Tesla SDU capacitor size / precharge
Tesla SDU capacitor size / precharge
I have put this question in the getting started section as I didn’t want to clutter the Tesla board.
Despite extensive googling and searching this forum and others I cannot find what Value capacitors are in the SDU I’m trying to calculate what value precharge resistor I need with a volt battery to get a precharge around 4.5 seconds.
From my searches it appears you can throw in roughly 30 - 100 ohm and it won’t cause any issues?
But I’d like to try to do things properly and get as longer charge time as possible if I can.
Despite extensive googling and searching this forum and others I cannot find what Value capacitors are in the SDU I’m trying to calculate what value precharge resistor I need with a volt battery to get a precharge around 4.5 seconds.
From my searches it appears you can throw in roughly 30 - 100 ohm and it won’t cause any issues?
But I’d like to try to do things properly and get as longer charge time as possible if I can.
Re: Tesla SDU capacitor size / precharge
If you use same as Tesla does, it should be properly? I my model S pack it was 23ohm.
Have used 50ohm myself (50W)
Have used 50ohm myself (50W)
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Re: Tesla SDU capacitor size / precharge
I'm running a Leaf precharge resistor with my SDU - 40 ohm IIRC, precharges pretty darn fast.
Why do you prefer a long charge time?
Why do you prefer a long charge time?
Re: Tesla SDU capacitor size / precharge
Thank you for the info
I think it will be more or less correct, but Tesla batteries are a slightly lower peak voltage than the Vauxhall’s so the delta across the contactor would also be bigger, however I don’t know how much of an effect that will have on the current hitting the capacitors .
Thanks for the help
I gather that it’s the inrush of current which can damage the Capacitors, by extending the time I think I also lower the current? Therefore extend the lifetime or mitigate the risk to the capacitors.
I may tune it down if the 5 seconds annoys me, but certainly to start with I am happy being cautious if it stops me popping a motor.
But I actually know so little it’s scary I’m reading and learning as much as I can but there are a lot of gaps
Re: Tesla SDU capacitor size / precharge
The main reason for precharge is to save the main contactor, and the resistor have to be big enough to prevent precharge relay arcing/burn.
Thomas A. Edison “I have not failed. I've just found 10,000 ways that won't work"
Re: Tesla SDU capacitor size / precharge
Thank you yea that makes sense.
I have read about inrush current to capacitors being a problem? But i only ever hear it mentioned in relation to inverters? Am I hunting capacitor values which don’t exist?
Re: Tesla SDU capacitor size / precharge
The panasonic capacitors are marked 430V 150uF x3
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Re: Tesla SDU capacitor size / precharge
So in the 75kWh pack =>
14modules * 25.2Vmax per module = 352.8Vmax per pack
Imax = 352.8V / 23ohm = 15.34A
So the the pre-charge contactor would just need to handle 15.3A peak. Correct?
Re: Tesla SDU capacitor size / precharge
Yes, looks sane to me. If the capasitors is seen as full short?alexbeatle wrote: ↑Tue Jun 28, 2022 7:15 am
So in the 75kWh pack =>
14modules * 25.2Vmax per module = 352.8Vmax per pack
Imax = 352.8V / 23ohm = 15.34A
So the the pre-charge contactor would just need to handle 15.3A peak. Correct?
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Re: Tesla SDU capacitor size / precharge
I haven't measured the capacitance, but I am precharging my SDU through a 25R resistor. That's a 12A peak current. I'm charging through a contactor rated for 10A continuous, 30A peak.
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Re: Tesla SDU capacitor size / precharge
That would be the nature of the capacitor under DC - short when fully discharged, open when fully chargedjoromy wrote: ↑Wed Jul 06, 2022 6:02 pmYes, looks sane to me. If the capasitors is seen as full short?alexbeatle wrote: ↑Tue Jun 28, 2022 7:15 am
So in the 75kWh pack =>
14modules * 25.2Vmax per module = 352.8Vmax per pack
Imax = 352.8V / 23ohm = 15.34A
So the the pre-charge contactor would just need to handle 15.3A peak. Correct?
Re: Tesla SDU capacitor size / precharge
Hi,
I am learning about this topic, i wanted to understand if it is an electrolytic capacitor?
Thanks
I am learning about this topic, i wanted to understand if it is an electrolytic capacitor?
Thanks
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Re: Tesla SDU capacitor size / precharge
Only film caps are used nowadays for better reliability. Capacity is not important, ripple current rating is. And that is always quite poor for elcaps.
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