openinverter forum

uhi22 wrote: ↑Wed Jan 22, 2025 10:01 am The wiki says that internal it has 16V. So it has a bidirectional DCDC converter. I assume it will not care whether it sees 13V, 14V or 15V externally, and just charge according its internal needs.

Edit: or, wait, do they have NO DCDC? Do they just connect the 4S directly to the cars 12V line?

Yes, there only 4s and bms that can disconnect battery.

Ahh, ok. This would mean the DCDC in the car should provide something between 15 and 16 V to have a halfway full battery. Or even slightly above 16V. Would need some tunable DCDC I guess.

uhi22 wrote: ↑Wed Jan 22, 2025 5:08 pm Ahh, ok. This would mean the DCDC in the car should provide something between 15 and 16 V to have a halfway full battery. Or even slightly above 16V. Would need some tunable DCDC I guess.

yes, i think tesla has them sit a 16v. seems most dcdc converters can happily do 16v so no issue there.

in the penthouse of a M3/Y, the PCS has a small constant HV supply. so even when the contactors are open, the PCS can keep the LV system happy/ LV battery charged.

m.art.y wrote: ↑Wed Jan 22, 2025 9:20 am
That single green comms wire is LIN? Does it only send soc and voltage data over it or does it needs some commands as well to balance etc? As far as I have seen tesla keeps those cells 80% charged so at ~3.88v. So with another dcdc converter for 12v lead batteries that charge to 13.6 -14v cell voltages should be lower so even less capacity? Thinking to use one but what would happen if the car is left for a while and parasitic drain would discharge it. Would it prevent itself from discharging too low and would it be possible to then simply recharge it or would it get locked?

no comms need to balance. that done internally.

the benefit of using one is that it shares its soc and voltage over lin. So you could have your VCU fire up the dcdc when the voltage drops below a certain threshold.

no need for an external LV battery monitor.

Bratitude wrote: ↑Wed Jan 22, 2025 5:38 pm the benefit of using one is that it shares its soc and voltage over lin. So you could have your VCU fire up the dcdc when the voltage drops below a certain threshold.

Yea but with the minimal stored energy it will be quite often, even with a standby current of some 200mA (Zombie does 150mA standby at the moment) you are already nearly at 5Ah a day. This means you need to wake up you HV supply every day to top up the battery. Plus you will need to figure out how much energy needs to be in the battery to allow it to do this in every scenario (mainly temperature).

Ofcourse you also need VCU logic to prevent the HV battery from draining too far itself.

tom91 wrote: ↑Wed Jan 22, 2025 5:52 pm Yea but with the minimal stored energy it will be quite often,...... you are already nearly at 5Ah a day. This means you need to wake up you HV supply every day to top up the battery. Plus you will need to figure out how much energy needs to be in the battery to allow it to do this in every scenario (mainly temperature).

Ofcourse you also need VCU logic to prevent the HV battery from draining too far itself.

its small capacity is not ideal, but a LV battery tending logic definitely is a valuable feature.

being most cars are used almost every day, or pluged in, this doesn't seem to be a huge issue.

6ah liion vs 45ah lead acid. 1 day vs 9 days till dead. ill trade that for the weight and size benefit.

what are you thoughts on long-term storage for an ev- should the LV system be fully disconnected?

Bratitude wrote: ↑Wed Jan 22, 2025 6:16 pm you thoughts on long-term storage

For any vehicle 12v should be disconnected. I tend to champion an +50Ah battery any day as most people can jump it or use a trickle charger on it.

Bratitude wrote: ↑Wed Jan 22, 2025 6:16 pm 1 day vs 9 days till dead

A factor of 9, with lower standby draw this becomes a difference of weeks quickly. So easily a win, for the lead acid, those 15-20 KG wont matter on anything but a racecar. Its peanuts compared to most of it.

Keep in mind any large loads (Powersteering, Powerbrakes, Fans/HVAC) I strongly prefer large 12V batteries, to stabilize the power peaks.

tom91 wrote: ↑Wed Jan 22, 2025 6:27 pm For any vehicle 12v should be disconnected. I tend to champion an +50Ah battery any day as most people can jump it or use a trickle charger on it.



A factor of 9, with lower standby draw this becomes a difference of weeks quickly. So easily a win, for the lead acid, those 15-20 KG wont matter on anything but a racecar. Its peanuts compared to most of it.

Keep in mind any large loads (Powersteering, Powerbrakes, Fans/HVAC) I strongly prefer large 12V batteries, to stabilize the power peaks.

true on the larger LV loads, maybe i am running to far in trying to simplify, and reduce parts.

do you use any IBS modules such as: https://www.hella.com/soe/en/Products/P ... /?pid=2501

Bratitude wrote: ↑Wed Jan 22, 2025 6:39 pm do you use any IBS modules such as: https://www.hella.com/soe/en/Products/P ... /?pid=2501

I looked into it before, in the end if you have a VCU you might as wel monitor the 12V battery via an ADC input directly. This way no need to program it and you can just measure it and set a threshold, or even have a simple separate device capable of waking the vcu.

Hi, not sure if this is the correct thread to ask, but I'm encountering an issue with my Model Y PCS/16V LV battery system. I connected an inverter to my PCS DCDC converter output terminals with proper precharge circuit and circuit breaker. The inverter system functions alright, providing power to my computer.

However, whenever I use my computer, which generates 100 - 350W load, the 16V li-ion battery would report cell imbalance, and triggers a warning on car computer for replacing LV battery. I went into service mode and saw that when my computer is on, the reported cell voltages have a 0.1-0.4v fluctuating imbalance. As soon as the load is gone, the cell voltages balance again to <0.05v imbalance.

Could someone help me understand what's causing this LV battery cell imbalance?

dimonlipko wrote: ↑Wed Jan 22, 2025 3:53 pm Yes, there only 4s and bms that can disconnect battery.

hello! how to erase crash data from BMS after read flash? at which addresses exactly???Battery Tesla 16V is bloked.Please!