Why use remote for delaying or terminating charging??

Can anyone explain why I would need to set timer on or off for charging? I appreciate the 'convienence' but cannot understand a practical use - besides the fact that you'd want to avoid keeping the charger plugged in for an extended period of time after achieving a full charge??? Anyone??? =)

One simple answer would be to charge the car during certain hours with time-of-use metering from your power company.

Of course an alternative would be to simply put a timer on your charger instead.

myimiev, there's another reason for limiting the charge time and terminating it before achieving a "full" charge: it's my understanding that Lithium Ion batteries are happiest at mid-charge and thus for battery longevity it's best to keep them away from both extremes. The iMiEV does not have the Leaf's feature which allows programming the charger to terminate at 80% SOC (which they recommend), and thus, for example, I try to stop my everyday charging at around 14 bars, and only fully charge if I'm about to take a longer trip. It's my understanding that having the battery pack fully fully charged and then subjecting it to temperature extremes (e.g., freezing nights or 100+deg days) may not be that healthy for the battery. Despite my confidence in our BMS, since this technology is still relatively new I'm giving my iMiEV every possible chance for a nice long life.

Thank you - I also referenceed Nissan leaf boards. It seems you may be onto something; the recommendation there is to charge only to 80% (barring expected long trips). This practice would definitely legitimize the use of the remote to set charging durations - TY!!

But don't you think MM thought of that and programmed it into the BMS. IOW, when you think you have maximally charged your battery, it might only really be at 85%

And, TaosEV - it does makes sense to use the remote to delay charge until appropriate time to accommodate local utility usage times/rates (my home's solar panels provide 100+ % of my electric power consumption, so mine's powered by the sun, fortunately.)

Fjpod, you really got me thinking on that!! It's entirely possible Mitsi already determined the "85% rule" ... and though the indicator may show 'full', it's actually only at 85% to accommodate this....too bad the manual's entirely unclear on this point.

Myimiev and fjpod, when dealing with the intricacies of Lithium Ion battery charging, you need to understand the enormous tradeoffs being made by the design engineers when trying to produce something that is state-of-the-art and yet subject to a heavily-regulated automotive consumer environment - it's amazing to me that major manufacturers are even daring to tread there! Having an 8-year warranty on this product is incredible IMO - and yet very hopeful: look how fantastically the NiMH batteries used in the last decade's hybrids have performed over time!

The major tradeoffs are maximizing battery useful capacity (range) and output power (i.e., vehicle acceleration) vs. battery life, subjected to clueless consumers in a hostile abusive operational environment.

You have to understand that the "battery" is a pack comprised of 100-or-so(?) individual cells in cell subpacks, all of which are individually managed (not simply monitored) for parameters such as voltage, current, temperature, individual cell state-of-charge (SOC) and/or depth-of-discharge (DOD), and then the rate of change for each of these parameters in an attempt to keep the pack's individual cells balanced and protected to maximize the battery pack's life. It's mind-boggling and very proprietary for each manufacturer. If you want to know more about this topic get the book "Battery Management Systems for Large Lithium-Ion Battery Packs" by Davide Andrea.

The battery management system (BMS) is designed to minimize stresses on the battery, and, for conservatism, especially preclude the cell and battery pack excursions into the upper and lower limits (e.g., individual cell open-circuit voltage is but one parameter of concern). Operational limits are well under the maximum limits at each end, which is why the charger undoubtedly stops charging the battery some percentage below its maximum and the BMS first warns and then stops the car at some percentage above the destructive minimum. Over-discharge and over-charge of a Lithium cell can be fatal to the battery, unlike the response of the very abuse-tolerant conventional lead-acid battery.

I wouldn't expect the manufacturer to divulge the amount of conservatism they've put into the operational limits of their BMS, and would be hesitant to associate any specific percentage with what they're doing. For myself, I'm content to operate my iMiEV in a fuel gauge range between two and 14 bars, adding a further level of conservatism which will hopefully result in a long and happy battery life. I have no qualms about fully charging my iMiEV just before a longer trip, and at the bottom end I simply don't want to push its limits for my own personal peace-of-mind.

Well, I'm going to keep the charge between 4 and 14 unless preparing for a long day.

fjpod said:

Well, I'm going to keep the charge between 4 and 14 unless preparing for a long day.

Click to expand...

Your battery will thank you

I'm not sure I am doing this timer thing right. The device is a little less than intuitive and I have checked the short user guide, and I understand that I can delay the start time by whatever hours I want, but my question is if I want, say, 6 hours of charging, do I program a 6 hour difference between the two or add the time delay to the total charge time that I want?

IOW, if I want a one hour delay and six hours of charge, do I set the off timer to 6 or 7?

I charge mine full every night because i have a long drive to work and i charge at work so i guess i am worse case on battery life we will see how it goes.

I am not to worried about it because BMS is setup to keep the cells below the level that will start to hurt the battery pack. Plus the amount of money i am saving vs driving the truck that in 8 years they will will better cells that can go in this battery pack i will buy them and keep the car rolling but with better range.