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Old 21-01-2013, 13:47   #91
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Re: Basic Designs for LiFePO4 Battery Systems

Lloyd entertains himself with stirring the pot, best ignored, he contributes nothing which is a shame because i think there's some knowledge there. Might be a short bloke?
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Old 22-01-2013, 11:21   #92
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Re: Basic Designs for LiFePO4 Battery Systems

Quote:
Originally Posted by Maine Sail View Post
Please can someone lead me to some proof of LiFePO4 fires. I would like to read how they happened or even if they exist. I've been reading for many, many months and all I seem to find is that LiFePO4 is very, very safe except to your wallet when you over charge or go beyond the discharge knee..
As with most fires it is hard to pin down exactly how they started. Neil Youngs LincVolt is a well publicized case.
There was a high-tech boat that burned down. Some college teams had their car burned up. San Francisco has had a couple EVs burn up while being charged at public stations.

The LiFePo batteries themselves are not dangerous AT ALL. It is the charging circuits and wiring where things can go wrong. For an EV, it is particularly dangerous because people want to "fill up" in as short as time as possible, so the power being stuffed in the battery can be huge, to recharge in an hour or two. At these power levels, any resistance can create large heat sources.

JackB
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Old 22-01-2013, 12:10   #93
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Re: Basic Designs for LiFePO4 Battery Systems

JackB, the question at hand is hot "fires" but fires in LiFePO4 applications. The LincVolt web site makes no metion of LiFEPO4, and the NYTimes refers to that car having a "lithium-ion" battery, which is usually not how the proud patent holders for LiFEPO4 refer to their products.

Whether the issue is the batteries or the charging circuits, the question about lithium battery systems in general, is whether there is a fire danger. Building a charger that has no inherent fire hazard is easy, it has been done millions of times. But then again, even wall warts and toaster ovens cause fires.
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Old 22-01-2013, 14:03   #94
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Quote:
Originally Posted by nimblemotors View Post

As with most fires it is hard to pin down exactly how they started. Neil Youngs LincVolt is a well publicized case.
There was a high-tech boat that burned down. Some college teams had their car burned up. San Francisco has had a couple EVs burn up while being charged at public stations.

The LiFePo batteries themselves are not dangerous AT ALL. It is the charging circuits and wiring where things can go wrong. For an EV, it is particularly dangerous because people want to "fill up" in as short as time as possible, so the power being stuffed in the battery can be huge, to recharge in an hour or two. At these power levels, any resistance can create large heat sources.

JackB
The EV versus large house bank's total stored energy is not terribly different. I have a 15 kWh bank, and that is somewhere in the middle of homebuilt EV's. Not a Tesla though for sure....But the difference is EVs have lots of volts, at least 100V but 200V or more is not unheard of either. My bank would be 153V at 100Ah in an EV. Few would charge at over 100A, most at 50A or less but I charge at 150A all the time. Cell resistance is probably an issue, but not so much interconnects. The "big" safety issue is the voltage, not sure how much additional fire risk, but the electrical shock risk will get your attention real fast.
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Old 13-02-2013, 12:07   #95
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Re: Basic Designs for LiFePO4 Battery Systems

I was looking through the Balqon web site and saw this battery for sale:

"HIQAP Series 12 Volt Battery system is designed to provide long life and high discharge rates when compared to industrial lead acid batteries. System consists of lithium iron phosphate batteries connected in series with nominal output of 13 volts DC, ideal for solar installations, wind and other energy storage applications.
  • Nominal Capacity :700 AH
  • Battery type: Lithium Iron Phosphate with Yttrium
  • Enclosure: Steel enclosure, painted black
  • Battery Management System: Individual cell balancing (temperature, voltage), CAN BUS output
  • Power Cables: 4/0 power cables, SB350 Connector standard
  • Operating Voltage:11.2V~16.0V
  • Weight:412 lbs +/-3 lbs
  • Dimensions:25.25"11.75"16.5"(LXWXH inches)
  • Operating Voltage : Charge 16.0 VDC
  • Operating Voltage : Discharge 11.2 VDC
  • Max Discharge Current : < 3CA
  • Cycle Life @ 80% DOD : 2500 Cycles
  • Operating Temperature : -45 - +85 deg C
  • Five Year Warranty"


The ad seems to imply that it includes a BMS and the price is $2640, which would be reasonable for such a large capacity. What are you thoughts on the feasibility of using something like this for a large house bank (apart from the weight issue)? Can the CAN bus be used to provide monitoring and how would it be used?
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