Recent content by halcyon_m

Designing a motor with a characteristic current (current when shorted) to the nominal rating allows the controller to just short the motor terminals in a fault scenario. The issue bobc mentioned just goes to show that "converter fault --> all switches open" is not always the best assumption...

I purchased 3 of these. 1 was puffed, and then 1 cell died after I left it connected to a small load for a week. All other cells were fine. I'm split on buying a replacement, since it was ~$160 for 3 4s, 16Ah shipped. Now it will be ~$100 for a single replacement 4s, 16Ah. So, good? if...

Hi everybody. I've been using my 12S balancing manager for a few weeks now on my 1kW e-bike, and I'm about to do another board spin. Does anyone have any request for features? Here's the quick pitch: It makes sure you don't over-charge or over-discharge any cell in the batch, and has some...

I should specify that when i offered to develop products for the ES community, that it would be as a separate venture. My current employer is not currently in a position to serve the enthusiast community. Im guaging market needs. There are currently many electric cars and bikes on the market...

Hi all, I wanted to bump this thread, since it's been a few years. I used to have some EV projects that centered around making items that weren't easily or cheaply sourced. I imagine many of the people here have similar issues. I currently work for a electric vehicle manufacturer, but I, and...

Yeah, I'd like to know as well. Did the lipo's last at all?

The deliverable is a 7 page explanation with designs and material lists. With the right people together, this could take a weekend.

I would suggest doing a 2-piece (T-style including one face and half the core) that can be more easily machined if you go away from the solid construction. This would allow you to wind the copper separately and then insert the half-cores into the form-wound coil. I think a lot of their value...

It would help to know more about what you're expecting from the project in terms of performance, available budget, time to completion, among other things, but I see you need a proposal quick. For simplicity purposes, I'd suggest a DC motor (PERM, AGNI, E-TEK) and a Kelly controller. I'm sure...

What are the goals of your project? How much time do you have? What is the experience level of you (and your team)?

This is very interesting to see that even at 340A, it falls off quickly, but then rebounds to 4V, presumably where ~80% capacity can be extracted. When they say 'burst 90C', they really mean it. At 300A, I calculate with rough numbers for weight from a 3.5Ah pack on HK, that this cell only...

A battery fab facility is a hard thing to start up, so that's likely why there are few boutique batteries out there. Although, if you can tell from the growth of the RC hobby, they are demanding better and more powerful batteries, particularly in the competition sector. When conducting a test...

Do you have any data points you could throw out at us? I see the test from the SAFT cells got 14kW/kg at 20C initial temperature, but considering a 3S, 2600mAh LiPo, rated at 130C max, (229g), the power density is 16.4kW/kg NOT considering any internal resistance. If you figure they rate using...

What happened to the SAFT 200-400C cells we were discussing or other similar pulse-power cells? LiveForPhysics brings up a good point about the 50% rule (peak power from a cell comes at or above 50% of the open-circuit terminal voltage). Also, thanks for the 70% (30% sag) rule-of-thumb. Maybe...

most motors will have significantly more force pulling the rotor to contact the stator, rather than move parallel to it. Typically that factor is 3:1 or 10:1, so the mechanics of constraining the rotor and stator become significant. There are tricks to balance forces, like maintaining equal...