BMS issue?

[cpaquette]

Hi,

I have a 2016 LEAF SL with 96,000km. I'm currently waiting for my new 40kWh battery replacement under warranty as I'm sitting at 60% SOH (max 16.6kWh at 100% SoC).

This winter I've noticed a disturbing phenomenon. When the car gets to approximately 65% SoC and I'm driving on the highway at 100km/h, the SoC drops off rapidly at an alarming rate. Over a 10km stretch, the BMS went from showing 65% SoC down to 20%. Once I excited the highway and came to a stop and then continued at city speeds (50-60km/h), the SoC slowly climbed back up to 40%.

Has anyone experienced this? I haven't tried maintaining the 100km/h speed to see what would happen when it got to a reported 0% SoC despite the pack still having energy. I will be discussing this with Nissan when my replacement battery comes in but I thought I'd see if others also have seen this behaviour.

Thanks,

Chad

 

[LeftieBiker]

Welcome. Yes, this is quite common with batteries with bad or marginal cells - especially the problematic 30kwh batteries. The weak cell(s) trigger power cuts by the BMS, especially in cold weather under higher loads. There is often no error recorded by the car, so dealerships often have to drive the car in frigid weather, doing things like flooring the accelerator going uphill, in order to produce a high enough load to trigger a power cut by the BMS.

 

[GerryAZ]

I saw that type of activity with my 2015 toward the end (battery was at 8 capacity bars when traded for 2019). The cells were fairly well balanced, but internal resistance was increasing. The increased internal resistance of the battery causes lower voltage at the motor terminals which causes the motor to draw more current which causes more voltage drop which causes even higher current draw. This is a cascading situation with high power draw needed for highway driving. Slowing down reduces current which reduces internal voltage drop which further reduces current so the BMS sees higher cell voltages and hence higher SOC. This is why it is important to get off the highway and slow down if range becomes a severe issue.

 

[dhyatt]

Hi,

I have a 2016 LEAF SL with 96,000km. I'm currently waiting for my new 40kWh battery replacement under warranty as I'm sitting at 60% SOH (max 16.6kWh at 100% SoC).

This winter I've noticed a disturbing phenomenon. When the car gets to approximately 65% SoC and I'm driving on the highway at 100km/h, the SoC drops off rapidly at an alarming rate. Over a 10km stretch, the BMS went from showing 65% SoC down to 20%. Once I excited the highway and came to a stop and then continued at city speeds (50-60km/h), the SoC slowly climbed back up to 40%.

Has anyone experienced this? I haven't tried maintaining the 100km/h speed to see what would happen when it got to a reported 0% SoC despite the pack still having energy. I will be discussing this with Nissan when my replacement battery comes in but I thought I'd see if others also have seen this behaviour.

Thanks,

Chad

battery performance sucks in winter.... at zero degrees I have about 20-30 mile range (50KM)... if I dont have the heater and defroster on... the seat heater and steering wheel heater dont impact range

 

[hornstudio]

There already is a thread named "The 40KWH Battery Topic". Its about the same issue.