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Powerchair "Control Systems" E.G. Penny & Giles, Dynamic, etc.
If
like me you have an interest in these things, since you want power, speed, with huge
controllability you will want to learn about the BEST and most powerful available
systems.
And
importantly the "differences" between them relating to Powerchair performance
and control. This
page is only concerned with this one aspect. The manufacturers own sites
are a better place to see the "range" of addon's lighting, actuators, fancy
screens and other capabilities. I am only discussing power and control.

Over the past ten or twelve years
I have been building my own, or very heavily modifying various different powerchairs
because I wasn't happy about their comfort, indoor and outdoor capability, power
(torque) or speeds.
Whilst doing this I learned a lot!
I have had very involved discussions with tech guys from P & G (Penny and Giles)
who make rather a lot of these controllers! The P and G ones we are interested in
here are the top end units such as the Pilot Plus, RNet controllers. Pilot Plus
is still available but superseded by the newer RNet design. Which is basically
the same, but with a fancy screen and more flexibility.
Controllers and
ratings...
These things are sold by every manufacturer in "AMP" RATINGS. In
all cases they claim to be able to provide say 100 AMPS to both motors
simultaneously. Now while this is true, its NOT the whole story! I have
been doing some digging and measuring.
We all "presume" that this means 100 amps at the 24v batter
voltage to each motor. To do that they would need to take 200 amps from the
batteries. But when you measure this under a stalled full power condition like
when trying to climb a curb and it wont move, its actually 100 Amps from the
battery only. Now you cant get anything for nothing so either there is only 50
amps going to each motor or 100 amps at half the battery voltage. HALF the power
we expected. Its actually the latter. About 12v at 100 Amps goes to each motor
and we don't move up that curb...
The manufacturers conveniently forget to mention that they mean
100 amps at HALF the battery voltage. So in reality the controller is half the
real power we expected.
Penny & Giles
All of the different Penny and Giles power modules from 50 to 120
amps can output that "Amp rating" to each motor. So a 100 Amp system
can provide 100 Amps to each motor at the same time. While this is
happening there is still only 100 Amps at 24v being drained from the powerchairs
battery. Now any schoolboy can see that that isn't actually possible unless the
motors are receiving half the volts each. So effectively that's what happens.
And half the volts means half the number of watts of energy to each motor. And I
have measured it. And discussed it with them at length.


A 100 Amp Penny & Giles controller can
therefore provide a MAXIMUM of 100Amps x 24v = 2400Watts Nominal Power.
Or actually less as measured.
Half what we are led to expect. Why does this matter? Well it means torque and
control is reduced at the very times we require it to climb a ramp or get over a
threshold. Not so good.
An RNet 120 Amp controller can deliver a maximum of 60 amps to
the motors, at half the battery voltage. So it has a little more torque and
control but only as a "boost" for a short time and its really not a large
amount. Effectively that is almost the same as 60 Amps at the proper battery
voltage... The same number of watts.
That is a MAXIMUM total value. This
effectively means that the 100 Amp units are really just behaving like 50 Amps when you need
the power on a ramp for e.g. They are effectively only HALF of their rated values
once the total possible output is taken into consideration.
This means that when trying to climb a ramp into a van or cross a
threshold into a building you only have just 1200 watts per motor (total
theoretical) on a 100 Amp system to propel and control you. And that is not
really enough for a heavy person in a 6mph powerchair. Forget about doing this
in an 8mph chair. Its be even worse.
In reality group 24 Gel batteries like MK's Gel favoured by the
industry for e.g. have trouble doing this even
when fully charged and new. They really cant do it when old or a little
discharged. So your 100 amp Pilot Plus Controller really only gives about 40
real amps equivalent power to each motor at very best... That's why
you get stuck on curbs, ramps & thresholds with little power or control in difficult situations.
It is a combination of battery voltage dropping and the control systems limited
"power" (watts) capability.
The the newer 120 amp RNet controllers behave in exactly the same but with a
100 amp output that is boosted to 120 amps peak for a short time. (10 seconds) So it can
take 120 amps from your batteries and deliver half the power (120 amps at half
the voltage) to each motor maximum at the
same time. Batteries allowing... The same applies to VR2 and VSI
controllers too! And some of those are just 50 Amps to begin with!

With this in mind I had a lot of email
communication with P and G technical guys. After about 1000 words and 4 emails
we finally got to the point!
They replied:
Dear Mr
Again, you are absolutely correct in stating that a reduction
in voltage will result in a reduction of current. However, please bear in
mind some typical values of resistance you might expect to see from a
highspecification motor. A value of 0.05Ohms would not be atypical. This
would mean that a current reduction would only be experienced at controller
outputs voltages below 6V, roughly 25% wheelchair speed.
Best Regards  name removed for P and G.
So the very point where we need power 
at the slower end of the powerchairs speed range, for ramps and other
difficult manoeuvring operations the power is missing... Remember this
the next time your chair is stalled and will not turn, or go up a curb/ramp
without a run up!
So how does the Dynamic DX (80 Amp) and DX2
(90 Amp + boost) Systems compare?
Well there are MANY similarities. These too reduce voltage to the
motor at lower speeds and so can also provide the full rated "Amp" capability as
claimed, but again at reduced power (voltage). Although under some circumstances
the Dynamic systems can actually pull the full rated Amps x2 from the battery.
So have more power. (Double the system Watts)
E.g. the Dynamic system (DX2) can actually pull 2x 90 amps from
the battery. 180 Amps at 24v. So some 4320 watts total power capability (claimed
but not measured. So unlike the P and G system it is not limited to only 100
Amps (120 on boost?) from the battery (or just 2400 watts).
It can only do this however at the point where the motor voltage
is at "full 24v" and not demanding more that 90 amps per channel. And so at
about 1.5 mph or above. And as soon as demand increases on say a hill the full
power is scaled back to a lower level.
An email here from Dynamic:
Hello John
The maximum current from the battery for the DX2PMA90 is 180Amps. This is split
90A per motor. This will ONLY be achieved into a true 90A load at maximum speed
demand. If you reduce speed, you will not get the maximum power output. If you
increase load (increase the current) above 90A (current limit) you will not get
maximum power. Above 90A, the power reduces through reduction in motor voltage
in order to limit current.
Best regards  name removed.
So they both do the same tricks at the slow
speed end of things, but dynamic "claim" that they can supply full power (2x the
rated amps) and draw 180 amps from the battery. Although I actually think that
the guy is mistaken.
So in real world use with Gel batteries there will be little
benefit anyway as they cannot give this amount of power. However swap batteries to Odyssey or Optima AGM batteries that
can actually produce
this much current (amps) and the benefits in torque and power, especially off road and
ramps, or with tall gearing are obvious to any spirited user.
So, if you are buying a new powerchair, which is the best system?
The maximum number of total watts your controller can provide is very important.
MORE is always better even if you never actually use them or need that extra
torque to turn or climb a ramp. They are simply a "reserve" of power for the odd
occasion that its important. This is not the same as "amps". What matters is the
total system power.
But for a manufacturer to fit a "big" Amp controller they need to make sure that
the batteries and battery cables can and will survive that bigger load. And that
the motors and gearboxes have enough strength to survive the extra torque. And
that in fact a stalled or almost stalled motor actually draws that much current.
Meaning in some cases a heavier motor.
All of which ads up to COST for them...
Bear all of that in mind when looking at powerchairs. Then you will see why some
chairs have 50 Amp controllers... You want the BIGGEST Amp controller you can
get for the best performance on ramps etc., while maintaining safe control. All of this
stuff above is subject to
Correct Programming!
And as we saw
above its not even that simple because some systems do not do what it says on
the tin, or they do "technically" but at lower voltage. So you don't get the
power you expect. Hence this table below so you can see what is what!
SYSTEM  Read details its very important!
 Some systems have HALF their expected power! Especially check out
the Dynamics Systems.
Penny & Giles 
Pilot Plus
100


100 Amps
Total System Maximum
from batteries, or
100
to each motor but at half the voltage. So
half the power. Total max system power
2400 watts.
Oops 
this is why thresholds and steep ramps are difficult with loss of
control at times.

Penny & Giles 
Pilot Plus
80


80 Amps
Total System Maximum
from batteries, or
80
to each motor
but at half the voltage. So half the
power. Total max system power
1920 watts.
Oops 
this is why thresholds and steep ramps are difficult with loss of
control at times.

Penny & Giles 
Pilot Plus
50


Don't bother!

Penny & Giles 
RNet
120 

100 Amps Total System Maximum but with 10 second extra 20 Amp "boost"
from batteries,
or
100
to each motor but at half the voltage. So
half the power. Total max system power
2400 watts.
(with 20 percent boost for 10 Secs.)However maximum is
1200 Watts to each motor simultaneously!
Oops  this is why thresholds and steep
ramps are difficult with loss of control at times. This systems
has fancy colour screens and added gadget interconnectivity but
otherwise is much the same as the Pilot Plus System with an added short
term "boost" capability. And a small gain in efficiency.

Penny & Giles 
RNet
LOW Amp Output


Don't bother! Use the RNet 120.

Dynamic
DX 80 

160 Amps Total System Maximum from
batteries, or
80 Amps
to each motor simultaneously!
But only at the speed that means the motors draw rated current.
Better for control. But as speed is reduced the same voltage reduction
applies as in the case of P and G systems. So that means no gain in
actual stall torque over P and G systems. Although PEAK watts is 3840
(If their statement above is correct).

Dynamic
DX2 90 

180 Amps Total System Maximum from
batteries (claimed), or
90 Amps
to each motor simultaneously!
But only at the speed that means the motors draw rated current.
Better for control. But as speed is reduced the same voltage reduction
applies as in the case of P and G systems. So that means no gain in
actual stall torque over P and G systems. Although PEAK watts is 4320
(If their statement above is correct).

Penny & Giles 
VR2 50, 60, 70, 90 Amp Systems 

50, 60, 70, 90
Amps
Total System Maximum
from batteries, or
full rate amount
to each motor but only at HALF the
voltage when high current is demanded.
Only the
90 Amp unit is worth looking at for low end Powerchairs.
However maximum is HALF power to each
motor simultaneously! Oops 
this is why thresholds and steep ramps are difficult with loss of control.

Penny & Giles 
VSI 50 Amp Systems 

50 Amps total. 25 Amps to each motor simultaneously.
Don't bother unless you are very light
and 103 years old... My model helicopter uses a 60 amp with 80 amp
"boost"!!! And I am not sat on that...

Added, By JoeC in the forum and moved here as its
useful info for many:
"Qtronix is just a rebadged P&G Pilot+. The programmer is the same, the
connectors and plugs are the same, as far as I can tell only the mould they used
for the joystick housing is different. Oh, and any stickers or decals which is
what I meant by rebadged."
"In my experience, a lot of the Dynamic DX module that I bought on EBay were
originally installed in Pride chairs. Some of these chairs are rated for users
up to 500 or 600 pounds, so they really couldn't cut corners on the electronics
or the chair wouldn't be able to get over the threshold out of the showroom".
"It should be noted that Invacare owns Dynamic, and some of the controllers in
Invacare chairs are based on controllers you see described on the Dynamic
website. The Gearless Brushless controller appears to be made or designed by
Dynamic, and some of the MK5 controllers I have seen on EBay appear to be based
on Dynamic Shark controllers (a lower end model that's more on par with the P&G
parts)."
A forum post discussing this is
here  one of many! Sign up to ask any questions
More to come asap!!!
________________________________________________________________________
And
FINALLY
after messing about designing my own chairs for the last 13 years and getting
sick to death of a total lack of power from the industries hi end Controllers I
decided to do things my own way as usual.
On the 28th of Sept 2010 I ordered a
ROBOTEQ True 150 Amps per channel Robotics controller for these reasons.
It actually truly gives you 150 real amps per channel.
No reduced voltages to "share" the power.300 real Amps
total from the batteries. And it is happy to work from
10 volts right up to 50 volts.
I plan to use 36v and three Odyssey batteries to start
with. That means a true 6000 watts
of power to work with. Finally!
www.roboteq.com and my controller is
this Click for specs and PDF manuals etc. At last I can stop messing
about with gutless mobility products! This is going in my generation 3 hi
speed 12 mph powerchair.
It will be used on the
MK3 Version 45V and 15 mph! of
my home built powerchair!
1. POWERCHAIR
ONLY:
Detailed Full PowerChair Related ONLY Menu HERE
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Detailed Wheelchair Accessible Vehicles ONLY menu HERE
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ELSE:
Detailed Menu of Everything else HERE!

