Contactor control during charging/driving

Post Reply
nilsvr
Posts: 43
Joined: Fri Mar 18, 2022 9:49 pm
Location: Germany
Has thanked: 1 time
Been thanked: 3 times

Contactor control during charging/driving

Post by nilsvr »

Hello,

I have not started any work on my tesla Gen 2 charger yet but already have a „problem“.
My plan was to connect my BMW I3 battery with the OEM BMW contactors in line to the Tesla Model S rear HV junction box. Said junction box seemed like a nobrainer for me since it has the fuses and connections for the Gen 2 charger and LDU (also the possibility for dc fast charging if I ever want to experiment with that).
In my planned configuration (Battery + contactors in the front and Charger + junction box + motor in the back) the charger now would sit way behind the contactors (just as it would do in a Tesla or BMW as I suppose).
Now to the problem: I planned on having the LDU control the contactors instead of my SimpBMS (to protect the inverter? Is that necessary?) but how would i then ever get the contactors to close when not having the key in the ignition/the LDU in its idle state?

tl;dr
I kind of want the LDU to keep control of the contactors for start up and driving but need the SimpBMS to handle them during charging… what is the solution?

I also would appreciate just a schematic or explanation of your HV setups even if they offer no solution to my problem.

Best regards
User avatar
elShankos
Posts: 43
Joined: Thu Jun 30, 2022 9:17 am
Location: Cape Town
Has thanked: 25 times
Been thanked: 5 times

Re: Contactor control during charging/driving

Post by elShankos »

Hi there,

I seem to be where you were a little while back perhaps. I have a Tesla SDU + GEN2 Charger arrangement and contactors but I'm not sure how to "manage" the switching of the contactors - i.e. when you want to charge then the SDU inverter shouldn't see main voltage from the pack right? I have most of my kit and and starting the conversion process but this is the biggest bit that I haven't figured out yet...
I wonder what you came up with as a solution?

Thanks!
User avatar
johu
Site Admin
Posts: 5683
Joined: Thu Nov 08, 2018 10:52 pm
Location: Kassel/Germany
Has thanked: 153 times
Been thanked: 960 times
Contact:

Re: Contactor control during charging/driving

Post by johu »

Contactors are low side driven, i.e. pulled to ground by a switch in the inverter or simpbms. You could just hook them up in parallel. If either of the two wants them to close, they close (wired or)

The reason we don't recommend the BMS to run the switches alone is you don't want them to open for some stupid reason while driving. Depending on the logic of SimpBMS that might not happen anyway. Tom would have to chime in on that.
Support R/D and forum on Patreon: https://patreon.com/openinverter - Subscribe on odysee: https://odysee.com/@openinverter:9
tom91
Posts: 1273
Joined: Fri Mar 01, 2019 9:15 pm
Location: Bristol
Has thanked: 97 times
Been thanked: 201 times

Re: Contactor control during charging/driving

Post by tom91 »

Contacts should be switched by what ever is responsible for the Battery safety. So it only cares about the batteries and shuts the contactors only when the batteries are within operational conditions. If a serious error occurs it should disconnect the pack, this can end up damaging certain inverters that cannot dissipate energy in collapsing magnetic/spinning fields.

If you have a BMS system (SimpBMS / EVS-BMS / Other) the "easiest" way to do it is have the BMS do the contactors. If you want to not have the batteries disconnect during an error you can have the inverter control them or even have a stand alone way of controlling contactors. This then means you are fully responsible for keeping the batteries in their operating conditions (you are anyway since you are designing building and programming your conversion).
Founder Volt Influx https://www.voltinflux.com/
User avatar
elShankos
Posts: 43
Joined: Thu Jun 30, 2022 9:17 am
Location: Cape Town
Has thanked: 25 times
Been thanked: 5 times

Re: Contactor control during charging/driving

Post by elShankos »

johu wrote: Fri Dec 30, 2022 10:03 am Contactors are low side driven, i.e. pulled to ground by a switch in the inverter or simpbms. You could just hook them up in parallel. If either of the two wants them to close, they close (wired or)

The reason we don't recommend the BMS to run the switches alone is you don't want them to open for some stupid reason while driving. Depending on the logic of SimpBMS that might not happen anyway. Tom would have to chime in on that.
Thanks very much for the reply. I got my SDU board the other day - thanks! I think maybe I should draw a diagram of my quandary but maybe I can explain quickly:

I was interested in the scenario of when the vehicle is at rest and you want to charge: so starting up the charger to spit out 400V but the contactors are open.
I assume when you park the car and switch off the ignition here there the contactors will open:
image.png
So how to get them to close so that the pack can be charged? And then when they do close then the inverter will see 400V straight onto its bus unless there is a pre-charge cycle before the charging can begin?

I was also wondering if there is a way for the SDU to receive a signal (emergency stop (pull out stop button on the dashboard type arrangement) or from the BMS) to then shut down safely?
I think I understand your suggestion for having the BMS OR the SDU close the contactors so thanks for that.

I promise I have been trawling through a lot of info for many months and I really hope I'm not asking silly questions!
User avatar
elShankos
Posts: 43
Joined: Thu Jun 30, 2022 9:17 am
Location: Cape Town
Has thanked: 25 times
Been thanked: 5 times

Re: Contactor control during charging/driving

Post by elShankos »

tom91 wrote: Fri Dec 30, 2022 10:57 am Contacts should be switched by what ever is responsible for the Battery safety. So it only cares about the batteries and shuts the contactors only when the batteries are within operational conditions. If a serious error occurs it should disconnect the pack, this can end up damaging certain inverters that cannot dissipate energy in collapsing magnetic/spinning fields.

If you have a BMS system (SimpBMS / EVS-BMS / Other) the "easiest" way to do it is have the BMS do the contactors. If you want to not have the batteries disconnect during an error you can have the inverter control them or even have a stand alone way of controlling contactors. This then means you are fully responsible for keeping the batteries in their operating conditions (you are anyway since you are designing building and programming your conversion).
Thanks very much for taking the time to reply. It makes complete sense for the BMS to be able to open the HV circuit in an emergency scenario - I have a hybrid PV system with Lifepo4 batteries and a DALY BMS which I built and this is how it works - sometimes you can have a single cell out of balance and then during charging it's voltage can climb way up while the overall pack voltage actually looks fine. So I have some experience of this kind of arrangement.

Anyway I guess I am trying to figure out the best way to get the BMS + SDU+IO board + charging integrated without creating too complicated a system as I'm not a programmer (unfortunately).

There is almost no charging network here in South Africa (and probably will be limited for a long time to come) and so I'm not planning any DC fast charging or anything - just slow, basic charging at home off the PV system (loads of sun!).

I made a post about my conversion here in case you would like to take a look:
https://www.diyelectriccar.com/threads/ ... on.208076/

Thanks very much again for taking the time to respond!
User avatar
elShankos
Posts: 43
Joined: Thu Jun 30, 2022 9:17 am
Location: Cape Town
Has thanked: 25 times
Been thanked: 5 times

Re: Contactor control during charging/driving

Post by elShankos »

elShankos wrote: Sun Jan 01, 2023 2:29 pm Thanks very much for taking the time to reply. It makes complete sense for the BMS to be able to open the HV circuit in an emergency scenario - I have a hybrid PV system with Lifepo4 batteries and a DALY BMS which I built and this is how it works - sometimes you can have a single cell out of balance and then during charging it's voltage can climb way up while the overall pack voltage actually looks fine. So I have some experience of this kind of arrangement.

Anyway I guess I am trying to figure out the best way to get the BMS + SDU+IO board + charging integrated without creating too complicated a system as I'm not a programmer (unfortunately).

There is almost no charging network here in South Africa (and probably will be limited for a long time to come) and so I'm not planning any DC fast charging or anything - just slow, basic charging at home off the PV system (loads of sun!).

I made a post about my conversion here in case you would like to take a look:
https://www.diyelectriccar.com/threads/ ... on.208076/

Thanks very much again for taking the time to respond!
I'm slowly figuring things out from the SimpBMS manual:
image.png
I also just found a CAB500 sensor on eBay for on $60! So hopefully it works.
Then I found some Teensy3.2s on eBay as well as no-one seems to have the actual full SimpBMS available so I will see if I can get it together...

I was trying to avoid all the heavy costs of an Orion BMS.
nilsvr
Posts: 43
Joined: Fri Mar 18, 2022 9:49 pm
Location: Germany
Has thanked: 1 time
Been thanked: 3 times

Re: Contactor control during charging/driving

Post by nilsvr »

Since I am currently seperated from my beloved project back in my parents garage due to university far away, I just continued the thinking part of this problem.
I found multiple solutions that all have their specific flaws:



1) Charger directly connected to Battery, Motor connected via (inverter controlled) contactors.
  • + Vehicle can charge while ignition is turned off
  • - Vehicle can drive away while plugged in (not allowed in Germany)(solvable by inhibiting the power to the gear selector or something
    similar while cahrging)
  • - Need extra HV cables (almost full length of the car) for connecting the charger

2) Charger and Motor behind (inverter controlled) contactors.
  • + In my case the most elegant HV wiring setup (one pair of cables from battery to contactors then to OEM HV junction box and splitting off into motor and charger (right next to each other in the rear of the car, just as intended by Elon)
  • - you have to leave your key in the car for charging... not good
  • - the inverter is fully turned on while charging, just not in drive (not very well informed on that topic but feels like that would cause unnecessary wear

3) Charger and Motor behind (simpBMS controlled) contactors.
  • + Battery is nice and protected (but i am already only waiting for my car running and then an excuse to swap my 21kWh BMW I3 batteries for something bigger anyways...)
  • - Possibly frying the inverter due to contactors opening for battery protection (LDU in Germany basically unobtanium rn, so big no no)

4) Charger and Motor behind (parallel controlled (logic OR)) contactors.
  • + same elegant HV wiring as option 2)
  • - again not very well informed here: during charging the ignition could stay turned off (if simpBMS gets permanent 12V), but that would mean the (turned off) Inverter sees full voltage. Not sure if it cares but i can imagine that this situation is suboptimal for the inverter. But I am very open to correction on that.
  • - same goes for the startup of the car (only if still plugged in). The contactors are already closed with full voltage at the inverter, then ignition turns on the inverter -> inverter might not like or maybe doesnt care...i dont know


Right now i am, due to my low amount of knowledge on what inverters like and what they dont like (and low motivation to learn that by breaking my stuff), drawn to option 1).
The "suboptimal" double pair of HV cables running along the car is really not much more than a tiny inconvinience while building and a small to medium dent in my engineering heart.

If option 4) gets cleared by somebody with a lot more knowledge on inverters I would be happy to do the (unproportional) amount of extra 12V wiring work to save a few meters of visible HV cables.
User avatar
johu
Site Admin
Posts: 5683
Joined: Thu Nov 08, 2018 10:52 pm
Location: Kassel/Germany
Has thanked: 153 times
Been thanked: 960 times
Contact:

Re: Contactor control during charging/driving

Post by johu »

Keeping the inverter energized won't hurt it. The LDU has some active discharge circuit that seems active while the inverter is unpowered (12V) so that'll burn off a few Watts.
Support R/D and forum on Patreon: https://patreon.com/openinverter - Subscribe on odysee: https://odysee.com/@openinverter:9
User avatar
muehlpower
Posts: 570
Joined: Fri Oct 11, 2019 10:51 am
Location: Germany Fürstenfeldbruck
Has thanked: 12 times
Been thanked: 96 times

Re: Contactor control during charging/driving

Post by muehlpower »

A topic that also concerns me. Here is my current status again. The idea behind this is few, manageable contactors. There is only HV or no HV. Perhaps someone can confirm here that it is not a problem if the drive unit (tesla LDU) is supplied with HV when charging and the charger (tesla gen3) when driving. At least that's how it is with the Model 3. The 12V are switched off. (LDU at charging no 12V, Charger
at driving no 12V)
HV Schaltbild.png
nilsvr
Posts: 43
Joined: Fri Mar 18, 2022 9:49 pm
Location: Germany
Has thanked: 1 time
Been thanked: 3 times

Re: Contactor control during charging/driving

Post by nilsvr »

muehlpower wrote: Wed Jan 25, 2023 10:11 pm At least that's how it is with the Model 3. The 12V are switched off. (LDU at charging no 12V, Charger at driving no 12V).
I feel/think the same, looking at OEM hardware they all (i think) just use one set of contactors to cut the battery off for all HV components at the same time.

To repeat your question:
Do we get the OK to run HV into a

turned off (no 12V) LDU/SDU(/generic) inverter,
turned off (no 12V) gen2/gen3/PCS(/generic) charger and
turned off (no 12V) model-s(/generic) dcdc converter?

I will mark all systems that dont care about HV while turned off green and all that dont like it red.

The list can be expanded if you have more parts where you (dont) know that they (dont) work.

Of course the whole list is kind of useless if all HV parts survive HV while being turned of. But I dont know that (yet).
User avatar
muehlpower
Posts: 570
Joined: Fri Oct 11, 2019 10:51 am
Location: Germany Fürstenfeldbruck
Has thanked: 12 times
Been thanked: 96 times

Re: Contactor control during charging/driving

Post by muehlpower »

I have supplied all my devices with HV, without 12V. So far no problems. However, as johannes noticed, it may be that I have small losses at the expense of efficiency. Of course, you also have to note that the route via precharge is always taken and that all devices are at zero power until the main contactor is closed. In my case, this is ensured via CAN / LIN signals and enable lines.

it also seems useful to run the DC/DC converter in both cases, since there is also a 12V consumption when charging. Water pumps and fans for battery cooling are also useful for fast charging and consume a lot of 12V power.
nilsvr
Posts: 43
Joined: Fri Mar 18, 2022 9:49 pm
Location: Germany
Has thanked: 1 time
Been thanked: 3 times

Re: Contactor control during charging/driving

Post by nilsvr »

Good to know that all your (and probably everybody elses) parts survived HV while being turned off.

To go a little more into detail with your setup:

What BMS do you use? (all those question kind of only make sense if you use simpBMS or something similar capable of more than only balancing)
Does you BMS have permanent 12V or gets turned on with the ignition?
Do you already have a running setup with "parallel" contactor control by the inverter and the bms?
If yes or it is in planning rn. How will the BMS know to start the precharge for charging. (could one use the PP (proximity pilot) of the charging cable as "key on"?)
User avatar
elShankos
Posts: 43
Joined: Thu Jun 30, 2022 9:17 am
Location: Cape Town
Has thanked: 25 times
Been thanked: 5 times

Re: Contactor control during charging/driving

Post by elShankos »

nilsvr wrote: Wed Jan 25, 2023 9:30 pm Since I am currently seperated from my beloved project back in my parents garage due to university far away, I just continued the thinking part of this problem.
I found multiple solutions that all have their specific flaws:



1) Charger directly connected to Battery, Motor connected via (inverter controlled) contactors.
  • + Vehicle can charge while ignition is turned off
  • - Vehicle can drive away while plugged in (not allowed in Germany)(solvable by inhibiting the power to the gear selector or something
    similar while cahrging)
  • - Need extra HV cables (almost full length of the car) for connecting the charger

2) Charger and Motor behind (inverter controlled) contactors.
  • + In my case the most elegant HV wiring setup (one pair of cables from battery to contactors then to OEM HV junction box and splitting off into motor and charger (right next to each other in the rear of the car, just as intended by Elon)
  • - you have to leave your key in the car for charging... not good
  • - the inverter is fully turned on while charging, just not in drive (not very well informed on that topic but feels like that would cause unnecessary wear

3) Charger and Motor behind (simpBMS controlled) contactors.
  • + Battery is nice and protected (but i am already only waiting for my car running and then an excuse to swap my 21kWh BMW I3 batteries for something bigger anyways...)
  • - Possibly frying the inverter due to contactors opening for battery protection (LDU in Germany basically unobtanium rn, so big no no)

4) Charger and Motor behind (parallel controlled (logic OR)) contactors.
  • + same elegant HV wiring as option 2)
  • - again not very well informed here: during charging the ignition could stay turned off (if simpBMS gets permanent 12V), but that would mean the (turned off) Inverter sees full voltage. Not sure if it cares but i can imagine that this situation is suboptimal for the inverter. But I am very open to correction on that.
  • - same goes for the startup of the car (only if still plugged in). The contactors are already closed with full voltage at the inverter, then ignition turns on the inverter -> inverter might not like or maybe doesnt care...i dont know


Right now i am, due to my low amount of knowledge on what inverters like and what they dont like (and low motivation to learn that by breaking my stuff), drawn to option 1).
The "suboptimal" double pair of HV cables running along the car is really not much more than a tiny inconvinience while building and a small to medium dent in my engineering heart.

If option 4) gets cleared by somebody with a lot more knowledge on inverters I would be happy to do the (unproportional) amount of extra 12V wiring work to save a few meters of visible HV cables.
Hi, so I also started out with my idea being around 1) above. I.e. to keep HV away from the inverter when charging but then I didn't have pre-charge on the auxiliaries and more contactors and HV wiring and it seems like its fine to put HV on the inverter when its not doing anything (charging). My Rev 3 diagram in my build post here is like your 1) arrangement: viewtopic.php?p=52044#p52044
image.png
image.png (90.69 KiB) Viewed 1021 times
So now I've moved onto my next idea which is to use a rear Gen 2 HV JB and just link in the rear charger there so more like your 4) here above but with a "charge switch" on the dash somewhere and hopefully more in line with what Johannes was saying above as well. Like you mentioned this has more 12V wiring etc but less HV wiring. This is shown on my REV 4 diagram here: viewtopic.php?p=52121#p52121
Options 2 and 4 are like you said : more like Elon intended :D
image.png
image.png (111.49 KiB) Viewed 1021 times
I also have a Tesla charge port and cables etc - got them at short notice for cheap in the US so I want to try and use them - and they will tie in naturally to the Gen2 Rear JB.

Thanks for the input and it would be good to hear what your latest thoughts are on the various arrangements :)
nilsvr
Posts: 43
Joined: Fri Mar 18, 2022 9:49 pm
Location: Germany
Has thanked: 1 time
Been thanked: 3 times

Re: Contactor control during charging/driving

Post by nilsvr »

Your rev 4 looks a lot how i was planning on doing mine. The only difference is that i would prefer to keep my contactors groundswitched directly by the OI and the simpBMS for simplicity.
I have contactors out of an I3 (that should be fine without an economizer circuit) and Tesla Model S contactors that should need an economizer circuit.
I do not fully understand the setup of all the relais in front of your contactors.

My problem is that the simpBMS seems to only have a 12v switched output for the precharge, but i guess that would not be too complicated to switch over to groundswitched with the help of a relay.

As much as I like tinkering and problemsolving, I am not looking forward to designing a PCB for all of this wiring spaghetti to plug into…
nilsvr
Posts: 43
Joined: Fri Mar 18, 2022 9:49 pm
Location: Germany
Has thanked: 1 time
Been thanked: 3 times

Re: Contactor control during charging/driving

Post by nilsvr »

Ok so I asked in the simpBMS subforum if my ground switched OR configuration is doable with the simpBMS and the only compromise I have to take seems to be a single additional relay to swap the 12v precharge signal to a "ground signal". Main and negative contactor signals are available as both ground and 12v switched.
Post Reply