Search found 421 matches

by zeva
Wed, 23 Jan 2013, 19:39
Forum: Members Machines
Topic: Ian Hooper's RX7 Conversion
Replies: 102
Views: 23717

Ian Hooper's RX7 Conversion

A quick news update.. I sent the first Hairball back for testing/repair late last week. Later that same day I did a test drive around the block and the Zilla tripped out again with the new Hairball, and I had to get it towed home again (fortunately only a short distance this time) http://forums.aeva...
by zeva
Fri, 18 Jan 2013, 22:34
Forum: Batteries, charging, management and monitoring
Topic: Wanted - an amp hour meter
Replies: 69
Views: 11620

Wanted - an amp hour meter

Yep, so still using the FGD to do coulomb counting, but its output can drive a voltmeter (turning it into a SoC meter, sort of). Fuel gauges in cars are basically reduced-scale voltmeters (in series with a varying resistance fuel tank sensor), the FGD gets tuned to match battery capacity with gauge ...
by zeva
Fri, 18 Jan 2013, 19:44
Forum: Batteries, charging, management and monitoring
Topic: Wanted - an amp hour meter
Replies: 69
Views: 11620

Wanted - an amp hour meter

Hi guys, the FGD is not really ideal for driving a digital gauge because its output is analogue (well, PWM), and the capacity adjustment also analogue (we could hard code that but usually there's an interplay between capacity adjustment and gauge scaling). You could get a decent result using a (digi...
by zeva
Mon, 14 Jan 2013, 21:32
Forum: Members Machines
Topic: Ian Hooper's RX7 Conversion
Replies: 102
Views: 23717

Ian Hooper's RX7 Conversion

Well, it is a possibility since the current diff is quite tall (4.3:1). However it is a very good diff (a strong Torsen-type LSD) so I imagine would be very expensive to change! Certainly much cheaper to add series/parallel switching, which would enable better high-speed performance without losing a...
by zeva
Mon, 14 Jan 2013, 00:32
Forum: General EV Discussion
Topic: LAMs and EV Bikes
Replies: 19
Views: 2427

LAMs and EV Bikes

Also there are a handful of 250cc bikes which are *not* LAMS approved, such as Aprilia RS250, Honda NSR250, Suzuki RGV250, which will probably come down in price a lot since RE license holders can't ride them anymore, and R license holders won't want them over say a 600-1000cc. I'd rather like an el...
by zeva
Mon, 14 Jan 2013, 00:05
Forum: Batteries, charging, management and monitoring
Topic: how long will uncharged lifopo4 battery last?
Replies: 2
Views: 658

how long will uncharged lifopo4 battery last?

LiFePO4s generally have very low self-discharge and may still be holding a charge after 3 years depending on what SoC they started at, though if there's a BMS attached it might've drained the cells completely (possibly to the point of damage, depending on the BMS). Safest bet would be to measure the...
by zeva
Sat, 12 Jan 2013, 21:02
Forum: Members Machines
Topic: Ian Hooper's RX7 Conversion
Replies: 102
Views: 23717

Ian Hooper's RX7 Conversion

Oh sorry, Zilla controllers have a separate power box and control box, with a comms cable in between. The control box is called the "Hairball", presumably because it usually has lots of wires coming out of it, resembling something a cat might cough up. http://forums.aeva.asn.au/uploads/112/Hairball....
by zeva
Sat, 12 Jan 2013, 20:52
Forum: Members Machines
Topic: Weber and Coulomb's MX-5
Replies: 1698
Views: 343121

Weber and Coulomb's MX-5

Take out some of the batteries from behind the rear axle? Since they add more than their own weight to the rear axle load, and actually reduce front axle load. The weight balance isn't terrible (about 48:52 front/rear, ~5% rearward shift) but that rear axle loading sure has gone up a lot. I'd be ver...
by zeva
Sat, 12 Jan 2013, 20:06
Forum: Members Machines
Topic: Ian Hooper's RX7 Conversion
Replies: 102
Views: 23717

Ian Hooper's RX7 Conversion

A quick update, I heard back from Zilla support last night (decent response time) who had a few suggestions, mostly banking on a faulty comms cable (which we had tried swapping) but also suggesting swapping the Hairball, so I went ahead and put Rob's loaner in. Happily, the car seems to be running f...
by zeva
Fri, 11 Jan 2013, 23:56
Forum: Members Machines
Topic: Ian Hooper's RX7 Conversion
Replies: 102
Views: 23717

Ian Hooper's RX7 Conversion

Yeah hopefully nothing too serious.. Rob from EV Works kindly loaned me another Hairball to try but I'll wait to hear back from Zilla support before trying anything (in case it just damages the new Hairball too!) Until the cutouts started, the car drove really well. I have the Zilla turned down to 1...
by zeva
Fri, 11 Jan 2013, 06:37
Forum: Members Machines
Topic: Ian Hooper's RX7 Conversion
Replies: 102
Views: 23717

Ian Hooper's RX7 Conversion

Hey, no new videos as yet, but some interesting updates.. I got a temporary movement permit and drove the car out to EV Works today (a 70K round trip) to get inspected, weighed, and to sort out the NCOP paperwork. Behaved perfectly the whole way there. One of the smoothest, nicest EVs I've driven. B...
by zeva
Mon, 07 Jan 2013, 03:57
Forum: Members Machines
Topic: Weber and Coulomb's MX-5
Replies: 1698
Views: 343121

Weber and Coulomb's MX-5

At the risk of further increasing the signal-to-noise ratio of the thread, I feel I must point out that a 2060kJ caramel slice at say $3 per unit works out at $5.24/kWh, which is 19x more expensive than electricity. Factoring in the efficiency difference weber points out, it'd be 76x more expensive ...
by zeva
Thu, 03 Jan 2013, 03:40
Forum: Batteries, charging, management and monitoring
Topic: Lithium Starter Batteries
Replies: 12
Views: 2741

Lithium Starter Batteries

13.2V does sound a bit low for LiFePO4s (3.3V/cell isn't fully charged). FWIW personally I'm in favour of bottom balancing when one does a 4-cell pack without BMS. The reason for this is that overdischarging is one of the most common reasons for damaging lithium cells, and occurs if one cell goes fl...
by zeva
Mon, 24 Dec 2012, 23:45
Forum: Members Machines
Topic: Ian Hooper's RX7 Conversion
Replies: 102
Views: 23717

Ian Hooper's RX7 Conversion

coulomb wrote: Time to change the topic's title, perhaps?

Good idea Image
by zeva
Mon, 24 Dec 2012, 00:10
Forum: Members Machines
Topic: Ian Hooper's RX7 Conversion
Replies: 102
Views: 23717

Ian Hooper's RX7 Conversion

Hi all, Big news: THE RX7 IS FINISHED! Hooray! http://forums.aeva.asn.au/smileys/smiley10.gif Well, basically. There are of course a few things I plan to add and I'm sure it'll be an ongoing project, but the car is now fully drivable, roadworthy (I think), and ready to start the licensing process. I...
by zeva
Sat, 22 Dec 2012, 22:17
Forum: General EV Discussion
Topic: EV Conversion Research
Replies: 17
Views: 2648

EV Conversion Research

To throw another spanner in the works.. there is a problem with running a battery pack sized for only short driving range: The smaller your battery pack is, the harder it has to work (proportionately) to drive your vehicle. Generally the most economical cells around (say flooded lead acids, or large...
by zeva
Tue, 18 Dec 2012, 17:58
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 386
Views: 54302

Low cost BMS

Ah yes I heard that individually fused rule in NZ. For a completely "centralised" BMS, i.e having trace wires from every cell all coming to a single location in the vehicle, I agree with the ruling; there's no safe alternative to individual fusing each of those trace wires, using fuses rated to full...
by zeva
Mon, 17 Dec 2012, 22:39
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 386
Views: 54302

Low cost BMS

I am also planing how to use a LTC6802 to be able to read a string of 12Cells with each slave board. This would reduce the power consumption, component count and board size. I'll be interested to hear how you get on with the LTC6802 chips. Did you get the 6802-2 addressable version? I read up on th...
by zeva
Sat, 15 Dec 2012, 20:59
Forum: Batteries, charging, management and monitoring
Topic: Battery Weight
Replies: 26
Views: 3108

Battery Weight

Apparently there are bags that you can get specifically for putting your Lithium Polymer batteries into while charging. The idea is apparently that if they overheat, there won't be much of a fire, as the oxygen in the bag is very restricted. I would be skeptical about these working very well with l...
by zeva
Thu, 13 Dec 2012, 04:33
Forum: Technical and conversion discussion
Topic: Voltage help
Replies: 11
Views: 1785

Voltage help

How much power are we talking? A DC/DC converter is the usual solution, but can be expensive.

http://www.digikey.com.au/product-searc ... ers/590047
by zeva
Tue, 06 Nov 2012, 18:38
Forum: Members Machines
Topic: Ian Hooper's RX7 Conversion
Replies: 102
Views: 23717

Ian Hooper's RX7 Conversion

Thanks coulomb, constructive criticism is always welcome! I might have to do a bit of a rain test on the charge door. Perhaps if necessary I can get it to seal up a little better when it's closed (add an o-ring or something). In other cars I've used those Clipsal weatherproof charge plugs with their...
by zeva
Mon, 05 Nov 2012, 23:35
Forum: Members Machines
Topic: Ian Hooper's RX7 Conversion
Replies: 102
Views: 23717

Ian Hooper's RX7 Conversion

Hi all, Another update to the blog, and some big news: Today I test drove the car for the first time! Here's the inaugural video of it pulling out of the garage and going for a gentle little drive: RX7 First Drive This was only running off the rear battery pack, and there are still quite a few jobs ...
by zeva
Tue, 30 Oct 2012, 21:09
Forum: Members Machines
Topic: Ian Hooper's RX7 Conversion
Replies: 102
Views: 23717

Ian Hooper's RX7 Conversion

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...
by zeva
Tue, 30 Oct 2012, 17:26
Forum: Members Machines
Topic: Ian Hooper's RX7 Conversion
Replies: 102
Views: 23717

Ian Hooper's RX7 Conversion

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...
by zeva
Tue, 30 Oct 2012, 16:52
Forum: Members Machines
Topic: Ian Hooper's RX7 Conversion
Replies: 102
Views: 23717

Ian Hooper's RX7 Conversion

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 ...