Hi all,

Hope everyone is doing well.

I would like to propose a small backup power system and see what you think.  It's not a design yet, just a rough idea for now.  If you don't tell me here that it's a terrible idea, I'll probably continue to refine it into a more detailed design and post again.

Here's the use case:

• Backup power for small residential use.  Two retired people at home.  Mostly loadshedding and some extended outages.
• There's an exercise ongoing at the moment using a kill-a-watt meter to measure expected load.  I expect it to be small though.  300-500W.
• We need backup power for
  • Home interior lights (standard LED bulbs).  Not many lights are on at a time (only 2 people).
  • TV station:  it's one 42" TV, dstv, wifi.
  • Selectively, one fridge.  Fairly small fridge, no freezer.  Probably not used during loadshedding but when there's an extended outage we want the option to cool down the fridge again once or twice.
• Requirement is to get something up and running as cost-effective as possible.   We could always improve, extend and expand later on.  That means though the system must be designed now to cater for that.

Typical Hybrid solar solutions (Sunsynk / Deye etc) are off the table for now due to cost.  Even the most cost effective solutions 3KW/4kw with Growatt and a few panels are too expensive for now.  FiveStar has some hybrid inverter solar solutions that are more cost effective BUT, still too costly and ...   anyone trust FiveStart?

You do get these mobile inverter solutions on a trolley.   Might be an option but those are already 50-60% of the maximum I can spend now and they typically only come with one 12v 100ah cheap battery, weak chargers etc.

So here's the plan:

 

 

Disclaimer:

- I'm a complete electricity NOOB.  Hardly know my amps from my volts.

- I won't personally fiddle in the DB Board.  Will get a sparky for that.

 

 

Any thoughts?

Thanks

Christoff

 

To quote the local idiom... goedkoop koop is duurkoop...

If you are looking at expanding this from a UPS to longer term potentially off the grid or solar setup, you should probably look at an inverter that is a bit larger, I'd suggest a 5kW unit and don't stuff around battery wise, look at a LFP setup, there are guys on here that have rolled their own LFP batteries, by getting LFP cells from outer mongolia/china and a BMS to keep the cells safe and in line, this would be the most likely cost effective route that will at least not be wasted money, longer term. As for the inverter, an Axpert 5kW high voltage unit would probably be the most cost effective route as well and again, not be wasted money long term, just ensure, if your power needs will exceed 5kW, that the unit can be paralleled with another one or two, in the future, if you can live with 5kW + a wee bit peak, then a single unit would be ok.

I have a friend who is trying to develop a suk R10k solution for about 2kVa… and it just doesnt work… fridge motor starts up, uses 800-1200w instant, draws a lot of current from lead acid battery, inverter screams… switches he has quite thick battery cables, but actually 12v 0.05 ohm cable resistance, 2kVa load and the voltage the inverter sees drops to 4v

@Christoff83

I am also on a budget and trying to survive loadshedding.

What did you implement in the end?

@Christoff83 I also want to know. I don't want to spend more than 6k.  Just need to keep my Internet and of with 1 or 2 lights going

On 2022/09/13 at 9:01 AM, McGuywer said:

I am also on a budget and trying to survive loadshedding.

Also
 

1 hour ago, Antony said:

I also want to know. I don't want to spend more than 6k.  Just need to keep my Internet and of with 1 or 2 lights going

 

https://www.takealot.com/loadshedding-rechargeable-led-7w-b22-cool-white-5-pack/PLID72547923
+
https://www.takealot.com/backup-power-supply-5-9-12vdc-mini-dc-ups-ideal-for-wifi-router-/PLID73113499

= Less than R1000
 

1 hour ago, Antony said:

@Christoff83 I also want to know. I don't want to spend more than 6k.  Just need to keep my Internet and of with 1 or 2 lights going

Keeping Internet going a simple mini UPS designed for routers can keep the WiFi going. No rewiring or cutting. Straight plug router DC into the UPS. The UPS has a DC ug at either end. Larger on the UPS side than the router so you cannot connect is wrong. External 220V charger from wall socket to charge the lithium battery inside the MINI UPS. About R650

For lights a cheap China intelligent charger to a 12V lead acid battery will see you through if LED lights. The key is for LS not to discharge for days without charging.

6 minutes ago, Scorp007 said:

Keeping Internet going a simple mini UPS designed for routers can keep the WiFi going. No rewiring or cutting. Straight plug router DC into the UPS. The UPS has a DC ug at either end. Larger on the UPS side than the router so you cannot connect is wrong. External 220V charger from wall socket to charge the lithium battery inside the MINI UPS. About R650

I have one of those that I linked above, it is enough to power my mikrotik router and fibre router, and I have tested it, runs for about 4 hours no prob. And charges up again in about 4 hours so should make it with stage4 loadshedding, maybe not stage 6 though.
You do not need a charger for it, its builtin

1 hour ago, WannabeSolarSparky said:

I have one of those that I linked above, it is enough to power my mikrotik router and fibre router, and I have tested it, runs for about 4 hours no prob. And charges up again in about 4 hours so should make it with stage4 loadshedding, maybe not stage 6 though.
You do not need a charger for it, its builtin

Yes from the 1st model that needed an external small charger like 12V 2A at R100 the design evolved to include the 15/24V for POA equipment. The one in the link is a great unit for the price. I got one for a friend more than 2 years ago and then it was available in 2 sizes. The lower storage was good for about 2 hrs but I went for the larger one with double the storage. Mine was the one sold by Geewiz.

Interesting to see that the OP adds a auto transfer switch when on a low budget. That unit can nearly buy a 100Ah lead acid battery but then one must do manual switching which I would rather do if Rands need to be stretched.

Edited September 14, 20223 yr by Scorp007

4 hours ago, WannabeSolarSparky said:

Also
 

 

https://www.takealot.com/loadshedding-rechargeable-led-7w-b22-cool-white-5-pack/PLID72547923
+
https://www.takealot.com/backup-power-supply-5-9-12vdc-mini-dc-ups-ideal-for-wifi-router-/PLID73113499

= Less than R1000
 

I swear, I was going to say that same thing (more or less), but held back thinking folks were looking for a full-on system. Anyway, have to concur, you don't need much to run a couple of 5W LED lights or have internet, I got by for a long time on a 150W modified-sine-wave car inverter, a cheap 2A charger and a couple of 7AH alarm batteries.

Personal take, once you start looking at running a fridge and one or two extra plugs, but only one major appliance at a time, the (barest of bare) minimum is probably a pure sine-wave 3kVA 24V Genuine Axpert PWM inverter/charger with 2x 120Ah Lithium 12V batteries, just charging from the grid with no panels, and no intention to expand. Estimated cost R20K for main parts. 

One step lower, the Axpert VM2 1200VA/1200W 12V with a single lithium 120Ah battery could be around R12K, but then it's mainly for LED lights, TV, PC, wifi, and no major appliances.

But speak to an installer first.

Edited September 14, 20223 yr by GreenFields

1 hour ago, GreenFields said:

 

One step lower, the Axpert VM2 1200VA/1200W 12V with a single lithium 120Ah battery could be around R12K, but then it's mainly for LED lights, TV, PC, wifi, and no major appliances.

But speak to an installer first.

As long as you happen to find the right installer that can guide you and not just get you what he/she installs. I have had chats to about 4 installers that had no clue or that grid tied inverters do exist.

Appliances come in all shades of grey. Amazed that some people battle with washing machines on inverters. I ran a top loader from 1 x 12V battery connected to a 270W panel. As long as you don't expect to wash more than 1 bundle say every 2-3 hours. The same with fridges. If one has a inverter fridge you can get along with a small pure sine wave if you really want to power it during LS which I normally don't. Tonight with 2 sessions of 20h-22h00 and 04h-06h00 I will power the fridges while running on inverter/battery for lights inside and outside.

Like the comment from a major installer - "no inverter can ever work without a battery"

7 hours ago, Antony said:

@Christoff83 I also want to know. I don't want to spend more than 6k.  Just need to keep my Internet and of with 1 or 2 lights going

This 1500/3000W 12V inverter without charger can get a long way. Provided you have suitable batteries/charger it will run any household fridge and any non heating washing machine. I have even started 2 fridges at once with it provided you don't try it with just 1 x 100Ah lithium. Not that one needs these items for beating LS but handy to know you can if there is a long outing. Cost around R3000.

A major plus is that no fan comes on below 300W.

 

Edited September 14, 20223 yr by Scorp007

Lots of valuable advice here, thanks guys

On 2022/09/14 at 8:08 PM, GreenFields said:

I swear, I was going to say that same thing (more or less), but held back thinking folks were looking for a full-on system. Anyway, have to concur, you don't need much to run a couple of 5W LED lights or have internet, I got by for a long time on a 150W modified-sine-wave car inverter, a cheap 2A charger and a couple of 7AH alarm batteries.

Personal take, once you start looking at running a fridge and one or two extra plugs, but only one major appliance at a time, the (barest of bare) minimum is probably a pure sine-wave 3kVA 24V Genuine Axpert PWM inverter/charger with 2x 120Ah Lithium 12V batteries, just charging from the grid with no panels, and no intention to expand. Estimated cost R20K for main parts. 

One step lower, the Axpert VM2 1200VA/1200W 12V with a single lithium 120Ah battery could be around R12K, but then it's mainly for LED lights, TV, PC, wifi, and no major appliances.

But speak to an installer first.

how does the geewiz compare with the Axpert VM2?

https://www.geewiz.co.za/long-run-ups-inverter-battery/123033-geewiz-2400va-inverter-trolley-2x-100ah-batteries-8-hour-battery-life-kit-1440w-150-200-cycles.html?sfdr_ptcid=2961_617_657962698&sfdr_hash=ba129d5de1b4751e429086393c6b1593&gclid=CjwKCAjw4JWZBhApEiwAtJUN0Iw5NMklJR9ByE3a_2ElLmP45onN5Zu_9yi9PuIOOUp8mZOAczCt6hoCPfcQAvD_BwE

 

I forgot to mention I need to power my PC as well, no good having internet without a PC 😉

Edited September 17, 20223 yr by Antony

 

5 hours ago, Antony said:

how does the geewiz compare with the Axpert VM2?

https://www.geewiz.co.za/long-run-ups-inverter-battery/123033-geewiz-2400va-inverter-trolley-2x-100ah-batteries-8-hour-battery-life-kit-1440w-150-200-cycles.html?sfdr_ptcid=2961_617_657962698&sfdr_hash=ba129d5de1b4751e429086393c6b1593&gclid=CjwKCAjw4JWZBhApEiwAtJUN0Iw5NMklJR9ByE3a_2ElLmP45onN5Zu_9yi9PuIOOUp8mZOAczCt6hoCPfcQAvD_BwE

Just very generally speaking. Best to do more own research on this. This Geewiz-branded inverter is a modified-sine-wave inverter. Typically this type of inverter doesn't output the kind of "clean" sine-wave as a pure sine-wave inverter. Typically not suitable for very sensitive electronics, electric motors or microwaves, but can still be useful for many appliances, such as those that run off power supplies. Also not something you would typically wire in to your house, but keep it plugged in to a wall socket, with a multiplug coming out of it.

Edited September 17, 20223 yr by GreenFields
Text Correction

29 minutes ago, GreenFields said:

Geewiz is just the online retailer, like Takealot. Those are both Axpert machines. Can't 

Just very generally speaking. Best to do more own research on this. This Geewiz-branded inverter is a modified-sine-wave inverter. Typically this type of inverter doesn't output the kind of "clean" sine-wave as a pure sine-wave inverter. Typically not suitable for very sensitive electronics, electric motors or microwaves, but can still be useful for many appliances, such as those that run off power supplies. Also not something you would typically wire in to your house, but keep it plugged in to a wall socket, with a multiplug coming out of it.

Just look a bit further and one will find a Axpert type 3kVA with all the settings one needs and can also take PV up to 1500W. It is also sold on a trolley and you can even as an option upgrade to 2 x S120 Hubble lithiums. I rate Geewiz highly from quick delivery to the best service levels.

Edited September 17, 20223 yr by Scorp007

20 hours ago, Scorp007 said:

Just look a bit further and one will find a Axpert type 3kVA with all the settings one needs and can also take PV up to 1500W. It is also sold on a trolley and you can even as an option upgrade to 2 x S120 Hubble lithiums. I rate Geewiz highly from quick delivery to the best service levels.

Did you see one somewhere that I could look at?

This stage 6 is going to be too long for basic systems. Not enough time to recharge

50 minutes ago, Antony said:

Did you see one somewhere that I could look at?

https://www.geewiz.co.za/long-run-ups-inverter-battery/178350-3000va-mecer-axpert-pure-sine-inverter-2x-120ah-lithium-battery-trolley-12-hour-battery-life-kit-3000w-with-hubble-lithium-battery-2000-cycles.html

4-6 weeks delivery with lithium batteries. Just look in this section and you will see all the other 3000VA Axpert and Axpert type with a trolley. The Mecer offer although R1500 more expensive a better buy.

Edited September 18, 20223 yr by Scorp007
Added picture

 

2 hours ago, Antony said:

This stage 6 is going to be too long for basic systems. Not enough time to recharge

Thats why the lithium offer is a must. They just haveso much more usable power and can charge quicker than lead acid. I get along quite OK with the same unit. Yesterday I even heated the geyser via heat pump and solar with mine. Stage 6 call for management of what is a essential load and what is nice to keep connected. We all have to make that choice during stage 6 or higher.

Fridges can stay off for 2.5hrs. For longer outings one can use a cycle timer like this to extend running time. Sonoff basic and a 16A 3 pin plug socket connected via WiFi.

 

Edited September 18, 20223 yr by Scorp007

3 hours ago, Scorp007 said:

https://www.geewiz.co.za/long-run-ups-inverter-battery/178350-3000va-mecer-axpert-pure-sine-inverter-2x-120ah-lithium-battery-trolley-12-hour-battery-life-kit-3000w-with-hubble-lithium-battery-2000-cycles.html

4-6 weeks delivery with lithium batteries. Just look in this section and you will see all the other 3000VA Axpert and Axpert type with a trolley. The Mecer offer although R1500 more expensive a better buy.

4-6 weeks, yikes

11 minutes ago, Antony said:

4-6 weeks, yikes

This reminds me of if you snooze you........ In July during LS there were also no stock of about all items while China also had a lock down to make things worse.

4 hours ago, Scorp007 said:

https://www.geewiz.co.za/long-run-ups-inverter-battery/178350-3000va-mecer-axpert-pure-sine-inverter-2x-120ah-lithium-battery-trolley-12-hour-battery-life-kit-3000w-with-hubble-lithium-battery-2000-cycles.html

4-6 weeks delivery with lithium batteries. Just look in this section and you will see all the other 3000VA Axpert and Axpert type with a trolley. The Mecer offer although R1500 more expensive a better buy.

Surely I could connect solar panels to this to charge batteries and / or run my load? Priority on running load? Or is this Inverter not "clever enough"

Reading the manual now, and it looks like it can be connected to PV...

Edited September 18, 20223 yr by Antony

20 minutes ago, Antony said:

Surely I could connect solar panels to this to charge batteries and / or run my load? Priority on running load? Or is this Inverter not "clever enough"

Reading the manual now, and it looks like it can be connected to PV...

Yes just make sure that you get the model that has a 145V MPPT solar controller of 1500W. I used some 1250W panels yesterday on mine to run my heat pump for the geyser. No power came from the battery. At times it was even charging the batteries with about 3A. The moment I switched off the heat pump it was charging at 21A and only using 540W from the panels. This current can also be adjusted as can the grid charge level be set. You will see you can also select to charge from PV only or PV and grid. Then also as a UPS which means the load is fed from grid and batteries are always charged. If no grid is present or switched on and there is PV then you can select the option to power the load 1st and if PV left it will charge the battery as per my example with the 3A above. If no grid PV is used if set as 1st priority and if not enough then battery will be used to supplement for given load.

Battery protection is also included to prevent deep discharge and destroying lead acid. Also a setting to indicate when it can return to using the battery if one selected it to use grid to charge once a certain level is reached. All these settings are covered if you look at the manual.

This is looking more and more like a load shedding Plus solution. I can run my home office and CCTV off this.

I have solar geyser and gas. I may just consider the fridge if and when necessary.