Sodium ion batteries

the only problem with sodium ion, is they have lower energy density and shorter cycle life than LiFePO4.  

general comercial are sitting around 2000-4000 cycles based on a 80%-20%-80% cycle (typicaly)  Vs 4000+ based on a 100%-0%-100% cycle so thats 40% more energy per cyce plus the better energy density.  the energy density only matters for the size/weight though if AH are equal the LiFePO4 will give you up to 40% more usable energy with out hurting cycle life.  the newer ones are up over 4500 at 100% usage, but a 90-10-90 they are up close to 8000 cycles. (they started including that cycle rating when they were being introduced to EV's so you could compare apples to apples with the charge cycle of nickle based LI.

for cold weather yes they can dischare and charge down to -40, but the capacity sufferes also so after a cold soak they only have 65% of the original capacity which is still deicent.  with the advent of heated LiFePO4 though this almost becomes a non issue.

also a 200AH sodium is 1300.00 Cdn from solar superstore canada and they list it at 4000 cycles at 70% depth of discharge, its 56Lbs and is roughly 20.5" x 8.5" x 8.5"  

to compare that to a currant purchase of a LiFePO4, a 200AH by DChouse (first one that popped up on amazon.ca) is roughtly 14.5" x 7.4" x 10.7", 44lbs and good for 4000 cycles at 100% DOD.  so 30% more energy a little lighter and a little smaller.

compare that to the wattcycle 314AH mini that is 15.12 (L) x 7.64 (W) x 9.76 (H) weighs 57lbs and is 579.99 Cdn. 

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