AEVA Forums

Why no balancing? How will you do (have you done) the initial balance? I'm working on a hypothesis that (a) the only reason cells get out of balance is differences in self-discharge and (b) self discharge is very low, so differences in self discharge should be very very low. All in the name of scie...

And please tell me that the presumably unfused wires to the BMS boards will be getting a liberal coating with silicone or some other strain relief. I know fuses are a nuisance when the current through them isn't enough to keep mechanical contacts (like fuse to fuse-holder) clean, but those long unp...

What's the PD across that strip of insulator you've got between rows? Please tell me the insulator is a little bit proud of the connector strips to stop dropped metal things making contact? PD = Potential Difference? I suppose about 80V, worst case. The plastic is 1.5mm polycarbonate - super tough ...

Hi all, I've just finished another update on the blog, in case anyone's interested to read about the latest progress. The big milestone: The drivetrain works! I fired it up for the first time a few days ago. A great relief to see it runs smoothly and vibration free. Here's a short video of that (not...

Yeah, don't listen to the racing guys, $10K is plenty to do a motorbike conversion http://forums.aeva.asn.au/smileys/smiley1.gif I think the trick with range will be achieving it at highway speed. Motorbikes are relatively poor aerodynamically, so whilst 5kWh might get you 100km at city speed, you'd...

Interesting, that eBay one has Chennic branding - they've been around for a while. Surprisingly that quality was so bad. Quite a few people have Meanwell converters in their EVs. In fact back when I was with EV Works, we stocked them for a while. They did have a few problems though for EV use (just ...

How can I know this? Because of Farady's law of electroplating. The number of Li+ ions plated out as neutral Li atoms cannot be more than the number of electrons that pass through the cell. Phew, that's actually a relief to hear. I suspected this but couldn't back it up with science http://forums.a...

The point is that a few cells are sagging below 1.8 V while the others are still above 2.5 V. Apologies, it is easy to get off topic and ruin a thread's signal-to-noise ratio ;) But it is interesting to hear all the different opinions. Although after a couple of years it's probably a good idea to d...

Another option is to replace your 4A isolated gate driver with a high-speed optocoupler like a 6N137 just to pass the PWM through, then use a regular high current gate driver IC like a MIC4452, which enables you to use a 1-2ohm gate resistance. If my understanding is correct, the purpose of a -ve ra...

Richo wrote: Not particularly suitable for an eV

Assuming a typical 250wh/km energy consumption, one of those cells could move an EV approximately 4cm

And it seems like it only works out to 10wh/kg energy density? But still interesting tech, for sure.

An assortment of comments… - If you're drawing 500A from 100Ah Sky cells, it is to be expected that they will sag down to below the 2.5V threshold where EV Power BMS modules signal a warning - not that it would be damaging the cells, just the BMS modules are getting confused into thinking the cells ...

I certainly sympathise about the psychological hurdle of possibly ruining an expensive car! That's how I felt when I was about to take an angle grinder to the boot of this RX7.. and I have a lot of EV builds under my belt. I can't imagine having the confidence (or ability) to do this one as my first...

Mine was actually somewhat more expensive than $19K due to being a Type RS, a higher auction grade (4.5), and lower K's. But $19K for a Type RB seems OK. It's probably pretty cheap because it's right up near the 100,000km mark, which if often considered "engine rebuild time" for rotaries - not that ...

Some more progress to report on the RX7 - feels like it's getting pretty close to being drivable now! (But still plenty of work to do...) Here are quick links to the new parts of the blog on my website for full details: OIl Circulation for Tailshaft Bushing Front battery box All of the new Electrica...

They should be fine, in my experience LiFePO4 are only damaged from discharge if they get driven negative (all the way to zero and then some more) - and if that had happened they would be showing zero volts now. (Hopefully some others will chime in in agreement so you don't have to trust just me htt...

*cringe* http://forums.aeva.asn.au/smileys/smiley2.gif But what you suggest is probably on the right track for absolute cheapest EV. The main caveat I can think of is that any road-going vehicles kind of need a minimum performance to be "roadworthy" (either to pass licensing, or just to not be too a...

Hi Paul, Pretty much reiterating/expanding on what Johny said.. Internally the "12V lithiums" are actually just four LiFePO4s in series - and they cost the same as four individual cells of the same capacity. So in general you're better off going for individual cells, allowing better flexibility in p...

According to NCOP14 it's in ADR 16.42: "The removal of the engine will necessitate the provision of an alternative source of heat for demisting air (or, perhaps, alternative demisting arrangements). A performance comparable to the original demisting system must be maintained" Interesting that A/C mi...

I've just posted another update to the blog, mostly starting about halfway down the Battery page ( http://zeva.com.au/Projects/RX7/?section=batteryPacks ) plus a bit of new content in Drivetrain too. I also started the Auxiliaries section (for vacuum pump, heating, 12V battery etc). In summary: - EV...

My initial thoughts: - I agree about the possibility of corrosion on battery terminals reducing performance. Terminals should always be cleaned before installation, but corrosion (Al2O3 in particular) reforms over time if you don't have Noalox (or similar) keeping moisture & oxygen out. I know peopl...

Despite a plethora of other distractions getting in the way of my RX7 conversion, there has been some progress happening http://forums.aeva.asn.au/smileys/smiley36.gif I've posted an update to the blog - basically details of the motor cradle fabrication. A couple of the pics from the blog below too....

My 2c: As a rule of thumb I usually suggest 5C as the maximum real-world discharge from ThunderSky/Winston or Sky/Calb cells (e.g for long enough accelerate 0-100), and 1C continuous if you want your cells to last a long time. (FYI the 5C is based on voltage sagging to 2.5V at normal operating tempe...

Most controller designs use electrolytics because they're an order of magnitude cheaper than the film caps (by capacitance), but they're certainly not as good. There are two factors in play, one is dynamic voltage sag due to capacitor ESR, and the other is voltage ripple due to the actual charging/d...

Very nice caps there, but very expensive! You get what you pay for I guess. Most controllers (AFAIK) just use cheap electrolytics, which cost perhaps $10 per 1000uF - but have far higher ESR, hence needing more of them. (Panasonic TS-ED and TS-EE series are worth a look.) As for my own project, I ha...

For instance, my model works fine with the 5,000uF capacitor bank with hardly any DC bus ripple switching upto 400V 600A, however it seems most home builds use more than this. Just a quick comment on the capacitors, it's usually not the capacitance but the rated ripple current (due to the ESR) whic...