Tesla has a great electric motor basics post on their site, here. Good comparisons between electric power and gas, with curves and all, that even the mathularly challenged can understand. Have a looky. (LOVE that title, too…)
Archive for January, 2011
My wife is fond of saying, “I don’t know if the guy only has one stick or he has two and hasn’t figured out how to rub ‘em together yet.” She has a way with words… but sometimes that’s how I feel. It just occurred to me that there’s probably a crap-ton of information in the way of videos out there. Well, duh.
Here’s one, with a sweet list of suggestions along with it.
Good thing. The forecast is for snow. Again.
Continuing my obsession with connectors, from Ypedal, a really comprehensive video showing a bunch of connectors, featuring the Anderson Powerpole. Great stuff, and thanks!
The secret of the LiPo battery configuration is how you tie together the balance tabs. Sorry, can’t tell you more than that… I’m on an NDA with one RC, but suffice to say I’m looking into the various methods to make connections and adaptations to the basic configuration. The Turnigy packs have what’s called a JST-XH connector, and it seems the easy way to set them up would be to fabricate some sort of pigtail with this going to a PC board/connector dealy. In my searches, I found this site, which tells you just about everything you’d ever want to know about the balance connectors on those crazy LiPo packs.
Just one more example of the RC/battlebot guys figuring out a lot of stuff we’re just starting to find out about- from TJin Tech’s “All about lipo balance connectors”, well, all about lipo balance connectors.
Between ES, Facebook and ElMoto.net I’m feeling a little over-extended. I made the decision this weekend to just stick to posting the progress thread to Endless Sphere, especially since I’m moving into the realm of the Turnigy LiPo process- the information I got to do that basically came directly from there – credit where due. Here’s the link, and I hope to see you there!
As always, my long-suffering Facebook friends are stuck with seeing endless photos pop up in their feed constantly… ah well. I just opened that gallery up to the public, so if you prefer Facebook, well, have at it. Thanks for all the support and interest!
This is the most inspiring thing I’ve heard about electric motorcycling. Do yourself a favor. Make a nice pot of coffee, have a little set-down and listen to this interview of Azhar talking about the Mavizen, the TTXGP and his views on the future of electric motorcycling. It’s the one dated Jan. 15.
It’s an inspiration. Every time I hear this guy speak, I’m more impressed…
I got a note from John Fiorenza, the designer and manufacturer of the legendary Mars motors we all know and love and the owner of Mars Electric, saying they’d changed their name to Motenergy. New domain – motenergy.com – and site, but same great line of motors as well as other green energy products. Some interesting stuff I passed by on my way to motors, too- a Pelton-type water wheel for hydro-electric generation, and a 5 hp long-shaft electric outboard- cool stuff. (And me without a sailboat… sad, really.)
John is a great source of support and information and filled me in on the history of the Etek motor and other interesting tidbits for my post, “A Short Primer on the History of the Etek Motor, and Other Tales”. John just released the “Agni Killer”- the ME1003, a 11.5 KW continuous and 23 KW peak PMDC motor that’s gonna be the next beast that’s going into my build…
Best wishes John, and thanks for the heads-up!
Yes, the more some things stay the same. Batteries.
Last year at this time I was all torn about running what everyone else was running – Thundersky – and maybe trying Headways. Headways were the big unknown, and seemed to be more stable, capable of higher discharge rates, and overall cooler looking than the blocky, slow Thundersky. As winter moved into spring, it became clear that the newly branded CALB were slightly better than Thundersky, and that the Headways were getting used, proving reliable, if problematic from a BMS standpoint. My big anguish was where to put my money, and a not inconsiderable amount of money. This anguish spawned my second big anguish- how to build a battery mount.
Thus, my idea to build a bracket arrangement that would allow me to use several different sizes and styles of battery. Here’s one of the early photos of that.
When it came time to buy the batteries, I made the decision to go with cheap lead-acid AGM 22ah mobility batteries. I did this for a few reasons. First, they were cheap, at about $300 for the whole thing, second, they were about the same weight as what I wanted to run in lithium. I also felt that prices and technology were moving pretty fast in batteries and whatever I bought would be obsolete pretty soon, and that since this was my first build, the chances of blowing up or melting whatever I had were pretty high.
All of those reasons turned out to be pretty much on target.
Even Brammo, with the release of the Enertia 2, has introduced a new battery with twice the range. Enter LiPo- lithium polymer, around for a while in the RC and robot circles. LiPo seems to be right where Headway was last year, a little new, not really tried and proven, but with such compelling advantages they seem certainly worth considering. So. I’m back to not being quite sure exactly what packs I’m running, so torn about how to configure the mounting system.
The good news is, as you can see in the previous post, I could fit the same capacity of LiPo in half the space of the Headways. The weight savings is considerable- almost a third. So it’s a lot less of a challenge, but still. I’d love to be certain of what the technology will look like by May, and know how to build the packs.
But then, what fun is certainty?
1 pack – 22V, 5ah (rated 20C)
4 packs – 88V, 5 ah
4 packs x 4- 88V, 20 ah
16 packs @ $60 = $960
16 packs @ 2 x 2 x 6 = 384 cu in
1 cell – 3.2V, 10 ah (rated 10C)
28 cells – 89.6V, 10 ah
56 cells – 89.6V 20 ah
56 cells @ $20 = $1120
56 cells @ 1.5 x 1.5 x 6 = 756 cu in
Now, that’s not to say that the Turnigy are a slam dunk. LiPo is touchy, and if you’re looking at these you should start by looking here, at the LiPo noob thread on Endless Sphere. But still…
Let’s start with this. If you’re using a switch to handle a specific voltage and current, then match the specs of the switch to the voltage and current. Period. End of discussion. Why is that? Because switches have to handle two things- the overall load- current – that it can handle, much like a fuse. If the switch is too small, it will melt under full current. The second thing is the voltage. Think of the voltage as the pressure. If a switch is rated for 12V it may arc when you’re trying to disconnect, say, 72V. If you’re using it for an emergency disconnect, and it arcs, it may fuse shut as it melts, or simply not quench the arc, both resulting in a failure to disconnect. Bad. That $15 500amp 12V sound-system disconnect from PepBoys is not what I’d bet on for an emergency.
One important note. With AC current, you have a cycle from positive to negative flow, right? Through zero. With DC, you don’t, just a constant flow. This is why AC will “quench” an arc so much faster and easier than DC current. …and this is why you need to know the DC volt rating of a switch, not the AC.
You can read my Switches Made Simple post here, for a little more.
So let’s start by stating the goal here. I want to cut my battery pack out of the circuit, assuming it’s shorting out, crashed, or somehow the motor is under load. We’re talking 72V at maybe 300amps. Via DIYelectriccar.com, where I go for badass big information, since most of those boys are running systems that dwarf my motorcycle, in all ways, I found this discussion on high voltage, high amperage cutoff switches… along with the requisite discussion on the deal I just talked about above. Here’s what I came up with.
First, the Curtis SD/ED line, specifically the SD150L. Curtis caters to the forklift/golfcart guys, it’s no surprise they have this pretty well covered. I can’t find a voltage rating, but you’ve got to assume it’s at least 48V, standard for golf carts. Tracking down a supplier is a little bit difficult, though, but here’s the Curtis US distributor list, for a start.
Next, I found this little gem, certainly the coolest badass switch, and it says “Emergency Cutoff” all over it – something that’s nice considering the people who may want to find and use a switch like this may not necessarily be you, or even an emergency responder. This is the EZ-Safe Disconnect, from http://www.rechargecar.com. It’s a good price, too, at around $100. This uses Anderson connectors, and doesn’t make the connection itself, so you’re going by the connector specs, here. They also look like a pretty new product, so buyer beware.
Finally, there’s the Chinese knockoff of the Curtis, here. from Chennic. I’d probably go with the Curtis, but the cool thing about this is that it gives us voltage specs- listing it at 80V. I’d want to confirm it, but that would make me assume that the Curtis will do just fine with 300A at 72V.
I’m going to post a disclaimer here, I know, it’s not something I often do, but this is for a pretty important emergency device so I really need to make sure you understand where my advice is coming from. I don’t represent or work for any of these companies. I don’t even have experience with these products, yet, and can in no way attest to their use or appropriateness for the application. Contact the manufacturers or the distributors and do what they say. I am in no way responsible for any claims they make or any stupid crap someone may do with the information here. Especially since my advice is simple: use the correct rated switch for the job you need it to do.