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EV2Go
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Post by EV2Go » Tue, 23 Nov 2010, 18:30

:?:
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Post by Johny » Tue, 23 Nov 2010, 18:51

Wow - Christmas is early for you this year.

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Post by EV2Go » Tue, 23 Nov 2010, 20:14

:?:
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Post by Renard » Tue, 23 Nov 2010, 20:58

Thanks for taking trouble over the photos. That's a whole lot of gear: buses, cables, units etc, and a current sense loop I see also.
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Post by EV2Go » Wed, 24 Nov 2010, 22:06

:?:
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Post by Johny » Wed, 24 Nov 2010, 22:21

It mostly depends on the BMS capability in terms of "headroom" on their current measurements. Try to get an answer to the "will it limit current readings to 500 Amps" question.
It's unlikely any damage would result. Most of these types of sensors can handle many times their rated current for brief periods. The 1000Amp most likely is the same device with different scaling.

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Post by EV2Go » Wed, 24 Nov 2010, 22:34

:?:
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Post by a4x4kiwi » Wed, 24 Nov 2010, 22:49

I would say if you want accurate current measurements, and therefor accurate state of charge indication you should get the 1000A sensor.
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Post by 7circle » Thu, 25 Nov 2010, 00:48

I'm not sure of this exact sensor but many are specified on with lower rating than their peak capability.

But it needs to not max out to supply rail when measuring peaks in the battery current you expect while normally operating on the drag strip too.

It is there to give alarms at max current.

Does it have any model number info on it?

As it uses magnetic fields for the isolated measurement, the peaks even over 1000A must not saturate the device. If they do the linearity will be out.

They do have a point about it being more accurate but with out any real numbers to consider its all "trust me I'm a doctor and want to prescribe these drugs to see what they will do...." Image

I'd get some more info before demanding a swap.

What would be the maximum current it (the 500A model) can measure?

[Edit: Just thought I'd keep the cuplrit in question in the spot light]
Image
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Post by 7circle » Thu, 25 Nov 2010, 00:52

Usually you need to calibrate such sensors to get very accurate measurements.

Have they explained how to do this or is it pre-calibrated to your system in the factory?

What do you think of the central display mini-computer?
Is it touch screen, using zone or accurate X-Y positions?

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Post by woody » Thu, 25 Nov 2010, 02:08

Also is it Battery current (500A = 8+C) or motor current.

Can't recall your battery specs, but I half recall 60AHA CALB which means they'll max out at 600A anyway.

Motor current will not be used for battery charge state.
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Post by EV2Go » Thu, 25 Nov 2010, 04:08

:?:
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Post by 7circle » Thu, 25 Nov 2010, 06:22

The Sensor needs to cope with the ripple not just the DC average of the battery current.

I'd say they don't have 1000A amp model as standard.

If you plan to get up near the max of the Soliton1 of 1000A you might want to make sure the sensor can go this high.

If you hou had a 1000A model you could just put two turns through it (if they fit) to get 500A with double scalling. But you can't go the other way and go for 1/2 a turn.

Some current sensors use a current output that can be scalled to coltge using different size resistors. But this is getting a bit to techie for the WICOM BMS. It should be more plug and play (or pray).

Was there any info on the blue current sensor?


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Post by EV2Go » Thu, 25 Nov 2010, 06:37

:?:
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Post by Johny » Thu, 25 Nov 2010, 14:41

Loose facts time - assumptions galore.
Since the sensor is measuring battery current, taking off at the lights is unlikely to get to 500 Amps - at least up to 60km/h (the motor current is another story entirely). When the battery current gets over 500 Amps you will be in the maximum power range of the motor which means higher RPM. It is possible that this could occur for several seconds while accelerating up a hill at speed - but it won't be common.

On the other hand...

If we assume for a moment that they are using 10 bit A to D and the current sensor is bi-directional then pulling 500 A means about 1 Amp per bit. Using a 1000 Amp sensor would bring this down to 2 Amps per bit. This represents an accuracy of 1% for 500 A sensor or 2% for the 1000 Amp sensor. This also applies to charging (assuming they measure current during charge).

So is higher accuracy for most of the time more important than the odd missing Amps when the sensor flat-tops?

(Equivalent missing amps for 1% inaccuracy is pulling a full 1000 Amps (BATTERY current) for 18 seconds in a single 30 minute ride.)
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Post by 7circle » Thu, 25 Nov 2010, 18:15

When it's DIY you want to know the capabilities of the gear your using.

Even if the first battery pack is not capable of 1500A the next one may easily do it.

These type of HALL Sensors are replaceable modules in equipment in industry.
I'm sure you could find a replacement for it if WICOM can't get you one after the warranty period is over.

But it would be helpful to know what it is without having to test and measure it your self. They often have this sensor may be able to go to 2.5x 500A = 1250A like many other types.

I'm not sure how much stuffing around you will go through in knowing what you can get out of your custom Battery Back. But using this sensor, if its accuracy and frequency response is capable beyond the PWM of 16kHz, then you will be able to know how well the batteries are coping. You may need to monitor the signal with something other than the BMS sensor.

People often don't look at the high PWM ripple currents. They just look at the average DC or even the RMS or true RMS, but if the device is only capable of mains 50 or 60Hz frequencies they wont show you what's happening at the frequencies that the problems occur at.

If the controller capacitor bank is failing, the ripple current will be large and may not be detected.

Your battery back is bigg $$$ and if your wanting high performance you would want to know what's happening in the circuit.

The BMS is there to protect your big $$$$ dollar investment in the battery back. If the linearity of the current sensor at the high amps like 600A to 1000A is poor then the fuel gauge feature will be poor.

But you want to know that if you set the Alarm at 950A that the battery will be protected and if their is a 10% ripple of 95A that is pushing the peak to 1045A. Remember that I^2 x R is power loss so those ripple peaks take alot of loss from the batteries.

It won't hold up your progress with the trike either way. I just hope you can get the big battery wire end with crimp terminal through the hole!


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Post by a4x4kiwi » Thu, 25 Nov 2010, 19:08

Are there any part numbers at all on the current sensor?
Perhaps you can identify it http://web4.lem.com/hq/en/content/view/269/206/
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Post by EV2Go » Thu, 25 Nov 2010, 20:02

:?:
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Post by Johny » Thu, 25 Nov 2010, 20:13

By bi-directional I meant it can measure drawing current from the pack and charging the pack.
Those markings are great.
Here are some of the details on the sensor:
Image
You can see that it is good for +/- 750 Amps.
Got data from
http://www.bjsse.com.cn/en/uploadpic/pr ... 533663.pdf

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Post by EV2Go » Thu, 25 Nov 2010, 20:24

:?:
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Post by 7circle » Fri, 26 Nov 2010, 00:46

[Edit - No point confusing things with other similar device types]

The 20Khz -3dB limit of the open loop devices may limit the measurement of the 16kHz Ripple as the ripple is triagnular and has higher frequency compenent or A/uSec change rate.

A closed loop type have bandwidth upto 100kHz which would be better but cost more.

If the problem comes up you can always change it later if you need to. The BJSSE have these types available.
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Post by 7circle » Fri, 26 Nov 2010, 02:02

Bit hard to see on the web page in Mozilla there is a graph hiding in the murky blackness at the bottom of the page
Image

And the other mechanical link is here too:
Image

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Post by EV2Go » Fri, 26 Nov 2010, 15:22

:?:
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Post by woody » Fri, 26 Nov 2010, 15:51

EV2Go wrote: Figured the plug wasn't going to fit, but hoped it might... no biggy.
Is the other end an IEC? You should be able to get a 15A IEC cable with a 15A Australian plug on it without too much trouble.

It would be naughty to use a normal 10A IEC cable.
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Post by EV2Go » Fri, 26 Nov 2010, 16:05

:?:
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