Range Calculation

[aminorjourney]

I reckon your range is whatever it is in miles between the batteries being charged and discharged

Seriously though, expect your range to be less initially than it will be in a few months

As for more, I can totally recommend Lithium Ion and the fantastic Reap BMS

[EVguru]

My Reliant Kitten would do 25 miles or so on a 100Ah 96 volt pack of liesure batteries.

The batteries will need breaking in. Their capacity will grow for the first 10-30 cycles or so and may well be quite a lot below spec now. You shouldn't push them too hard when they're new. Many batteries have their life expectancy reduced by range testing a newly built vehicle.

Ideally you 'bench' cycle them. You discharge them with a constant load (or heater element, string of lightbulbs, etc.) at as high a rate as you can manage (at least 5 hour rate) keeping a close eye on individual battery voltages. Note the readings at five minute intervals and discharge untill the lowest battery drops to 11 volt (you need to check the voltages more often as you approach the voltage cut-off). Once you've got a good idea of run time you can walk away for the first bit, but make sure you've got an alarm clock with you to alert you to go back. Each charge cycle should show an increase in run time. Try and start each test with the batteries at the same temperature since this has quite a large effect on capacity.

The batteries are broken in when the capacity stops increasing (or at least when the rate of increase drops off). In the absence of a load bank, I've tested batteries by putting a vehicle on stands and spinning the wheels in top gear. You need to keep tweaking the trottle to maintain a contant load as everything warms up.

If you measure the current at the beginning and end of the test you get an idea of the average current. By multiplying this by the run time you get an Ah value for the weakest battery. If you program about 80% of this value into a capacity gauge, you've got a good chance of getting a good life from the batteries.

If you think this sounds time consuming and boring, IT IS!

I don't like to think of the hours I've spent testing batteries. Having access to a Zivan programmable load bank was pure luxury when working on the race car. These days I make do with sections of storage heater element.


There are various places you can measure the current.

In the Motor circuit.

That's good for making sure you don't overheat the motor and also for running the motor at it's most efficient speed/load. Too low a current and you're wasting energy in friction and windage. Too high a current and you're wasting energy in I2R. Most motors have a sweet spot at around their rated current.

You can measure the current in the battery circuit.

That tells you what's actually coming out of the battery and will therefore effect your range.

You can measure the peak current in the MOSFETs (or other power switches). The controller needs to do this anyway to protect the power devices and you can extrapolate the battery and motor currents from it if you know the PWM duty cycle. It's rarely available as an external signal on a non uProcessor based controller.

The Zapi has a shunt to measure current, but I can't remember which circuit it's in. I think it must be the motor loop for use in regen.

Do you know which current the console is actually displaying?

[geekygrilli]

Dunno what current the Console is actually displaying, the manual only says 'Maximum Current of the chopper'

Anyway, half an hour ago i found out why my controller blew up the first time around...It appears that if I set the current to max, the motor must arc or something - cos it just happened again.....

Anyone know where I can get some IRFP250N and 30CPF06 MOSFETS, I seem to have blown a few.

I guess swear words are not allowed on this forum, and i am not learning from my mistakes.

[geekygrilli]

Right, its sort of OK...

My wife didn't give me a b#ll#cking for blowing stuff up, and having to spend more money on the car!

Plan of action is:-

Get controller fixed
Get a new motor - any suggestions of a 96v motor?

Get some lessons learned!

Like Paul said - you can't do it for less than £3000, and he was right. Its going to be that when I've finished now! (I thought I'd topped out at £2200)

[EVguru]

With the dollar so weak, it may be a good idea to import a motor from the US.

One of these would be ideal;

http://www.evparts.com/shopping/product ... ct_id=1112

The last time I imported a motor it cost US$300 for three day airfreight, but these days EVparts a likely to use UPS or similar and the cost will be a lot higher (the charge for filling in the export forms is often as much as the shipping).

Many of my EV parts have come from the US (usually by private shipping through firiends).

You could also look for a second hand motor from the various EV trading sites.

Anyone know where I can get some IRFP250N and 30CPF06 MOSFETS, I seem to have blown a few.

The 30CPF06 is a fast recovery diode and both parts are available from www.farnell.co.uk

You'll need to check the gate resistors (flame proof type), gate protection zenners and the gate driver (I.C. as I recall rather than discrete components).

I'm a little surprised it's blown. The higher voltage H2s have had their problems, but I thought they were a good deal more robust that your's seems to have been.

[geekygrilli]

It must be my motor making it pop. The fuse didn't blow, its rated at 375Amp on the input side.

Its my fault, the acceleration is fine with teh Max Current set to 5/10. But I was running through all variables with my brother driving and me logging the numbers objectively and my brothers subjective views.

Again, wasn't accelerating hard. Ho hum. So far the repairs have cost me nothing - this'll be teh first one I pay for, so in that light its not so bad!

I have already called Advanced DC - $1800 for a motor, is not too bad?! I have a FedX account so I might be able to ship it myself for a very good rate.

We'll see. Its tempting fate even considering trying one of the other 2 motors I have.

Thanks so much for yor help Paul. If it were for you and Dave of electricvehicles I would be completely stuck.

I do hope my posts and your replies are helpful to others too.

[EVguru]

I have already called Advanced DC - $1800 for a motor, is not too bad?!

How much (Jaw drops to floor)!!!!

Which motor was that for?

EVparts have the L91 for US$965.21 and I've driven VW Rabbit (Mk1 Golf) conversions with the motor and they perform quite well at 96 Volt.

A few years ago (when EVparts were Wilde Evolutions) I used to be able to deal with Rod Wilde direct (I knew him from the EV racing) which made things easier (if not actually cheaper), they've grown and changed considerably since then, but they've still got a good reputation. You may still find the motor cheaper elsewhere.

ADC went through a sticky patch a while back when they started selling motors for passenger EV use with the brush timing set at Zero degrees (causing motor damage and controller failures) and it took quite a bit of work to get them to admit their mistake, but they're a reasonable product at a reasonable price and have probably put more conversions on the road than anybody else.

In fact that's just given me an idea. Have you checked your brush timing?

If the brushes are set at Zero, they should line up dead centre with the field poles. If they're advanced, they should be rotated away from Zero opposite to the rotation of the armature.

You should be Ok if they're set at Zero, but would get better performance and less brush wear with them advanced, but if they're actually retarded that may well explain your flashover problem.

[geekygrilli]

Hmmm, MOSFETS are £7 each, and I need about 25 of them!
Diodes are £3.50 and I need 6 of them

I also need a few 160v 1000uF capacitors £4 each and like you said the flame proof gate resistors, lucky they are cos some have bits missing, and a few of the diodes are cracked.

Wow, i actually understood what bits you meant!

It will probably not be worth me trying to fix it, if Zapi can do it for £300 or £400!

Thanks for the motor link - I will probably get the one you spec'd. The one that ADC quoted $1800 for is available for $1450 on the evparts site.

[EVguru]

Hmmm, MOSFETS are £7 each, and I need about 25 of them!
Diodes are £3.50 and I need 6 of them

I also need a few 160v 1000uF capacitors

You blew caps?!

That's rather fishy. I wouldn't normally expect that to happen.

Mind you, the last 96 volt H2 I took apart had 200 volt capacitors.

After an event like this you'd be advised replace all of them. If you'd blown just a couple, ok, but with this many visably blown , the rest may well have been damaged and could fail at any time.

How much are EZ asking for a new, bare (less contactors), controller these days?

It might be more reliable than having yours fixed.

[geekygrilli]

Well, there was a 'pop' or two, and it sounded like a a capacitor to me. Some of the FETS have completely disintegrated, lost their legs and blown in half.

I'll take some pics tomorrow and post them for all to see!

Maybe I can just get them to supply me with a new 'high power' board with all the caps and FETs and I can just slot it in.

My caps are definitely 160v 1000uF.