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To expand on my previous comment.

Numbers vary, but the most optimistic numbers says you'll get 7000 cycles up to 70% DoD. The least optimistic numbers says you'll get 2000. I personally think you're going to get somewhere upwards of 3500. My reasons:

  • Early stats from Tesla owners. These batteries were rated for 2000 cycles, but 3000 cycles are achieved in the field. These batteries are NMC (Nickel Manganese Cobalt), which technically has a lower cycle life than your typical LFP (Lithium Iron Phosphate) batteries.
  • Lithium Ion batteries are rated at C1. In off-grid situations they will rarely work that hard.
  • The battery is considered at the end of its life when it has lost 20% of its capacity. Lead acids are considered EOL at 50%. If you were to allow the same 50% rule for Li-Ion, they'd likely come up at double the cycles.
  • Li-Ion degrades more linearly. It doesn't just drop off a voltage cliff on some random Tuesday like lead acids do.
  • Round trip efficiency is significantly better, you can discharge them deeper, and allowed discharge rates are higher, so you can go with a bank half the size.
  • Much much much cleaner and no gassing.

If we assume that 4500 cycles are achievable, then at a cost of roughly R9500/kwh, each the cost is 9500/(4500*0.7) = R3.02. That beats the lead acids by a tidy amount.

Now, back to an old discussion. I have found more info. We have roughly three suppliers of LFP batteries: BlueNova, FreedomWon, and MyPower24.

  • BlueNova uses Winston cells. They swear it is better than the others. They build a battery rated at C10. Keep that in mind when doing comparisons.
  • MyPower24 uses CALB cells. They swear it is better than the others. They build a battery rated at C1.
  • FreedomWon uses Sinopoly cells. I think they have the most sophisticated BMS of the lot, but I don't think the Axpert will work well with this.

So the choice is yours, but I maintain that it would be very hard for myself to spend 50k and know that I could have had a better (although smaller) battery for the same price.

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2 hours ago, plonkster said:

370Ah, 1600 cycles to 50%. So 1000*5800/(370*6*1600*0.5) = R3.27/kwh.

Honestly, I'd spend 50k on a 4kwh lithium bank instead. You'll probably have a tiny bit of change spare...

For  R48K you can have 7.2 kWh Pylontech Lithium

53 minutes ago, plonkster said:

To expand on my previous comment.

Numbers vary, but the most optimistic numbers says you'll get 7000 cycles up to 70% DoD. The least optimistic numbers says you'll get 2000. I personally think you're going to get somewhere upwards of 3500. My reasons:

  • Early stats from Tesla owners. These batteries were rated for 2000 cycles, but 3000 cycles are achieved in the field. These batteries are NMC (Nickel Manganese Cobalt), which technically has a lower cycle life than your typical LFP (Lithium Iron Phosphate) batteries.
  • Lithium Ion batteries are rated at C1. In off-grid situations they will rarely work that hard.
  • The battery is considered at the end of its life when it has lost 20% of its capacity. Lead acids are considered EOL at 50%. If you were to allow the same 50% rule for Li-Ion, they'd likely come up at double the cycles.
  • Li-Ion degrades more linearly. It doesn't just drop off a voltage cliff on some random Tuesday like lead acids do.
  • Round trip efficiency is significantly better, you can discharge them deeper, and allowed discharge rates are higher, so you can go with a bank half the size.
  • Much much much cleaner and no gassing.

If we assume that 4500 cycles are achievable, then at a cost of roughly R9500/kwh, each the cost is 9500/(4500*0.7) = R3.02. That beats the lead acids by a tidy amount.

Now, back to an old discussion. I have found more info. We have roughly three suppliers of LFP batteries: BlueNova, FreedomWon, and MyPower24.

  • BlueNova uses Winston cells. They swear it is better than the others. They build a battery rated at C10. Keep that in mind when doing comparisons.
  • MyPower24 uses CALB cells. They swear it is better than the others. They build a battery rated at C1.
  • FreedomWon uses Sinopoly cells. I think they have the most sophisticated BMS of the lot, but I don't think the Axpert will work well with this.

So the choice is yours, but I maintain that it would be very hard for myself to spend 50k and know that I could have had a better (although smaller) battery for the same price.

Pylontech have an Axpert compatible firmware.

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1 hour ago, Chris Hobson said:

For  R48K you can have 7.2 kWh Pylontech Lithium

That is true! I forget...

Full Circle Solar lists them on their site at 15k each. So for 45k you can indeed have 7.2kwh. If that isn't an old price...

Edit: They claim 6000 cycles to 80%.DoD. 48000/(7.2*0.8*6000) = R1.38. That's less than Cape Town lower-end domestic. Even if it lasts only 4000 cycles that's worth it.

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23 hours ago, Chris Hobson said:

For  R48K you can have 7.2 kWh Pylontech Lithium

Pylontech have an Axpert compatible firmware.

Pylontech May not work ( Axepert)  inOffgrid  Setup  unless there is large no. the batteries are heavily derated for continuous operation. Please check the datasheets  I think for 5 KW you need minimum 2 or more  - e.g. BYD with similar setup recommends atleast 3 units of 2.5 KWh for  5 KW off grid but only one unit of 2.5 KWH for ongrid 5 KW 

 

https://www.wattuneed.com/en/lithium-batteries-/1928-lihium-battery-pylontech-phantom-s-0712971131125.html

 

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On 10/30/2017 at 4:11 PM, DeepBass9 said:

The problem comes in when you have invested in lead acid compatible charging gear. My 2 mppts and inverter/charger won't do lithium (I assume), so I am stuck with LA for the time being.

That's a once-off "upgrade" fee you would have to pay ;) And you can sell your 2nd hand MPPT's to recover some costs. 

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7 hours ago, ghatikar said:

for continuous operation

True, they are 50Ah modules, and they can do 2C (25 amps) for a minute, according to their spec sheet. My Vickies (based on Winston cells) can do 0.5C continuous, though 1C is recommended.

I missed that. That is a tad disappointing.

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15 hours ago, ghatikar said:

Pylontech May not work ( Axepert)  inOffgrid  Setup  unless there is large no. the batteries are heavily derated for continuous operation. Please check the datasheets  I think for 5 KW you need minimum 2 or more  - e.g. BYD with similar setup recommends atleast 3 units of 2.5 KWh for  5 KW off grid but only one unit of 2.5 KWH for ongrid 5 KW 

https://www.wattuneed.com/en/lithium-batteries-/1928-lihium-battery-pylontech-phantom-s-0712971131125.html

 

7 hours ago, plonkster said:

True, they are 50Ah modules, and they can do 2C (25 amps) for a minute, according to their spec sheet. My Vickies (based on Winston cells) can do 0.5C continuous, though 1C is recommended.

I missed that. That is a tad disappointing.

The old Pylontechs could do 5kW for 1 min max.

The new Pylontechs are charging 25A  recommended (2C) , 50A  max (1C) and 100A for 15 sec. I don't find this insurmountable as in a off-grid situation one 2.4 kWh unit is not going to carry you through the night. Three Pylontechs (or 4:D) is where one should be aiming at and now we have 75A charging (recommended) 150A max and 300A for 15 seconds.

Pylontech.PNG.caf6fdf7a554fe0ab9c4f0bed13cbda1.PNG

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1 hour ago, Chris Hobson said:

I don't find this insurmountable

Technically that probably makes them better for off-grid purposes, because you won't be doing 5kw for prolonged periods anyway. And then, compared to Lead Acid (where C5 was really the highest you could go), they still represent a good option. It does limit their use in a self-consumption+small backup rig though (where you might very well have just 2kwh).

From the L16REs you'd get a total of 17kwh of which you'd use maybe half, that's around 8.5. On the Li-Ion side you have 7.2 of which you'd use 70%, that's 5kwh. So 8.5kwh vs 5, 1600 cycles vs at least 3500, same price. You'll recharge the Pylons much faster the next day though, because of the famed high round trip efficiency. The question you'd have to answer is if you can make it through the night on 5kwh... if you can, go with the Pylons.

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15 minutes ago, plonkster said:

Technically that probably makes them better for off-grid purposes, because you won't be doing 5kw for prolonged periods anyway. And then, compared to Lead Acid (where C5 was really the highest you could go), they still represent a good option. It does limit their use in a self-consumption+small backup rig though (where you might very well have just 2kwh).

From the L16REs you'd get a total of 17kwh of which you'd use maybe half, that's around 8.5. On the Li-Ion side you have 7.2 of which you'd use 70%, that's 5kwh. So 8.5kwh vs 5, 1600 cycles vs at least 3500, same price. You'll recharge the Pylons much faster the next day though, because of the famed high round trip efficiency. The question you'd have to answer is if you can make it through the night on 5kwh... if you can, go with the Pylons.

5Kwh is a bit too little for me, if I had to go 100% offgrid. At 5Kwh, it could deliver about 263W per hour. Just, just too little for my current needs. 

But, going this route, IMO is much better than using the L16RE's.

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8 minutes ago, plonkster said:

Technically that probably makes them better for off-grid purposes, because you won't be doing 5kw for prolonged periods anyway. And then, compared to Lead Acid (where C5 was really the highest you could go), they still represent a good option. It does limit their use in a self-consumption+small backup rig though (where you might very well have just 2kwh).

From the L16REs you'd get a total of 17kwh of which you'd use maybe half, that's around 8.5. On the Li-Ion side you have 7.2 of which you'd use 70%, that's 5kwh. So 8.5kwh vs 5, 1600 cycles vs at least 3500, same price. You'll recharge the Pylons much faster the next day though, because of the famed high round trip efficiency. The question you'd have to answer is if you can make it through the night on 5kwh... if you can, go with the Pylons.

For the 3500 versus 1600 cycles I would add one more Pylontech and now you have just under 7kWh which will carry me through the night.  For me the biggest advantage is you don't have to pony up the money in one go. I  liken the purchase of Pylontechs like the purchase of 105Ah lead acids. First you have one string and then your second and so on without all the problems of lead acids of different ages. 

Calculate your requirements or determine your budget and buy x number of Pylontechs. If you made a mistake/ your requirements increase or your budget allows further expansion buy another.  With the Axpert where there is no BMS communication between the inverter(s) and battery bank your battery bank size is unlimited. You are however restricted to stacks of four but a busbar install will allow multiple stacks. So 1,2 3,4, (3x2) and (4x2) are possible combinations.

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1 hour ago, Chris Hobson said:

biggest advantage is you don't have to pony up the money in one go.

True, but in my experience there is a limit on how long you can wait. Things get EOLed and soon that specific model you need to expand the stack might not be available anymore. So you really have to do the extension within a year or two. Still... that is a significant advantage over lead acid. Just add more batteries a little later.

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On 01/11/2017 at 8:11 AM, Chris Hobson said:

For the 3500 versus 1600 cycles I would add one more Pylontech and now you have just under 7kWh which will carry me through the night.  For me the biggest advantage is you don't have to pony up the money in one go. I  liken the purchase of Pylontechs like the purchase of 105Ah lead acids. First you have one string and then your second and so on without all the problems of lead acids of different ages. 

Calculate your requirements or determine your budget and buy x number of Pylontechs. If you made a mistake/ your requirements increase or your budget allows further expansion buy another.  With the Axpert where there is no BMS communication between the inverter(s) and battery bank your battery bank size is unlimited. You are however restricted to stacks of four but a busbar install will allow multiple stacks. So 1,2 3,4, (3x2) and (4x2) are possible combinations.

Based on BYD and Victron combination recommendations 5 KW requires at least 3 Bplus ( each 2.5 Kwh) ( Quattro with DG backup) or 5 units  B-box ( multiplus) . Although Axpert can handle 4 KW max I would say 3 units is on safer side inase you switch inverters or to carry peak loads on regular basis. With two batteries I will stick to 60 amps x 50v = max 3 KW peak 

Please remember the continuous current capacity is quoted at 25 DEG C . my BYD were reporting 130 Amps Max Continous discharge current at 30 DEG C instead of the theoretical 140 

 

see attached for BYD specs and recommendations 

 

Quattro compatibility list.JPG

Charge current .JPG

Discharge current.JPG

Multi battery requirement .JPG

Tech Specs.JPG

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