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Re: [EVDL] Phd in Materials Science on LiFePO4 batteries video WAS: Lithium 60ah 144v

martinwinlow wrote:
AMPhibian wrote:
>> Even if capacity
>> drops over time the voltage should still have the same relationship
>> to SOC.
> And this is the problem - 'should'. No one yet knows what will happen
> in a real world situation when a pack has been 'cycled' at varying
> amounts each time between charges over several years and it is the
> uncertainty about it all that I am worried about. Especially when
> someone who hasn't a clue drives the EV - they may not stop pushing
> the vehicle to keep going when the controller starts cutting back -
> eventually there is a danger of cell reversal. I do not have the
> money to spend on replacing cells that, for the sake of a cheap and
> simple BMon and/or ManS could be completely avoided.Other than a DIY BMS
> it's actually less money if you have to replace a few cells than buy a
> BMS, but it's worth noting that none of us that run BMS free have had to
> replace a cell, at least not that I'm aware of, and some people have had
> to replace cells because of faulty BMS's. I look at the occasional manual
> monitoring and possible re-balancing about the same as an oil change,
> though less messy, and free.

> When the technology matures, it may be a different matter. In the
> meantime the other advantage of having BMMS is that the data from real
> vehicles is able to be logged and analyzed for the benefit of all.
> All the data I've seen looks exactly the same, I don't bother to look any
> longer.

> And besides, isn't a system which measures the pack voltage and
> regulates the power the controller can take out of it a Battery
> Monitoring/Management System anyway?
If you want to call the controller a BMS then I guess so, but I call it the
controller, and it's pack level not cell level.
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