Stellantis- SAFT Ibis Battery with converter - Page 1
Forum section: electronics / general

author: f4eru
author_rank: Super Contributor
timestamp: July 25, 2023, 08:26:17 pm
content: Hello,Just saw this :https://www.evspecifications.com/en/news/6fa7807https://www.stellantis.com/fr/actualite/communiques-de-presse/2023/july/ibis-stellantis-et-saft-devoilent-une-batterie-intelligente-et-plus-efficace-pour-les-vehicules-electriques-et-le-stockage-stationnaireThe concept is interesting, it seems to be a research object more than anything else.Also, SAFT and stellantis are not at all known to be proactive in the EV space.Seems patents have been filed. Are those already public ?I suppose there are 3 strings of 8 microconverters in it, acting together as "microstrpping" architecture, each with presumably a bunch of cells attached separately, so working on 40-50V or so.Serializing 8 half-bridges built out of cheap LV Silicium MOS is probably competitive somehow in the performance view. Also, distributed cooling is easier.The small converters could nearly completely eliminate PWM, and use small steps, with perhaps only one of the 8 PWM'ing at a time, rotating, removing many filter components and DC-bus caps, removing a big part of switching loss and EMC emissions, as well as reducing HF eddy losses in the motor.Now, it would need a really deep specific optimization of the basic block to get anywhere near economically competitive against a more typical 2x 3-half bridge solution, but there is probably an opportunity, wit some heavy risks involved.

author: johansen
author_rank: Super Contributor
timestamp: July 26, 2023, 03:54:25 am
content: I dont think they are utilizing a multi level inverter topology but rather paralleling a whole bunch of pwm inverters, based on thr language used in the press release.With enough effort you can make a multi level inverter structure work (running a dozen h bridge battery modules in series) but you have to put a lot of effort into discharging each battery module equally. Essentially you have to rotate which battery module is used at what point in the cycle, continuously.For charging, the same effort has to be made. Unless you have an active bms (which is relatively cheap)

author: f4eru
author_rank: Super Contributor
timestamp: July 26, 2023, 05:47:13 pm
content: Quote from: johansen on July 26, 2023, 03:54:25 amThat is absolutely not difficult.Series makes much more sense than parallel.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 26, 2023, 05:58:20 pm
content: Smells like utter BS to me.Lots more electronics to go wrong, inside inaccessible battery modules.Lots of small inverters/chargers vs. one big on - no way is it going to be more efficient.Can't see any advantage, and lots of downsides."Intends to make it available before the end of the decade"... if it's just electronics, why would it take that long ?And what will Tesla be doing by then?Nothing to see here. Just a pathetic attempt to pretend that most legacy automakers like themselves won't be dead in a few years.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 26, 2023, 05:59:16 pm
content: Quote from: johansen on July 26, 2023, 03:54:25 amHow is that going to handle the hundreds of amps when you put your foot down?Or rapid DC charging?

author: f4eru
author_rank: Super Contributor
timestamp: July 26, 2023, 08:19:09 pm
content: That's the topic. it is pretty good to be able to remove nearly all of the switching losses, and HF eddy losses in the motor, by reducing PWM energy by a factor of a 100x, roughly.That opens a whole new dimension to the power handling, and the distributed nature of heat dissipation also brings a huge advantage.Quoteit's tech research, made by people with no idea about mass production, that always takes many years to go over to a real product.QuoteAgree. as an answer to today's vehicles, it is just futile.

author: johansen
author_rank: Super Contributor
timestamp: July 27, 2023, 06:22:05 am
content: Quote from: mikeselectricstuff on July 26, 2023, 05:59:16 pmMulti level inverters made up of discrete h bridges fed from separate dc sources have been around for a long time, and for a while, dc to ac inverters utilizing a 4 h bridge, 4 transformer topology was more efficient than pwm and were sold commertially for the 3 to 12kw off grid market. At 4 levels they can make a 95% clean sine wave at a 50% range in voltage.Basically mosfet losses at low frequency and voltage even including the LF transformer losses were less losses than darlington transistors at 400 volts and 4khz pwm. But now we are lazy so we use 6000 amps worth of mosfets to drive hf transformers then rectify it then convert back to ac with more mosfets. 60hz transformers smaller than 100kva are now less efficient then mosfets. It wasn't always this way.Igbts got better, with 1 to 2 volts conduction losses at 600volts and 500 amps in a smaller footprint and less losses than 6000 amps at 50 volts worth of mosfets.So high voltage battery pack. Not much of an inductor, let the motor filter it out.

author: johansen
author_rank: Super Contributor
timestamp: July 27, 2023, 06:35:17 am
content: In theory, 10 x 72volt battery packs could each have an h bridge made from a 100 amp capacity 100 volt mosfet h bridge, you then run 3 of those strings in delta or Y with 3 inductors to generate a peak voltage of 720 volts dc or 480v ac. You can then charge or discharge it into any waveform, ac or dc, according to your algorithm for which h bridges spend more time on, off, or -on. This would work well for a half megawatt vehicle.There are multi dozen megawatt vfds that are built like this, and they can handle up to something like 20% of the individual inverters failing, they just disconnect them and short them together, then reprogram the rest of the system to deliver a (non sinusoid) so that the output is a sine wave, at reduced power.I saw a photo of one of the transformers on reddit.. 24 separate 3 phase coils all summing up to one output. For the usual mission critical high reliability no downtime in 10 years guaranteed stuff.. you know, like your moms tesla.

author: Lukas52
author_rank: Contributor
timestamp: July 27, 2023, 04:18:02 pm
content: Wouldn't that also mean that your power is always in direct proportion to your battery capacity?So no more big batteries + small power combination for better range at lower cost...Feels like a step backwards, like actually removing modularity rather than adding it.

author: johansen
author_rank: Super Contributor
timestamp: July 28, 2023, 10:13:00 pm
content: Quote from: Lukas52 on July 27, 2023, 04:18:02 pmLithium batteries are pretty flat, so no, the voltage and current is available until the battery is dead. No one is suggesting sequentially discharging the packs

author: Lukas52
author_rank: Contributor
timestamp: July 29, 2023, 09:05:38 am
content: What i meant was, if you tie your inverter to a battery pack, your output power scales linearly with battery capacity, not state of charge

author: johansen
author_rank: Super Contributor
timestamp: July 29, 2023, 10:19:48 pm
content: Quote from: Lukas52 on July 29, 2023, 09:05:38 amIn that case you could sell vehicles with upgradeable battery packs that would increase both range and HP