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Cost per kWh of different battery chemistries


Scubadude
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Hi all!

While debating the optimal storage capacity of a hybrid PV storage installation with my brother-in-law I made a quick sum and, from what I can see, even the most cost effective batteries cost more than Eskom power per kWh (at least for now). If this is true storage capacity should only cover night-time loadshedding for essential appliances.

Has anyone done a comparison like this one based on locally available batteries and pricing? [URL]https://www.fortresspower.com/how-to-calculate-the-energy-cost-of-different-battery-chemistries/[/URL]

Edited by Scubadude
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My rough sum was R19000 for a 3kWh battery, 80% DOD and 3000 cycles (half of the claimed 6000 cycles as real world never matches theoretical calculations or similated conditions in a lab) for a conservative R 2.64/kWh without taking time value of money into consideration.  I am on prepaid and currently pay between R2.24 and 2.69 per kWh, so lets call it parity for now, but there is no great saving in trying to bump battery capacity to save the last R 2.24 kWh. Not yet, but Eskom increases and battery decreases will get us there soon.

Most articles I read point to a sharp drop in storage prices in the next 2 to 3 years. Where my thinking is now is to install a 5kW hybrid inverter with just enough gel battery capacity to bridge essential use on a 4 hour loadshedding stint at night (already an overkill as we normally have 2 hours).  For this calc essential is lighting, security and low draw pugs only; no geyser, stove or kitchen appliances, not even the fridge.  When the battery clutches out in a 2 or 3 years I'll replace it with better tech at lower than current prices.  Good iead, bad idea?        

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Spend the money on panels, nowadays with plenty of sunshine, I use less than 1 kWh per day ( to maintain zero export ) from Eskom, the other 20 kWh comes from solar. If I had known, what I know now, would have gotten the cheapest battery set up.

 I would suggest the 5 kW Sunsynk, does everything I need.

Edited by Tariq
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16 hours ago, Speedster said:

What would the correct sum be for this calculation? Quick back-of-the-napkin estimate says LiFePo4 batteries are about R10k per usable kWh, and are good for 6000 cycles. That is R1.66/kWh which is quite a bit below Eskom prices if I'm not mistaken. 

As per the AU study you can expect approximately 4000 cycles and then your batteries would have "faded" to  about 60% of new power. This is an extrapolation, assumes a linear fade over time/cycles.

I think this is probably the most realistic view, and all the LiPO4 batteries will probably perform the same, despite what the marketing teams claim, says and promises!

Edited by FixAMess
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13 hours ago, Scubadude said:

My rough sum was R19000 for a 3kWh battery, 80% DOD and 3000 cycles (half of the claimed 6000 cycles as real world never matches theoretical calculations or similated conditions in a lab) for a conservative R 2.64/kWh

Always an interesting discussion with many different perspectives.  I haven't done a detailed analysis but I have a DIY LifePO4 battery (6kWh @ R19300) and using the 3000 cycles/80% figure,  I am sitting at R1.34/kWh which beats Eskom by a bit.  Battery cost/kWh is pretty much fixed whereas Eskom cost/kWh is a moving target and will increase over time, 15.6% in April for starters.  If I treat my batteries with kid gloves, I could achieve more than 3000 cycles which will be a bonus
 

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3 hours ago, FixAMess said:

As per the AU study you can expect approximately 4000 cycles and then your batteries would have "faded" to  about 60% of new power. This is an extrapolation, assumes a linear fade over time/cycles.

I think this is probably the most realistic view, and all the LiPO4 batteries will probably perform the same, despite what the marketing teams claim, says and promises!

Could you link to this AU study? I'd like to give this a read. 

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9 hours ago, smurfdbn said:

I have a DIY LifePO4 battery (6kWh @ R19300) and using the 3000 cycles/80% figure,  I am sitting at R1.34/kWh which beats Eskom by a bit.  
 

Half-price batteries sound interesting! What did you get and how does it integrate with the rest of your system?

Edited by Scubadude
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8 hours ago, Scubadude said:

What did you get

I am planning to go off-grid but not there just yet, still a work in progress. There are a few guys on the forum that have gone the DIY route, buying cells and related components to build your own.  You can also buy ready built units. Bain and his team at Lithium Batteries SA (LBSA) provide a quality product/service - link at the bottom

Got my first 48v 120ah (16s) setup in August last year and acquired an additional set each month thereafter - 4 banks, 24kWh.  Since I was getting 1 bank/month, initially I ran them as separate banks, each with it's own BMS.  While this works, this setup is not ideal as charge/discharge rates differ from bank to bank.  I have since acquired a 250a Smart BMS and combined all cells into 1 large battery - 16s4p.  BMS has a phone App and one can monitor battery/cells - much better

 

8 hours ago, Scubadude said:

how does it integrate with the rest of your system

I have a Victron Quattro and at the moment, the BMS is not connected to the Inverter, so I have my setup charging at reduced voltages to avoid cell voltage runaway -  equates to between 90%-95% of battery capacity.

Hope to soon try out a serial battery driver for Victron created by @Louisvdw

 

Here's a thread on DIY build using BMS with no comms 

 

Here's another thread on DIY battery - if I recall, Justin has a Sunsynk inverter

 

and finally, here's the link to LBSA - https://lithiumbatteriessa.co.za/

Good luck, have fun

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