So by SAFETY system, what do you want to do? I guess I only see two things
A. Stop the Car.B. Stop the Charger.
Suppose you queried 1 time per second. Suppose you got 3600 good readings then
ONE bad one (or failed to get one), then started getting good ones again, would
you really want to
A. Stop the car
B. Start and stop the charger?
I would think that you could tolerate some error rate with a little bit of
software intelligence such as
IF last readings were near limits then execute safety stop
IF last reading was well within tolerance, ignoreIF Failed to get reading for N
consecutive seconds the execute safety stop
Would this really be so unreasonable or unsafe?
On Tuesday, April 28, 2020, 9:10:40 PM PDT, Lee Hart via EV
<ev@lists.evdl.org> wrote:
Peri Hartman via EV wrote:
> The BMS for each cell would normally be quiet and only send something when
> prompted by a central BMS component.
I think it is important to consider just what you want a BMS to do.
- Is it just there to provide feedback on what each cell is doing?
(battery MONITORING system)
- Is it there to actively balance cells?
(battery BALANCING system)
- Is it a safety system, there to prevent damage and fires?
(battery SAFETY system)
These are three very different devices, with completely different design
requirements.
When you talk about systems with a computer on every cell, and CAN bus
networking with TCP/IP, you're talking about a Monitoring system. It's
supposed to provide accurate real-time data on things like cell
voltages, currents, and temperatures. It probably needs a fancy display
(blinkinlights), and data logging (pretty charts and graphs).
Such a system is necessarily complicated, with correspondingly high cost
and low reliability. It will need hundreds, perhaps thousands of parts,
and so have many failure modes. Given the heavy dependence on software,
it will be nearly impossible to predict what happens when it fails.
And, it's going to be the exact opposite of a safety system.
Lee Hart
--
If happiness is on your mind, here's a daily list to find:
- something to do
- something to look forward to
- someone to love
- someone to take good care of
- and misbehave, just a little
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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