How to use a clamp meter?

[faico_26]

Hi,
I need to measure the amps that my Q300R motors (4 pole 10 km/h) draw in my Q300R which has a VR2 90amp unit. BM you told me in another post to use a clamp meter and I've seen your video with the clamp meter on your knee and I read many posts. But I still have doubts about how should I plug or use the clamp meter.
Is it just to connect a wire to the battery or how it works? Could you explain it for me?
Many thanks!!

[Burgerman]

This will get complicaed fast.
I already replied to that other thread in depth just now...

1. A battery current can be 10% of the motor current. And as you speed up, the battery current can be 100% of the motor current. So BATTERY and MOTOR current are 2 completely seperate independant things.
2. Measuring battery or motor current wont tell you much unless you understand a lot more about how and what is actually happening!

And I will leave it there until you ask a few questions one at a time!

To measure MOTOR current (battery current will tell you nothing useful here) you need to measure the current in ONE motor wire. So you must extend the wire from one motor brush, to the clamp meter on your knee and back again... Unless you do you cant measure anything!

With one SIMPLE exception. Buy R-Net as that can show you battery voltage, battery current, motor 1 volts, and current, motor 2 volts and current all in real time as you drive, speed up, slow down and stall the chair...

See here:

[Burgerman]

Sure beats running long cables and doing this!!!

https://www.wheelchairdriver.com/gopro/motoramps.mp4

But let me tell you what I think is your problem.

1. You have the thing programmed in full hovercraft mode and that will always limit current what you need it anyway.
2. Your settings as per the previous post may be incorrect.
3. Your motor compensation may be too low. My 6mph 4 pole Linix are set to 50 mOhm. Up from stock. Lots of torque.
4. Your battery may be too high impedance or faulty limiting current. Which you can test easily with a voltmeter connected to the charge port as you LOAD the chairs motors.

The problem will be 1 of these above or a combination of the above.

[faico_26]

This will get complicaed fast.
I already replied to that other thread in depth just now...

1. A battery current can be 10% of the motor current. And as you speed up, the battery current can be 100% of the motor current. So BATTERY and MOTOR current are 2 completely seperate independant things.
2. Measuring battery or motor current wont tell you much unless you understand a lot more about how and what is actually happening!

And I will leave it there until you ask a few questions one at a time!

To measure MOTOR current (battery current will tell you nothing useful here) you need to measure the current in ONE motor wire. So you must extend the wire from one motor brush, to the clamp meter on your knee and back again... Unless you do you cant measure anything!

With one SIMPLE exception. Buy R-Net as that can show you battery voltage, battery current, motor 1 volts, and current, motor 2 volts and current all in real time as you drive, speed up, slow down and stall the chair...

See here:

Thanks for the detailed explanations BM! I’m sorry I duplicated my questions in both posts. I’ll buy the clamp meter and I will try to do what taught me: “ you need to measure the current in ONE motor wire. So you must extend the wire from one motor brush, to the clamp meter on your knee and back again”

[Burgerman]

When it reads low, what will that tell you?

Because it will.
How do I know? Because you have almost no torque. And torque is directly proportional to Amps.

We already know that. So what does that tell you?

[Burgerman]

Questions.
How heavy is your chair?
How heavy are you?
Is this mid or rear drive?

Because all my own chairs are 6mph (10kph) and NEED that 120A even with low impedance batteries, and GOOD correctly set up programming.
Why? Because unlike 6mph chairs from say 10 or 20 years ago they are now DOUBLE the weight. Most of my chairs are now 170 to 190KG up from the 80 to 90 in the past.

I too have added a few pounds over the years as many do as we get older.

So now those same 6mph motors that worked fine with an 80A controller in yesteryear need to move double the mass. That takes double the current. That would really require motors that were HALF the impedance (it didnt change) and controllers that can do double that 80A which also didnt happen. So the motors do not pull enough amps, and if they did then the controllers couldnt provide that power anyway. If they could then the BATTERY which has not grown also cant supply this current.

Can you see why batteries no longer last, chairs cant climb curbs. Controllers roll back power. Etc etc. Its a doom loop!

[faico_26]

Questions.
How heavy is your chair?
How heavy are you?
Is this mid or rear drive?

Because all my own chairs are 6mph (10kph) and NEED that 120A even with low impedance batteries, and GOOD correctly set up programming.
Why? Because unlike 6mph chairs from say 10 or 20 years ago they are now DOUBLE the weight. Most of my chairs are now 170 to 190KG up from the 80 to 90 in the past.

I too have added a few pounds over the years as many do as we get older.

So now those same 6mph motors that worked fine with an 80A controller in yesteryear need to move double the mass. That takes double the current. That would really require motors that were HALF the impedance (it didnt change) and controllers that can do double that 80A which also didnt happen. So the motors do not pull enough amps, and if they did then the controllers couldnt provide that power anyway. If they could then the BATTERY which has not grown also cant supply this current.

Can you see why batteries no longer last, chairs cant climb curbs. Controllers roll back power. Etc etc. Its a doom loop!

How heavy is your chair? Not 100% sure but the Q300R stock is 130kg and mine has seat lift, so I guess is 160kg or more.
How heavy are you? 60kg
Is this mid or rear drive? Rear drive

[martin007]

Clamp meter for beginners...

> https://es.aliexpress.com/item/1005006766865627.html

[Burgerman]

Which?
Be sure it does DC current on the clamp.

[faico_26]

When it reads low, what will that tell you?

Because it will.
How do I know? Because you have almost no torque. And torque is directly proportional to Amps.

We already know that. So what does that tell you?

What does it tell me? Maybe that compensation is too low? Or batteries can’t provide the needed power?
I was actually thinking what you said in other posts and that is that my 90amp unit is not enough do the amps that the motors draw. I mean, very heavy chair and only 90amp. I want to measure the amps and see how many amps the clamp meter shows when trying to climb a curb. If the amps are higher than 90amp then I Should change to R-Net 120amp.

[Burgerman]

The power module CLOSELY watches the current. It will never exceed 90. It may only do 90 for an instant then it may roll off due to anti stall current reduction to protect motors, because of temperature, because the boost limit is limited to a second, because its protecting the battery and sees the voltage drop under load, because of a bunch of settings that add these things together, including time (historic), and / or because the whole programming settings are set too "hovercraft" or because acceleration settings set too low and the current strats rolling back before that 90 is reached, or compensation, etc. Or because motors are warm and impedance increased.

Unless you know what to look for, are able to adjust things to test, to monitor battery voltage while watching current at the motors etc and use logic and reasoning to diagnose its not going to tell you much.

You need an OEM programmer, a voltmeter, a current clamp meter, and some diagnostic skills.

[Burgerman]

Isnt THIS https://www.wheelchairdriver.com/board/ ... &mode=view
Just a whole lot easier! It measures everything and displays it on screen as you roll...

And you can fit 120A per motor, and a colour joystick and all seating options for £80+£50 a 33% gain in current/torque.

IMAGES BELOW - £130 total.
Joystick (I offered £80 he accepted) NEW.
Power module (120A), + 6 axis seating actuator and lights, + 2 bus cables, = £50 complete. USED but super clean.

Thats actually even cheaper than you think!
Why? Because now you can sell your old 90A VR2 power module, and seating actuator module, and the VR2 joystick. Probably make a fair profit!
AND you no longer need a clamp meter as it does that internally for free... More savings.

Now you have a full 120A system and you can monitor all motor and battery voltages and currents as you roll. Free, but you now need an R-NET programmer!

Aquire these things when the price is right over the next year.

[Burgerman]

Note.
There are 2 different VR2s that have either identical connectors to R-Net, so plug and play. Or a diffferent one. I THINK sunrise use the common connectors one so that they can offer either R-Net or VR2 on a chair and its plug and play. Check.

Do your motor and battery connectors look like this R-net, if so plug and play:

[faico_26]

Note.
There are 2 different VR2s that have either identical connectors to R-Net, so plug and play. Or a diffferent one. I THINK sunrise use the common connectors one so that they can offer either R-Net or VR2 on a chair and its plug and play. Check.

Do your motor and battery connectors look like this R-net, if so plug and play:

Yes, I think so, because when ordering the chair they give you the option to choose between VR2 or R-Net so I guess it's the same connectors. I have checked again the ordering form on Sunrise Spain webpage and I noticed the R-Net they offer on the order form a 90AMP unit. It's always the same, they offer the minimum and paying a fortune. If you want the 120AMP then you have to pay even more. The VR2 90AMP system I have is included in the 4500€ the chair costs.

If I had decided to go to R-Net instead of VR2 I would have payed extra for:

- R-Net ISM-6L (ref. QML110032) (lighting, seat module) - 215€
- Joystick (screen colour) - 600€ or 800€
- R-Net 120AMP module - 520€
- (((R-Net PC Programmer about 500-600€)

I will check the connectors in my chair, it will take a few days. I'll post photos.

Thanks,
F.

[Burgerman]

>>>- R-Net ISM-6L (ref. QML110032) (lighting, seat module) - 215€
£40 to 50 typically, I have 4 of these spare.

>>>- Joystick (screen colour) - 600€ or 800€
I only buy NEW joysticks.
Or brown box brand new "refurb" UNITS. (These are actually part ex units that come from PG Drives, and are indistinguishable from new as they are fully remanufactured.) They may contain some used parts internally. Externals are all new. Screens all new. Buttons etc all new. Its impossible to tell they are not new. Or maybe they are!
I paid £40, and £50 for basic LED joysticks.
I paid £80 for a CJSM as far as I can tell brand new.
I paid 125, 125, 150 for my 3 spare CJSM2 new joysticks.

>>>- R-Net 120AMP module - 520€
£40 to 45 typically eBay as new or clean used.
As you see I have 5 of them!
Including one that was £50 including a couple of bus cables, and the ISM-6L included too...

All this stuff DOES come up on eBay. Usually its for a matter of minutes and its gone. Or the price is almost right, so I make an offer. I lok for stupid descriptions. like "brain" or wheelchair joystick, or control module, etc Because they get relisted to sell cheap as nobody can find them. On german, US, UK, spanish, whatever eBay. It takes patience and perseverance. Dont buy used joysticks. Make silly offers...

[faico_26]

>>>- R-Net ISM-6L (ref. QML110032) (lighting, seat module) - 215€
£40 to 50 typically, I have 4 of these spare.

>>>- Joystick (screen colour) - 600€ or 800€
I only buy NEW joysticks.
Or brown box brand new "refurb" UNITS. (These are actually part ex units that come from PG Drives, and are indistinguishable from new as they are fully remanufactured.) They may contain some used parts internally. Externals are all new. Screens all new. Buttons etc all new. Its impossible to tell they are not new. Or maybe they are!
I paid £40, and £50 for basic LED joysticks.
I paid £80 for a CJSM as far as I can tell brand new.
I paid 125, 125, 150 for my 3 spare CJSM2 new joysticks.

>>>- R-Net 120AMP module - 520€
£40 to 45 typically eBay as new or clean used.
As you see I have 5 of them!
Including one that was £50 including a couple of bus cables, and the ISM-6L included too...

All this stuff DOES come up on eBay. Usually its for a matter of minutes and its gone. Or the price is almost right, so I make an offer. I lok for stupid descriptions. like "brain" or wheelchair joystick, or control module, etc Because they get relisted to sell cheap as nobody can find them. On german, US, UK, spanish, whatever eBay. It takes patience and perseverance. Dont buy used joysticks. Make silly offers...

Thank you, that's really valuable information that only I can find here in this forum, I really appreciate it.
Going back the question of this post, how to use a clam meter. You explained that it should be with a wire from one of the brushes to the clamp meter and back to the brush again? I am sorry, I have to ask someone to do this for me and I'm NOT sure I'm understanding well how to do this. Could you please explain the connection way for a beginner like me? Thanks BM!!!!

[Burgerman]

You will need to make an adapter. That allows you to plug in between a motor and the power module. One wire can go straight to the power module. About 6 inches long. The other one needs to go wherever your clamp meter is. A long loop. 10 sq mm cable.

Its easier and quicker to just fit the R-Net and let it tell your laptop the batt voltage and current, and each motor voltage and current as you roll.

[Burgerman]

Why?
Because to be USEFUL you need to understand the relationship between pulsewidth, battery current, and motor current and also be able to read simultanious current in 3 places while watching the voltage at motors (a 50% pulsewidth or half throttle which happens even at a 10% stick movement due to compensation is 12V) and see what that does at the battery.

The battery in the chair below is already being pulled down to 24.1V which would be "all the lights out" if it wasnt averaged, while pulling only 24.9A from it.
And because of the pulsewidth the controller is using then the motors are both well over 100A/113A each. And look at the motor voltage, that is the proxy for pulsewidth. Or the amount of "gas" the controller is applying due to load. (compensation) In this case turning in my hallway in place.

Look at M1.
Its 10V (around a 45% pulsewidth) and because almost stalled drawing 100A plus. Thats a 10 to 1 relationship. If the controller sent 20V (ABOUT 90% pulsewidth) that motor would pull 200A. The controller cant do that though... This motor must be turning.
If compensation was set higher, it would be sending around 12V and 120A. And would turn in place better.

Look at M2
It has 113A and still only 10.7V. So that motor has either a lower impedance (maybe colder) and is pulling more than 10X the voltge in amps. But these are both cold motors. So that means that THIS motor is turning slower or stalled as its drawing more amps per volt than the other one.

I also see that theres no thermal rollback as the mosfets are just 7C warmer than my house was.
Your controller will heat up faster because its using "smaller" higher resistance mosfets. So yours may roll back power sooner.

Thats what I see here.

[martin007]

Which powerchair do you have, faico_26?
How much do you weigh approximately?

[faico_26]

Which powerchair do you have, faico_26?
How much do you weigh approximately?

My chair is a Sunrise Q300R with seat lift. And I’m 60kg.

[martin007]

You weigh less than I do.
However, your powerchair weighs almost twice as much as mine.
My powerchair is a QUICKIE Rumba.

[faico_26]

You will need to make an adapter. That allows you to plug in between a motor and the power module. One wire can go straight to the power module. About 6 inches long. The other one needs to go wherever your clamp meter is. A long loop. 10 sq mm cable.

It’s easier and quicker to just fit the R-Net and let it tell your laptop the batt voltage and current, and each motor voltage and current as you roll.

I understand now how to measure amps, thank you. It’s clear R-Net is the best option, lots of information easily accessible. First I will measure amps with my current VR2.

[Burgerman]

Q300 is a narrow ligher weight chair.

It uses small batteries (meaning they dont much like heavy loads because higher impedance) and generally are sold with quite low spec, so VR2 and 4mph and thats partly because price and partly because small batteries dont much like 4 pole/120A controllers/6mph... And yes with the seat lift etc its heavy!

I dont think 4 pole 6mph motors, are a good idea with small batteries and a heavy chair.

[Raro]

Faico already has the programming cable and the software to use it, so why don't you send him a modified file like you did with JohnnyUK? It seems he was happy with the change.

[faico_26]

Faico already has the programming cable and the software to use it, so why don't you send him a modified file like you did with JohnnyUK? It seems he was happy with the change.

Yes, BM very kindly told me could modify my programming file, I still have not sent it to him.

[faico_26]

Q300 is a narrow ligher weight chair.

It uses small batteries (meaning they dont much like heavy loads because higher impedance) and generally are sold with quite low spec, so VR2 and 4mph and thats partly because price and partly because small batteries dont much like 4 pole/120A controllers/6mph... And yes with the seat lift etc its heavy!

I dont think 4 pole 6mph motors, are a good idea with small batteries and a heavy chair.

That’s true, Sunrise only offers small 60ah batteries for Q300R. I checked the Sunrise web and it seems that the Q300R only can use a specific battery size.

[Burgerman]

Well I could do that on R-net and garantee pretty much I know how it will respond. But thats R-Net. This is VR2 which I have no experience of. So while many settings might respond the same way I cant know this... So it would be a little risky!

[faico_26]

Well I could do that and garantee pretty much know how it will respond. But thats R-Net. This is VR2 which I have no experience of. So while many settings might respond the same way I cant know this... So it would be a little risky!

Yes, you warned me about it, thanks!