Search found 773 matches

by Nevilleh
Wed, 23 Oct 2013, 12:52
Forum: Members Machines
Topic: Weber and Coulomb's MX-5
Replies: 1698
Views: 347925

Weber and Coulomb's MX-5

Well done, guys! I haven't looked on here for quite a while as I sold my BMW to a very happy new owner and haven't done any EV stuff for some time, but I thought I'd better get an update on the MX-5 and - lo and behold! - I see its registered and driveable. Not to say "finished" because, like mine, ...
by Nevilleh
Sat, 22 Jun 2013, 18:41
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 388
Views: 55531

Low cost BMS

Yes, R1 is the phototransistor collector load. I didn't bother trying a cap across the diode emitter as I never really had an interference problem after I re-routed the comms wires properly. The only reason for trying a cap across R1 was because I occasionally received a bad packet or two and it was...
by Nevilleh
Thu, 06 Jun 2013, 16:19
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 388
Views: 55531

Low cost BMS

When I first got mine going in the car, I experienced some corrupt data packets when accelerating at full throttle and I fitted a .01 uF cap across R1 which got rid of some high frequency noise on the data signals. I connected my 'scope across R1 and chose the value by the amount of rounding it caus...
by Nevilleh
Thu, 06 Jun 2013, 14:17
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 388
Views: 55531

Low cost BMS

I guess the o/p would be saturated with your optos and they may be a lot slower, its hard to tell without looking at the signal waveforms. Anyway, working is the main criterion! The accuracy of the bms voltage measurements depends on the accuracy of the voltage reference and also the resolution whic...
by Nevilleh
Wed, 05 Jun 2013, 13:36
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 388
Views: 55531

Low cost BMS

I am pleased that you solved your problem! I guess if the parts list says to use a 6mm bolt, you better not substitute it with a 1/4" one. I hope you used the correct optos on the cell modules. Edit: I had a look at the specs for both optos and your SFH one works with a much lower current - you didn...
by Nevilleh
Wed, 01 May 2013, 13:00
Forum: General EV Discussion
Topic: eRider goes up in flames!
Replies: 19
Views: 3727

eRider goes up in flames!

Last year, I arranged the importation of an eRider electric motorcycle/scooter for a fellow with no experience of either EVs or importation and I thought it might be quite a good machine - how wrong I was! When it did arrive, I found the build quality quite shoddy, with panels not lining up, bolts m...
by Nevilleh
Sun, 21 Apr 2013, 20:50
Forum: Batteries, charging, management and monitoring
Topic: Wanted - an amp hour meter
Replies: 69
Views: 11796

Wanted - an amp hour meter

A year or more ago, a fellow in the US designed am instrumentation display to interface with the Cougar controller, but it has lots of other features too, such as measuring the EV battery voltage. He did it with a linear opto plus a small dc-dc converter so it all ran off the 12 V supply. Here's his...
by Nevilleh
Wed, 17 Apr 2013, 17:50
Forum: Batteries, charging, management and monitoring
Topic: Wanted - an amp hour meter
Replies: 69
Views: 11796

Wanted - an amp hour meter

Ah, your message reminded about that - I had forgotten you asked for another board! I've just had a look and I do have most of the parts, but I am flat out at the moment and won't be able to get around to assembling one for a while. If Richo sorts yours out, let me know and I won't worry about it fo...
by Nevilleh
Wed, 17 Apr 2013, 15:13
Forum: Batteries, charging, management and monitoring
Topic: Wanted - an amp hour meter
Replies: 69
Views: 11796

Wanted - an amp hour meter

Here's some .jpg images:


Image
Image

This is the upgraded version with outputs to drive a tachometer as an ammeter and a fuel gauge as a battery capacity meter.
by Nevilleh
Tue, 16 Apr 2013, 16:34
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 388
Views: 55531

Low cost BMS

Ok I solved my problem. Since some of you are working on your BMS i guess it is good to explain. I changed comm lines to soft UTP computer cable. The thing is thin! But it works very good. I now have comms stable through all RPM and up to 200A (havent tried it faster :)). However when i start to ta...
by Nevilleh
Tue, 12 Mar 2013, 12:18
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 388
Views: 55531

Low cost BMS

Well, it looks like it should be all right. As I mentioned earlier, the transistor is probably not getting enough base drive to fully saturate at 1 A and the voltage drop down that track from the emitter to -ve is reducing it still further. You can reduce R5 to 160 ohms and that will give you 25 mA ...
by Nevilleh
Mon, 11 Mar 2013, 18:33
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 388
Views: 55531

Low cost BMS

I'm told that the screen can act as an antenna and actually increase the coupling of EMI into the signal wires, especially if they are not a twisted pair. Another thing people do is ground both ends and then the earth current flowing induces interference into the signal wires.
by Nevilleh
Mon, 11 Mar 2013, 12:24
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 388
Views: 55531

Low cost BMS

The pcb tracks are not designed to carry 1 amp. Where did you fit the 3R3 resistor? The ones you describe certainly wouldn't fit on the pcb. If the shunt transistor is getting hot, it probably doesn't have enough base drive. Measure the Vce while its on and measure the voltage drop across the base r...
by Nevilleh
Mon, 25 Feb 2013, 12:49
Forum: Batteries, charging, management and monitoring
Topic: Wanted - an amp hour meter
Replies: 69
Views: 11796

Wanted - an amp hour meter

Yes, its not so easy, is it? I tested it with my bench power supply which can only deliver 6 A and it agreed perfectly with the ammeter on that which can read to about .1 A so I know it is pretty accurate at that low current level. Be interesting if you can compare it with your clamp meter at that s...
by Nevilleh
Sun, 24 Feb 2013, 22:24
Forum: Batteries, charging, management and monitoring
Topic: Wanted - an amp hour meter
Replies: 69
Views: 11796

Wanted - an amp hour meter

Trouble with your load resistor is that is is highly temperature dependent ie what you calculate for 25 deg will be a bit out when you pass a couple hundred amps through it, even in a bucket of water. Depends how accurate you want to be. I just would like to know how good my ammeter is! I have one o...
by Nevilleh
Sun, 24 Feb 2013, 12:29
Forum: Batteries, charging, management and monitoring
Topic: Wanted - an amp hour meter
Replies: 69
Views: 11796

Wanted - an amp hour meter

Be nice if you could measure the current with a device of known accuracy, just to check. Maybe a proper shunt resistor and a voltmeter?
by Nevilleh
Thu, 21 Feb 2013, 19:17
Forum: Batteries, charging, management and monitoring
Topic: Wanted - an amp hour meter
Replies: 69
Views: 11796

Wanted - an amp hour meter

Those resistors are the current limiter for the backlight. I find that the acklight voltages vary quite a bit depending on the brand of lcd and what is OK for one may be a bit more current and hence heat than another. You could make them bigger and dim down the backlight a bit if you want. Probably ...
by Nevilleh
Mon, 18 Feb 2013, 12:52
Forum: Members Machines
Topic: Weber and Coulomb's MX-5
Replies: 1698
Views: 347925

Weber and Coulomb's MX-5

The trials and tribulations of the EV maker! Wondrous to behold - speaking of which, that 3D business completely escapes me and all I get is blurred vision! Are you sure you're not having us on? Image
by Nevilleh
Sun, 17 Feb 2013, 17:35
Forum: Batteries, charging, management and monitoring
Topic: Wanted - an amp hour meter
Replies: 69
Views: 11796

Wanted - an amp hour meter

Just because I could, I added some stuff to this thing. One, a pwm output that can be used to drive a fuel gauge. If you program in your battery capacity, the fuel gauge will read full down to empty as you use up the amp-hours. Two, a variable frequency square wave output that can drive your tachome...
by Nevilleh
Sat, 02 Feb 2013, 01:48
Forum: Batteries, charging, management and monitoring
Topic: One for the BMS-o-philes
Replies: 38
Views: 5706

One for the BMS-o-philes

And if you can't understand it, its mathematics.
by Nevilleh
Fri, 01 Feb 2013, 17:05
Forum: Batteries, charging, management and monitoring
Topic: One for the BMS-o-philes
Replies: 38
Views: 5706

One for the BMS-o-philes

I think you are needlessly concerned about a shunt failure running your battery flat. The probability of that is vanishingly small. Modern electronics, properly designed, has a very long lifetime. I think I explained some very good reasons for why I abandoned the central monitoring idea and I’ll be ...
by Nevilleh
Fri, 01 Feb 2013, 14:58
Forum: Batteries, charging, management and monitoring
Topic: One for the BMS-o-philes
Replies: 38
Views: 5706

One for the BMS-o-philes

Only just saw this thread and read it with some interest! It does highlight some of the issues of monitoring a big, high voltage battery, doesn't it? When I first started looking at battery monitoring/management, I built a "centralised" system with wires running from each cell, but when it came time...
by Nevilleh
Wed, 30 Jan 2013, 16:45
Forum: Batteries, charging, management and monitoring
Topic: Wanted - an amp hour meter
Replies: 69
Views: 11796

Wanted - an amp hour meter

I've zipped up all the files for this and here they are: AH_Meter_Files.zip The compiler is the CCS C compiler running on MPLAB V8.88. The .sch and .pcb files are DesignSpark. I got the pcb from ITEAD and it is a "shared" one, so if you want one they should be able to supply without having to re-sen...
by Nevilleh
Wed, 30 Jan 2013, 16:17
Forum: Batteries, charging, management and monitoring
Topic: Wanted - an amp hour meter
Replies: 69
Views: 11796

Wanted - an amp hour meter

Trying for maximum range! The meter will go to 65535 AHrs - that's because its a 16 bit variable else you'd be stuck with a max of 255. It checked out very well. I set it for 100 A and timed it while it counted up to 100 AHr and the error was too small to see on my stopwatch. The main source of erro...
by Nevilleh
Wed, 30 Jan 2013, 12:54
Forum: Batteries, charging, management and monitoring
Topic: Wanted - an amp hour meter
Replies: 69
Views: 11796

Wanted - an amp hour meter

Thanks, both good ideas. I thought also to include two other outputs: a pwm signal that could drive the car's fuel gauge and show full to empty. That would require the battery capacity to be programmed in, of course. Probably only for Li cells as I couldn't be bothered with Pb-A and all that Peukert...