IanL
Posts: 267
Joined: Tue Feb 18, 2020 12:57 pm
Location: Jersey, English Channel Islands

Re: The origin of the 'B' mode setting.

Thu Nov 25, 2021 3:46 pm

I agree with all you said.

As for the fear that a large amount of regenerative braking would have an adverse effect on the battery, I have found the opposite. My battery's SOH has improved from 95% to 102% since I acquired the car, and I always use B Mode.

I was recently loaned a Mazda EV while my car had its annual service. It had paddle control of the regen, which reset to zero every time the vehicle was switched off, and it was a great nuisance having to apply three or four (I forget which) flicks of the paddle to get the equivalent of B Mode whenever switching on. And the top setting was not as effective as B Mode.

I won't be changing my car for a newer EV any time soon, unless someone abandons the paddle fashion and brings back B Mode.

MassDeduction
Posts: 118
Joined: Tue Feb 25, 2020 3:24 pm

Re: The origin of the 'B' mode setting.

Wed Dec 22, 2021 12:32 am

IanL wrote:I agree with all you said.

As for the fear that a large amount of regenerative braking would have an adverse effect on the battery, I have found the opposite. My battery's SOH has improved from 95% to 102% since I acquired the car, and I always use B Mode.

I was recently loaned a Mazda EV while my car had its annual service. It had paddle control of the regen, which reset to zero every time the vehicle was switched off, and it was a great nuisance having to apply three or four (I forget which) flicks of the paddle to get the equivalent of B Mode whenever switching on. And the top setting was not as effective as B Mode.

I won't be changing my car for a newer EV any time soon, unless someone abandons the paddle fashion and brings back B Mode.

Is it even possible to recover actual SoH through use? To me that sounds more like the BMS "re-learning" a more accurate SoH than actually improving the health of the battery. Once the battery is damaged, in however small a way, it's damaged for good (short of some kind of physical refurbishing/replacement). And that's OK, these are tools to be used, not pieces of art. If a few reasonably best-practices are followed, any reasonably modern car (including 2018 and later Soul EVs will probably have batteries that last the life of the car).

But if we want to get into the weeds... in a perfect world, your charging amperage would not exceed 25% of the battery pack's Ah rating. So, for example, with a 120 amp-hour pack, you would ideally not exceed charging at a rate above 30 amps. Not a problem to do occasionally, but not something you'd prefer to do frequently.

I have observed when using Soul EV Spy that on the 64 kWh Soul EV that regen braking rarely exceeds the ideal charging level (and when it does, it isn't by any significant amount). And hard regen is generally for very brief periods of time. And since the damage potential drops logarithmically as you get closer to the safe threshold, the amount of battery aging potential is very minor.

I think the smaller battery pack (39.2 kWh) variant of the 2020 and newer Soul EVs would likely more routinely exceed the ideal charging rate during hard regen, but again probably not by enough, or for long enough, to generate significant battery aging. Then again, it has a weaker motor, so perhaps it produces weaker regen? I'm not sure about that, but if so then it's likely a total non-issue (rather than just MOSTLY a non-issue ;) ). Hmmm... now you've got me wondering if a stronger motor = stronger regen, and a weaker motor = weaker regen.

The 2019 and earlier Soul EVs have weaker regen, I believe, so I can't speak to whether they commonly regen hard enough to potentially contribute to battery aging in any way (let alone by how much). I have yet to plug my OBDII adaptor into one and check it out during a drive (as a passenger, naturally). Perhaps that's something to do for kicks, one of these days. :) But my guess is the smaller battery pack, paired with the weaker regen, would keep it in the realm of regen being little to no problem.

IanL
Posts: 267
Joined: Tue Feb 18, 2020 12:57 pm
Location: Jersey, English Channel Islands

Re: The origin of the 'B' mode setting.

Thu Dec 23, 2021 1:27 am

Very interesting discussion - much food for thought. I can't say those points had occurred to me. My only experience with the Mazda I was loaned did not confirm the "higher power=higher level of regen braking" (in fact, the opposite was the case), but that could be the choice of the designer rather than an inherent characteristic.

Specifically, about "recovering SOH", I am not using the BMS data. I calculate it from the raw data I record, The method suffers from rounding errors of the data, but averages out over sufficient iterations. Why the battery should improve its capacity is not clear, but perhaps not all capacity loss is irreversible. Lead-acid batteries recover capacity after a gassing charge, and perhaps Li-ion batteries can experience a similar benefit from an improved usage and charging regime? The previous owner of my car clocked up quite a high mileage over the two years he had it in mainland UK, and it reasonable to assume he did some long distances and high speed driving, whereas I live on a small island (9x5 miles) with a 40 mph speed limit, and stick to a 30-80% charging regime.

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