Blue" Aluminum LiFePO4 batterie
I have studied many posts in different Forums regarding "blue" Aluminum LiFePO4 batteries, and came up with some comments.
When testing the power of a battery you should use the current specified as the optimal for batteries, in the example it was a 75Ah battery and then you would have discharge with 37.5A ie 480W and not with 150A corresponding to 2C, which battery but can with less capacity and higher heating. The probability is that Ri also rises when you discharge the battery and then the loss effect increases even more.
It became too much rattling over the enclosure and difficult to get stable battery pack, and it became hot 60 degrees (loss> 28W at 12V versus 7W at 12V and 0.5C). The accompanying interconnection was also poorly made, easy to change to the usual flat copper paths normally used.
If you take Wh / Kg as a comparison between aluminum and plastic-enclosed batteries, the flat-enclosed battery is probably also plastic around an aluminum enclosed battery. If you count on the weight of a 5mm thick plastic capsule and reinforced top and bottom, it will be approximately, (Winston 200Ah) 7.9-2.3-0.2 = 5.4Kg. A little closer to an aluminum enclosed battery that weighs about 4.1Kg for equivalent capacity. The difference after this calculation is that the plastic battery has a slightly larger volume, which may be because it has better structure for having better balanced Ri differences.
When building DIY with aluminum encased, you have to think a little more about how to assemble the individual cells into a package. The advantage of aluminum enclosed must be that the thermal connection to the environment is better. It would be interesting to discharge a plastic battery with 2C a full discharge and then measure the temperature of that battery.
When choosing a battery, one must take into account the purpose of the battery pack. If it is to be able to drive for example 10KW, then you have to count backwards and see how much current my converter needs, depends on the voltage. For example, in a 48V system need to be able to leave about 200A, if the normal discharge current of the used batteries is 0.5C then you must have 400Ah batteries or parallel connected batteries with lower Ah values which together give 400Ah.
My own design is to take out maximum of 2500W, which gives about 100A in a 24V system to my boat. I have expected to use 16 pieces of 202Ah cells from RJ-Energy, and I have had contact with a seller at
www.rj-lithium.com. After some mail exchanges to sort out document differences on their website, I have received a price and shipping cost proposal, depending on the shipping method. The price including shipping was $ 140.125 and $ 120.125, respectively.
I had thought of incorporating the cells into a stainless steel box (0.5mm thickness) the size of the AGM batteries ie 510x232x225mm, where it can also fit BMS, fuse, switch, temperature sensor, DCDC for + 13.6V / 5A for various systems in my boat, see attach file.
Comparison LiFePO4 batteries
Prismatic plastic housing Calculated
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Without
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .plastic. . . . . . . . . . . . . . . . . . . . . . . . . . . Optimal. . . . . . .Max
Brand / Dist.. . . Color. . . . Ah .......Wh /Kg.. . . .Wh /Kg. . . .Ri mOhm. . . .Wh / l. . . discharge. . . . . discharge
Winston. . . . . . . Yellow. . .200 . . . .81 . . . . . . . .114. . . . . . . . .<0.4. . . . . . .36. . . . . . .0.5C. . . . . . . . . 3C. (Pulse 10C)
Sinopoly. . . . . . . Black . . . .200.. . . .110 . . . . . . .151. . . . . . . . .<0.4. . . . . . .58. . . . . . .0-3 C. . . . . . . . 3C
Prismatic aluminum with blue plastic
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Optimal. . . . . . .Max
Brand / Dist.. . . . . . . . . . . . . . . Color. . . . .Ah. . . Wh / Kg. . . . Ri mOhm. . . Wh / l. . . .discharge. . . . . .discharge
RJ Energy/ rj-lithium.com . . . .Blue. . . . 202. . . . . .157. . . . . . . .<0.5. . . . . . 107. . . . . . . . . 1C. . . . . . . . . 2C
ETC /BLS. . . . . . . . . . . . . . . . . . . .Blue. . . . 206. . . . . .164. . . . . . . .<0.4. . . . . . 106. . . . . . . . .0.5C. . . . . . . . .1C (Pulse 3C)
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