Inverter and batteries

Dairyfarmer

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Ok so it's time to get a backup system for our power outages. Load shedding is ok as we can plan for it. We do have a 100kva generator that we run when we expect long power outages, but the dairy takes priority as it doesn't have the capacity to run the dairy and houses.

I wanted something that I could run my lights (all led now), tvs, router, etc. I will not be connecting geyser, chest freezers, dish washer, oven, microwave and laundry to it. I have a gas hob so even the kettle will not be connected. I am undecided about the fridge. It's 400w I can do without for now. I am looking for 2 hours of 3kva backup. 3 hours if we are careful.

So looking around I have decided that an Axpert MKS 3kva/3000w/24v pure sine inverter is my choice. I chose this one because the budget is right, it is 3000w not 2400w, 24v not 48v. I have decided not to go for a system that can have multiple inverters. What I like about this inverter is it has an inbuilt charging system and can get power from any source. My plan later is to add panels to supply the load during the day (maybe then connect laundry) and use Eskom as a source at night. During extended outages I would run the generator for 2 hours and then get another 2 hours from battery.

I do have 3 phase. So I plan to isolate everything that would run on the inverter onto one phase and everything that will run from Eskom or generator onto another phase (will just cost another earth leakage). That way no one can accidently turn the dishwasher on when there is no Eskom/generator.

The batteries are where i am getting a bit stuck. I have worked out that if everything is on I'll be just over 2000w but conservative I expect around a 1500w draw when there is no Eskom (a tv, router, android box, pc and a few lights). 2 x 105ah batteries should give me an hour (to 50%) or 4 batteries for 2 hours. Mostly we are not home during the day so charging from solar would not make much difference. I don't want to be short on batteries because it's not ideal to add new batteries to old ones. But batteries are expensive so I don't want to end up with hours of backup I don't need. We can be more mindful of power consumption during power outages.

The inverter cost around R7k (seen it for less than R6K) and a 5kva I have seen at R8-R9k. So it is so tempting, but then the batteries needed starts going up pretty quickly. R2k for good batteries (3000 cycles). I want to try keep the cost below R15K without panels.

If you have some serious comments please post them.
 

TheChamp

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Buy the batteries you can afford for now and add another ones later, the batteries would not have degraded that much in say a year or two from now, it is not like you will be permanently running on the back up, through the load shedding period I have never had to run my batteries until they die.
 

thehuman

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No losses
750w per battery or just above 60 amps
You need to find out the capacity of batteries at 60 amp discharge rate , most probably between 60 and 80 ah
 

Dairyfarmer

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I have confirmed that I can get the Axpert 3000VA/3000W 24v pure sine wave inverter (MKS-3K) - 80A MPPT (1500W) from Geewiz R6094 including delivery. Around R700-R1000 cheaper than most everywhere else.

There is also this option Solar kit for R10k that includes 2 x 250w panels and 2 x 100ah batteries. I'm just waiting to hear back about the inverter specs. It looks much like the Axpert but confused why it also comes with a solar charger. There is a version of the 3kva Axpert that is really cheap. It's probably that one.
 

Dairyfarmer

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One more thing. 200ah batteries work out a bit cheaper than 2 x 100ah batteries. Would it be advisable to use 2 x 200ah rather than 4 x 100ah?
 

Jaws677

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Seeing that you know better but for what's worth. There are a lot of "fake" axpert type inverters on the market. The only one worth considering is the one made by Voltronic.

The powerstore.co.za for legit ones.

The other ones are all cheap China ****.
Also by sticking to 24V you wount be able to get Pylon batteries later on after you realise the mistake you made by getting lead acid batteries now.
 

The_Traveller

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Seeing that you know better but for what's worth. There are a lot of "fake" axpert type inverters on the market. The only one worth considering is the one made by Voltronic.

The powerstore.co.za for legit ones.

The other ones are all cheap China ****.
Also by sticking to 24V you wount be able to get Pylon batteries later on after you realise the mistake you made by getting lead acid batteries now.
where do you think voltronic get/make theirs?
 

The_Traveller

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One more thing. 200ah batteries work out a bit cheaper than 2 x 100ah batteries. Would it be advisable to use 2 x 200ah rather than 4 x 100ah?
Would be better to go for 200Ah size but just make sure you charge them properly using a 30A-40A charger.
 

Dairyfarmer

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OP can I put something like that in my office?
Depends on how big your office is. Remember a pc is pulling around 300w. You can swap out 100w incandescent light bulbs with 20w of led lights for the same effect. You would need to do a bit of calculating.
 

Jaws677

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I recon you are way over with you estimated running load. With the equipment listed I would expect a constant draw of 750 W unless you have a lot of lights.

Split your circuits now and measure the current to get a better idea of the load .
 

Dairyfarmer

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8 rooms@ 30w of led lighting = 240w
2 pcs @ 300w = 600w
2 tv with android boxes @ 300w = 600w
1 wifi router + ap + switch = 100w
4 security light @ 20w = 80w
2 usb charges (tablets, phones) @ 20w = 40w
1 double door fridge/freezer @ 300w
1 chest freezer @150w
Electric fence, gate and alarm = 300w

That is 2390w at full load or 1195w at half load (i.e. only half the lights and equipment which would be a normal situation). Consider that most 3kva inverters only put out 2400w, this is very close should I wish to run a full load.

I would rather have sufficient to run everything if needed rather than run around and say that this has to be turned off before I can use that. Also consider that the inverters go 1kva, 3kva and 5kva ..... although you do get a 1.5kva which would not do.

For long periods of outages I may want to run the microwave (1000w+) or washing machine (2000w+) if needed. So having 2400w available should I need it. 5kva would only make sense if I went the whole hog, but then you also need even more batteries .

I can live with 2400-3000w available without the need to overly pedantic about what I can use on that circuit.
 

Dairyfarmer

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Ok so I was at my brother-in-law's place on Wednesday. Hes is completely off grid with solar and a 5kva Axpert. He also has a generator as standby for heavy loads. He has 16 x 200ah batteries. So it looks like a 3kva and 2 x 200ah batteries will be my start. Solar panels to follow and some more batteries in the near future as prices dictate.
 

Pineapple Smurf

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Ok so I was at my brother-in-law's place on Wednesday. Hes is completely off grid with solar and a 5kva Axpert. He also has a generator as standby for heavy loads. He has 16 x 200ah batteries. So it looks like a 3kva and 2 x 200ah batteries will be my start. Solar panels to follow and some more batteries in the near future as prices dictate.
Great idea.
I would also love to see his batteries wired up, please take a photo next time you there.
Sounds like his system in 48 volts running 4 x 4 banks. Just my guess. :thumbsup:
 

Dairyfarmer

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He has made a table with 8 on top and 8 below. They are joined in series/parallel creating 2 x 400ah 48v batteries.
2cec58b70.jpg


I was just looking at some batteries. I can get 200ah Fivestar vrla batteries for R3000 or 100ah vlra batteries for R1300. Not sure what the cycle life is on these batteries @ 50% DoD. with everyone on holiday it's useless trying to contact companies atm.
 
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