Re: [EVDL] Leaf with interior fire, probably due to auxiliary battery extension in the trunk
I decided to remove the BMS from the water-logged Leaf battery pack to see what survived inside. Essentially nothing. Two of the sense connectors have several pins burned clear through apparently from the Leaf cells discharging into the BMS when the vehicle caught fire and the auxiliary battery pack shorted out, causing the BMS sense chips to blow up: every single one of the 24 sense chips has a crater in the chip where you can look inside to the silicon, that is how forceful of a short developed across each sense chip so one by one they blew up violently. My guess is that the pack (wiring?) opened under load so the full battery *negative* voltage appeared across one sense chip at a time, until it blew and shorted, causing a cascade of blowing chips. Due to this burning, the entire PCB is covered with a thick brown residue as a blanket, only outlines of components are visible. I might try to remove the memory chip to read its contents and see what it has stored, just for fun. Hopefully it survived the violence around it! Cor van de Water Chief Scientist Proxim Wireless office +1 408 383 7626Skype: cor_van_de_water XoIP +31 87 784 1130private: cvandewater.info http://www.proxim.com This email message (including any attachments) contains confidential and proprietary information of Proxim Wireless Corporation. If you received this message in error, please delete it and notify the sender. Any unauthorized use, disclosure, distribution, or copying of any part of this message is prohibited. -Original Message- From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Cor van de Water via EV Sent: Sunday, October 16, 2016 6:14 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Leaf with interior fire,probably due to auxiliary battery extension in the trunk Today I opened the battery pack of the Leaf to see how it held up when the vehicle above it was on fire. I now understand why the fire started in the auxiliary battery pack in the trunk. Believe it or not, it was caused by rainwater. Ironical as it is that a fire starts from rain water, I can come to no other conclusion. Or actually - it was caused by incorrect weather-proofing. See, the auxiliary battery was directly connected (cell-to-cell) by a 97 wire umbilical cord from the auxiliary pack in the trunk to the Leaf's battery pack. For that wire bundle, there was a 3" hole cut in the side of the Leaf's battery box under the car, close to the point where all BMS sense wires converge on the side of the box, very close to the rear tire. I found a layer of water inside the Leaf Battery box, heavy corrosion (so it was not from the last days or weeks, this has been going on for about a year at least) and a thick layer of white corrosion on the Alu BMS enclosure, it looked as if it was a cake with too much frosting. And lots of burned wires inside and a very unhealthy looking BMS and contactor set. In other words, the rain splashed up by the rear tire entered the battery box through the hole for the wiring (which did have weather-proofing on it, but it is extremely difficult to close such a big hole and so many wires) and it pooled inside, corroding everything and sloshing around until it destroyed enough of the BMS sensing circuits or wires that the BMS started to malfunction and something happened that started destroying the cells, either the BMS continued charging while some cells were already full, or the BMS allowed continued driving even though the cells were already empty or the owner noticed that the car would not charge somehow (because the BMS malfunctioned and would not allow charging) and he needed it, so he hooked up an external charger without the BMS protecting the now imbalanced pack, causing the fire when some cells were pushed way over their boundaries. The cells in the horizontal stack have a steel end plate with open frame across them. They looked like balloons, puffed up almost an inch in the middle, bending the end plate and stretching things to the breaking point. I made sure to put the battery box cover back on and re-engage all bolts, so that if corrosion and stress causes bolts to break and nuts to become projectiles, at least they will be caught by the sheet steel of the box. I originally opened the box in hopes to at least salvage the BMS and other parts and then see if the cells would be able to be revived, but the interior of the Leaf Battery box looked pretty hopeless. So - a warning to all who use a Leaf (or other) BMS with their cells: These computers are *not* able to withstand outside environment, they are not water-proofed as they are completely weather-protected inside the Leaf battery box. Also, there is close to 400VDC present across the PCB (printed circuit board), so any moisture in the BMS will cause serious leakage currents, which cause migration and deposit of metal, which causes short circuits across the PCB, resulting in the moisture being the
Re: [EVDL] Leaf with interior fire, probably due to auxiliary battery extension in the trunk
Today I opened the battery pack of the Leaf to see how it held up when the vehicle above it was on fire. I now understand why the fire started in the auxiliary battery pack in the trunk. Believe it or not, it was caused by rainwater. Ironical as it is that a fire starts from rain water, I can come to no other conclusion. Or actually - it was caused by incorrect weather-proofing. See, the auxiliary battery was directly connected (cell-to-cell) by a 97 wire umbilical cord from the auxiliary pack in the trunk to the Leaf's battery pack. For that wire bundle, there was a 3" hole cut in the side of the Leaf's battery box under the car, close to the point where all BMS sense wires converge on the side of the box, very close to the rear tire. I found a layer of water inside the Leaf Battery box, heavy corrosion (so it was not from the last days or weeks, this has been going on for about a year at least) and a thick layer of white corrosion on the Alu BMS enclosure, it looked as if it was a cake with too much frosting. And lots of burned wires inside and a very unhealthy looking BMS and contactor set. In other words, the rain splashed up by the rear tire entered the battery box through the hole for the wiring (which did have weather-proofing on it, but it is extremely difficult to close such a big hole and so many wires) and it pooled inside, corroding everything and sloshing around until it destroyed enough of the BMS sensing circuits or wires that the BMS started to malfunction and something happened that started destroying the cells, either the BMS continued charging while some cells were already full, or the BMS allowed continued driving even though the cells were already empty or the owner noticed that the car would not charge somehow (because the BMS malfunctioned and would not allow charging) and he needed it, so he hooked up an external charger without the BMS protecting the now imbalanced pack, causing the fire when some cells were pushed way over their boundaries. The cells in the horizontal stack have a steel end plate with open frame across them. They looked like balloons, puffed up almost an inch in the middle, bending the end plate and stretching things to the breaking point. I made sure to put the battery box cover back on and re-engage all bolts, so that if corrosion and stress causes bolts to break and nuts to become projectiles, at least they will be caught by the sheet steel of the box. I originally opened the box in hopes to at least salvage the BMS and other parts and then see if the cells would be able to be revived, but the interior of the Leaf Battery box looked pretty hopeless. So - a warning to all who use a Leaf (or other) BMS with their cells: These computers are *not* able to withstand outside environment, they are not water-proofed as they are completely weather-protected inside the Leaf battery box. Also, there is close to 400VDC present across the PCB (printed circuit board), so any moisture in the BMS will cause serious leakage currents, which cause migration and deposit of metal, which causes short circuits across the PCB, resulting in the moisture being the cause of the failure of the cells that the BMS needs to protect. In this case, even resulting in fire in the vehicle as well as burned wiring in the Leaf Battery box, besides the corrosion due to the presence of water. Cor van de Water Chief Scientist Proxim Wireless office +1 408 383 7626Skype: cor_van_de_water XoIP +31 87 784 1130private: cvandewater.info http://www.proxim.com This email message (including any attachments) contains confidential and proprietary information of Proxim Wireless Corporation. If you received this message in error, please delete it and notify the sender. Any unauthorized use, disclosure, distribution, or copying of any part of this message is prohibited. _ From: Cor van de Water Sent: Friday, October 14, 2016 6:00 PM To: 'Electric Vehicle Discussion List' Subject: Leaf with interior fire, probably due to auxiliary battery extension in the trunk I saw a burned-out Leaf in a tow yard and asked what caused the interior fire (The contents of the motor bay are fine, so if anyone is interested in a 2011 Leaf motor, inverter, front suspension, brake controller, ..., then let me know! The front bumper and radiators and lights are gone.) It had an after-market secondary battery pack added in the trunk, probably by a hobbyist or someone building a prototype. There was a 97 wire loom coming out of the Leaf battery pack that fed into the auxiliary pack in the trunk, plus two high voltage/high current wires for the power. The auxiliary pack consisted of 18650 style cells in a wooden box in the trunk. The maker of this FrankenLeaf apparently wanted to avoid a BMS for the aux pack and thus wired all the Aux cells in parallel to the Leaf's 96 cell series string. My strong suspicion is that the failure
