40 years and in stores one only sees the metric sizes. 

Locally we have been using the metric system since some time in the 1970's. Some conversions I can still remember from the imperial system but not this one. 😀😀

Herewith on the metric sizes:

Edited February 26, 20233 yr by Wimmas

4 minutes ago, Wimmas said:

Herewith on the metric sizes:

Inverter to RCD and RCD to multiplug can be 4 sq mm unless you have a long run to get to the multiplug. Other sizes all seems fine. Ensure the 125A MCB is for DC use. 

1 minute ago, Scorp007 said:

Inverter to RCD and RCD to multiplug can be 4 sq mm unless you have a long run to get to the multiplug. Other sizes all seems fine. Ensure the 125A MCB is for DC use. 

👍

Will report back once build is done!

28 minutes ago, Wimmas said:

Herewith on the metric sizes:

Just 1 legal installation issue, the 3 pin wall socket is wired with 2.5mm² wire maximum rating 23Amps and the socket is rated at 16 amps so instead of 32amp breaker from 3pin wall socket use 16 amp breaker between wall socket and inverter 32amp breaker won't protect the 2.5mm² wire

1 hour ago, TaliaB said:

Just 1 legal installation issue, the 3 pin wall socket is wired with 2.5mm² wire maximum rating 23Amps and the socket is rated at 16 amps so instead of 32amp breaker from 3pin wall socket use 16 amp breaker between wall socket and inverter 32amp breaker won't protect the 2.5mm² wire

Never too old to learn. In my younger days working on wiring at houses we always used 4 sq mm for sockets. 2.5 was only used if on a ring supply.

I just wonder how many large houses with 2.5 used will actually pass the voltage drop test if it still applies?

AFAIK the 32A MCB is there to protect the 6 sq mm wire. 

Edited February 26, 20233 yr by Scorp007

8 minutes ago, Scorp007 said:

Never too old to learn. In my younger days working on wiring at houses we always used 4 sq mm for sockets. 2.5 was only used if on a ring supply.

I just wonder how many large houses with 2.5 used will actually pass the voltage drop test if it still applies?

AFAIK the 32A MCB is there to protect the 6 sq mm wire. 

Your last statement is true but think about this for a moment. You are connecting a 32amp curcuit breaker in line with a 20amp curcuit breaker in the db board feeding the socket with 2.5mm² wire so you will trip the breaker in the db board before you disconnect the 32amp breaker. All ac wires from the wall socket needs to be 2.5mm² wire up to the multiplug with a RCD either just after the wall socket or just before the multiplug it doesn't matter as long as jou have earth fault protection in island mode(LS) on the output to the appliances

@Scorp007FYI copied from Sans 10142-1 5.3.2 Voltage drop
5.3.2.1 When all conductors of an a.c. installation are carrying their maximum
estimated load, the difference in voltage (the voltage drop) between the point of supply and any point of outlet or terminals of fixed appliances shall notexceed 5 % of the standard voltage or of the declared phase-to-neutral
voltage (see also 6.2.7).

I am very confused at the moment as the more I am thinking of it the more questions pop up.

1. Do I use a normal 3 pin plug or a surge protector plug for the plug connecting the the wall socket? A plug like this is what I am referring to:https://www.takealot.com/united-electrical-16a-high-surge-protection-3-pin-plug-top/PLID72796115
2. How will the grounding work? The cable coming from the wall socket will be 3-core (L,N,G) going into the 16A 2 pole breaker, but only L & N goes through the breaker. Will G then go straight to the inverter and same with the output side through the 25A earth leakage protector?
3. Based on various suggestions if I revised the cable sizes and kept AC input and output to 2.5mm

Does the above make sense? If I buy a 2.5mm 3 core cable it means I will have to split the cable and hopefully not damage the G cable, or cut the cable and reconnect G through soldering/lugs and an insulation sleeve.

On another note, I have seen a few systems like the one I am planning on building that do not have any breakers or earth leakage protection like the suggestions on this forum for my setup. I have attached a few pics. It looks like there might be a battery fuse but I am not sure. Selling for R28.5k.

Edited February 27, 20233 yr by Wimmas

13 minutes ago, Wimmas said:

I am very confused at the moment as the more I am thinking of it the more questions pop up.

1. Do I use a normal 3 pin plug or a surge protector plug for the plug connecting the the wall socket? A plug like this is what I am referring to:https://www.takealot.com/united-electrical-16a-high-surge-protection-3-pin-plug-top/PLID72796115
2. How will the grounding work? The cable the coming from the the wall socket will be 3-core (L,N,G) going into the 16A 2 pole breaker, but only L & N goes through the breaker. Will G then go straight to the inverter?
3. The AC output cable will be 3 core with G going into the 25A earth leakage protection, and L / N going straight to the multiplug
4. Based on various suggestions if I revised the cable sizes and kept AC input and output to 2.5mm

Does the above make sense? If I buy a 2.5mm 3 core cable it means I will have to split the cable and hopefully not damage the G cable, or cut the cable and reconnect G through soldering and a sleeve. Same with the L and N cables at AC output, or is there a simpler way?

On another note, I have seen a few systems like the one I am planning on building that do not have any breakers or earth leakage protection like the suggestions on this forum for my setup. I have attached a few pics. It looks like there might be a battery fuse but I am not sure. Selling for R28.5k.

1. Surge arrestor plug is good.

2. Ground wire straight to inverter.

3. Nooo the Live and Neutral goes through the earth leakage(same as breaker) and ground goes to multiplug with L and N from the bottom of the earth leakage.

4. Keep the cable size 2.5mm²

Run a 3 core cable but use a seperate earth( yellow and green or green) wire cable tied to the outside.

The one in the picture is not legal as jou won't have ground fault protection in island  mode( during LS)

2 minutes ago, TaliaB said:

1. Surge arrestor plug is good.

2. Ground wire straight to inverter.

3. Nooo the Live and Neutral goes through the earth leakage(same as breaker) and ground goes to multiplug with L and N from the bottom of the earth leakage.

4. Keep the cable size 2.5mm²

Run a 3 core cable but use a seperate earth( yellow and green or green) wire cable tied to the outside.

The one in the picture is not legal as jou won't have ground fault protection in island  mode( during LS)

Thanks - I realized that I messed up the wiring through the earth leakage and fixed it

So I will then use 2-core (L & N) and a separate ground cable running outside the 2-core cable? I am just concerned for safety with the ground cable not having dual insulation and the insulation on it might not be adequately protected if a sharp object or something catches it and exposes it?

16 minutes ago, Wimmas said:

Thanks - I realized that I messed up the wiring through the earth leakage and fixed it

So I will then use 2-core (L & N) and a separate ground cable running outside the 2-core cable? I am just concerned for safety with the ground cable not having dual insulation and the insulation on it might not be adequately protected if a sharp object or something catches it and exposes it?

That is not a problem you could even run bare copper wire on the outside