I spent years as an engineer in Industrial Lithium Ion technology. Mostly BMS like Lithium system charging design and such. I actually even own an EV and its really cool but its just not prime time and I never see it go there.
As loud as I can type it, I would never ever fly using a LIthium Ion battery as an engine starting battery and I would only fly behind AGM. The very thing that makes Lithium Ion so called great for propulsion batteries is the same thing that makes them extremely dangerous. That benefit is low resistance. Let me explain. In an AGM or any wet cell battery, when it goes bad it in 99.9999 % of the time it creates an open within its cell banks. So, instead of having 12 VDC you have 10 VDC or 8 VDC or 6 VDC. All fine. In a LIthium Ion cell that great low resistance will end up as a dead short within the cell array. Now typically what will happen first is probably what you are experiencing. The dead short is causing a logic voltage ( VCC or TTL) where your logic voltage is typically 5 VDC which is a portion of the 12 VDC of the battery by way of a voltage regulator circuit of 12 VDC. Since a Lithium Ion battery has such a low resistance, the effect will cause the 5 VDC VCC to vary to say 3.5 VDC. This will cause very strange effects in the logic circuits and you end up with very strange things happening. Now, the worst thing that happens is if you get enough Lithium Ion cells that go bad and short to ground, you get heat and a fire. This is why Chevrolet recalled all of its Bolt EV's and why when I was working the industry I saw so many odd things happen with the logic of a system or so many fried BMS 's or DC power systems. Don't get me started on the myth that there is so much new tech in Lithium Ion. Bunk...it's the same as it was 40 years ago. The changes are in the BMS systems. The pipe dream magic LIthium cells are far too expensive to produce at a cost effective means. The battery in my EV had to be replaced at a cost of $ 32,000. Thankfully it was under warranty. Its not under warranty anymore. Would you like to buy a very well cared for EV? W. Jeff York On Wed, Jun 12, 2024 at 9:13 AM mark jones via KRnet <krnet@list.krnet.org> wrote: > Yesterday I was doing a taxi test and had the following happen more than > once. This scares me enough that I am now very hesitant to use a Lipo with > BMS. > After about five minutes of taxi, my engine shut off as if the ignition > switch had been shut off. There was absolutely no power at the ignition > switch. The BMS took over and shut the system down. After about 10 minutes, > The battery came back to life and she started right up. Only to again shut > down after a few minutes of running. Why is this happening? Is it due to > the Dynamo? Why wouldn't my engine keep running just off the Dynamo. Does > the BMS somehow disable the entire system? I am feeling like Larry Flesner > said. I think I too will only fly with AGM batteries. Seems this BMS in > Lipo batteries is a source of failure we do not need. > > Mark Jones (N771MJ) > Oldsmar, FL > > flyk...@gmail.com > www.flykr2s.com > -- > KRnet mailing list > KRnet@list.krnet.org > https://list.krnet.org/mailman/listinfo/krnet >
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