Small scale household backup system

Iwojima

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Joined
Jan 16, 2007
Messages
3,947
So I've currently got a Mecer 720w system paired with 2x 100ah deep cycle batteries. It sits in the room next to my lounge and when needed I get out an extension cord and run it to whatever I need powered (typically my PC and/or TV, Amp, media center, etc).

Issues:
- Inconvenient having to run cables every time (missus struggles when I'm not around)
- TV/amp in particular does not seem to be happy with modified sine
- Noisy when under load
- Limited household lighting
- Ugly ass unit taking up space in the room

Wants:
- Easier or even seemless transition to backup
- Less noise (db located in my garage)
- All household lighting on backup
- Solar charging (if I choose to add some panels later)
- Expandability if I choose to run more appliances on backup later, eg a fridge. Typical evening load for now will be around 600w
- Some form of smart monitoring (a nice to have, not essential)

Possible solution:
- Get a 3kva, 24v pure sine inverter professionally integrated into the db with all lighting on backup and isolate plug circuits where necessary
- Reuse current 2x100ah batteries in series

Thoughts?
Possible inverter recommendations?
Anything I'm not considering?
 
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Mike Hoxbig

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Apr 25, 2010
Messages
40,575
If you have a view towards solar then get the best inverter and battery that you can afford. Especially since you're doing a db integration, better you do it properly upfront.

5/8kW hybrid inverter and 5 kWh battery. You could re-use your current batteries but if your budget allows then rather go lithium. This should set you back 50-60k incl installation.

You'll want something that scales properly with the future in mind. Instead of a bunch of 3 kva 24V inverters and having to ensure that you get compatible batteries. It's going to cost more in the long run...
 

Paul_S

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Joined
Jun 4, 2006
Messages
5,186
If you have a view towards solar then get the best inverter and battery that you can afford. Especially since you're doing a db integration, better you do it properly upfront.

5/8kW hybrid inverter and 5 kWh battery. You could re-use your current batteries but if your budget allows then rather go lithium. This should set you back 50-60k incl installation.

You'll want something that scales properly with the future in mind. Instead of a bunch of 3 kva 24V inverters and having to ensure that you get compatible batteries. It's going to cost more in the long run...

Depends on the installation and requirements but from what I've read so far the average costs seem to be along the lines of:
R20K for installation and CoC (especially if splitting of loads and additional DB required)
R10K to R20K for misc items (switch gear, cabling, fuses, etc.)
R25K for 5kWh lithium battery
R20K to R35K for decent 5kW to 8kW hybrid inverter
Total = R75K to R100K
 

Mike Hoxbig

Honorary Master
Joined
Apr 25, 2010
Messages
40,575
Depends on the installation and requirements but from what I've read so far the average costs seem to be along the lines of:
R20K for installation and CoC
R10K to R20K for misc items (switch gear, cabling, fuses, etc.)
R25K for 5kWh lithium battery
R20K to R35K for decent 5kW to 8kW hybrid inverter
Total = R75K to R100K
Installation is very high for just an inverter and battery. A full solar install costs about 5k less.

Also misc items is much less for a full solar install.

20k - 35k depending on 5kW or 8kW inverter.
25k for 5kWh battery
5k misc items
~7k-ish installation

The most amount of work for installations is the panels. Other than that it's just basic wiring...
 

TheChamp

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Joined
Feb 26, 2011
Messages
49,033
So I've currently got a Mecer 720w system paired with 2x 100ah deep cycle batteries. It sits in the room next to my lounge and when needed I get out an extension cord and run it to whatever I need powered (typically my PC and/or TV, Amp, media center, etc).

Issues:
- Inconvenient having to run cables every time (missus struggles when I'm not around)
- TV/amp in particular does not seem to be happy with modified sine
- Noisy when under load
- Limited household lighting
- Ugly ass unit taking up space in the room

Wants:
- Easier or even seemless transition to backup
- Less noise (db located in my garage)
- All household lighting on backup
- Solar charging (if I choose to add some panels later)
- Expandability if I choose to run more appliances on backup later, eg a fridge. Typical evening load for now will be around 600w
- Some form of smart monitoring (a nice to have, not essential)

Possible solution:
- Get a 3kva, 24v pure sine inverter professionally integrated into the db with all lighting on backup and isolate plug circuits where necessary
- Reuse current 2x100ah batteries in series

Thoughts?
Possible inverter recommendations?
Anything I'm not considering?
Why not the 1200W pure sine wave? It has a 500W solar input and It's much cheaper and will do the job of powering lights and electronics with ease. You shouldn't spend much on temporary loadshedding measures you will have to throw away when you build a proper system.
 

Gaz{M}

Executive Member
Joined
Feb 9, 2005
Messages
7,289
So I've currently got a Mecer 720w system paired with 2x 100ah deep cycle batteries. It sits in the room next to my lounge and when needed I get out an extension cord and run it to whatever I need powered (typically my PC and/or TV, Amp, media center, etc).

Issues:
- Inconvenient having to run cables every time (missus struggles when I'm not around)
- TV/amp in particular does not seem to be happy with modified sine
- Noisy when under load
- Limited household lighting
- Ugly ass unit taking up space in the room

Wants:
- Easier or even seemless transition to backup
- Less noise (db located in my garage)
- All household lighting on backup
- Solar charging (if I choose to add some panels later)
- Expandability if I choose to run more appliances on backup later, eg a fridge. Typical evening load for now will be around 600w
- Some form of smart monitoring (a nice to have, not essential)

Possible solution:
- Get a 3kva, 24v pure sine inverter professionally integrated into the db with all lighting on backup and isolate plug circuits where necessary
- Reuse current 2x100ah batteries in series

Thoughts?
Possible inverter recommendations?
Anything I'm not considering?

You don't mention your budget which will entirely determine what solution you will be recommended.

You can do a dirt cheap 3kw inverter near your db and get an electrician to install a simple changeover switch for a few grand. Then it's up to you to flip off the breakers you don't want to use during loadshedding.
 

Iwojima

Expert Member
Joined
Jan 16, 2007
Messages
3,947
If you have a view towards solar then get the best inverter and battery that you can afford. Especially since you're doing a db integration, better you do it properly upfront.

5/8kW hybrid inverter and 5 kWh battery. You could re-use your current batteries but if your budget allows then rather go lithium. This should set you back 50-60k incl installation.

You'll want something that scales properly with the future in mind. Instead of a bunch of 3 kva 24V inverters and having to ensure that you get compatible batteries. It's going to cost more in the long run...
I hear you. Buy the right thing and spend money once.

But the primary intention here (and perhaps I shouldn't have listed all the nice to haves) is to duplicate what I have in an easier to use setup. Scaling up will be limited in scope.

The solar component as an example is only one that I see a use for if there are extended power outages rather than normal load shedding. The logic being that even if I'm out for 24hrs at least my batteries will recharge and I can have some power for that evening.

Why not the 1200W pure sine wave? It has a 500W solar input and It's much cheaper and will do the job of powering lights and electronics with ease. You shouldn't spend much on temporary loadshedding measures you will have to throw away when you build a proper system.
My thinking with going for the 3KVA is that if I wanted to add say my fridge to the backup it would have the capability of doing the in-rush current associated with the compressor starting up.

Open to suggestions on the 1200W unit though? What would you recommend? As long as it can integrate with the db and circuits I choose to isolate.

You don't mention your budget which will entirely determine what solution you will be recommended.

You can do a dirt cheap 3kw inverter near your db and get an electrician to install a simple changeover switch for a few grand. Then it's up to you to flip off the breakers you don't want to use during loadshedding.
Budget is not really the concern here. It's more about getting what I already have on backup in an easier to use format with the additional capability of adding household lighting/some additional appliances and solar to the mix if need be.

The property is not one I want to over capitalize on as it probably won't be my primary residence within the next 5 years. If this was what I'd consider my "forever home" you can be certain I'd drop the 100-150k on the full fat solution in an instant.

I do like the alternative idea of the changeover switch. Not quite as elegant as automatic cutover, but still something I'm sure my missus could use without too much hassle (I hope).
 
Last edited:

TheChamp

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Joined
Feb 26, 2011
Messages
49,033
My thinking with going for the 3KVA is that if I wanted to add say my fridge to the backup it would have the capability of doing the in-rush current associated with the compressor starting up.

Open to suggestions on the 1200W unit though? What would you recommend? As long as it can integrate with the db and circuits I choose to isolate.
The same Mecer/Axpert comes in 1200W 12V guise, as do take note about the restrictions on inverters if you are in the Independent Republic.
 

Gaz{M}

Executive Member
Joined
Feb 9, 2005
Messages
7,289
I hear you. Buy the right thing and spend money once.

But the primary intention here (and perhaps I shouldn't have listed all the nice to haves) is to duplicate what I have in an easier to use setup. Scaling up will be limited in scope.

The solar component as an example is only one that I see a use for if there are extended power outages rather than normal load shedding. The logic being that even if I'm out for 24hrs at least my batteries will recharge and I can have some power for that evening.


My thinking with going for the 3KVA is that if I wanted to add say my fridge to the backup it would have the capability of doing the in-rush current associated with the compressor starting up.

Open to suggestions on the 1200W unit though? What would you recommend? As long as it can integrate with the db and circuits I choose to isolate.


Budget is not really the concern here. It's more about getting what I already have on backup in an easier to use format with the additional capability of adding household lighting/some additional appliances and solar to the mix if need be.

The property is not one I want to over capitalize on as it probably won't be my primary residence within the next 5 years. If this was what I'd consider my "forever home" you can be certain I'd drop the 100-150k on the full fat solution in an instant.

I do like the alternative idea of the changeover switch. Not quite as elegant as automatic cutover, but still something I'm sure my missus could use without too much hassle (I hope).

Ok then get a 3kva Inverter, 600W solar panels and use your existing 2 LA batteries. Get the electrician to split your db into essential lights and plugs and non-essential circuits. Then when mains is off, those essential loads will keep running uninterrupted.

Sounds like this is what you want. Cost is

+- R6k inverter
+- R6k solar panels
+- R6k mounting/wiring
+- R5k electrician
 

initroot

Senior Member
Joined
Jul 30, 2011
Messages
882
I'm paying 15k for my installation, COCT registration and CoC of full solar. Would love to get installer only charging 7k in Cape Town.
 

The Door

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Joined
Jul 18, 2008
Messages
58,479
So I've currently got a Mecer 720w system paired with 2x 100ah deep cycle batteries. It sits in the room next to my lounge and when needed I get out an extension cord and run it to whatever I need powered (typically my PC and/or TV, Amp, media center, etc).

Issues:
- Inconvenient having to run cables every time (missus struggles when I'm not around)
- TV/amp in particular does not seem to be happy with modified sine
- Noisy when under load
- Limited household lighting
- Ugly ass unit taking up space in the room

Wants:
- Easier or even seemless transition to backup
- Less noise (db located in my garage)
- All household lighting on backup
- Solar charging (if I choose to add some panels later)
- Expandability if I choose to run more appliances on backup later, eg a fridge. Typical evening load for now will be around 600w
- Some form of smart monitoring (a nice to have, not essential)

Possible solution:
- Get a 3kva, 24v pure sine inverter professionally integrated into the db with all lighting on backup and isolate plug circuits where necessary
- Reuse current 2x100ah batteries in series

Thoughts?
Possible inverter recommendations?
Anything I'm not considering?
Sunsynk lifelynk if your budget is small.
 

AlphaJohn

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Joined
Sep 10, 2012
Messages
12,174
You looking for em starter kits:


I got 3Kw Sako + 2 x 250W solar + 100AH24V for about R20 000

For now I'm using Solar + Battery on the 24V Mecer. Will swap to Sako and do the DB board hook-up in December (Bonus) and get Sparky to come certify.
 

Iwojima

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Joined
Jan 16, 2007
Messages
3,947
3kw Mecer is now installed. Ended up moving all plug circuits onto the inverter.

Both the fridge and freezer now have smart plugs installed and I'm currently sorting out the automation via Home Assistant to switch both of these off on AC loss and back on when AC returns.

The above will be the setup until I've decided what the new battery setup will look like, after which fridge and freezer will remain on backup permanently.
 
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AlphaJohn

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Joined
Sep 10, 2012
Messages
12,174
3kw Mecer is now installed. Ended up moving all plug circuits onto the inverter.

Both the fridge and freezer now have smart plugs installed and I'm currently sorting out the automation via Home Assistant to switch both of these off on AC loss and back on when AC returns.

The above will be the setup until I've decided what the new battery setup will look like, after which fridge and freezer will remain on backup permanently.

Nice, can also look for EasyStart for the fridge/freezers. They are costly but work like a charm.

 

Iwojima

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Jan 16, 2007
Messages
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itareanlnotani

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I have no idea how that works :D

On a side note I'm connecting the batteries layer today. Should they have an inline fuse on the positive side as well as a breaker?

I'm thinking the breaker would be advisable when switching out batteries later.
Yes, both is good to have, otherwise disconnecting/connecting can be "fun".

DC Breaker so you can disconnect / reconnect safely.
Fuse so that you can protect in case of short or too much current draw.


I have one of these for mine (DC on / off) -
 
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AlphaJohn

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Joined
Sep 10, 2012
Messages
12,174
I have no idea how that works :D

Just basically a demand based cap that reduce the motor start spike on your power draw.

On a side note I'm connecting the batteries layer today. Should they have an inline fuse on the positive side as well as a breaker?

I'm thinking the breaker would be advisable when switching out batteries later.

Personally I use/recommend a breaker. Just make 1000% sure you use DC breaker on battery and not AC.
AC breaker on DC power = Fire.
 

Iwojima

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Jan 16, 2007
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Is there a rule of thumb to follow for sizing the DC breaker?

I assume they are all as simplistic as having the + and - cables passing through between the inverter and battery (ie no need to bridge breaker multiple terminals)

Also the manual indicates that for 3KW that the cable sizing is 35mm. I'd seen conflicting info stating that 25mm is OK.
 

TheChamp

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Messages
49,033
Is there a rule of thumb to follow for sizing the DC breaker?

I assume they are all as simplistic as having the + and - cables passing through between the inverter and battery (ie no need to bridge breaker multiple terminals)

Also the manual indicates that for 3KW that the cable sizing is 35mm. I'd seen conflicting info stating that 25mm is OK.
I don't understand mm, I understand current ratings and mm will automatically fall into place. 3kW, if it's truly 3kW and not 2.4kW(perhaps that's where the conflicting sizes stems from) will be 125A, maybe you will understand which mm corresponds to that, I suspect 25mm?

The DC breaker is straight forward positive pole and negative.
 
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