Vehicle Variation

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Paul9
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Vehicle Variation

Post by Paul9 » Mon, 04 Jul 2011, 21:00

Hi people,

My mate and I are in the process of finishing off our Suzuki Swift 1993 model. An Engineer's Cert and a bit of polish and we should be ready to see the RTA for rego.

My test driving of this ev has shown it to produce the performance promised - it is great for doing the shopping, going to golf, visiting family and all the other 10km trips we do a number of each day. Unfortunately Sydney is rich with long hills with 80kph speed limits and our little EV has trouble keeping up with this traffic. We installed the Goombi (Eugen) kit as follows:

Motor 96volt DC F series, 8.5 kw continuous 2800 rpm
Controller 300 amp 96vDC
Pot Box and 15amp Charger 96voltDC
96vDC-12vDC Converter

We actually bought two Goombi kits as we are going to build a second vehicle soon. The only mistake we made was thinking that we would be on our fourth car by now and so had imported 40 SANTAKUP AGM 100 Amp Hour batteries of which we have 32 left!

What I am now wondering is there a configuration of the components we have which could produce an EV with superior performance to our existing vehicle be that top speed, range or acceleration. As we have so many batteries we can use 8, 10 or even 12 batteries in this next EV. What we want to do is rather than waste the components we have is to use as many as possible in the next vehicle while still being prepared to spend a thousand or two on upgrading.
For instance:
a)Would we increase range if we used ten batteries (we have plenty of them!) ie. 3 batteries wired in parrallel = 300amphr capacity at 12 volts plus another 7 batteries wired in series to those three giving a total of 96v dc?
b) What would happen if we bought a 120v dc controller and used the existing 96v motor - better performance or won't they work together?
c) What if we bought a 120v dc motor and used the existing controller? Waste of time?

I suppose the basic and "real" question - is there any configuration of the components we have, or could substitute for a thou or two, that would give us superior performance to the vehicle we have at present? We don't wish to waste the components we have but would like to squeeze a bit more out of them even if we have to spend a bit to substitute.

I should point out that in no way am I dissatisfied with our first EV. I now know what the "EV grin" is!

Thanks
Paul

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Post by KDRYAN » Tue, 05 Jul 2011, 11:54

The Chinese motor you have can handle higher voltage and higher peak amps than you are now using. 120 volts would make a big difference to power (with higher amp controller) and higher speed due to the higher volts.

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Post by gttool » Tue, 05 Jul 2011, 13:56

Hi Paul good to hear that you got it finished
120v and a higher rated controller will make quite a difference
the controller that comes with the super zebo would be better off in a golf cart or if you have two you could try using both paralleled at 96v i believe it would be possible and would make it a bit more spirited in performance

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Post by antiscab » Tue, 05 Jul 2011, 14:41

Paul9 wrote:
a)Would we increase range if we used ten batteries (we have plenty of them!) ie. 3 batteries wired in parrallel = 300amphr capacity at 12 volts plus another 7 batteries wired in series to those three giving a total of 96v dc?


Hi Paul,

more battery does = more range, but you have to hook them up right.

If you put all 10 batteries in series you will get 120v 100Ah, or around 6kwh usable.

if you put 7 in series with 3 parralleled batteries, you will get 96V 100Ah or around 4.8kwh usable.

to get 96v 300AH you need 8 series 3 parrallel or 24 batteries.

how much mass can the car take?
is 10 batteries the most it will handle?
and you go to say 16 (or 96v 200AH)?

Matt
Last edited by antiscab on Tue, 05 Jul 2011, 16:41, edited 1 time in total.
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Post by Johny » Tue, 05 Jul 2011, 15:00

I agree with Kdryan. Running 10 batteries and a controller that will handle 120V will make a big difference. The problem is that your charger and DC-DC are 96V input. The DC-DC may well be rated to 120V so check that. The charger is unlikely to be able to be cranked up to 120V - but not impossible and worth checking out.
Unfortunately it means you may be up for:
1. New controller
2. New charger
and of course a couple of batteries.


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Post by woody » Tue, 05 Jul 2011, 15:59

Paul9 wrote: a)Would we increase range if we used ten batteries (we have plenty of them!) ie. 3 batteries wired in parrallel = 300amphr capacity at 12 volts plus another 7 batteries wired in series to those three giving a total of 96v dc?
antiscab wrote:if you put 7 in series with 3 parralleled batteries, you will get 96V 100Ah or around 4.8kwh usable.
(Usable in lead-acid is about 50% due to something called the peukert effect. Most lead acid batteries are rated on their 20 hour rate (called C/20). So you can get 100Ah from your batteries if you draw at 100/20 = 5amps for 20 hours. An EV draws power much faster than that, so it doesn't last as long due to something like the different speeds of different chemical reactions in the battery.)

This 1x3 + 7x1 will give you the same as if you had 8 in series. What happens is that the 7 will go flat before the 3, but you won't be able to use what's left in the 3.
antiscab wrote:If you put all 10 batteries in series you will get 120v 100Ah, or around 6kwh usable.
Agreed.
antiscab wrote:to get 96v 300AH you need 7 series 3 parrallel or 21 batteries.
8x3 = 24 batteries :-)

8s2p = 16 batteries should give you about twice the range, less a bit due to the extra weight. Performance will be bit less - less because of more weight + a bit more because less resistance through the batteries as they are in parallel.

cheers,
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Post by antiscab » Wed, 06 Jul 2011, 02:40

woody wrote:
antiscab wrote:to get 96v 300AH you need 7 series 3 parrallel or 21 batteries.
8x3 = 24 batteries :-)


shhhh, its fixed now :)
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Post by Paul9 » Wed, 06 Jul 2011, 04:33

Thanks people for the replies - very much appreciated.

It appears, if I understand your replies correctly, that we could build the second ev as a psuedo 120v dc by buying a 120volt controller and using the existing 96volt motor? I could check the specs for the DC-DC converter and charger and see if I can use the exisitng 96volt converter and charger in the psuedo 120volt ev?

Maybe I could, as suggested by gttool, add the second 96volt controller to my first ev in parralel with the current (pardon the pun) controller to get a bit better performance out of my first ev? Would the range of my first ev decrease due to the increase in amps pulled by two controllers in parralel?

Thanks again
Paul

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Post by Electrocycle » Wed, 06 Jul 2011, 04:42

the range would decrease if you drive faster :)
ie more current available means more power, so if you go up hills faster you'll be using more from the batteries.

the 96v motor will work fine at 120v, so a 120v battery pack and controller will add range as well as performance.
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Post by coulomb » Wed, 06 Jul 2011, 05:30

Paul9 wrote: Maybe I could, as suggested by gttool, add the second 96volt controller to my first ev in parallel with the current (pardon the pun) controller to get a bit better performance out of my first ev?

I don't think you can just parallel controllers. Maybe there are some that can be synchronised, but I'm sceptical.

Someone please correct me if I'm wrong there.
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Post by gttool » Wed, 06 Jul 2011, 13:51

the altrax controllers can be paralleled together it shows them on their website would possibly need to contact kelly to check but this would reduce the range but increase performance

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Post by antiscab » Wed, 06 Jul 2011, 14:06

Controllers have to be designed to be parralleled:
The gates inside each controller has to switch simultaneously, otherwise the current limit will not work (it has the effect of applying twice the target voltage to the motor).

the only way to parrallel two controllers that were not designed to be parralleled is two use a separate external inductor on each controller.

Matt
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Post by antiscab » Wed, 06 Jul 2011, 14:24

If you do parrallel two controllers not designed to be parralleled, they will operate at twice the target voltage with no current limit.

heres what happens:

controller 1 turns its gates on.
the current rises to controller 1's current limit as measured by controller 1 through its gate.
controller 1 turns its gate off.

The freewheel current is shared between the freewheel diodes of each controller.

at some point before controller 1 turns its gate on again (this could also be before controller 1 turns its gate off) controller 2 turns its gate on.
full motor current flows through the gates of just controller 2.
as there is already current flowing in the motor, the current rises past current limit faster than the control section can act.

The rate of current rise actually increases the more current you put through the motor as the motors effective inductance falls due to saturation (bigger controllers need control sections that can shut the gates down much faster than smaller controllers).

1 of two things happen:
1) the controllers switch far apart and the gates in controller 2 sees too much current and fails (catastrophically)

or

2) the controllers switch almost simultaneously.
In this case, while the gates in both controllers are on, the current is shared between the two controllers.
when any one controller turns the gate off, the full motor current will flow though the other controller:

for instance:
2 x "500A" controllers.
controller 1 shuts down at 5010A
controller 2 shuts down at 490A.

when controller 2 reaches 490A, controller 1 will also be conducting 490A for a total of 980A.
controller 2 shuts down, resulting in controller 1's gates conducting the full 1050A (the current is still increasing).

Matt
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Post by Paul9 » Wed, 06 Jul 2011, 18:30

Thanks people,

Even though I don't understand most of what you guys are talking about (I am an accountant) it seems that two parallel controllers is a risky business. I doubt there is any low cost way of improving the first ev's performance? Your comments however will be of great value with the second "psuedo 120v" ev!!

Oh, and by the way antiscab, if you would like three 7's to equal 24 then I think that is fine! After all, getting three 7's to equal anything except 21 is my job.

Cheers
Paul

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Post by Paul9 » Sat, 28 Jan 2012, 04:54

Hi people,

In this thread I was advised by a number of people that a 120 volt controller would improve the performance of my 96 volt motor and that the 96 volt motor could handle the increase in voltage to 120 volts comfortably.

I raise this question because I have just bought a 2nd hand golf cart with a 36 volt motor and controller in it. It's performance is a bit weak and I was wondering if I could improve it's performance by adding a 48 volt controller but retaining the 36 volt motor.

In short will the 36 volt motor handle the increase in voltage to 48 volts?

As usual thanks,
Paul

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Post by Richo » Mon, 30 Jan 2012, 21:32

Golf cart as in ride on?
I would think it would.
The downside will be the extra heat if asked to do too much or if there was a failure.
So the short answer is NO but the long answer is YES.
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