PHET 7.5Ah or YESA 12Ah: which would you choose?
Hi, first time poster, long time reader! :)
I'm about to build a new e-bike with a Golden Motor rear hub, and I'm about to choose the battery. Of course, I want some LiFePO4, and I have a few choices.
If you had a choice between C-LiFePO4 36V 7.5Ah from PHET or LiFePO4 36V 12Ah from YESA, which one would you choose and why? I need to do an flat (but windy) trip to work 50-60km roundtrip every day. I could recharge at work if necessary (but that would reduce the life of the battery! half as many cycles/roundtrips)
I was thinking that 1Ah is 1Ah, whether it comes from a NiMH or a LiFePO4. Am I right? What kind of kilometrage can we expect from a 7.5Ah battery vs a 12Ah? I'm about 180lbs.
Thanks for any input on this!
Hmmmm, thanks for noting that but without seeing the reference it's hard to know what the research was based on? I guess that will be one of the values we'll hope to learn more about once the Sandia Report comes out for our cells. Have to keep an eye out for that - thanks again!
My info on LiFePO4 degradation with temperature comes from http://www.batteryspace.com/prod-specs/HLCF18650PLi-ion.ppt
I would be delighted to hear that this data is not typical.
I have looked at this document twice and unless I am missing something on one of the graphs, I cannot find a specifice reference to "degradation with temperature" ?
Look at the graph labled "1C Discharge curve under various temperature condition"
I can agree that there is a capacity loss at lower temperatures.
For example I do know cyclindrical 10Ah LiFePO4 cells. While the capacity is even above 10Ah at 20 degree C° the discharged capacity at 0 C° (32F) is reduced to about 8Ah which means only 80% of the initial capacity! Even though, the working conditions are quotet with -20 to 45 degree C°. Hence, it seems that LiFePO4 has a remarkable decrease of its capacity at lower temperatures.
Here's what we got in our tests:
Characteristics After fully charged, maintain the cell at different temperature for 60 minutes, and then perform 0.2C discharge until the voltage reaches 2.1V
-10℃: >6300 mAh
0℃: >8100 mAh
40℃: >9000 mAh
55℃: >9000 mAh
I would have to compare these values with other cell chemistries before I would concur that LiFePO4 has a "remarkable" decrease of its capacity at lower temperatures compared with any other battery chemistry ?
It would be a good thing to make such a chart in order to see and have all cells use the same criteria as our test used.
At Minus 40 Celsius a lot more than your Lifepo4 will stop functioning and if you are riding your e-bike at 180 Celsius Above you are likely in Hell
Yes, Cycle9 Your Charts are correct and nicely done, I might add! One thing also that should be mentioned is the "safety" of LiFePO4 also far outweighs that of Li-Ion about as much as the Life Cycle advantages. I have answered the other part of this question on other posts regarding the price point for LiFePO4. Once the automated battery mfg. plants are built and you have a normal "mass produced" product - you will see prices coming down. This will happen in due course over the next few years as the wheat is separated from the chaff in this field.
I know this may not be the forum for actual product questions, but it seems that the battery needs of e-bicycles versus scooters and motorcycles are so different that we e-scooter owners seem to have a lot fewer options.
I need a 60 volt, 40 AH, 100 amp pack that will fit in:
1. A space about 29 cm by 22 cm by 19 cm, plus,
2. an additional space about 15 cm by 18 cm by 22 cm.
Note that the 29 cm dimension in #1 and the 15 cm dimension in #2 adjusted a couple cm at most.
Any ways you can help?
PJD, You might want to check out our new 1210C Modules! You can link them to form a spec. that will probably fit your needs ? For more information, please see the attached spreadsheet on specific packs which will be available by mid- January of 2008. They include VMS & Chargers with our 3 Year Warranty.
Please see attached documents (2)
Best, Don Harmon
Here are the files again - they don't seem to post ?????
You may have to contact me off-list for the spreadsheet file ???
Thanks for the positive feedback! I agree that the safety advantages for LiFEPO4 are great. In fact, that's why I first started researching them for my own use, since i carry my daughter on my bike regularly. I mentioned the safety in the notes for the table, but those are so small most people probably won't notice them. Based on your suggestion, I've added a new note to the website mentioning the safety aspect. Thanks!
I agree that prices will come down, but it may take a year or two to satisfy pent up demand.