Electronics > Power/Renewable Energy/EV's

high power dc-dc isolated bidirectional

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max_torque:
What a silly thread.

if yhou do the math, then there is clearly a winning solution, which is to spend the money you were/are going to waste on this ridiculous dcdc on just buying some more cells for your vehicle


And of course, fundamentally you can't high power charge a "small" battery anyway, because the C rate of the cells becomes limiting, esp at high / low voltages and temperatures.  I'm going to guess you haven't got any significant BMS or BTMS experience as you are not asking anything like the correct questions

You also are foolish to connect something unproven, DIY, and completely uncertified at any public fast charger. The network operates are going to chase you for damages if you blow up their charger! And HV public liabilites insurance is expensive.


BTW I actually develop BEVs for a living, both OE and motorsport, and have power electronics experience to 1kV and 1MW in this field.


The "Best" route to DIY BEVs is simply to repurpose existing componentry, ie use a BMW CCS controller, an Leaf inverter/DCD or any number of Tesla parts that have all been hacked and provide a very cheap, very reliable, and importantly, VERY SAFE, architecture.  Even if you do all this, there are still hundreds of ways you can kill or set fire to yourself and others......

Faringdon:

--- Quote ---What a silly thread.
--- End quote ---
You're joking, right? This is a forum..a place to discuss and encourage this kind of thing....and by the way, your actual points are well received and a good contribution either way. so thanks for that.
Most Power Electronics in the West has now been outsourced to China so please  lets please not discourage some activity/discussion  in this area......the more the better.


--- Quote ---basicaly i building a ev and want to take advantage of dc fast chargeing with out the need for a larger battery
--- End quote ---
This a great idea, and  well worth looking into.


--- Quote ---if yhou do the math, then there is clearly a winning solution, which is to spend the money you were/are going to waste on this ridiculous dcdc on just buying some more cells for your vehicle
--- End quote ---
Thanks but i think they have a great idea.....maybe he wants to look into a cheaper, /lighter battery


--- Quote ---You also are foolish to connect something unproven, DIY, and completely uncertified at any public fast charger.
--- End quote ---
Thanks, but i dont think they  are saying they are going to connect anything to a public fast charger at this point.

And to the OP, i confess that bidi chargers are amazing, but would a  "one-way_t'other way" type thing be out of the question?.......it may be a little bigger i would admit.
I mean, these things tend to be stationary and not mobile items. So does it really need to be "smallest"?
If so then the DAB  i state above is the way to go.


--- Quote ---And of course, fundamentally you can't high power charge a "small" battery anyway, because the C rate of the cells becomes limiting, esp at high / low voltages and temperatures.
--- End quote ---
In Battlefield situations, you often take a risk and way overcharge batteries, because you need to take the risk.
In Formula E, they way overcharge batts......and yes they start smoking!...my ex gaffer used to be in charge of batts for UK Formula E.

max_torque:
No, this thread is moronic and your reply is pretty stupid as well, sorry..

The OP said

" i building a ev and want to take advantage of dc fast chargeing with out the need for a larger battery"


Which tells me they have no actual understanding or expertise in power electronics, energy storage, battery electric vehicles or anything of any use.

Lets start at the beginning.  What IS the advantage of dc fast charging?  Obvious isn't it, it allows a high POWER charge to occur.  So when does one NEED to leverage that advantage?  Again, obvious, when one wants to rapidly charge a large capacity battery.


So fundamentally, it's stupid to want to leverage the only advantage of a system that is in no way applicable to the system the OP is saying they are going to install......


AC charging at up to 22kW (3ph) or 7kW(1ph) is going to be absolutely sufficient for a small storage battery. To accept the high power of a DC charger (50kW to 1MW) you absolutely need a large battery.

As result, half arsing some sort of converter together to allow one to plug a small (low voltage unless the cells they are using are tiny capacity, which would be idiotic as well) battery into a DC fast charger is stupid, dangerous and would be a legal nightmare, esp in the UK, where the OP claims to be from.



^^^ That's just the fact of it, it makes no difference what they do on a 'Battlefield' or in FormulaE or whatever... (btw i have designed powertrains and energy storage systems used in both those those environments to good (championship winner for FE)effect :-)

Faringdon:
Thankyou this is excellent knowledge, i often think on this, since once i was terminated because i refused to implement a huge battery charger without a BMS...they insisted i just shovelled the output of our multi kW voltage output regulated power supply into it (this was a supply which we were using for something else). We had been told not to charge with over 70A, (it was another co's battery) but putting that supply on it would have meant way more than that, as it had really high current output clamp level, way over 70A. It was for a one-off demo for the MOD, so i was told the battery would survive it for that one go. I guess it wouldnt have from what you say. (im not harping on, but that co had all their actual sellable products made in China, and received the MOD grant based on the turnover they made from that operation)

Zero999:
Yes. Silly thread. Ask a question about an advanced topic, then precede with beginner questions. I didn't bother responding when he asked what the turns ratio of the transformer needs to be. If you don't know how to work out something that simple, then you lack the knowledge and experience to design something as complicated as this. At least build a small scale power supply more complicated than an LM78xx circuit first.

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