Bill is right, the DC-DC cannot be expected to provide all the power, especially for transient loads. Both the brake booster and the power steering can draw large surges of power, this is one of the reasons why most EVs still have a big old lead-acid battery. (bus stability)
In a normal ICE car, you know when your 12v is on its last legs because it won't crank the starter. You have no such early warning in an EV or many Hybrids. If your 12v is more than a few years old and has been subjected to deep discharges and low voltages, it's likely heavily sulfated and cannot provide a "clean" 12v voltage to the car. I'd replace it first and then see if the brake problems go away. I bet you they will! On Sun, Mar 27, 2022 at 3:29 PM Bill Dube via EV <ev@lists.evdl.org> wrote: > The voltage on a lead-acid battery goes _up_ in cold weather, by the way. > > Under load in cold weather, however, the higher impedance will tend to > make the 12 volt battery voltage sag under load. > > But the the vehicle DC-DC is working when the brake issue arises, so the > battery will play a smaller role. Worth looking at the 12 volt system > voltage when the brakes are applied. > > Perhaps there are additional loads such as power steering load that will > cause the 12 volt sag when the brake boost becomes an issue. > > Bill D. > > On 3/28/2022 3:15 AM, mark hanson via EV wrote: > > Hi Folks, > > > > > > > > I checked the 12V aux voltage through the cigarette lighter socket with a > > DVM and shows 13.0V during operation. The low voltage storage codes over > > time were caused by the vehicle sitting a long time and the ghost loads > > dropping the battery voltage to 10V and had to recharge externally (also > > sets low voltage codes when replacing the battery). I don't see *how* > the > > aux voltage operating at 13V has *any* effect on the brakes in *cold* > > weather. I'd love to see a technical explanation on this rather than > "just > > replace the good battery with a more expensive one". > > > > > > > > Best regards, > > > > Mark > > > > > > > > From: mark hanson [mailto:markehans...@gmail.com] > > Sent: Wednesday, March 23, 2022 10:08 PM > > To: 'Electric Vehicle Discussion List' > > Subject: Nissan Leaf 2013 Cold Brake (dropout) Recall > > > > > > > > Hi Folks, > > > > > > > > After seeing this recall, 46.9K Leafs 2013-2016 and having my brakes drop > > out in the cold (apparently regen appears to shut off when cold > > intermittently), I took it to the wheeler-dealer: > > > > > https://www.csmonitor.com/Business/In-Gear/2016/0318/2013-2015-Nissan-Leaf-r > > > ecalled-for-braking-problem-46-000-vehicles-affected#:~:text=Nissan%20is%20r > > ecalling%20more%20than,braking%20ability%20in%20cold%20weather. > > < > https://www.csmonitor.com/Business/In-Gear/2016/0318/2013-2015-Nissan-Leaf- > > > recalled-for-braking-problem-46-000-vehicles-affected#:~:text=Nissan%20is%20 > > > recalling%20more%20than,braking%20ability%20in%20cold%20weather.&text=A%20Ni > > ssan%20Leaf%20electric%20car,(January%2012%2C%202016> > > &text=A%20Nissan%20Leaf%20electric%20car,(January%2012%2C%202016 ). I was > > asked to report on the actual response (below) > > > > > > > > The Roanoke VA Southern team Nissan dealer told me that the warranty > expired > > and had to charge me $250 for an hour of labor (I must be in the wrong > > business) to read the software through the OBD-2 port and see if it had > the > > brake update. I was told it had the latest update although I hadn't > brought > > it in before. (In 2015 it was in for an air conditioner failure under > > warranty.) I was then told that the *12V Aux* battery is what was > causing > > the cold brake drop out *after* I printed out a photo of the red > exclamation > > point and temperature display at 25F *and* the recall notice, showed to > > them. (I guess they thought they would sell me a pricey battery). I > drove > > it to Advance Auto and bought a new fancy Optima Yellow Top $330 battery > to > > replace the 2019 (Advance Auto battery I replaced still under warranty). > > Since the present battery was still under warranty, they tested it and > said > > it was OK but gave me $189 store credit. > > > > > > > > Dealer service dept response: > > > > iPhone Message 3/8/22: "Hi This is Southern Team, we are calling because > we > > are looking over your vehicle. Unfortunately what we are saying is you > *do* > > have the latest and greatest software installed to your vehicle regarding > > the brakes and what we are noticing however is that your regular 12V > battery > > is registering 300 CCA to 397CCA and should be closer to 500CCA. You > also > > have a bunch of low-voltage codes stored in the system from where we have > > obviously plugged it in to perform a software update and see what > software > > version was installed last. We think that the battery is what's causing > the > > light on the dash and resistance with your brakes - is actually related > to > > where your system doesn't have the appropriate amount of electrical > current > > running through it so they're recommending that you actually replace your > > battery." > > > > > > > > The printout after service reads in caps: "A CUSTOMER IS REQUESTING NEW > > BRAKING SOFTWARE TO BE UPLOADED. CUSTOMER BELIEVES THIS WILL CORRECT THE > > CONCERN OF THE TRIANGLE LIGHT POPULATING AT TIMES WHEN BRAKING, FEELS > LIKE > > BRAKE BOOSTER ISN'T WORKING, ESPECIALLY WHEN BELOW FREEZING. TAKES A > LOT OF > > EFFORT TO BRAKE --- UPLOAD SOFTWARE ONLY - 1.0 NBE INSPECTED VEHICLE AND > > FOUND LATEST SOFTWARE FOR BRAKE SYSTEM ALREADY INSTALLED - LOW VOLT CODES > > STORED - REC REPLC 12V, 381 CPN $250 > > > > 41859 1.00 CUSTOMER REQUEST WE PERFORM A SOFTWARE UPDATE TO THE BRAKING > > SYSTEM FOUND ONLINE WHERE IT WOULD FIX THEIR CONCERN. CHECK BRAKE PART > > NUMBER AND ADVISE CUSTOMER THERE IS NO UPDATE AVAILABLE FOR THE BRAKING > > SYSTEM - IT HAS ALREADY BEEN REPROGRAMMED ELSEWHERE. DID FIND MULTIPLE > LOW > > VOLTAGE CODES STORED DUE TO WEAK 12V BATTERY. THIS CAN CAUSE THE SAME > > CONCERNS YOU HAVE - RECOMMEND BATTERY REPLACEMENT." > > > > > > > > Question: has anyone heard of with this recall with the 12V battery > causing > > the braking regen to drop out on cold weather - or is this *junk > science* ? > > > > > > > > > > > > Have a renewable energy day, > > > > > > > > Mark > > > > > > > > Mark E. Hanson > > > > 184 Vista Lane > > > > Fincastle, VA 24090 > > > > 540-473-1248 phone & FAX, 540-816-0812 cell > > > > REEVA: community service RE & EV project club > > > > Website: www.REEVAdiy.org (See Project Gallery) > > > > UL Certified PV Installer > > > > My RE&EV Circuits: www.EVDL.org/lib/mh > > > > REEVA Demo: http://youtu.be/4kqWn2H-rA0 > > > > Fincastle Solar Weather Station > > < > https://www.weatherlink.com/embeddablePage/show/a88920376f864ecabaed843dd89 > > 75b8d/signature> > > > > > > > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20220327/590362ae/attachment.html > > > > _______________________________________________ > > Address messages to ev@lists.evdl.org > > No other addresses in TO and CC fields > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > > ARCHIVE: http://www.evdl.org/archive/ > > LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > > > _______________________________________________ > Address messages to ev@lists.evdl.org > No other addresses in TO and CC fields > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > ARCHIVE: http://www.evdl.org/archive/ > LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org > -------------- next part -------------- An HTML attachment was scrubbed... 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