Which Series DC Motor to Choose?

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4Springs
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Which Series DC Motor to Choose?

Post by 4Springs » Sat, 01 Jan 2011, 23:42

I'm planning to convert a Subaru Brumby, approx 1300 kg total weight (with batteries).
I’d like to be able to go 100 km/h, which I think will require about 20 kW on a level surface. So I’ll need to be able to run at 20 kW for a time (say ½ hour) without overheating. I’d like to have a lot more power than this for short periods of time, to accelerate, get up hills, tow my tractor, etc.
I’m thinking of a 144 V system.

I’ve found it very difficult, as a novice, to compare motors from the different suppliers. I managed to find some information about each option, but they are not in any standard format, and some are more comprehensive than others. I’ve narrowed it down to these three, which I think would all be suitable:

Kostov 17R
$1750 from EV Works
60 kg
30 kW continuous, 72 kW peak, estimate 50 kW @ 500 A
Estimate 170 A @ 20 kW
Performance curves at: http://www.evworks.com.au/store/datashe ... Curves.pdf

Netgain ImPulse 9
$2395 from EV Works
60 kg
Estimates: 30 kW continuous, 70 kW peak, 70 kW @ 500 A
Estimate 350 A @ 20 kW
Performance curves at: http://www.evworks.com.au/store/image_v ... 62&index=2

ADC FB1-4001
$2750 from EV Motors
65 kg
21 kW continuous, 75 kW peak, estimate 50 kW @ 500 A
Estimate 250 A @ 20 kW
Performance curves at: http://www.evmotors.com.au/products/download/fb144.pdf

I have listed the power at 500 A, since I may go for a 500 A controller, which would limit my peak power available. Where I have said “estimate”, I have taken the value by looking it up on the supplied performance curves.

Ok, my question!
Have I interpreted the data correctly from the graphs? So for instance, for the Kostov, I want to find the current drawn at 20 kW of power output. So I find the power curve, and estimate that at 20 kW, it is giving about 30 Nm of torque. I then look at the current curve, and find that at 30 Nm of torque, it is drawing about 170 A. Is this correct? Is this how the graphs are used?

antiscab
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Which Series DC Motor to Choose?

Post by antiscab » Sun, 02 Jan 2011, 00:24

Welcome to the forum :)

btw if you are a paying association member, PM me so I can update your profile.

The continuous power of a motor is usually at a specific rpm.
its all about heat management.

all those motors have shaft mounted fans.
The faster it turns, the more air that moves through.

most of the heat that comes through is from resistive heating.
The more current (torque) the more heat.

continuous power increases radically with rpm.

anyway, on the graph, the lines labelled S2-60min lists the continuous torque/current for the 17R.
its 200A or 40Nm, 24kw at full traction voltage and 5700rpm.

The graphs are drawn in terms of motor torque.
the current (I) and torque are linear.
the rpm curve is maximum at the rated traction voltage.

The controller acts as a buck converter, so you can have the same torque at a lower rpm.

peak power, curiously, occurs between 2000 and 3000rpm, depending on your motor and battery voltage.

I like the kostovs the most as they have interpoles, and are built for higher voltage.

the 17R will be powerful enough if you have a gearbox.
If you do not use a gearbox, you will still be able to do 100kmh, but may run into heat issues.
half an hour at 100kmh without gearbox should be ok with a high ratio diff. acceleration will be poor at speed however.

what is your approx budget?
how far and fast do you need to go?

I would suggest something along the lines of:

~120km range@100kmh
Kostov 20R
soliton1 1000A controller 300V ($4k)
90 cell 100Ah pack ($14k)
and a few other things ($4k)

70km range @ 100kmh:
kostov 20R
soliton1 1000A 300v controller ($4k)
90 cell 60Ah battery ($8k)

you can reduce performance to half of the kostov 20R and soliton1 combo (not a bad idea with a smaller pack), but that only saves you ~$2k.
thats with a smaller controller, motor and retaining the gearbox.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
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4Springs
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Which Series DC Motor to Choose?

Post by 4Springs » Sun, 02 Jan 2011, 01:41

Thanks Matt, that has answered a few niggles about those graphs. The Kostov graph seems more professional than the others, which is an influence towards choosing that brand!
So for the comparisons in the previous post, it looks like I’d choose the Kostov for a good range (lower current at a given power), or the Netgain if I wanted heaps of power at a 500 A limit. The ICE in a brumby is rated at 60 kW, so I think the Kostov would be fine.

My ‘budget’ is as little as possible, and a fair bit less than what you suggest! I guess you’d call it a budget conversion.
I was impressed with Goombi’s Brumby, but decided that I’d like to go just a little bit faster. I’d like to go 100 km/h, whereas I think his will reach 80-90 km/h in a pinch. He gets a great range, which I probably don’t quite need.
I’d love to do the conversion for under $15k.

I will mainly use this vehicle to travel to work and back – a distance of 15 km one way. I hope to convince them to allow charging at work. This is the trip that I can go fast on.
I’d also like to also use this vehicle for less frequent trips to Launceston, our nearest city. This is 30 km via a hilly, windy road, or 40 km via a much flatter, faster road. We may have access to charging in Launceston, but I can’t count on it yet. These trips can be slower, to help with the range. I think that 80 km/h would be ok.
I’d like to be able to use 4WD, and to tow heavy loads at very low speeds. This is not something that I do every day, but it would be nice to have the option.
So the range requirements are 15 km @ 100 km/h, and infrequently 80 km @ 80 km/h.

My embryonic plans so far are:
Use the gearbox and the rear diff & tailshaft.
AGM batteries – about 20 kWh @ 144 V : $4000
Kostov 17R motor : $1750
Some kind of controller (Curtis or Logisystems) : $2000
Some kind of charger (Zivan?) : $1500

I’m leaning towards AGMs both because of upfront cost, and also simplicity. The battery management system required for a Lithium battery scares me. If I get the right charger though, it sounds like I could go for an upgrade of battery technology after I wear out the first lot of AGMs. I’ll probably post an entry in the battery forum soon, asking for comments on the research I’ve done.

Cheers,
Christopher.

antiscab
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Which Series DC Motor to Choose?

Post by antiscab » Sun, 02 Jan 2011, 03:59

Hi Christopher,

so 40km @ 80kmh is really worst case range energy wise.
40km @ 80kmh I estimate to be ~5kwh usable.

you need to be able to do 100kmh comfortably though, but only for 15km.
That dictates a controller that can do ~300A@144v continuous.

towing heavy stuff slowly, keeping the gearbox is a good idea, or using a bigger controller.

so controllers that can do 300A continuously:
zilla 1k LV (350A cont)
soliton1 (700A+ cont)
kelly 156v 800A controller (~350A cont)

steer clear of both logisystems and curtis.

ELCON make chargers better than Zivan.
isolated, active PF corrected, and around half the price.

batteries that give a minimum of 5kwh and 12kw continuous:
144v 100Ah AGMs (12 x 12v batteries)
144v (45 x 3.2v cells) 60Ah LiFePO4.

I suggest getting bigger batteries than the minimum if you can, but thats the smallest that should do it.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

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Which Series DC Motor to Choose?

Post by bga » Sun, 02 Jan 2011, 08:50

Hi Christopher,

Don't forget the BMS for LiFePo.

LiFePO4 batteries will need a means of balancing the cells so that they all stay usable and range is maximised. The EvWorks (EVpower) unit works well in most conversions.

I agree that more than the minimum battery capacity is needed. There has to be considerable margin for depth of discharge (80% max) and degredation of the battery (20%) over a few years.

Using about 25kWh per 100km is probably a safe estimate of the performance of the brumby, allowing for speed, controller and motor losses. It will worse with the tractor on the back.

You could start with lead-acid and upgrade to Lithium when the lead-acid battery gets too tired. This would suffice for the 15km trips, but not the 80km trips. 12 or 13 x 100AH Lead Acid (PbSO4) will be needed to get a 30km round trip range reliably, see below.

(At highway EV discharge rates, PbSO4 batteries suffer from considerable chemical 'peukert' inefficiencies, such that only about 70% of the battery's nameplate capacity is available. The battery has to be approximately 30% oversized to allow for this)

(13 x 100AH x 12V = 15.6kwh * 70% = 10.92kwh / 25kWh/100km = 40km)
Probably OK.

The 80km trip will be a harder problem, this will likely need a lithium battery in the 20kwh+ territory, say 45 x 160AH TS cells. Not cheap.

Cheers

Bruce Armstrong
Last edited by bga on Sat, 01 Jan 2011, 21:53, edited 1 time in total.
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4Springs
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Which Series DC Motor to Choose?

Post by 4Springs » Sun, 02 Jan 2011, 17:46

Thanks for your reply Bruce, I've been struggling with these calculations for a few days now...
bga wrote:Using about 25kWh per 100km is probably a safe estimate of the performance of the brumby, allowing for speed, controller and motor losses. It will worse with the tractor on the back.
I'd agree to 25 kWh @ 100 km/h road speed. Is this what you were basing it on?
But I'm thinking that 80 km/h would be ok for these long trips - say 15 kWh per 100 km?
(13 x 100AH x 12V = 15.6kwh * 70% = 10.92kwh / 25kWh/100km = 40km)
Probably OK.
So the calculation becomes:
(12 x 140AH x 12V = 20.1kWh * 70% = 14.1kWh / 15kWh/100km = 94km)
The '1300kg' in my original post was based on this size battery.
Driving slower may also mean that the '70%' in the calculations goes down a bit? Especially if the batteries have a good rest in the middle of the 80km trip.

Let me know if these calculations look good (or bad!).

Cheers,
Christopher.

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Which Series DC Motor to Choose?

Post by 4Springs » Sun, 02 Jan 2011, 23:10

Thanks for that Matt, you've given me some research to do. <goes away for a few hours and Googles things...>
Matt (antiscab) wrote:so controllers that can do 300A continuously:
zilla 1k LV (350A cont)
soliton1 (700A+ cont)
kelly 156v 800A controller (~350A cont)

steer clear of both logisystems and curtis.
The 'zilla doesn't seem to be manufactured at the moment.
The Soliton1 looks like overkill for this EV.
The Kelly is new to me, it hadn't come up in my research to date. They have some nice features, a range of models, at a reasonable price with the $AU the way that it is at the moment. I spent quite a while at the Kelly website - lots of pretty things to distract me...

Why the warning about the Logisystems & Curtis controllers?
ELCON make chargers better than Zivan.
isolated, active PF corrected, and around half the price.
Again, hadn't heard of Elcon (now called tcCharger). I found the forum threads on the chargers, and they do look good. The local importer is concentrating on Lithium chargers, hopefully he could import a lead-acid one for me (or maybe adjust one himself - presumably just a difference in firmware?)...

Cheers,
Christopher

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Post by antiscab » Mon, 03 Jan 2011, 02:21

Hi Christopher,

Nancy will sell you a lead acid charger directly.
shipping is a little pricey, total is around AUS$600 for a 1500W unit in any flavour, delivered.

That was the last time I had one priced.

I also have a 144v seal lead acid charger made by chenic sitting on my odds and ends shelf I can sell you more cheaply when the time comes.
Same specs as an TC Charger 1500W, just not made by them.

Both Curtis, and logisystems, are analogue controllers.
They don't have variable motor side current limit, no battery side current limits, and have poor thermal management.
most controllers back off when they get too hot, curtis and logisystems blow up instead.

Theres a myriad of other reasons why they aren't that great, but those are the main ones.
4Springs wrote: (12 x 140AH x 12V = 20.1kWh * 70% = 14.1kWh / 15kWh/100km = 94km)
The '1300kg' in my original post was based on this size battery.
Driving slower may also mean that the '70%' in the calculations goes down a bit? Especially if the batteries have a good rest in the middle of the 80km trip.


I would have it more like this:

(12 x 140AH x 12V = 20.1kWh * 50% = 10.0kWh / 15kWh/100km = 66km)

The 50% is a combination of keeping total discharge to less than 80%, and peukets.

A rest in the middle of the trip will slightly increase the safe discharge depth, again a peukets thing.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

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Which Series DC Motor to Choose?

Post by 4Springs » Wed, 05 Jan 2011, 01:44

This has made me look up the Chennic website now.
Any comments on their controllers? I don't see any prices...

Christopher.

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Post by antiscab » Wed, 05 Jan 2011, 02:22

Chennix 144v 8A

I bought mine as I needed a 144v charger really quickly for my Vectrix.
I ended up buying an Elcon from Rod as he could have it to me the very next day.

The unit works out of the box, but thats as much experience as I have had with them.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

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Which Series DC Motor to Choose?

Post by 4Springs » Wed, 05 Jan 2011, 02:30

That's the charger, but they do controllers as well.
I've had a bit of a surf since, and found opinions that they are very cheap, and you get what you pay for! Comments along the lines that the chargers & DC-DC converters are ok, but the controllers aren't much.
Did you buy the charger direct from them?

Christopher.

antiscab
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Which Series DC Motor to Choose?

Post by antiscab » Wed, 05 Jan 2011, 02:31

I bought mine from ebay.

I could have been the same guys, or a reseller, I'm not sure.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

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