[Ovmsdev] net.c SOC alert obsolete?

Michael Balzer dexter at expeedo.de
Wed Apr 20 17:20:19 HKT 2016


I was not thinking about removing both SOC alerts, 
just the fixed one, and maybe then default the 
configurable to 5%.

Self discharging rates are very low on lithium 
cells in general, and the BMS will normally cut 
off the battery long before reaching critical 
voltage levels, leaving several months of self 
discharging without damage. All third party BMS 
systems I checked during the last year or so 
support this.

I understood from reading a web report on this, 
that the roadster BMS does not cut off the battery 
by a relais, the car electronics will continue 
operation until the battery is dead. The first gen 
Twizy has the same problem on the 12V aux battery, 
that's why I introduced the 12V alert. That's also 
a bug, consequences are just not as expensive.

I don't need the low SOC alert at all, I use the 
car nearly every day (the Twizy is my only car), I 
always know the SOC and take care to charge it up 
as soon as possible, to keep cycles shallow and 
charge while the battery is warm. Parking at 100% 
SOC is also no problem on the Twizy, as the 100% 
mark is at ~ 4.12 V per cell, well below spec max.

But the situation is of course different when 
you've got plenty of capacity and fast charging 


Am 20.04.2016 um 09:15 schrieb HONDA S-2000:
> Michael,
> Any battery will continue to self-discharge, even after it is disconnected from everything.
> The Tesla Roadster does disable driving when the battery is below the single-digit cutoff, but I would still want a warning so I can come rescue the car! For example, if it were parked somewhere for a long term and the charge reached 5% (or even 7%), then I'd want to know about that because it's not a good idea to ignore the system and leave it when the charge is that low. It's certainly a warranty-voiding situation (although surely no Roadsters are in warranty any longer).
> In other words, it's not a BMS bug. Chemistry dictates that all batteries will self-discharge, even if very slowly.
> What I'm curious about is why other electric car owners would not also want to know if their battery was low enough to trigger an automatic cut-off.
> Brian
> On Apr 18, 2016, at 2:23 PM, Michael Balzer <dexter at expeedo.de> wrote:
>> Tom,
>> so the roadster doesn't cut off the battery to avoid deep discharging?
>> Sounds like a bad BMS bug...
>> Ok, that's a very good reason why this kind of alert should be sent out
>> on all channels available.
>> Thanks & regards,
>> Michael
>> Am 18.04.2016 um 20:56 schrieb Tom Saxton:
>>> Personally, I like having the second backup warning that doesn’t depend on a setting being right. It’s a big deal if our Roadster gets down to 5% accidentally.
>>>    Tom
>>> On 4/18/16, 8:35 AM, "Michael Balzer" <ovmsdev-bounces at lists.teslaclub.hk on behalf of dexter at expeedo.de> wrote:
>>>> Hi everyone,
>>>> we've currently two low SOC alerts in the framework, one is the
>>>> configurable (feature #9) min SOC alert in vehicle_ticker(), the other
>>>> is the OVMS_SOCALERT code in net_state_ticker600().
>>>> The latter is fixed to 5% and does not respect user channel &
>>>> notification configuration. Is there still a use case for this or is it
>>>> obsolete?
>>>> Regards,
>>>> Michael

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