19 minutes ago, DeepBass9 said:

I'm not sure that these type of battery calculations make any real world sense. To compare different batteries perhaps? Ultimately your aim is to use as little battery power as possible to prolong the battery life, so the cost of solar power generated should be your yardstick as to whether to go off grid or not, batteries are just there for continuity.

The question is whether I should at night discharge the battery and recharge it tomorrow (with solar capacity), or whether I should just keep the batteries charged and power the loads from solar power during the day. If it is cheaper to buy the electricity from Cape Town, I should not cycle the batteries (I should perhaps not even have batteries at all).

But working out the exact per kWh cost of each battery is not trivial. Of course, as long as you do it the same way for each type of battery it makes a brilliant yardstick for comparing batteries to each other, as you mentioned, but to compare it to a different technology is always difficult.

For example, what is your cost per kilometer on your car? Well, first there is the opportunity cost. If you left the money in the bank/home loan rather than buying a car. Then there is the depreciation each year. Insurance. Fuel. Maintenance. For me, we're talking around R35000 a year on my present vehicle. That's 3k a month. I drive around 600km at most per month. So my cost is R5/km. If I lived in a place with good public transport I would not have a car at all... but as it stands, the next step up is a meter taxi and that's R10/km.

The same exercise should be done for the total cost of batteries, in other words, just like you can't just take your car's fuel efficiency and multiply it by the fuel price to get a rand/km value, so you also cannot multiply the cycle life with the capacity and divide the cost into it for a battery. It's more complex than that... and different for everyone.

But there is also a point in time where the argument becomes so clear that you don't even have to do the math. Farmers for example. Next cheapest source is a Diesel generator. You hardly have to crunch much numbers 🙂

What I am unsure of (but would love to know) is the exact point when batteries starts to undercut grid costs, obviously over a certain time period (say 7 years).

Edited March 19, 20197 yr by plonkster

One of my cars is so old it started appreciating in value...

1 hour ago, plonkster said:

What I am unsure of (but would love to know) is the exact point when batteries starts to undercut grid costs

another factor to consider is the environment and hoppy/satisfaction aspect. I am prepared to pay a bit more for electricity coming from my batteries and PV system. So for me the point has already been reached 😀. 

28 minutes ago, Fuenkli said:

another factor to consider is the environment and hoppy/satisfaction aspect

Yes, what one might call the "justified luxury" component. When I hear all the generators roaring up and down my street, I can only conclude that to many of these people the luxury of expensive power is worth it... even at R10/kWh or more. If you've already conceded this argument... you should not complain about battery cost 🙂

16 minutes ago, plonkster said:

even at R10/kWh or more

is that about the cost p kwh with your run-of-the-mill petrol gennie?

Sounds a bit high? Diesel is about R5-6/kWh. You get best efficiency when running the engine at close to full power, light loads on a generator are more expensive.

Edited March 19, 20197 yr by DeepBass9

12 minutes ago, gabriel said:

is that about the cost p kwh with your run-of-the-mill petrol gennie?

According to google, a typical 5KVA generator uses 18 US gallons of fuel every 24 hours. That's about 70 liters, which will cost around R1000 at the pump (thumb suck and hand wave). R1000/(24*5) = R8.33/kwh. So yes, perhaps a bit high. But that excludes maintenance cost of the generator, and you don't run it at full load all the time, and so on. So I'm probably not too far off 🙂

Edit: And yes, Diesel costs less per kWh, @DeepBass9 is probably right on the money.

Edited March 19, 20197 yr by plonkster

8 hours ago, Chris Louw said:

Good example . Electric supplier has a 24 volt Axpert installation done in his shop . 6mm battery wires can not be called cables . No battery disconnect or fuse . ???

Yet he sell them by the dozen! 

8 hours ago, plonkster said:

Since I use more than 600kWh a month, it means every unit I offset at the peak price of R2.55/kWh. But even at the <600kWh price of R1.85 it makes sense.

However, as we've said many times before, the killer is the opportunity cost (if you had just left that 100k in an interest bearing vehicle), the replacement cost after a decade, and the fact that you also have to pay for (and replace) all those other equipment (inverters, chargers, etc). When you add it all up, the consensus was that grid-tied has an actual ROI whereas batteries only made sense if the backup facility actually makes you money (eg, for an office where your employees can continue working instead of having a 2-hour smoke break).

But the very first hurdle has always been just getting the battery cost BELOW the grid cost, because once that happens, people who already have a grid-tied setup (ie the other half of the cost is accounted for to some extent) can add battery backup and it might actually make sense.

I think I calculated my battery cost at around somewhere between R1.50 and R2.50 per kWh. So I pretty much use it only to shave off the bit above 600kWh for now.

The picture suddenly changes when you have to fork out R15/L diesel to run a generator for 4 hours, just to have lights and food on the table. Try and feed 5 people for less than R200 on takeaways?

Cost savings isn't always just about the immediate money you think you're saving. If a battery bank like this could be used during peak hours, you save R1.40/Kwh. During off-peak hours you save a few cents. In July it will cost you 13.5% more. And there's a guarantee that it will increase again next year. 

The Pylontech, as a pure example, have 3500 cycles at 80%. That's 16.4 year's cycling every single day. 

6 hours ago, plonkster said:

According to google, a typical 5KVA generator uses 18 US gallons of fuel every 24 hours. That's about 70 liters, which will cost around R1000 at the pump (thumb suck and hand wave). R1000/(24*5) = R8.33/kwh. So yes, perhaps a bit high. But that excludes maintenance cost of the generator, and you don't run it at full load all the time, and so on. So I'm probably not too far off 🙂

Edit: And yes, Diesel costs less per kWh, @DeepBass9 is probably right on the money.

In 2015, through experience, a friend learned that loadshedding cost him an average of R1500/pm on fuel for his generator. I am sure their "typical 5KVA generators" are not the cheapies we buy at the [insert favorite brand name] hardware store

22 hours ago, Chris Louw said:

Good example . Electric supplier has a 24 volt Axpert installation done in his shop . 6mm battery wires can not be called cables . No battery disconnect or fuse . ???

Chris as someone about to install a system prob in the R180-250k mark, what SHOULD I be looking for? Very difficult to know what should be there and what is not necessary.

1 minute ago, Moose said:

Chris as someone about to install a system prob in the R180-250k mark, what SHOULD I be looking for? Very difficult to know what should be there and what is not necessary.

Properly sized battery cables, probably 35mm or bigger if I look at your budget. And proper fuses. Generally you would use a fuse disconnector with big square white fuses.  This is just on the battery side. On the inverter side it's best to have an isolator and both ends (i.e. Eskom feed and inverter feed) along with surge arrestors. On the PV side make sure there are PV fuses. The common favorite is a 10mm x 30mm white PV fuse, rated at either 600V or 1000V, depending on your installation. 

1 hour ago, Moose said:

Chris as someone about to install a system prob in the R180-250k mark, what SHOULD I be looking for? Very difficult to know what should be there and what is not necessary.

There is a lot of info on the forum . What is your energy use and what can you do to lower it . More efficient lights and other equipment . What is your area standards . What is legal and what not .

What do you want to connect to the system . Must it be grid connected or offgrid . What capacity and amount battery storage do you want .

 Get a quote . It must be a detailed quote . Wire sizes , fuses, Pv combinerbox , DC disconnector , DC breakers , Tipe and size inverter , panels , batteries , control system and extras you want . Get a qualified person to check . After installation get system checked before final payment . 

There is some forum members that will assist you . Their knowledge helped my to get my badly installed system to a good standard . Your budget should get you a very nice setup .

15 hours ago, SilverNodashi said:

The Pylontech, as a pure example, have 3500 cycles at 80%. That's 16.4 year's cycling every single day. 

And because of the way LFPs are EOLed, that means that after 16 years it still has some oomph left... probably just half of what it had when it was new, but you might well be able to continue using it (at this point we don't know though).

15 hours ago, SilverNodashi said:

In 2015, through experience, a friend learned that loadshedding cost him an average of R1500/pm on fuel for his generator. I am sure their "typical 5KVA generators" are not the cheapies we buy at the [insert favorite brand name] hardware store

My neighbour says she can run the generator for 8 to 10 times on a tank. A tank is 25 liters and costs R370 (well now it does... soon it will be more). She's fairly energy conscious so the gennie is likely not running at even half capacity, but this might actually be the case for many homes, so it is a good example. If I assume she runs the same sort of loads that I do, less than 1kW most of the time, then she gets 20KWh for R370. That's R18.50 per kWh!

 

1 hour ago, plonkster said:

then she gets 20KWh for R370. That's R18.50 per kWh!

 

wow, and that EXCLUDES the initial 3-7k initial outlay for the gen and maybe 2k for wiring [if its used correctly...

2 hours ago, plonkster said:

And because of the way LFPs are EOLed, that means that after 16 years it still has some oomph left... probably just half of what it had when it was new, but you might well be able to continue using it (at this point we don't know though).

 

We'll have to wait and see. Same with solar panels with 25 year's warranties. 

2 hours ago, plonkster said:

My neighbour says she can run the generator for 8 to 10 times on a tank. A tank is 25 liters and costs R370 (well now it does... soon it will be more). She's fairly energy conscious so the gennie is likely not running at even half capacity, but this might actually be the case for many homes, so it is a good example. If I assume she runs the same sort of loads that I do, less than 1kW most of the time, then she gets 20KWh for R370. That's R18.50 per kWh!

 

My in-laws cook on their induction plate, on the generator. And use the kettle and microwave, TV, portable lights, and egg incubators. It all works well but obviously cost a lot to run. I know my dad also used to use the kettle on the generator and hookup all the fridges and TV

On 2019/03/19 at 11:26 AM, plonkster said:

The question is whether I should at night discharge the battery and recharge it tomorrow (with solar capacity), or whether I should just keep the batteries charged and power the loads from solar power during the day. If it is cheaper to buy the electricity from Cape Town, I should not cycle the batteries (I should perhaps not even have batteries at all).

But working out the exact per kWh cost of each battery is not trivial. Of course, as long as you do it the same way for each type of battery it makes a brilliant yardstick for comparing batteries to each other, as you mentioned, but to compare it to a different technology is always difficult.

For example, what is your cost per kilometer on your car? Well, first there is the opportunity cost. If you left the money in the bank/home loan rather than buying a car. Then there is the depreciation each year. Insurance. Fuel. Maintenance. For me, we're talking around R35000 a year on my present vehicle. That's 3k a month. I drive around 600km at most per month. So my cost is R5/km. If I lived in a place with good public transport I would not have a car at all... but as it stands, the next step up is a meter taxi and that's R10/km.

The same exercise should be done for the total cost of batteries, in other words, just like you can't just take your car's fuel efficiency and multiply it by the fuel price to get a rand/km value, so you also cannot multiply the cycle life with the capacity and divide the cost into it for a battery. It's more complex than that... and different for everyone.

But there is also a point in time where the argument becomes so clear that you don't even have to do the math. Farmers for example. Next cheapest source is a Diesel generator. You hardly have to crunch much numbers 🙂

What I am unsure of (but would love to know) is the exact point when batteries starts to undercut grid costs, obviously over a certain time period (say 7 years).

I would also like to know if you could power the load on battery at night I mean with so many cycles as advertised on most batteries, why not right ?

11 minutes ago, Treschen said:

I would also like to know if you could power the load on battery at night I mean with so many cycles as advertised on most batteries, why not right ?

Off course, why not?

On 2018/12/02 at 8:17 AM, Antony said:

How do these guys justify their prices

I think the reason for the discrepancy in that there are grey imports of used “second life” BYD branded batteries being bought into SA and these are not supported by BYD. This info came from reliable sources.

The authorised distributor is Segen Solar, and this stock is supported and carry the manufacturer warranties . That is the story I got.

I would stay clear of these cheap units, as the story goes of it’s too good to be true...............

2 hours ago, LivSol said:

I think the reason for the discrepancy in that there are grey imports of used “second life” BYD branded batteries being bought into SA and these are not supported by BYD. This info came from reliable sources.

The authorised distributor is Segen Solar, and this stock is supported and carry the manufacturer warranties . That is the story I got.

I would stay clear of these cheap units, as the story goes of it’s too good to be true...............

Oops. Seems I should have read further into the thread. This was covered and then some. 😉

Why not look at the Leoch Lithium batteries?

I sell the 48v 100ah for R22000 each. 

Bulk orders are welcome.

email: [email protected]

btw is the pricing still valid for the BYD batteries ?

On 2019/01/27 at 3:26 PM, KhanAfriplusBYD said:

Because of your support, we will have better pricing soon.

The Byd batteries are quite impressive from the experience with my own ones, however the price gap per kWh, compared to similar offerings, only appear to get ever bigger, especially over the last year, when prices from e.g. Pylontech seemed to have come down, when looking at prices from different suppliers online but Byd's prices seem to have increased.

It will be be a pity if they end up pricing themselves out of the (local) market because of the prices.

 

Way to resurrect a necro thread @WeNotGood

I bought a 10.2KW set of the Revov refurb batteries for 35k delivered vat incl. last year
Installed and running with them.  Fairly happy.  I do about 30-40% discharge overnight currently.
 

Rough back of envelope calc - 365 days x 10 years x 10 kw = 36500 KW @ R35000 = R0.96 /KWhr for product lifetime.
Haven't found anything near that cost since.

I just added more panels to my setup today. (finally got to 12 x 300W instead of 6 x 300W).
Next up I'll be replacing my FM80 with a Victron and going almost entirely Blue.



 

18 hours ago, shanghailoz said:

Way to resurrect a necro thread

:-)

Really good price on the batteries, unfortunately the "normal / official" retail prices on BYD is >> more than double what you paid.