I'm in the market for a 12v inverter but have come across one that seems too good to be true but I'm not sure if I understand the technical specs?

It's a 12v 3.5kva hybrid inverter with an output of 2100w (modified sine wave). This meets my requirements perfectly but when I tried to find similar inverters, none close to it exist. The closest is 12v 2kva 1800w (pure sine wave).

I just need to power a 50" TV, android tv box, wifi router, cpe & maybe an av receiver, active subwoofer & a laptop.

I'm going the 12v lithium battery route because of battery prices.

Any advice would be appreciated from those in the know!

Edited September 30, 20232 yr by cam083gp
Spelling error

24 minutes ago, cam083gp said:

I'm in the market for a 12v inverter but have come across one that seems too good to be true but I'm not sure if I understand the technical specs?

It's a 12v 3.5kva hybrid inverter with an output of 2100w (modified sine wave). This meets my requirements perfectly but when I tried to find similar inverters, none cose to it exist. The closest is 12v 2kva 1800w (pure sine wave).

I just need to power a 50" TV, android tv box, wifi router, cpe & maybe an av receiver, active subwoofer & a laptop.

I'm going the 12v lithium battery route because of battery prices.

Any advice would be appreciated from those in the know!

Based on the loads you want to connect a 12V unit of 1kW could be fine but yes you do get 12V inverters of up to 5kW. You need a massive bank of batteries to run 5kW from 12V.

I would not use a 12V at higher than 1.5kW short term and 1kW for your loads which could be on for hours. A 100Ah might just make it through a 2 hour LS cycle but becomes iffy for 4 hours LS.

Just bear in mind the current 12V lithium batteries are only 100Ah or 200Ah which can only provide 100A charge/discharge so you will not be able to use more than 1.2kW in loads. Also working the batteries at 100Ah could end in tears. 24V inverters are not much more expensive although the batteries will cost double vs a 12V unit.

This inverter can also just charge at 20A which will not be able to fully charge the battery in say 4-6 hours between stage 4 LS cycles when discharged by 80-90%.

Edited August 29, 20232 yr by Scorp007

22 minutes ago, Scorp007 said:

Based on the loads you want to connect a 12V unit of 1kW could be fine but yes you do get 12V inverters of up to 5kW. You need a massive bank of batteries to run 5kW from 12V.

I would not use a 12V at higher than 1.5kW short term and 1kW for your loads which could be on for hours. A 100Ah might just make it through a 2 hour LS cycle but becomes iffy for 4 hours LS.

Just bear in mind the current 12V lithium batteries are only 100Ah or 200Ah which can only provide 100A charge/discharge so you will not be able to use more than 1.2kW in loads. Also working the batteries at 100Ah could end in tears. 24V inverters are not much more expensive although the batteries will cost double vs a 12V unit.

This inverter can also just charge at 20A which will not be able to fully charge the battery in say 4-6 hours between stage 4 LS cycles when discharged by 80-90%.

Thanks @Scorp007 for this, it really makes the potential purchase easier knowing that it's technically possible.

For now, I will get a single 12v 100ah lithium battery & test actual load which I will try to keep under 1kw for the 2 hour load shedding we have been having lately...then I will add more load for convenience & if that starts to kill the battery too soon, then I will add another 12v 100ah battery. It's too expensive to go the 24v route while I'm still experimenting as adding extra batteries will be in increments of R10k!

Main goal for now is the ups functionality for the wifi during the day while I work from home & tv for the evening as my generator is too loud to run late at night.

I would also like to do the wiring myself as this would be connected to a regular 3pin plug point in my garage with seperate extension to each location where ups is required

Because your loads are sensitive electronics, I would stay away from modified sine wave inverters. Might cause problems or even damage to your devices.

 

31 minutes ago, meetyg said:

Because your loads are sensitive electronics, I would stay away from modified sine wave inverters. Might cause problems or even damage to your devices.

 

@meetyg, how will it damage my electronics? The reading I've done on this says that I'm good for what I want to power & only to stay away from appliances like refrigerators, microwaves, compressors, high current audio equipment & medical devices.

10 hours ago, cam083gp said:

It's a 12v 3.5kva hybrid inverter with an output of 2100w

Could you please do a specific assessment of the devices you want to power either get the watt rating from the device ratingplate or maybe use a Kill a Watt meter you can purchase as this is the most important step before deciding which system to purchase. Do you want to use solar generation now and/or in the future? Before deciding on a system make sure the unit in mind would serve you for the feature as your needs might change. I would not use modified sine wave merely for the reason of efficiency, i have seen some with power factors of 0.4 generating lots of wasted energy in the form of heat. We would gladly assist on this forum for you to make the best decision but we need accurate information. The inverter above as mentioned the 12v unit at 2100watts you will have the potential of drawing 195amps from the battery making your battery cable and fuses quite expensive. Like i said give as accurate consumption data and we would assist.

11 hours ago, Scorp007 said:

would not use a 12V at higher than 1.5kW short term and 1kW for your loads which could be on for hours

Yes thats the long and the short of it. 

Maybe have a look at one of these instead.

2 hours ago, meetyg said:

Because your loads are sensitive electronics, I would stay away from modified sine wave inverters. Might cause problems or even damage to your devices.

 

After loosing an expensive laptop PSU and a standing fan due to my 1st UPS being modified sine I got cured for life by not using a modified sine. 

49 minutes ago, TaliaB said:

Could you please do a specific assessment of the devices you want to power either get the watt rating from the device ratingplate or maybe use a Kill a Watt meter you can purchase as this is the most important step before deciding which system to purchase. Do you want to use solar generation now and/or in the future? Before deciding on a system make sure the unit in mind would serve you for the feature as your needs might change. I would not use modified sine wave merely for the reason of efficiency, i have seen some with power factors of 0.4 generating lots of wasted energy in the form of heat. We would gladly assist on this forum for you to make the best decision but we need accurate information. The inverter above as mentioned the 12v unit at 2100watts you will have the potential of drawing 195amps from the battery making your battery cable and fuses quite expensive. Like i said give as accurate consumption data and we would assist.

Thanks, will get that killer watt meter to measure what I intend using👍🏼

2 hour UPS is the main feature for now & 3 pin plug point charging...I will not use Solar in the next year as that will be part of the long term goal when I get a larger inverter for the entire home that will be connected via the db board.

Also, thanks for the wiring & fuse between the battery & inverter reminder!! Totally forgot about it! I don't plan on using 2100w ever, probably only under 1kw but I like the headroom for potential spikes...that being said, I should plan the installation based in worst case scenario👍🏼

1 hour ago, Jacques Ester said:

Maybe have a look at one of these instead.

This is more than 3× what my current pending spend is looking like so it's a nice to have for now but out of my budget

21 minutes ago, Scorp007 said:

After loosing an expensive laptop PSU and a standing fan due to my 1st UPS being modified sine I got cured for life by not using a modified sine. 

2nd vote in favour of pure vs modified...

Would the attached pure sine inverter be a better option? The efficiency of kva vs kw also seems better...

6 minutes ago, cam083gp said:

2nd vote in favour of pure vs modified...

Would the attached pure sine inverter be a better option? The efficiency of kva vs kw also seems better...

KVA is always higher and not much to read as far as efficiency. A lot of manufacturers quote both the same. 

4 hours ago, cam083gp said:

Thanks, will get that killer watt meter to measure what I intend using👍🏼

I have one of these. They're very useful. It will give you various data, and there are two in particular you should look out for. 
1) Total kWh drawn over the period you test for. Try to make the test at least two hours, and include powering on in that.
2) Is the PEAK kW drawn at any moment. This is on the screen with the word "Hi" at the bottom.

2) is important because some items take a lot more power to start up than to keep on running. If all the items you want to back up got turned on within a few seconds of each other, those peaks will add up and may exceed the capability of your inverter OR your battery. Either will trip if too much is demanded.

The sum of reading (1) for all the items you want to back up will allow you to calculate total steady draw. It is less likely, but not impossible, that this figure will exceed the capabilities of your inverter or your battery, but it will also allow you to get a good estimate of how quickly your batteries will run down.

The more they run down, the greater the importance of that 20A limit that @Scorp007 pointed out.

4 hours ago, cam083gp said:

will get that killer 🤣watt meter to measure what I intend using👍🏼

Here is a link for Geewiz not a bad price.

https://www.geewiz.co.za/gadgets/43656-digital-watt-meter-kill-a-watt-measure-your-electricity-usage.html?sfdr_ptcid=2961_617_121793010&sfdr_hash=105bbe2e1143851ca6a6836c4c2b3300&gclid=Cj0KCQjw0bunBhD9ARIsAAZl0E174YFL-UH9PPP8vMLoHzUQ8Za0ge8eI8qdvu-hdxwaPpEH__mWkbkaAstREALw_wcB

6 hours ago, cam083gp said:

2nd vote in favour of pure vs modified...

Would the attached pure sine inverter be a better option? The efficiency of kva vs kw also seems better...

This inverter has a higher charge current so will be able to charge the battery quicker between loadshedding which is always a win - especially when we hit stage 6+

 

12v 100AH battery is 1200WH (1.2KWH). If we work on an 80% Depth of Discharge that gives you 960WH (0.96KWH) before the battery is dead. This does not take efficiency into consideration.

 

So if you were to have a load of 960W, then a single 12v 100AH battery would last 1 hours.

If you were to have half the load, so 480W then a single 12v 100AH battery would last 2 hours.

This could help you work out what sort of battery capacity will be required. Keeping in mind that a 24V 100AH battery is roughly double the price of a 12V 100AH battery, it also offer double the capacity. 24v x 100AH = 2400W (2.4KWH)

For larger load, higher voltage is "better" or perhaps easier as you do not need to draw as much current and can therefore get away with thinner cables and lower current (amps).

 

Your AVR and active sub could quickly drain the battery as well. Chances are the amps are Class D or another high efficiency topology, although if they are Class AB like my big subwoofer amp then they will draw a significant amount of power while sitting idle.

Class AB amp rated for 100W continuous would consume around 25W while idle, 500W continuous would be 125W while idle. Until you upgrade to a larger inverter and bigger batteries it may be best to settle for your TV speakers during loadshedding - I have had to give up my speakers and subwoofer during loadshedding as I have been using a Mecer 12v Trolley inverter and during loadshedding I use a bluetooth speaker (I have a media PC, everything plays through there and with my setup its a mission to use my TV speakers).

8 hours ago, cam083gp said:

2nd vote in favour of pure vs modified...

Would the attached pure sine inverter be a better option? The efficiency of kva vs kw also seems better...

It looks OK but try and get a manual before you buy. The DC for charging from AC given as 13.5V looks a bit low for charging lithium. Check in the manual that it can be set to at least 14.2V.

2 hours ago, PsyCLown said:

This inverter has a higher charge current so will be able to charge the battery quicker between loadshedding which is always a win - especially when we hit stage 6+

 

12v 100AH battery is 1200WH (1.2KWH). If we work on an 80% Depth of Discharge that gives you 960WH (0.96KWH) before the battery is dead. This does not take efficiency into consideration.

 

So if you were to have a load of 960W, then a single 12v 100AH battery would last 1 hours.

If you were to have half the load, so 480W then a single 12v 100AH battery would last 2 hours.

This could help you work out what sort of battery capacity will be required. Keeping in mind that a 24V 100AH battery is roughly double the price of a 12V 100AH battery, it also offer double the capacity. 24v x 100AH = 2400W (2.4KWH)

For larger load, higher voltage is "better" or perhaps easier as you do not need to draw as much current and can therefore get away with thinner cables and lower current (amps).

Thanks, this is some very useful information for me👍🏼Not so worried about higher stages of load shedding, have a generator for that...In terms of cables, I will use the best ones available for the maximum possible draw of the inverter as they will be short because the installation is close to a plug point & the wall mount battery will be mounted close as well...same goes for the fuse between battery & inverter I.e. highest required fuse that will prevent damage either way. Do I need a fuse between the 3 pin plug & inverter for protection in case of a surge too?

2 hours ago, PsyCLown said:

Your AVR and active sub could quickly drain the battery as well. Chances are the amps are Class D or another high efficiency topology, although if they are Class AB like my big subwoofer amp then they will draw a significant amount of power while sitting idle.

Class AB amp rated for 100W continuous would consume around 25W while idle, 500W continuous would be 125W while idle. Until you upgrade to a larger inverter and bigger batteries it may be best to settle for your TV speakers during loadshedding - I have had to give up my speakers and subwoofer during loadshedding as I have been using a Mecer 12v Trolley inverter and during loadshedding I use a bluetooth speaker (I have a media PC, everything plays through there and with my setup its a mission to use my TV speakers).

I assumed that the AVR & sub would be a step too far but I will only add that if there is enough headroom...if not, I will just have to rewire my setup to use tv speakers...also, no class d in my audio chain, only AB so no efficiency there

47 minutes ago, Scorp007 said:

It looks OK but try and get a manual before you buy. The DC for charging from AC given as 13.5V looks a bit low for charging lithium. Check in the manual that it can be set to at least 14.2V.

Wouldn't the lower charging voltage increase the life of the battery? I don't need fast charging, just charging that doesn't decrease the life of the batteries

10 minutes ago, cam083gp said:

Wouldn't the lower charging voltage increase the life of the battery? I don't need fast charging, just charging that doesn't decrease the life of the batteries

No for lead acid and constant charging 13.5V would be fine to extend life but even lead acids need to be fully charged on a regular basis. 

Charging a lithium only to 13.5V you might end up with only about 70% capacity. Quite a waste to not be able to use 30%. Also this level will have a big effect on the time taken to recharge. 

Charging at say 10A @ 13V you only putting back 520Wh in 4 hrs. If you used more than this during LS then you have less power for the next LS cycle. After a few days your battery has very little to provide power to loads. 

Edited August 30, 20232 yr by Scorp007

Sorry i deleted previous post to much info🫣Basically lfp charge cc/cv charge regime 14.4 to 14.6v.   Cv after reaching the target voltage the charger maintains a constant voltage between 14.4 and 14.6v while decreasing the current until very little current flow indicating the battery is fully charged.

 

 

 

 

 

Edited August 30, 20232 yr by TaliaB

Just checking why my font size changed

Ok looks normal again

Edited August 30, 20232 yr by TaliaB
Checking font size

2 hours ago, Scorp007 said:

No for lead acid and constant charging 13.5V would be fine to extend life but even lead acids need to be fully charged on a regular basis. 

Charging a lithium only to 13.5V you might end up with only about 70% capacity. Quite a waste to not be able to use 30%. Also this level will have a big effect on the time taken to recharge. 

Charging at say 10A @ 13V you only putting back 520Wh in 4 hrs. If you used more than this during LS then you have less power for the next LS cycle. After a few days your battery has very little to provide power to loads. 

wait...so 13.5vdc means that I will not fully charge my 12v 100ah Lithium battery??

If I only use 70% capacity, then it's definitely a waste!!

Anybody familiar with the Inkwenkwezi inverter brand?

9 minutes ago, cam083gp said:

wait...so 13.5vdc means that I will not fully charge my 12v 100ah Lithium battery??

If I only use 70% capacity, then it's definitely a waste!!

Anybody familiar with the Inkwenkwezi inverter brand?

Just Google some spec sheets on 12V lithium and refer to the charge voltage for Hubble, Revov and some other known makes. 

May be consider your budget to over the indicated R10th level. 

Edited August 30, 20232 yr by Scorp007

9 minutes ago, Scorp007 said:

Just Google some spec sheets on 12V lithium and refer to the charge voltage for Hubble, Revov and some other known makes.  

thanks, found the chart...

10 minutes ago, Scorp007 said:

May be consider your budget to over the indicated R10th level

nah, I still have options under R10k for this basic UPS solution...this specific one just brought it to potentially under R8k