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post #1 of 9 Old 06-11-2019, 10:08 AM Thread Starter
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Acceleration Mod?

Is their a way to change the acceleration profile on the Ranger EV? In researching the Sevcon drive it looks like their is a built-in acceleration profile. I am not sure if this is controlled by a digital input or if it's a parameter in the controller. Anyone ever look into this or change this?
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post #2 of 9 Old 06-11-2019, 10:50 AM
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Yes, it's programmable in the Sevcon. I had mine tweaked some. Basically there are 3 profiles programmed as controlled by that L / M / H button, and each will have separate torque, max rpm and regen settings.


Last edited by cricketo; 06-11-2019 at 10:53 AM.
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post #3 of 9 Old 06-11-2019, 01:24 PM
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The low profile already has max torque available , but has a much lower max RPM, the High profile has a higher max rpm and a lower torque output.

On the Li Ion conversions, Im finding that customers get a much improved performance, as the voltage is highe (nominal 60 ish volts)and the voltage drop is significantly less as well. Quite a transformation, even on the 6 cell block version which has a 180ah pack.

I was asked by a customer if we could make theirs do 30mph, but 26 is about the max we have measured. and going to 30mph would edge the motor rpm up towards 8000. Not a good idea. So 26max is retained. On that particular machine I was also asked that the torque max was upped as it tends to run at higher speeds, and often well loaded. So far not proven to be a problem.

I have seen one ranger with a factory fitted heatsink on the back of the Sevcon. No idea why this was fitted, but its a good idea if higher performance is required.
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post #4 of 9 Old 06-11-2019, 02:19 PM
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Quote:
Originally Posted by Grumpyb View Post
Im finding that customers get a much improved performance, as the voltage is highe (nominal 60 ish volts)and the voltage drop is significantly less as well.
Which is completely irrelevant due to fact Sevcon performs DC to AC conversion, and can maintain any desired output (within range) regardless of the input.
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post #5 of 9 Old 06-13-2019, 02:10 AM
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Actually not irrelevant, The voltage drop on the Lead acid has a big hit on performance, the Sevcon can only deliver what the pack is capable of , it does not have infinite current capabilities and as the voltage drops so does the performance. Try driving one with a low state of charge on a Lead acid and you will see the performance is much worse.With both a higher voltage and a flatter under load voltage , the Ranger has a more constant and higher performance, with lower current draw.


If you dont do lots of use of a ranger you may not realise that the pack is losing capacity , Loss of acceleration can also be a useful sign that the Lead Acid pack is getting tired. Water first if you haven't recently done so, thats the biggest reason for Lead Acid failures I see.

One user even had a watering kit, but didnt realise the kit had a watering point on both sides. So only ever watered one side. Doh!!

Last edited by Grumpyb; 06-13-2019 at 02:32 AM.
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post #6 of 9 Old 06-13-2019, 07:35 AM Thread Starter
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Thanks for the info guys.
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post #7 of 9 Old 06-13-2019, 09:56 AM
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Quote:
Originally Posted by Grumpyb View Post
Actually not irrelevant, The voltage drop on the Lead acid has a big hit on performance, the Sevcon can only deliver what the pack is capable of , it does not have infinite current capabilities and as the voltage drops so does the performance.
Now you're mixing apples in oranges together. Voltage drop under load and initial pack voltage as well as the fact Lithium has a wide voltage swing (how come you didn't mention that one?) are not directly related.
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post #8 of 9 Old 06-13-2019, 12:06 PM
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In the working range Lithium does not have a big voltage swing. Sure absolute full to absolute empty the voltage range is large, but thats not how they are used. Like any pack if its inadequate in pack size then you will also get a big loaded voltage drop. But thats just an inadequate pack size. Im guessing your small pack of Pacifica blocks is showing a big voltage drop under load.
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post #9 of 9 Old 06-13-2019, 01:27 PM
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Quote:
Originally Posted by Grumpyb View Post
In the working range Lithium does not have a big voltage swing
Here are some numbers for you :

NMC cell nominal 3.7, fully charged 4.2.
LA cell nominal voltage 2 volts, fully charged ~2.12.

For "48" volt configurations :

14 cell NMC is 51.8 nominal, 58.8 volts fully charged (7 volt change)
24 cell (four 12v in series) LA 48v nominal, is 50.8 fully charged (2.8 volt change)

For 60v configuration :

16 cell NMC 59.2 volts nominal, fully charged 67.2 volts (8 volt change)
30 cell LA 60 volts nominal, fully charged 63.5 volts (3.5 volt change)

As a reminder, nominal voltage is the voltage of a battery cell at 50% of the charge.

Now sure, for longevity cells shouldn't be charged to full 4.2 volts. Let's for fun of it "charge" them to 4.1 volts :

65.6 volts charged, 59.2 at 50%, 48 volts near 10-15%.

So yeah, if you're cycling your cells within 10-20% range of their capacity, there won't be too much of a voltage swing. If you're cycling them from 95% down to 20% like recommended, they will have a significantly higher voltage swing than Lead Acid.
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