Page 1 of 1

deplete a battery for better pack health?

Posted: Wed Jul 10, 2019 2:02 pm
by LeafTaxi
Let's say that your car charged to 100% overnight. Then you decide to take a sick day/day off. It's 85F at breakfast, and the car already has "6 temp bars" without any driving (probably get to 7 bars by afternoon).

Do you try to deplete the battery (e.g. turn-on the A/C) to bring the SOC down to 95%? Or just leave it parked at 100% SOC for 24 hours in summer weather?

(I wonder if I could power a garage-window A/C unit from a 2kw inverter off the 12v battery?).

Re: deplete a battery for better pack health?

Posted: Wed Jul 10, 2019 2:25 pm
by SageBrush
LeafTaxi wrote: Do you try to deplete the battery (e.g. turn-on the A/C) to bring the SOC down to 95%?
Heating up the battery more to lower the SoC is a debatable strategy at best

Re: deplete a battery for better pack health?

Posted: Wed Jul 10, 2019 3:19 pm
by LeftieBiker
Your use of the word "deplete" is misleading here - that implies draining it fully or almost fully. If it were me I'd drive the car to get down to the low nineties - and I have done so quite a few times. Running the A/C might blow hot air on the pack. Still, if you can't drive it, running the A/C (and maybe the heater with it) is better than leaving it at indicated 100% in hot weather.
(I wonder if I could power a garage-window A/C unit from a 2kw inverter off the 12v battery?).
Interesting idea, but then you'd have to connect the car into that setup whenever you wanted to use it. I have an alternate suggestion: if you usually get 100% at about the same time every night, try using a daily charge timer that stops at about 95%.

Re: deplete a battery for better pack health?

Posted: Wed Jul 10, 2019 9:36 pm
by Oilpan4
The car draws around 700 watts of power continously when you turn it on, leave it in park, no A/C, no heat, no additional lights on.
Leaving it on will run the battery down, it just takes a while.

Re: deplete a battery for better pack health?

Posted: Thu Jul 11, 2019 2:25 pm
by LeafTaxi
LeftieBiker wrote:Your use of the word "deplete" is misleading .
You're right; that was the wrong word. I meant "reduce SOC a bit."
Heating up the battery more to lower the SoC is a debatable strategy at best
From what I've read here, the worst thing is the number of hours spent at high temp + high (or low) SOC. Drawing 1.5kw will raise temps a bit, but I've never seen street driving add a temp bar. I can drive Uber on city streets for 120 miles over 4 hours straight, taking SOC from 100% down to 20%, and not see an additional temp bar. But if I do a couple of 20-mile airport runs on the expressway, then I get an extra temp bar.
LeftieBiker wrote: try using a daily charge timer that stops at about 95%.


That would be nice; I have the S, which has no stop timer. Also, my use case is unusual (Uber driver). I usually drive AM rush hour, PM rush hour, then early bar hours, so I charge 2-3 times per day (about 8 hours of driving per day). In summer, the car will go 4+ hours (longer than I care to drive at once), so I don't really need to charge it to 100%. Rather than setting a stop timer two or three times per day, It would be really nice if Nissan had an 80% "mounutain mode" (I'm sure I'm not the first person to say that).

Re: deplete a battery for better pack health?

Posted: Thu Jul 11, 2019 2:52 pm
by LeftieBiker
Nope, we've been clamoring for them to restore the 80% mode for years - to no avail.
That would be nice; I have the S, which has no stop timer.
You can fudge it: set the start time late enough so it will fail to reach 100% by about 5-10% when you leave in the morning. Charging usually adds about 5-6% per hour, if that helps.