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  • li-fe-phosphate

    Why aren't lithium iron phosphate batteries more commonly integrated into solar systems. BYD patent. It seems to me that you would save money in the end. They are a bit heavy but seeing as a solar set up doesn't move that this is an ideal application.

  • #2
    Good Question! Deep cell batteries have only one weakness that I know. Low watt chargeing and slow discharging. Lithium batteries do not have that problem. I really don't know why Lithium batteries are not used.

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    • #3
      Because the cost?

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      • #4
        Lead vs LiFePo4 in solar apps

        Since I have built 2 ev's and 2 electric bikes I have had experience with both lead and lithium. Until lithium reduces in cost by about 2 to 3 times you arent going to want to use it for a stationary application. Lead and lithium are more similar in cost for an ev because you have to abuse the lead to get some decent range. This means deep cycling and fast discharging. The lithium is expected to last 3 to 5 times longer than lead in this application compensating for the cost difference. You don't have this issue with a solar system. You can oversize the battery bank and easily get 5 to 7 years out of it. Who knows where battery technology will be by then. The weight is the main drawback to lead. Lithium especially LiFePo4 cannot deliver any more power per pound than lead unless you have a very powerful and expensive lithium chemistry, such as Lithium Polymer and really expensive BMS. Lithium can store more energy per pound but that is not an important attribute for stationary solar applications. As far as your charging comment...Fast charging is not a problem with solar because your array should never be sized to charge your battery bank in much less than a winter day, otherwise you bought too much solar and not enough batt. Lithium batteries have their drawbacks. Most manufacturers recommend a 3C discharge rate as max the more expensive ones boast 5C. You can get 20C from lead. My electric bicycle has a lifepo4 batt made in HongKong, a cheapie, its great on range and weight but my 100 amp speed controller can trip the overcurrent protection circuit in the BMS if I am too agressive with the throttle; then I have to reset by reaching under the seat and turning the load off for about 1 second. It was about 5 times the cost of a lead battery and it only delivers 60 to 80 amps but its light weight and range make it worthwhile.
        Last edited by JustinSolarGuy; 06-24-2009, 01:22 PM.

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