I have a Ford Focus Electric (2013). How can I get it to charge to 80% then stop?
On Tue, Jan 5, 2016 at 8:07 PM, Ben Apollonio via EV <ev@lists.evdl.org> wrote: > Hi Jay, > > I think your approach is good. Some chargers (Elcon, at least) let your > BMS throttle charge current with an external voltage signal. If your > charger supports this, you could try wiring up a comparator and a flip-flop > to latch the signal at 0A when you hit your target voltage at 30A. > > Cheers > -Ben > > On Jan 3, 2016, at 9:28 PM, Jay Summet via EV <ev@lists.evdl.org> wrote: > > > I want to charge at maximum current to 80%, and then shut off. My > thoughts on this subject are listed as text below, or you can follow this > link to see the images of my charging profiles: > > > > > http://www.summet.com/blog/2016/01/03/default-charging-profile-charge-to-80-capacity-quickly/ > > > > I welcome any comments about issues or tricks I may have overlooked. > > > > Thanks, > > Jay > > > > > > > > Because I have a relatively short commute, and rarely anticipate needing > my full 100% pack capacity, I have chosen to charge my truck to an 80% SOC > on a daily basis to maximize battery life. One nice thing about the 80% > level is that most batteries can be charged at a relatively high rate of > speed up to 80%, and then you need to slow down the charging a bit to > prevent them from overheating. (This is why DC Quick Chargers will quickly > bring an empty battery up to 80%, but then slow down quite a bit after > that.) > > > > My first attempt at programming an 80% charging profile was very simple, > just set MaxV to 128.5 and set the TermC (termination current) to 2 amps. > This works well, it gets the pack voltage up to 128.5 volts and holds it > there until the battery stops accepting much current. The only issue is > that it is wasting time, because for a good amount of the charging period > the current flowing into the battery is less than the maximum 30 amps (4.0 > kW) that the chargers can produce. The charging curve looks like this: > > > > > http://www.summet.com/blog/wp-content/uploads/2015/09/charging_2amp_cutoff.png > > > > > > > > In an effort to speed up my charging, I set the MaxV to a higher amount > ( 128.9 volts) so that at the 128 volt level the battery pack would still > be accepting a higher current, and then set my TermC to the highest level > my EVCC allows (10 amps). This results in a charging curve that looks like > the following: > > > > > http://www.summet.com/blog/wp-content/uploads/2016/01/charging_10amp_cutoff.png > > > > > > As you can see, I spend more time delivering 30 amps before the current > draw from the pack starts to drop off, and the curve reaches the cutoff > point much quicker. My EVCC currently limits the TermC parameter to 10 amps > or less, probably because they have not anticipated somebody trying to > charge only to 80% as quickly as possible. > > > > If I could set the TermC parameter to 20 or 25 amps it would allow me to > set the MaxV up higher (131?). The goal would be to find a voltage setting > such that the pack would be drawing 20 or 25 amps right when it hit the > 128.5 volt level. So my curve would basically be flat, full on charging at > 30 amps up until the very end when it would start to taper off and the > charging would end at 25 or 20 amps. > > I’m not worried about setting the MaxV higher than the actual voltage > I’m attempting to hit, as it is still much lower than my pack’s actual max > voltage, and if something were to change with the pack chemistry making it > miss the TermC cutoff, the MaxV would still stop the pack from reaching > 100% charged. (and the termination timeout would eventually hit.) > > > > This is the end of my main thought, but you can continue reading for….. > > > > Extra Info about my pack, charging to the 80% level, etc… > > > > The 48 modules from my Nissan Leaf battery pack (LMO/LNO chemistry) are > arranged in a series of sixteen sets of 3 parallel cells. This gives me a > 180Ah battery with an absolute maximum voltage of 134.4 (4.2 volts per > cell). In actual use the 4.2 VPC level should never be reached, if you > charge the cells to 4.1 volts per cell they are around 99% charged. As the > extra 0.1 volt difference between 4.1 and 4.2 doesn’t really buy you much > extra capacity, most people use 4.1 volts per cell (131.2 volts) as a safe > “full” or 100% capacity on the Leaf Cells. My Mini-BMS units will start to > shunt voltage at 4.1 VPC, and raise an over-voltage alarm at 4.2 VPC. > > > > However, if you charge the cells to 4.0-4.01 VPC (128-128.5 volts) that > corresponds to about 80% of their maximum possible capacity. To maximize > cell and battery pack life, you want to minimize the time the cells are > fully charged or fully discharged. If you can keep the cells between a > 10%-80% state of charge (SOC) it will maximize their battery life. > > > > Keeping them above 10% SOC is easy…don’t drive until they are empty. > Keeping them at or below 80% SOC is also easy, simply turn off your charger > when they are only 80% charged. This is why the early Nissan Leafs had > the option to only charge the battery to 80%. (Removed in the newer Leafs > due to EPA regulations on how maximum range is calculated.) > > > > If you want the extra 20% of range that charging to 100% SOC would give > you, it is better to charge to 100% and then immediately discharge the pack > by driving it (as opposed to leaving it sitting at 100% charge all night). > This is one reason why Nissan Leaf’s have a charge timer, so that you can > tell the charger to finish just before you start your daily drive. (The > other reason is so that you can tell it to start charging only after the > low cost nighttime electricity rates start, if you are on a time of use > metering rate plan.) > > > > My 2nd charging profile will be a 4.1 VPC full 100% capacity charge, for > when I feel the need to really go long distances. (or to get the pack ready > for a top balancing equalization charge, my future 3rd charging profile.) > > > > Jay > > _______________________________________________ > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > Read EVAngel's EV News at http://evdl.org/evln/ > > Please discuss EV drag racing at NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Read EVAngel's EV News at http://evdl.org/evln/ > Please discuss EV drag racing at NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -------------- next part -------------- An HTML attachment was scrubbed... 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