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Old 03-03-2013, 06:29 PM   #379
_cy_ OP
Beastly Adventurer
 
Joined: Sep 2011
Location: Tulsa, Oklahoma
Oddometer: 4,463
Quote:
Originally Posted by JoelWisman View Post
Alright, Just finishing some load tests on all sizes of Antigravity from 4 cell through 20 as well as the ETX18 and 24 earthX. Also been playing with a lab freezer so I can freeze batteries down to whatever specific temperature desired and as always a lead/acid battery thrown into the mix for perspective.

Other then time, any other tests anyone can think of to differentiate these very different batteries? All of them are blowing the doors off of Shorai but I'm having difficulty figuring out how to simulate durability beyond the acid test of seeing what failure rates are in a few years.

FYI until I can get videos and graphs up know that two things are obvious. earthX can really put out a lot of current for it's AH above and beyond any other battery I have tested to date and also it self heats and ramps up current output quicker then any other LiFePO4 battery I have tested to date.

_cy_ I have tested the balance and AH capacity of every battery I have tested to date down to the individual cell and both at low rates and high rates to get at the pekurret, or however you spell that word and found that despite a great body of writing on the web to the contrary, LiFePO4 exhibits a considerable pekurette, meaning the AH out is heavily dependent on the rate of discharge.

So, thoughts anyone? What can we do to get at which of these battery qualities are best before finding out the hard way???
good to have you verify Earth-X cranking performance. IHMO unless someone else pops up with a stronger battery design. Earth-X incorporates the best of available components into a very strong LiFePO4 battery.

Earth-X and others takes advantage of cylindrical cell's inherent rigidity to make connection straps that can deliver punishing currents. but cylindrical cells liability shows when larger amp hour batteries are created.

the larger number of cells, the greater chance of cell(s) going out of balance and/or fail. this is assuming mfg has done their due diligence by matching up like cells. SOC or state of charge difference between cells can happen simply by aging.

Earth-X uses cylindrical cells for smaller AH batteries. but switches to prismatic cells for larger AH batteries. advantage for larger AH in 4s configuration, only four cells are used. 4s: 4x 14AH prismatic cells vs 24x 26650 A123 cells (4s: 6x 2.3AH = 13.8AH)

disadvantage of prismatic cells are less rigid construction making internal connection straps more difficult to achieve. Earth-X has really done their homework by using beefy internal straps on prismatic cells that delivers high current loads.

All Earth-X batteries are built with an internal BMS that balances cells and prevents overcharge. so most any automotive charger will work.

in the process of doing cell balance tests with chargers with balance ports and with charger using pulse technologies. more to come on that topic...

_cy_ screwed with this post 03-03-2013 at 06:41 PM
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