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Old 01-25-2015, 10:49 PM   #1631 (permalink)
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Hi OTR, that looks like an extreme case, not sure how it is implemented (didn't see many details) but it is likely very large for a vehicle.

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Old 01-26-2015, 01:34 AM   #1632 (permalink)
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I guess you could say I'm a little lost..

The problem here is the motor/controller requires the high voltage.

Whether the cells are connected is series or parallel, theoretically they will store the same energy. This company may have figured out a slick way to manage the batteries, but it still won't get past the EE 101 fact that a whole bunch of batteries connected in parallel will still put out the same voltage as 1 battery.

So, you could have 100 lithium batteries in this system, and the output voltage would be about 3.85 volts.

No matter how good the management system is, you will still need to do something to produce the voltage ( 600V or whatever ) that the motor and controller require.

I'm curious how they got around this issue - I can't find any info about that on their site.

- E*clipse

Oh, I'm just thinking (maybe not to well) out loud here, but would it be possible to build a 3 phase boost converter to both boost the voltage and control the motor, rather than than boosting the DC to a high voltage, then using a 3 phase buck converter to control the motor??





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Originally Posted by On The Run View Post
Hello there,

finally managed to catch up on the thread.

Today I'll stick my head out of the lurkers trenches for two reasons:

First I'd like to pay my respect to the fantastic work going on here.

Second: The solution to the voltage issue without putting tons of batteries in series and having to build a seriously beefy buck booster or whatever could be here:

w w w.asd-sunstorage.com/series-connection/

Due to the rules, you'll just have to eliminate the spaces between the w's

I was already working on a translation for you guys, but then I found the company already had an english press release which saved me the pain.

Looking forward to what you make of it.


Regards,

On the Run.
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Old 01-26-2015, 01:59 AM   #1633 (permalink)
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Quote:
Originally Posted by e*clipse View Post
Oh, I'm just thinking (maybe not to well) out loud here, but would it be possible to build a 3 phase boost converter to both boost the voltage and control the motor, rather than than boosting the DC to a high voltage, then using a 3 phase buck converter to control the motor??
I don't know if it works out, but I like the idea. Will have to give that some thought. Currently each phase has peak to peak of ~2x battery, might need inverting buck-boost just to compete.

edit and regen will flow unbucked and with an inductor in parallel with the battery... Not sure it's gonna work out so well...

Last edited by P-hack; 01-26-2015 at 02:07 AM..
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Old 01-26-2015, 02:56 AM   #1634 (permalink)
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Hello again,

As far as I gathered from little additional information available from other sources on the web, these electronics do the following:

- produce the desired voltage level for use in motor controller via dc/dc-converter
- monitor and protect the cell during charge and discharge (like a bms)
- provide the cell with appropriate power for charging (like battery charger)
- every cell provides it "high voltage" via its electronics in parallel into a common line, thereby adding up each "little" available current per cell instead of traditionally adding up the little voltage per cell by setting them up in series.

The cells don't have direct contact to each other anymore. The cell only "sees" the outside world through the electronics. The mockup that was shown in one of the news articles suggested, the electronics would be bolted to the battery terminals and roughly be the same size as the.top of the battery itself.

Sounds to good to be true - no balancing nessecary anymore; no extra charger to find room for in the car; full power available from the pack without having to worry about killing a cell...

Regards,

On the Run.

Last edited by On The Run; 01-26-2015 at 03:02 AM..
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Old 01-26-2015, 04:22 AM   #1635 (permalink)
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Problem is that we are at a pretty low level of specifics (core material/switching frequency/number of turns/number of strands/etc, and there isn't much useful in that article.

If they are using one large boost converter per cell, we can't really find room to do that on a car with 80 cells let alone cost effectively. at 3.2v per cell, to make the target 36kw the boost converters would need to supply 11250 amps. It is designed for stationary use. Any ideas on the costs per cell?
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Old 01-26-2015, 04:40 AM   #1636 (permalink)
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looking at a pic, it looks designed for large cells but not a lot of current per cell. But since it is stationary you can always throw more cells at it (not true for a car).

The inductors would have to be much larger (even with high frequency switching) to get the full output capacity of that battery (i.e. hundreds of amps of dc bias). Power density is critical in a vehicle. Still a BMS looks trivial by comparison. And a connector bar per cell is going to be far more affordable and efficient than a boost converter per cell. ( I sort of went through this parallel exercise when I was considering supercaps, and decided it was a bad idea)


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Old 01-26-2015, 08:42 PM   #1637 (permalink)
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Quote:
...and there isn't much useful in that article.
No kidding. This says ...nothing:


OTOH the current episode of EVTV (yootoob/watch?v=ZTkh_58ppoU) is up and it's mostly about best practices for strapping cells together.

I always get happy when I hear their theme song at the opening credit, then they fly the drone right at the door as it is opening.
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Old 01-30-2015, 06:19 PM   #1638 (permalink)
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I made an AC controller instructable if you guys want to check it out.
200kW AC Motor Controller for Electric Car

Feel free to vote for (or against) it in some random contest that I entered there. haha. Last time I lost to LED sneakers.

Partially I did it to help get my booty in gear for getting it to a place where people can assemble their own stuff.

I signed up for github finally. Now I just need to figure out how to upload and download files to my computer so I don't have to cut and paste the content.
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Old 01-30-2015, 08:33 PM   #1639 (permalink)
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Thanks! This is more comprehensible than the back and forth about the merits of various inductors.
Quote:
First, let's talk a little about what the control/driver board is. It has all of the safety circuits, as well as the brains for controlling the motor.
What about heating/cooling the battery pack, integrating the charger and dashboard display? Any recommendations there?
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Old 01-30-2015, 09:08 PM   #1640 (permalink)
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Don't tell the instructables people, but this is just the basic AC control board that I already made. It doesn't do anything very fancy. Just reads currents, temperature (from one source), and throttle, and protects the IGBTs from desaturation and overcurrent and +5v and +24v undervoltage. There are a few extra pins, but a dspic30F4011 isn't going to do much more than that.

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