How much should the battery be depleted before charging ?

RogerHalifax · Apr 7, 2016

We've a purchased a 2014 iMiev here in Halifax, NS. I have a question about charging: The manual says it is not good to top up the battery when it is near full charge. How high can the remaining charge be before charging up? Half full or ???
Thanks! Roger

PV1 · Apr 7, 2016

I would try to avoid topping off with the battery already above 90% (15 or 16 bars on the gauge). Does it hurt to do it every once in a while? Likely not, but it's not something you should do often.

If you're only driving a few miles each day, then what I'd recommend is to charge after you get below half charge. For example, Koorz is only driven 3-5 miles a day for three days a week. It only gets charged once every week or two, whenever it gets down to 4 bars or less. Because it gets charged with the stock cable, it doesn't usually get a full recharge, so it stays within 30-90% charge range.

Don · Apr 7, 2016

I try to recharge enough so that the car will easily make it to the next planned destination, which means it seldom gets a 100% recharge. Keeping the battery between about 30% and 80% should make it last longer. It gets a full charge whenever we need the max range, or once every 2 or 3 weeks, just to top balance the battery

Don

siai47 · Apr 7, 2016

Like Don said---It is important to let the battery fully charge every once in awhile to "balance" the battery. It won't balance until the charging current drops off after at least on cell in the Pack (there are 88) reaches its full voltage. It may take quite awhile for the balancing to complete the first time---just let it sit until the EVSE light shows its done. Other than that, if you do need full range, try to time the charge so it completes just before you are about to take your trip. A hot battery and a full battery cause the most damage. And avoiding either extends the life. If you are not going to drive the car for a long period of time, a 50% charge is good for storage. There is very little self discharge in a Li-Ion battery. You can find a lot about this by looking at old posts in this Form. Welcome to your new I-MiEV!

RogerHalifax · Apr 8, 2016

Thanks for your advice!
Interesting that the manual doesn't seem to say anything about not fully topping up the battery, in order to extend the batteries' life.
Roger

jsantala · Apr 9, 2016

It's a shame they haven't included an option not to fully charge the battery, like on the Leaf, for example. What I'd like to have is an option not to do the Constant Voltage phase of the Constant Current + Constant Voltage (CC/CV) charging that's commonly used on Lithium batteries. I firmly believe the battery would last longer if the CV phase was left out and the charging ended as soon as the upper voltage limit is reached on a cell or the battery. I think that happens at about 80% on Level 2 and it's probably what happens on Leafs when you st them to charge to 80% only. At least it has to be close to this scenario.

But yeah, when I'm not driving a lot I charge from around 50% to full ((by simply not bothering to monitor the progress).

Malm · Apr 9, 2016

5 years now. The warranty is over. Never took care about not charging when it is almost full. I assume the car could charge to over then 4,2V a cell, but it doesn´t (only charge to 4,105V maximum) for its own protection. So, that thing of charging to 80% is almost useless. The car never let the battery go to the maximum possible voltage. The new Nissan Leaf (30 kWh battery) doesn´t bring that option. Between March 2014 and Julliet 2015 only lost 1,4 Ah Battery Capacity. Only 1 Ah/year is an amazing number, and that was only possible because I avoid seeing temperatures over 21º C, even using the car AC to cool the battery. That´s what really counts, temperature in our battery. Now with 33,6 Ah (so, 70% of the original capacity), and lost 1,4 Ah since Julliet 2015. I haven' t been so obsessed lately in keeping my battery cool.