Adventures in an all electric vehicle.

[Ubique]

Doesnt the car have inbuilt protection software to protect it from being mis-charged (or charged outside of mfr recommended parameters) - so that "non-mfr" 3rd party charge points cannot damage the car???

"it should do" - and in most cases the BMS will do it's best (subject ot the programmers capability) to prevent a thermal event, in reality, it depends upon the build quality of the cells, only one going rogue can (and has) caused the whole assembly to turn to liquid fire, obviously consuming the whole vehicle.

 

[GRW]

"it should do" - and in most cases the BMS will do it's best (subject ot the programmers capability) to prevent a thermal event, in reality, it depends upon the build quality of the cells, only one going rogue can (and has) caused the whole assembly to turn to liquid fire, obviously consuming the whole vehicle.

Sobering.
Given there has been the ability to measure cell temps (& to get a charger to compensate & adjust its charge rate to suit) - and to measure cell voltages (so a cell temp & voltage variation outside of safe parameters can be used to trigger a charge cutoff, alarms etc)... for decades.... then the fact that there are "holes" in these EV systems - is genuinely surprising.

 

[Ubique]

That seems like a crazy system and oversight by Mfrs. I'd have expected them to ring-fence the charging security to prevent damage from 3rd-party charging!
That just seems well.... shoddy to me.

It's not that bad, the charge connector has a data loop in it so the DC fast charger can communicate directly with the BMS. The BMS can shut the communication down if there is an event that requires an immediate disconnect, but in some cases, the damage will already be done.

The charging cables in the photo look like fast DC to me.

 

[premmington]

"it should do" - and in most cases the BMS will do it's best (subject ot the programmers capability) to prevent a thermal event, in reality, it depends upon the build quality of the cells, only one going rogue can (and has) caused the whole assembly to turn to liquid fire, obviously consuming the whole vehicle.

I think the biggest risk from a public fast charger is physical damage from the plug and drop (ing) phase from incomers on high KW chargers.

We get dropping phases sometimes on our industrial estate - it has caused damage to CNC machines in the big sheet metal shop.

It is not the battery that would get damaged - they only suck power in - but the control gear on the car.

 

[willie.macleod]

I think the biggest risk from a public fast charger is physical damage from the plug and drop (ing) phase from incomers on high KW chargers.

I'm seeing more rapid chargers appearing with batteries inbuilt - allows rapid deployment as minimal network reinforcement required and effectively acts as a big UPS allowing quick topups of EVs and then top it's own battery back up. Not much good if you have queues of EVs waiting to charge but ideal in more remote sites or in areas like you mention with frequent line disruptions.

 

[Ubique]

@premmington Almost, cell voltage needs to be increased to push 'charge' into a cell, with Lithium, the voltage and current needs to be controlled to prevent cells overheating whilst charging, from what I remember, the DC chargers are pulsed initially to establish cell condition and 'cause & effect', then ramp up to continuous current, then back down to asymmetric pulsed controlled by cell temperature (IIRC by the highest individual temperature, not mean or average) - all well & good with 100% healthy cells.
Dropping a phase should only reduce the charge rate, not cause issues in the BMS or cells, if AC charging, then the charger will 'take the hit', if DC charging, the external charge controller should shut down.

 

[premmington]

I'm seeing more rapid chargers appearing with batteries inbuilt - allows rapid deployment as minimal network reinforcement required and effectively acts as a big UPS allowing quick topups of EVs and then top it's own battery back up. Not much good if you have queues of EVs waiting to charge but ideal in more remote sites or in areas like you mention with frequent line disruptions.

That seems a good solution

The EV charge network problem is here - the solutions will come.

As I said before - the problem always has to come first - the solution follows.

 

[GRW]

I think the biggest risk from a public fast charger is physical damage from the plug and drop (ing) phase from incomers on high KW chargers.

We get dropping phases sometimes on our industrial estate - it has caused damage to CNC machines in the big sheet metal shop.

It is not the battery that would get damaged - they only suck power in - but the control gear on the car.

Again though - I'd have expected the chargers to be required to have ph-ph & ph-n monitoring, with over/under-voltage & over/under frequency protection - & to shut-off instantly the feed went outside parameters (the generators I worked on all had these features in the controller specifically to protect the connected loads - so given the duty again I'm amazed if they aren't required!

 

[Ubique]

I'm seeing more rapid chargers appearing with batteries inbuilt - allows rapid deployment as minimal network reinforcement required and effectively acts as a big UPS allowing quick topups of EVs and then top it's own battery back up. Not much good if you have queues of EVs waiting to charge but ideal in more remote sites or in areas like you mention with frequent line disruptions.

That makes a lot of sense.

 

[premmington]

@premmington Almost, cell voltage needs to be increased to push 'charge' into a cell, with Lithium, the voltage and current needs to be controlled to prevent cells overheating whilst charging, from what I remember, the DC chargers are pulsed initially to establish cell condition and 'cause & effect', then ramp up to continuous current, then back down to asymmetric pulsed controlled by cell temperature (IIRC by the highest individual temperature, not mean or average) - all well & good with 100% healthy cells.
Dropping a phase should only reduce the charge rate, not cause issues in the BMS or cells, if AC charging, then the charger will 'take the hit', if DC charging, the external charge controller should shut down.

They don't always on a BMW - this is where all the KLE damage and burnt contactors in the SME come from (I think this is the pattern that is coming?)

 

[premmington]

That makes a lot of sense.

It does... (second postitive remark I made today)

 

[Ubique]

Again though - I'd have expected the chargers to be required to have ph-ph & ph-n monitoring, with over/under-voltage & over/under frequency protection - & to shut-off instantly the feed went outside parameters (the generators I worked on all had these features in the controller specifically to protect the connected loads - so given the duty again I'm amazed if they aren't required!

Fully agree about generators, I've worked with them too. EV's have AC & sometimes DC charge options, the AC is 'just' raw three phase with safety interlocks, the charge controller is onboard the vehicle and wholly controls the charging of the battery, with BMS oversight. AC charging can happily drop a phase or brownout with no detriment to the battery, if there is an issue, the AC charge controller is designed to be sacrificial.
DC charging has a seperate connector where it connects directly to the battery pack via a contactor and has a data link to the BMS, which does the cell monitoring and indforms the external charge controller of the required volts/amps & duty cycle. In the event of a bettery event, it will shut the data line down (which should immediately cause the charger to shut down) and open the DC input contactor.

 

[Ubique]

They don't always on a BMW - this is where all the KLE damage and burnt contactors in the SME come from (I think this is the pattern that is coming?)

Not only BMW's.... different terminology but similar repair costs.

 

[GRW]

Fully agree about generators, I've worked with them too. EV's have AC & sometimes DC charge options, the AC is 'just' raw three phase with safety interlocks, the charge controller is onboard the vehicle and wholly controls the charging of the battery, with BMS oversight. AC charging can happily drop a phase or brownout with no detriment to the battery, if there is an issue, the AC charge controller is designed to be sacrificial.
DC charging has a seperate connector where it connects directly to the battery pack via a contactor and has a data link to the BMS, which does the cell monitoring and indforms the external charge controller of the required volts/amps & duty cycle. In the event of a bettery event, it will shut the data line down (which should immediately cause the charger to shut down) and open the DC input contactor.

Why both AC & DC charge options? Why not use standardise to use the easiest one to provide to the car (AC)?
While I think about it - Why don't the cars have the ideal charger unit on-board - so then all that would be needed would be an AC Supply point (of suitable current rating) where the User plugged in, used his card to activate the metered charge supply (just like a Pay at Pump on a forecourt)?
It seems that the whole charging system.and network is needlessly overcomplicated (so is undoubtedly designed that way to ensure some people make a lot more money out of it than it should be)?

 

[willie.macleod]

To allow rapid charging you need a huge transformer plus ac/dc converter. Massive amount of weight and cost, cooling requirements and then you need a hefty socket to plug it into which as it's own issues. Current setup works well, a rapid DC charger costs as much as a EV!

Zoe's sort of had a half way house with fairly fast charge as they can charge at 22 kW with on board charger but they're lossy as they utilise the motor windings as part of the charging circuitry. Some other high end EVs can charge at 22kW as well but that tends to be additional money.

 

[premmington]

Why both AC & DC charge options? Why not use standardise to use the easiest one to provide to the car (AC)?
While I think about it - Why don't the cars have the ideal charger unit on-board - so then all that would be needed would be an AC Supply point (of suitable current rating) where the User plugged in, used his card to activate the metered charge supply (just like a Pay at Pump on a forecourt)?
It seems that the whole charging system.and network is needlessly overcomplicated (so is undoubtedly designed that way to ensure some people make a lot more money out of it than it should be)?

You raised a lot of good questions above - most of which I can answer

1. With AC charging you are limited for current flow by the AC to DC convertor size on/in your car.

2. With DC charging - the convertor is in the charger on the forecourt and it can be the size of the car - and you can charge at a higher rate.

All EV batteries need DC to charge.

All fast charging will become DC in the end - but you are reliant on the convertor in the charger which is not part of the car.

 

[premmington]

To allow rapid charging you need a huge transformer plus ac/dc converter. Massive amount of weight and cost, cooling requirements and then you need a hefty socket to plug it into which as it's own issues. Current setup works well, a rapid DC charger costs as much as a EV!

Zoe's sort of had a half way house, can charge at 22 kW but they're lossy as they utilise the motor windings as part of the charging circuitry.

Good explanation - I tried but you worded it better

 

[Ubique]

Why both AC & DC charge options? Why not use standardise to use the easiest one to provide to the car (AC)?
While I think about it - Why don't the cars have the ideal charger unit on-board - so then all that would be needed would be an AC Supply point (of suitable current rating) where the User plugged in, used his card to activate the metered charge supply (just like a Pay at Pump on a forecourt)?
It seems that the whole charging system.and network is needlessly overcomplicated (so is undoubtedly designed that way to ensure some people make a lot more money out of it than it should be)?

Essentially (in UK) you can theoretically charge from a 13A socket via an adaptor lead, a home charge point, usually single phase, or a commercial three phase - all of which are just a way of connecting to the onboard charge controller, and a DC charge input - which as mentioned, bypasses the AC charge controller onboard and communicates directly with the BMS.
The AC system is backwards compatible with earlier vehicles because the charge control is done onboard, so the charge rate is controlled by the vehicle, DC chargers control the charge rate external to the vehicle, based on data from the BMS. not all vehicles can accept DC charging (and don't have the unique socket to connect to) but all can accept AC charging, the rate is dependent upon the supply capability and the AC charge controller / BMS limits.

 

[GRW]

Thanks for the info folks.
Of course I was aware of the need to rectify AC to DC, but I hadn't considered that the actual power requirement of fast chargers was so high that it required 3-phase (when you think about it though, and how big the packs on the big Tesla's; the like must be, & they charge them in relatively short periods so LOTS of juice - it makes sense).

A standard 125A 3P+N+E IEE Form Socket can carry mathematically 86kW - that got me thinking that if "charge points" were basically just a metered industrial 3ph outlet it'd be far easier to roll out. However, if the AC-DC charger unit is too massive for the vehicle to cart about - that's the end of that.

It does highlight the magnitude of the issue and cost to the nation for the massive power infrastructure & generation needed to charge EV's though.... & the peak demands created by large numbers of EV's on fast chargers would be astronomical.

 

[premmington]

Thanks for the info folks.
Of course I was aware of the need to rectify AC to DC, but I hadn't considered that the actual power requirement of fast chargers was so high that it required 3-phase (when you think about it though, and how big the packs on the big Tesla's; the like must be, & they charge them in relatively short periods so LOTS of juice - it makes sense).

A standard 125A 3P+N+E IEE Form Socket can carry mathematically 86kW - that got me thinking that if "charge points" were basically just a metered industrial 3ph outlet it'd be far easier to roll out. However, if the AC-DC charger unit is too massive for the vehicle to cart about - that's the end of that.

It does highlight the magnitude of the issue and cost to the nation for the massive power infrastructure & generation needed to charge EV's though.... & the peak demands created by large numbers of EV's on fast chargers would be astronomical.

You got there...

Trickle charging a lightweight city EV overnight on a 240v 13amp AC charger at home - is viable now...

DC injecting at welding currents a heavy wieght supercar at speed with safety is gonna require infrastructure - it is coming...