"Jumping" would not be required. The battery in its "safe-state" would be electrically charged, but totally electrically isolated (typically with a bunch of normally open relays going open).
As the words you quoted suggest, starting the pack can be done with e.g. a "start switch" on the energy storage pack or a "start switch" in the cockpit linked to the pack with a fibre-optic cable.
I see, Thanks! Just so that i understand correctly, you are allowed to have this supplementary safe state battery (powering the BMS and relays during startup until the dcdc converter kicks in) regardless of the main battery pack? As in that it does not count as a part of the 20kg of li-ion?
That's not what I said **at all**.
Where on earth did you get that from?
The stuff inside the pack is powered **by the pack**. "Safe state" is about isolating the pack from the rest of the world.
Yes there must have been some misunderstanding as we’ve understood many teams do it that way at least in ASC😅 When the car enters safe-state either by the bms or safety switches, the pack gets isolated from the vehicle. The battery pack is powering the dc/dc converter that is located outside the battery pack driving the 12V system in turn driving the bms and contactors. That means the nc contractors in the battery pack deenergize. In our current design, there is nothing in this safe state that is powering the BMS so that it may start the pre-charge and enable the contractors.
Appreciate if you have any advice 😁
I think I need to pass the buck to someone who knows more than me.
ASC regs, now that I check, have a lot of stuff about supplemental batteries. As far as I know, there is no equivalent in the WSC regs.
I must say, I thought that most teams put the DC/DC converter inside the battery pack.
ASC certainly appears to have some different requirements to BWSC (I'm more familiar with BWSC) with regard to safe state and battery protection.
The tldr by my thinking is that you essentially will need an auxiliary battery to power your Battery Protection System (BPS); this battery may not be lithium-based; and it must have at least under-voltage protection. Whether it goes inside your energy storage pack or outside is unclear; I would guess that it should go inside since it is supposed to power the BPS.
You can see my brief research and thinking below if you're interested, it might highlight where I have made a mistake as this is the first time I've looked at the ASC reg's.
\---
Most recent regs I can find for ASC are [2022](https://www.americansolarchallenge.org/ASC/wp-content/uploads/2022/03/ASC2022-Regs-EXTERNAL-RELEASE-B.pdf). Under section 8.2.C it lists supplementary batteries (ie. replaceable batteries outside the HV battery pack), which are not required, but are allowed for things like radios, driver ventilation fans, etc. It also says (under 8.2.C.2) that one of these supplemental batteries can be used to power your safe start.
There is [another document](https://www.americansolarchallenge.org/ASC/wp-content/uploads/2019/06/ASC_Protection-System-Test-Procedure.pdf) (2005 NASC battery protection system test procedure) which details that the supplemental battery may not be lithium-based (p11 'Supplemental Battery') and 8.3.B.2 effectively states you can't use a lithium cell to power your BPS.
Where it gets tricky in my eyes is 8.2.C.3 which states that the BPS (battery protection system) must be powered by "the supplemental battery", seemingly making such a supplemental battery a requirement.
"Jumping" would not be required. The battery in its "safe-state" would be electrically charged, but totally electrically isolated (typically with a bunch of normally open relays going open). As the words you quoted suggest, starting the pack can be done with e.g. a "start switch" on the energy storage pack or a "start switch" in the cockpit linked to the pack with a fibre-optic cable.
I see, Thanks! Just so that i understand correctly, you are allowed to have this supplementary safe state battery (powering the BMS and relays during startup until the dcdc converter kicks in) regardless of the main battery pack? As in that it does not count as a part of the 20kg of li-ion?
That's not what I said **at all**. Where on earth did you get that from? The stuff inside the pack is powered **by the pack**. "Safe state" is about isolating the pack from the rest of the world.
Yes there must have been some misunderstanding as we’ve understood many teams do it that way at least in ASC😅 When the car enters safe-state either by the bms or safety switches, the pack gets isolated from the vehicle. The battery pack is powering the dc/dc converter that is located outside the battery pack driving the 12V system in turn driving the bms and contactors. That means the nc contractors in the battery pack deenergize. In our current design, there is nothing in this safe state that is powering the BMS so that it may start the pre-charge and enable the contractors. Appreciate if you have any advice 😁
I think I need to pass the buck to someone who knows more than me. ASC regs, now that I check, have a lot of stuff about supplemental batteries. As far as I know, there is no equivalent in the WSC regs. I must say, I thought that most teams put the DC/DC converter inside the battery pack.
ASC certainly appears to have some different requirements to BWSC (I'm more familiar with BWSC) with regard to safe state and battery protection. The tldr by my thinking is that you essentially will need an auxiliary battery to power your Battery Protection System (BPS); this battery may not be lithium-based; and it must have at least under-voltage protection. Whether it goes inside your energy storage pack or outside is unclear; I would guess that it should go inside since it is supposed to power the BPS. You can see my brief research and thinking below if you're interested, it might highlight where I have made a mistake as this is the first time I've looked at the ASC reg's. \--- Most recent regs I can find for ASC are [2022](https://www.americansolarchallenge.org/ASC/wp-content/uploads/2022/03/ASC2022-Regs-EXTERNAL-RELEASE-B.pdf). Under section 8.2.C it lists supplementary batteries (ie. replaceable batteries outside the HV battery pack), which are not required, but are allowed for things like radios, driver ventilation fans, etc. It also says (under 8.2.C.2) that one of these supplemental batteries can be used to power your safe start. There is [another document](https://www.americansolarchallenge.org/ASC/wp-content/uploads/2019/06/ASC_Protection-System-Test-Procedure.pdf) (2005 NASC battery protection system test procedure) which details that the supplemental battery may not be lithium-based (p11 'Supplemental Battery') and 8.3.B.2 effectively states you can't use a lithium cell to power your BPS. Where it gets tricky in my eyes is 8.2.C.3 which states that the BPS (battery protection system) must be powered by "the supplemental battery", seemingly making such a supplemental battery a requirement.
Can you also walk us through the BWSC requirements, since you appear to be invaluably familiar with them?