Greetings from the Netherlands

[Burgerman]

Because getting more amps requires a different controller and is, of course, very difficult, my dad and I came up with the idea to just double the voltage.

Since the limit in torque is the controller Amps, it doesenyt make any difference what battery voltage you use. The motors will have exactly the same stall torque, and it will occur when the motor voltage is around 4 to 7V in most cases. Depending on motor impedance. At this point, the controller throttle back, and will not allow the max amps to be exceeded.

The speed would double.
Controller stall amps and motor impedance determine stall torque,
Battery voltage determine speed. Your speed would double. But the controller will not survive, and will give errors and not work above around 32V.

The plan is to use 2 lithium batteries of 24 volts. We will power the motor with both batteries, 48 volts.

hOW EXACTLY?

And power everything else, my current controller as well, with one battery, which would be 24 volts, and the same as I currently have.
Do you have any thoughts on this?

tHAT WILL SEVERELY UNBALANCE THE LITHIUM BATTERY.
Sorry keyboard...

[steves1977uk]

99.99% of mobility controllers only work on a 24v setup Caz, and depending on how well the Q-Logic PM handles higher volts, it might error out when it sense an overvoltage of 30v+ or you might risk burning it out!

Also DC-DC step up voltage boosters between the PM and motors won't work since the chair will behave very erratically.

Steve

[Burgerman]

Not to mention that they will need to handle 120Amps and work from 0V to 26V. As a pulse width 26V signal. And in BOTH directions. I see much smoke in your future!

[CazSaa]

So, new plan.
I have been busy with school for a while but summer break is here, so I can continue with this plan.

BM, you said that your BM3 is not to be taken lightly because you have to build things such as the controller yourself. Because we don’t want to do this my dad came up with a different idea.

His idea is to use 2 different batteries, one with 24V and one with 48V. The 24V battery should all trivial stuff such as controller, lights and things like lift and tilt functions. While the 48V battery would only power the motors. This way we won’t have to make our own controller.
Any feedback for this?

Now I need to get into lithium batteries and the roboteq controller, which is gonna be hard.

Thanks.

[Burgerman]

Because getting more amps requires a different controller and is, of course, very difficult, my dad and I came up with the idea to just double the voltage. The plan is to use 2 lithium batteries of 24 volts. We will power the motor with both batteries, 48 volts. And power everything else, my current controller as well, with one battery, which would be 24 volts, and the same as I currently have.

Do you have any thoughts on this?

Yes. If you were to power the motor with 48V and no controller it will spit you out and destroy thegearbox.
If you were to power the motor with 24V from a standstil, same thing! The CONTROLLER moderates the current and the rate of acceleration. You cannot use it without this. If you try, the motors will hit 6mph in around 0.1 of asecond. And you will not be in it...

[CazSaa]

Because getting more amps requires a different controller and is, of course, very difficult, my dad and I came up with the idea to just double the voltage. The plan is to use 2 lithium batteries of 24 volts. We will power the motor with both batteries, 48 volts. And power everything else, my current controller as well, with one battery, which would be 24 volts, and the same as I currently have.

Do you have any thoughts on this?

Yes. If you were to power the motor with 48V and no controller it will spit you out and destroy thegearbox.
If you were to power the motor with 24V from a standstil, same thing! The CONTROLLER moderates the current and the rate of acceleration. You cannot use it without this. If you try, the motors will hit 6mph in around 0.1 of asecond. And you will not be in it...

I see now that I worded this poorly. I meant that I want to power the Q-Logic controller with the 24V, and try to make something work with a different controller between the 48V batteries and the motor. The roboteq controller for example, or maybe a different kind.

I hope this is more clear.

[Burgerman]

Not really.
1. What is the qlogics output used for? if the roboteq is connected to the motors.
2. And how do you power that qlogic, you cant take it from half of a battery?

I am saying, if you have a roboteq in charge, why would you want or need to also run a qlogic system?

Or are you thinking that you can use just the joystick, and stuff, to connect to the roboteq (you cant)?

[CazSaa]

Not really.
1. What is the qlogics output used for? if the roboteq is connected to the motors.
2. And how do you power that qlogic, you cant take it from half of a battery?

I am saying, if you have a roboteq in charge, why would you want or need to also run a qlogic system?

Or are you thinking that you can use just the joystick, and stuff, to connect to the roboteq (you cant)?

I was indeed thinking to connect the joystick to the roboteq. Is that not possible? Why not? Would I need a specific joystick?

[steves1977uk]

Think BM has used an APEM joystick on his BM3 chair, not sure which model he used though. But I think you'll struggle getting a mobility joystick to communicate with the Roboteq Caz. Different swing voltages etc...

Steve

[Irving]

Think BM has used an APEM joystick on his BM3 chair, not sure which model he used though. But I think you'll struggle getting a mobility joystick to communicate with the Roboteq Caz. Different swing voltages etc...

Steve

Interfacing the actual physical joystick component probably wouldn't be hard with some knowledge of electronics for signal conditioning, but physically connecting an 'as is' qlogic joystick module to the Roboteq is probably a non-starter.

[LROBBINS]

The qlogic joystick, as with other WC joysticks, uses one or another serial protocol to communicate with the rest of the system. John (Burgerman) and some others are just using a bare analog joystick to connect to the Roboteq, while I have designed my own multi-node CANbus system. Most Roboteq controllers, in addition to raw analog and digital inputs and outputs, also support RS232 and CANbus and the newer ones support other serial protocols as well. Using any of the serial methods does require programming the sending and receiving units so they can "talk" with each other. There's a thread here by someone from Australia with an example of talking with the protocol used by Shark controllers (a relatively simple serial system), but you'll have to search for it, or wait for someone to notice this thread and point you toward it. As Woody notes, if you directly connect to the wires on the joystick pot (inside the joystick pod), if it is an analog joystick you can connect it to a Roboteq - do note that some joysticks, however, e.g. the Shark, don't use analog joystick pots so you can't do that with those. A bare APEM analog joystick has a reasonable cost from electronics suppliers so it's probably an easier to implement choice for a Roboteq than using an existing joystick and bypassing all its electronics.

Now, I do have a prejudice about these things. I do NOT like multi-wire analog/digital connections to a Roboteq. Not only is the wiring complicated, but there's a risk of interference, and relatively little failure protection. I much prefer using CANbus - a robust, interference-resistant, self-correcting serial protocol originally developed for heavy (e.g. earth moving) equipment and now almost universally used in autos. Implementing it takes more programming and more electronics inside the joystick box (and any other modules in the system: seating actuators, lights, whatever), but everything connects together with just a 4-wire cable: B+, B-, CANhi and CANlo.

[CazSaa]

The thing I like about my current joystick control is all the information it gives me such as speed, battery percentage and the ability to control everything on my chair. I was hoping to keep these functionalities. Would this be possible with the roboteq controller? Which kind of joystick would give me these possibilities?

Also where can I find some threads of others who want to speed up their power chairs? I wasn't able to find a lot.

[Irving]

No you won't. The joystick and controller work together as a system. You can't use one without the other. You cannot significantly change speed while retaining the existing controller and you can't have all the nice functions of the existing system without the existing controller.

You cannot do what you want to do without re-engineering the whole system from scratch, as others have done. But that requires serious engineering skills and is not off the shelf. You will need to integrate parts from various suppliers, which may require electronics design, software development and other skills. Your new system will be unique, you have to understand it intimately. And be your own expert.

I'm sorry, but the questions you're asking just tell me you got a lot of learning to do before you can contemplate anything that radical.

And that why you won't find many examples. It's beyond the capability of most people.

[steves1977uk]

The thing I like about my current joystick control is all the information it gives me such as speed, battery percentage and the ability to control everything on my chair. I was hoping to keep these functionalities. Would this be possible with the roboteq controller? Which kind of joystick would give me these possibilities?

Also where can I find some threads of others who want to speed up their power chairs? I wasn't able to find a lot.

Simply not possible I'm afraid, not without a lot of electronic re-engineering as Irving said.

The only way to gain extra speed is to swap out the Q-Logic control system for a R-Net control system and up the motor voltage to 25v from 21v approx, along with a LiFePO4 lithium battery pack. And also bigger diameter rear wheels. That's your only easiest option without re-designing everything from scratch.

Steve

[Irving]

The only way to gain extra speed is to swap out the Q-Logic control system for a R-Net control system and up the motor voltage to 25v from 21v approx, along with a LiFePO4 lithium battery pack. And also bigger diameter rear wheels. That's your only easiest option without re-designing everything from scratch

A lot of effort, Steve, for good possibility but could equally end up just a lot of effort for a marginal gain. Wheel size 14 -> 15.5" is ~10%, 21 - 25v in theory could net 20+% give or take torque & start up issues.

[steves1977uk]

Hmmm yeah that's true Irving. Wonder if the motor voltage can be upped on the Q-Logic PM with an OEM level programmer?

Steve

[CazSaa]

Hmmm yeah that's true Irving. Wonder if the motor voltage can be upped on the Q-Logic PM with an OEM level programmer?

Steve

Shouldn’t the motor voltage already be the maximum of 24V?

[steves1977uk]

Nope, most are set to 21v approx to leave headroom for steering when using Lead bricks Caz. Once you go Lithium, voltage drop is never an issue until you get to the last 10% remaining power, then the drop-off is like a cliff.

Steve