Failing to precharge

Post Reply
ev340
Posts: 39
Joined: Sat Mar 20, 2021 12:06 pm

Failing to precharge

Post by ev340 »

My dumb arse can’t figure out why...

I was able to successfully precharge twice, I then made a HV box with much thicker wires. And the first time I tried to precharge it blew up the resistor I had been using.
I then used a kettle and it still fails to close the main contactor. (But it boiled the water so it was working)
It just opens the precharge one after 5 seconds.

I’m using a Vauxhall ampere battery, at 362v at the moment.
And a Tesla SDU.

My parameters are in the screenshots I couldn’t get them off the inverter on my phone.

The error code is 500 Precharge stopped.
Attachments
FD526C3F-E365-4CD5-B7CB-D818AEFF8D15.png
12B194A9-0695-4D68-9BE9-27C655D00C71.png
138C6C9F-CB7D-47EE-9BB6-D449F7078D29.png
arber333
Posts: 3241
Joined: Mon Dec 24, 2018 1:37 pm
Location: Slovenia
Has thanked: 74 times
Been thanked: 223 times
Contact:

Re: Failing to precharge

Post by arber333 »

ev340 wrote: Sat Jan 01, 2022 1:46 pm My dumb arse can’t figure out why...

I was able to successfully precharge twice, I then made a HV box with much thicker wires. And the first time I tried to precharge it blew up the resistor I had been using.
Do you have a DCDC converter or similar load connected AFTER precharge/contactor? In that case DCDC would pull current through resistor and voltage would never reach DCSW parameter. If you have Ampera battery you may want to use its precharge resistor and additional contactor for DCDC :).

Or like me, connect it directly to DC link via a 30A fuse. BUT then in the case of servicing HV you need to either disconnect battery in the middle or pull DCDCs HV connector - for safety.
ev340
Posts: 39
Joined: Sat Mar 20, 2021 12:06 pm

Re: Failing to precharge

Post by ev340 »

arber333 wrote: Sat Jan 01, 2022 2:53 pm
Do you have a DCDC converter or similar load connected AFTER precharge/contactor? In that case DCDC would pull current through resistor and voltage would never reach DCSW parameter. If you have Ampera battery you may want to use its precharge resistor and additional contactor for DCDC :).

Or like me, connect it directly to DC link via a 30A fuse. BUT then in the case of servicing HV you need to either disconnect battery in the middle or pull DCDCs HV connector - for safety.
Hey arber! Thank you! That makes sense!

There isn’t anything attached on the other side, I’m just testing it right now. So negative is directly from battery to motor, positive is through a contractor and precharge.

I am using a 20ohm kettle element, so would have thought it would reach udcsw (which I’m assuming is the same thing as DCSW?)

You have however given me the idea to monitor the voltage across there to see if it reaches it.

I’ll put my brave pants on and go and investigate!

I’m not keen to lower the udcsw value too far but I guess that would be a workaround temporarily?
User avatar
Peter
Posts: 310
Joined: Fri Dec 14, 2018 9:07 pm
Location: North West Lancs, UK
Been thanked: 8 times

Re: Failing to precharge

Post by Peter »

Does the SDU have reverse polarity protection, i.e. a diode ? Could you have the wiring reversed to SDU after your HV box build ?
ev340
Posts: 39
Joined: Sat Mar 20, 2021 12:06 pm

Re: Failing to precharge

Post by ev340 »

Peter wrote: Sat Jan 01, 2022 3:12 pm Does the SDU have reverse polarity protection, i.e. a diode ? Could you have the wiring reversed to SDU after your HV box build ?
I’m not sure if it does but I know for certain it’s not reversed, I checked it 100 times before connecting.

I literally have the money for this once... if I mess anything g up I’m finished :((

Which is why I’m so anxious over doing it right! 🤣

I was using really tiny gauge wire to test before and I think that was adding resistance and protecting the resistor last time.
User avatar
johu
Site Admin
Posts: 5684
Joined: Thu Nov 08, 2018 10:52 pm
Location: Kassel/Germany
Has thanked: 153 times
Been thanked: 960 times
Contact:

Re: Failing to precharge

Post by johu »

In fact every half bridge shorts out when connected in reverse because of the freewheeling diodes that are in it. It much sounds like you are precharging into a dead short, be it reverse polarity or something else.
Support R/D and forum on Patreon: https://patreon.com/openinverter - Subscribe on odysee: https://odysee.com/@openinverter:9
User avatar
Peter
Posts: 310
Joined: Fri Dec 14, 2018 9:07 pm
Location: North West Lancs, UK
Been thanked: 8 times

Re: Failing to precharge

Post by Peter »

Isolate the HV supply, disconnect the HV leads to motor and test resistance across the SDU motor HV input. Note readings with meter leads reversed too. You should see a resistance fall and rise due to the DC bus caps but resistance should settle in time once they are up to meter voltage. I would suggest you use a 12v supply such as car battery as your HV with your kettle element in series and set UDCSW to maybe 10v accordingly before going back to 362v later. Stay safe and put 362v aside until problem solved.
ev340
Posts: 39
Joined: Sat Mar 20, 2021 12:06 pm

Re: Failing to precharge

Post by ev340 »

Update!!

I have since put a voltage tester either side of the main contactor, and the voltage doesn’t rise, (the delta stays 360 volts) but the water in the kettle sizzles a little so current is flowing?

So that’s why the precharge fails...
but why is the voltage not rising at all across the main contactor?
johu wrote: Sat Jan 01, 2022 3:27 pm In fact every half bridge shorts out when connected in reverse because of the freewheeling diodes that are in it. It much sounds like you are precharging into a dead short, be it reverse polarity or something else.
This scares me and I don’t want to think of this being the case but I will check that now 😳
ev340
Posts: 39
Joined: Sat Mar 20, 2021 12:06 pm

Re: Failing to precharge

Post by ev340 »

Peter wrote: Sat Jan 01, 2022 3:37 pm Isolate the HV supply, disconnect the HV leads to motor and test resistance across the SDU motor HV input. Note readings with meter leads reversed too. You should see a resistance fall and rise due to the DC bus caps but resistance should settle in time once they are up to meter voltage. I would suggest you use a 12v supply such as car battery as your HV with your kettle element in series and set UDCSW to maybe 10v accordingly before going back to 362v later. Stay safe and put 362v aside until problem solved.
Thank you that’s really helpful!
It settled at 62.5k ohms.
Starting at 2mega ohms drooped to 1.7 then fell to 62kohms.

And I get different readings in different polarities... so that’s good?

As for the lower battery pack that’s a plan!!!
I didn’t know what voltage to go for though? I read that you can damage it with too lower voltage?
ev340
Posts: 39
Joined: Sat Mar 20, 2021 12:06 pm

Re: Failing to precharge

Post by ev340 »

Precharged fine at 12v.... tapped the ‘start’ wire to 12v and the main contractor clicked... is that it? Is it okay? :O ??
Is it just my settings are wrong?

I changed udcnorm to 11 from 360
Udcsw to 10 from 330


Can I test the throttle a little with 12v or is that a bad idea?
User avatar
Peter
Posts: 310
Joined: Fri Dec 14, 2018 9:07 pm
Location: North West Lancs, UK
Been thanked: 8 times

Re: Failing to precharge

Post by Peter »

You are looking for 0 volts across main contactor high current terminals when energised. You may be able to run motor on 12v if it can draw enough current, possibly 5A - 10A with no load on motor.
User avatar
Peter
Posts: 310
Joined: Fri Dec 14, 2018 9:07 pm
Location: North West Lancs, UK
Been thanked: 8 times

Re: Failing to precharge

Post by Peter »

What is your setting for Boost?
User avatar
Peter
Posts: 310
Joined: Fri Dec 14, 2018 9:07 pm
Location: North West Lancs, UK
Been thanked: 8 times

Re: Failing to precharge

Post by Peter »

Johannes, can setting udcmin above udcsw cause an issue?
ev340
Posts: 39
Joined: Sat Mar 20, 2021 12:06 pm

Re: Failing to precharge

Post by ev340 »

Peter wrote: Sat Jan 01, 2022 5:03 pm You are looking for 0 volts across main contactor high current terminals when energised. You may be able to run motor on 12v if it can draw enough current, possibly 5A - 10A with no load on motor.
Yeah I was getting 360v across when like you say I’d want close to 0v. :(

My car battery should do 10A no problem.
I will try spinning it up gently tomorrow then :)

And hopefully Johannes will have the answers 😍


Thank you all for your help so far I was feeling pretty shit about it before, but now I’m hopeful!!
User avatar
Peter
Posts: 310
Joined: Fri Dec 14, 2018 9:07 pm
Location: North West Lancs, UK
Been thanked: 8 times

Re: Failing to precharge

Post by Peter »

Set udcnom to 0 and set Boost at 6000 or possibly more as 12v is a low voltage.
ev340
Posts: 39
Joined: Sat Mar 20, 2021 12:06 pm

Re: Failing to precharge

Post by ev340 »

Peter wrote: Sat Jan 01, 2022 5:35 pm Set udcnom to 0 and set Boost at 6000 or possibly more as 12v is a low voltage.
I don’t fully understand the function of the parameters. I‘ll do some google tonight and see :)
User avatar
Peter
Posts: 310
Joined: Fri Dec 14, 2018 9:07 pm
Location: North West Lancs, UK
Been thanked: 8 times

Re: Failing to precharge

Post by Peter »

Setting udcnom to 0 stops the software from altering settings according to what the udcnom voltage is set to and what the battery pack is actually at. Therefore allowing Boost to be what you set manually without being changed by pack voltage. I was concerned because the boostcalc in your data showed 74000 which is too high by far.
ev340
Posts: 39
Joined: Sat Mar 20, 2021 12:06 pm

Re: Failing to precharge

Post by ev340 »

Peter wrote: Sat Jan 01, 2022 6:14 pm Setting udcnom to 0 stops the software from altering settings according to what the udcnom voltage is set to and what the battery pack is actually at. Therefore allowing Boost to be what you set manually without being changed by pack voltage. I was concerned because the boostcalc in your data showed 74000 which is too high by far.
Oh wow... that’s a lot...good spot thank you! I guess I’m going to have to really learn what all the parameters do and interact with eachother. Because I totally didn’t see that as an issue.
The database isn’t very in depth.
ev340
Posts: 39
Joined: Sat Mar 20, 2021 12:06 pm

Re: Failing to precharge

Post by ev340 »

johu wrote: Sat Jan 01, 2022 3:27 pm In fact every half bridge shorts out when connected in reverse because of the freewheeling diodes that are in it. It much sounds like you are precharging into a dead short, be it reverse polarity or something else.
-sigh- it appears you were correct, at least in part.

I had some success with a 12v car battery.
It was able to precharge, and then the main contactor clicked when start ‘button’ / wire was pressed twice.

But it has since stopped working again, and now shows short across the HV + and - . The short may have been present before, as my tester was playing up.

Have you got any ideas where in the inverter to inspect?
I know it’s quite enclosed in there, so I guess not is it a component that can be replaced?

Any help greatly appreciated thank you all for your help thus far!!
Post Reply