Posted: Fri Aug 15, 2008 4:05 pm
I appreciate your views, Paul, but it does depend very much on how the cells behave under load, the application vehicle type and the understanding of the operator. In my own case, this is for my own vehicle which will be carefully operated to avoid cell damage. I've incorporated a meter that reads total watt hours and amp hours used since last charge, plus system voltage and instantaneous current, to allow me to see just how much is left in the battery. It's also a short distance commuting bike, so will rarely exceed half its maximum range anyway - the LVC is really just a last ditch warning system.
Additionally, I'm using cheapish cells with a fairly high internal resistance. One consequence of this that there is a strong likelihood that cutting the current in half will bring the cell back up to the safe zone. Obviously, ignoring the warning to stop risks cell damage, but then that would be a very stupid thing to do, wouldn't it?
I could build in a more linear LVC, but it was much simpler to just use the half speed input on the controller as a warning mechanism. Were I building something to be driven/ridden by others then I'd almost certainly go for a more comprehensive protection system. As with all things, it's a matter of using the most appropriate solution for the particular application - I don't see that there can be a "one size fits all" solution that suits all EVs.
Jeremy
Additionally, I'm using cheapish cells with a fairly high internal resistance. One consequence of this that there is a strong likelihood that cutting the current in half will bring the cell back up to the safe zone. Obviously, ignoring the warning to stop risks cell damage, but then that would be a very stupid thing to do, wouldn't it?
I could build in a more linear LVC, but it was much simpler to just use the half speed input on the controller as a warning mechanism. Were I building something to be driven/ridden by others then I'd almost certainly go for a more comprehensive protection system. As with all things, it's a matter of using the most appropriate solution for the particular application - I don't see that there can be a "one size fits all" solution that suits all EVs.
Jeremy