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發表於 5-8-2018 23:43:17
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Hi C-hing,
Thanks for your time and effort to discuss the battery and charging info regarding BMW, it's pretty amazing and appreciate your valuable time
for all those material you have discussed in this thread..., actually, i have already read before i attempt to work on this project...
i would be more conviced that BMW is actually using phosphate-based lithium-ion as the cell voltage match with BMW spec:
I don't guess why most of the factory don't using it, what i know so far is german gov has some direction on car, which need to be 1M electric car running on the road by 2020...
https://abcnews.go.com/Business/ ... 20/story?id=8364933
For this LFP upgrade attempt is sure an unofficial way, instead of purely and blindly trust the LFP company that it's perfectly fit nor afraid not to use BMW approved battery, i do this attempt for interest and see how things go...
and that's why i try and even create a custom applicatoin to log out so many real data and do comparison and see if any strange pattern occurs, if yes, so that i will fall back to normal AGM battery...
so far it's been over 6000km in 2 months and everything running good...
I do this with several mindset which you may not agree but that's the case in my car, at least...:
1) when i rev up from idle to 4000rpm when car is parked, the voltage reading in INPA will drops to some point, with weak battery, it may reach 12.0V for about 0.5second, that indicate there is moment which alternator cannot cope up with the rate of change (some other say for performance consideration, the DME will even momentary disable the alternator to have max boost of the performance), i have no way to verify the software logic, but at least I aware the symptom on voltage drop when the car rev up quickly.
2) base on this, there is really several milli seconds is purely counting on the battery to provide spark, for a higher base voltage 13.2V comparing to 12.0V, it does have real different
3) i ohm checked the ignition coil, each of the primary coil ohm is around 0.5Ohm, with 12V battery, it will be 24A, and with with 13.2V battery, it will be 26.4Amp
for the power different which will be 12V * 24A = 288W while 13.2 * 26.4 = 348.48W, from pure calculation, it is large in my eyes (although it just few sparks, but u asking me if there is any different)
4) it's really cheap, just RMB1350, even cheaper than AGM, why don't take a try for fun?
5) AH usage is 90%, and u can see a very recent video, with same size of AH to same load, LFP far outperform with SLA and AGM... as they are in different chemical structure, for the AH value printed on the label, it's just base on 1C current test. (of coz, u may say there is no use for the battery, but please think of it this way, what if you alternator die, every mile is actually counting on battery, that will see the different, for normal 30Amp draw, the LFP can handle over 1 hr, while with 90AH AGM, which maybe only able to handle max 1 hr...)
https://www.youtube.com/watch?v=YNc4lm6FbI8&feature=youtu.be
6) why would people prefer AGM over normal flooded Lead acid? to me, coz it's just an upgrade... and i just want to see if it's possible to upgrade...
7) with the market price of my e90 330i 2005, it's already lower than 30,000 hkd, which i have nothing to lose in case of disaster happens. so it become a pure testing toys for me. Personally i enjoy working with engine, so will try to see how to make it runs better.
8) those overcharing/undercharing logic board isn't new stuff, the one I got also has it, and I tested with overcharing to 16V before installation.. so far it's fine..
and you see in my e90post, i even want to adjust the DME charging parameter to fit with it... (i am currently learning how to hack, but it's real difficult...)
at the time of release of this car, LFP does not even exists...
i am coming from computing background, which you can think of ssd is becoming popular 2014, and most macbook before 2010 is only comes with normal harddisk, while it still safe to upgrade as long as you know their interface matches ...
same for the LFP, as it's becoming popular in recent days, which lead to me see if it's possible to switch over... safely according to my personal views and findings :-)
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