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700-800W Baseload + load shedding power solution


mgoedeke
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Hi All

I want to keep some video surveillance and processing gear hooked up 24/7. Base load is about 700W with ancillary peaks at some 1kVA-1.5kVA max, though it could be capped at 1kVA.

I would like to have the system to be able to survive an outage for up 4-6 hours, obviously during the daytime a solar setup would help and because the base load is fairly constant +/- 100VA the solar panels seem to make sense.

Any suggestions? Hybrid MPPT inverter and battery/BMS or all in one hybrid inverter?

I was thinking whether one 5kW Pylontech battery or similar would be a good starting point though lead acid would likely also work, just be a lot heavier. The kit will be about 5-10m from the panels in an attic with a concrete slab floor, masonry walls, one large window for ventilation and a polycarb roof.

Regards

 

Martin

 

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17 hours ago, mgoedeke said:

Hi All

I want to keep some video surveillance and processing gear hooked up 24/7. Base load is about 700W with ancillary peaks at some 1kVA-1.5kVA max, though it could be capped at 1kVA.

I would like to have the system to be able to survive an outage for up 4-6 hours, obviously during the daytime a solar setup would help and because the base load is fairly constant +/- 100VA the solar panels seem to make sense.

Any suggestions? Hybrid MPPT inverter and battery/BMS or all in one hybrid inverter?

I was thinking whether one 5kW Pylontech battery or similar would be a good starting point though lead acid would likely also work, just be a lot heavier. The kit will be about 5-10m from the panels in an attic with a concrete slab floor, masonry walls, one large window for ventilation and a polycarb roof.

Regards

 

Martin

 

My Recommendations would be if I understand your terminology correctly you have a 700 Watt base load and a 1.5KW peak load not KVA as that is calculated with a power factor..

So based on that premise you can do the calculations as follows 

Load 700 Watt runtime 4-6 hours lets work on 6 

6 x 700 watt =4200 watt this tells us you need a battery that can store and produce 4200 watt of useable power so the battery you can look at is a BSLB 6.4 KWH or a Hubble AM2 5.5 KWH the Bull has a theoretical capacity of 6400 watt @100% dod and the hubble 5500 watt @100% both batteries are 1C which means they can charge and discharge at their capacity 125 amp @ 48v for the Bull and 115 amp @ 48v for the Hubble you may use a little additional capacity for the peak load of 1.5KW but its negligible.

Now for the Choice of the inverter.. 

Your Continues load of 700W and peak of 1.5KW dictates a small inverter but will limit you to expanding your system so the recommend system and this is based on value for money is a 3KW Axpert clone inverter but they have a lot of limitations 1 MPPT limited solar power short warranty 2 to 3 years and they are basically designed as battery backup solutions or you Could look at a True Hybrid inverter like a Sunsynk Solis Kodak or Goodwe all are decent hybrids 5 year warranty  you scope or aim will dictate what you need also note any 3kw Axpert inverter is 24v and not worth wasting money on the Kodak 3KW Hybrid as an example is 48v and will work with the suggested batteries they also have duel 500v MPPTs which is more flexible however a 5KW Sunsynk is probably going to be your best choice.

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Awesome responses. I'll post some questions below for tl;dr.

I can mount this setup about 5m away from the panels and will run only this application and perhaps rewire my 220V LED lights to it for lighting in the house. Because of the continuous load this might see RoE in 3 years perhaps.

I am looking at various options. I have an existing new in box Olson BPS-2436 24V inverter and a battery box with dead batteries from an old UPS that can house a good couple of  LA batteries. To add a solar charge module to that would mean a MPPT and some panels.

Because I have a 98-99% PF load I can look at VA simply and if one takes out the money for lithium batteries one might want to optimize the efficiencies right to the PC power supplies and cooling fans. The average load will be on the order of 790VA though if I upgrade it might go up to 1kVA. If the better inverters have 3-5 kVA capacity and solar charge controllers built in that would make a move easier but i suspect most ROI gains will be with solar and batteries.

I have an existing 25u rack mount chassis standing around that I could use for Li batteries and the like and looked at the Pylontech 3000C batteries with some hybrid inverters as an option. I am looking primarily at cost per drawable kW.hr and don't care for 1.0C over 0.5C that much. A quick search on the forum suggested the 3000C, i'll look into the others listed here.

Because of the continuous base load and >R2/kWh Tshwane electricity ripoff I suspect that the money is best spent in some moderate solar and some hefty batteries. i assume 8 hours charge and 16 hours discharge for one would need 3x base load in solar panels at 2.4kW? perhaps one can start at something smaller and grow? It seems like the money is best spent on LiION and solar capacity here.

 

Questions

 

How can I estimate solar irradiance and panel output in Pretoria?

Can one get anything for the old 100/200Ah batteries when buying some AGMs or similar?

Do the hybrid inverters have any benefits during periods where solar irradiance drops below my base load?

Please suggest good sources for LA/Lithium batteries and panels around Pretoria/Gauteng.

 

Regards

Martin

Edited by mgoedeke
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36 minutes ago, mgoedeke said:

Can one get anything for the old 100/200Ah

Hubble Lithium s-100 12v 1.2KW 100% dod batteries on the forum store for 5k each vat incl

 

37 minutes ago, mgoedeke said:

How can I estimate solar irradiance and panel output in Pretoria?

Estimated average solar production is Rated Solar power of panel @ 5 hours per day..I oversized by 100% panels are cheap..

Roi for me is over 25 years as I am off grid and works out to R24 per month...

40 minutes ago, mgoedeke said:

Do the hybrid inverters have any benefits during periods where solar irradiance drops below my base load?

Sizing your system correctly is important that includes batteries to get you through cloudy days..

 

41 minutes ago, mgoedeke said:

Please suggest good sources for LA/Lithium batteries and panels around Pretoria/Gauteng.

www.powerforum-store.co.za a great option..

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5 hours changes the setup quite drastically. Then it makes sense to limit capex and use some grid power and find some point where one can optimize the cost of the inverter with regards to the solar panels and battery bank. It also means that efficiencies become more critical.

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For for the Li-Ion batteries, which is currently the benchmark for W.h/R at rated discharge?  How does that compare to Lead Acid if one draws at 0.15 -0.2C for example to 50% DoD?

A good inverter is about the cost of a 3-5 kW.h LiIon battery bank it seems like. More batteries and panels might trump the fancy inverters for this?  For my low baseload power requirement, what are the recommended options around the 2-3 kVA mark among the Axpert and co crowd and what among the hybrid inverters of the world?

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I think best bang for buck is going to be a 5kw VMiii (Kodak or other brand) and some pylontech, probably 2x 3000 or 3x 2000, seeing that you don't need the high power output. I've been very happy with my kodak VMiii. And if the inverter does only last half as long, you can replace it with the R10k you saved. But if it does last, you score... My thinking anyway... not for everyone I know!

For panels, I think 5 x max output is only for perfectly sunny days. Don't use that when calculating ROI - my yearly average is closer to 3.5x with almost perfect load matching. You'll have to do the calcs for how close you can get to perfect load matching as when your batteries are full, you'll only produce as much solar as your load requires at that instant. So if batteries are full at 2pm then your panels will idle along the rest of the day only producing your base load of 800W vs the max possible of 2.4kw for example. I've just increased my battery size because of this exact reason. Here is today's graph (this is a very bad day as we were away this weekend), see the wasted solar production:

image.thumb.png.17d1ea80a936e70a33f4f4ccdfa10cbe.png

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So how would one spread ones bet for that rainy day? Say a 4x200 A.h LA battery and 2x3000C? I have the Olson BPS 2436 or Mecer also has some inverters in my power demand range... 

One can always power the geyser (we have 2 in series) with the remaining energy with spare capacity which would chop a significant amount off our monthly bill. Would one have to program a micro to do that or is that the realm of the fancy inverters (where one would spend 50% of the battery capacity on)

Unfortunately we're on PAYG. I hear that even some very fancy inverters can trip them?

I'll look at the options, seems like 3000C goes for R16k which seems like good value.

ANy suggestions for LA?

 

Edited by mgoedeke
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I think for a rainy day, you accept you'll use more eskom. And make up for it on sunny days. 

Adding geysers makes things more interesting - if you're up for figuring out the control it allows you to place nice constant loads on when you've got excess PV. Works well for me but I got the control for free because I already had a Home Assistant server running. I think the more expensive inverters can do some of this internally through the AUX port (Specifically thinking Sunsynk here). I use a wifi smart switch with temp sensor to do all the switching and monitoring (Sonoff TH16), but I also have a 1kw element which allows me to get away with a smaller switch. But if you're up for tinkering it's definitely possible.

I think the hardest thing for you is avoiding the temptation to add more and more to your inverter system for backup during loadshedding! Starts with servers, then lights, then maybe geysers etc etc... I had the same problem - initially just wanted a small UPS for computers, internet and TV. Now my whole house is covered 😂

I don't have any issues with my VMiii tripping our prepaid meter... but not sure if that's just our meter being forgiving.

No idea on LA unfortunately. Knew right from the start I wanted Lithium so never bothered researching.

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that is what i like about the proper hybrid inverters, where you can have all the heavy hitters on non-essential circuit, you still get the benefit of solar production, but have grid to balance out the load, i have gone up to 7.65 kW on a 5 kW Sunsynk, unfortunately it is double the price though

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