Just bought a Sodium based Battery

1076You know how Facebook is always asking you to post a status about what you just bought, like ‘I just bought a digital radio from Amazon’ or ‘I just bought seventeen sausages from Sainsbury’ – well ‘I just bought a S20-P08F Battery Stack from Aquion‘.

Why is this even vaguely noteworthy?

Well, in our research as to the direction of developments in Batteries, we at first focused on Lithium based batteries.  The momentum of electric cars and Tesla ‘powerwalls’ seemed to be focused on Lithium Iron Phosphate (And I still dont know whether I should really call it Lithium Ion Phosphate or Iron – people call them both? – anyway LiFePO4).  The price is continually dropping as  discussed in previously.  They are on the market and with the dropping price seemed prime candidate for any concept of Solar Electric Cooking.

However recently, some discussion has been had over Lithium Titanate batteries.  They cost more but they have a very different internal structure which makes them less vulnerable to temperature and rapid discharge.

However, any Lithium battery may have two key challenges in the very long term (and we are thinking this is a 15 to 30 year exercise).

One seems to be that there are doomsayers that suggest we might run out of Lithium.  Actually I believe we can extract it from sea water at a cost, so its not so much we will run out, but that the price may drift upwards again even if technical developments continue.  The raw material Lithium might rise (over the next 30 years).

The second is that I worry about waste.  Recycling of Lithium batteries is possible, but its not as cost effective as Lead batteries.  So the return and therefore the incentive to recycle is lower than existing batteries, and if we are talking millions of units for cooking, we could end up with a problem.

So as I said here, I have watching for new development ‘on the horizon’, and one is Sodium based batteries. As discussed back then, they have been used for a long time.  However they are low in energy density and that makes them heavier per kWh stored than say a lead acid, and Lithium battery.   Not going to be a contender for eletric cars very soon.

However Aquion has been developing the idea, and now produce stacks which could potentially work well in Solar installations.  Their stacks are priced mid point between lithium and lead at the moment (per kWh stored) BUT they claim that the stack can be discharged to zero.  Depth of discharge is a constraint that we find when trying to size a LiFePO4, and one thing we will have to deal with is people by passing the protection and discharging to a greater than recommended depth -and then complaining when their batteries dont do the advertised cycles.

However with an Aquion stack (if the manufacturers are right) this shouldnt be a problem.

And waste wont be a problem.  The key chemicals are non toxic.  And I could even imagine local assembly in Africa in say 2025.


  1. […] are emerging chemistries that might become even more appropriate and cheaper.  We have recently acquired a Sodium based battery that is higher in price than Lithium, but is said to have many more lifetime cycles, thus making […]


  2. […] his assumptions.  I dispute his 500 cycles for a lithium Iron Phosphate battery, but now consider the up and coming Sodium batteries.  They are already at about $400 per kWh, but the manufacturers claim 10,000 cycles!  Ok, lets […]


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