First thoughts, wheels much too small, too skinny, too fragile, and will sink on soft ground in winter or wont work on sand/mud/snow as we all encounter in winter dog walking or getting to the pub. Do you think we all live in a hospital room?
Many of us work in workshops, or wherever, and get out and about!
Understandable and that is why we are going to build AWD model with wider tires.
Well I wish you a lot of luck! It takes 5x as many Amps at least to skid steer, or 5x the torque at least to turn in place with 4x4 setups. Requiring a much mre powerful motor/controller setup. And then even my 3x bigger lithium battery that you are not using cant cope, and it tears up tyres and carpets. Been there and tried that!
Unless you mean like a scooter, with power steered casters? There are a couple of chairs like that, but horrid to drive and steer indoors. And heaavy. So not good for an active daily used chair. More outdoor only...
Those slab thingies things on the sides make the chair more bulky and wider. And look odd. That space would be better filled with batteries if you must have them... But they would be in my way a lot. I need/want my seat cushion touching the bed for easy reaching of things I am working on, or to get close to my pillar drill, or to get close enough to lift awquard heavy things. etc. It means pulling up tight to my bed at an angle. And they would hit my door in the van so couldnt be used to drive from. So they gotta go on day 1! JusT too big, and in the way.
This chair is 25" and can be parked flushed to bed. It can be hight adjusted to any table or give you opportunity to order at the bar in a pub.BM3 cannot as wheels are wider than cushion and there is no elevation or tilt.
The BM3 with its 6 inch wide tyres is no wider
in total than your chair. And in the centre of that is my seat cushion at 18 inches. On my black BM3 chair, or green 24 inch wide BM2 chair, I can get that cushion right next to my bed on either one (and my dressing bench in the shower room, work bench, lath, pillar drill, etc) because the front of the chair and the rear tyres go
under the edge. Same with my desk. it if I park at a slight angle to the bed the cushion touches the bed at the front, where I transfer. Cant do any of this with a big plastic thing in the way.
I CHOOSE not to fit a seat lift, tilt, recline, power footrests because a chair is a fine balance. And those things add mass that is too high messing up handling, stability, causing caster shake, and tipping me out on soft ground or on sand, ramps etc. CG is already too high, even with a 3.24kwh lithium battery as it is half the weight of the lead bricks. So it matters. So thats why I ask about your chairs stability. Heavy seating, heavy user, sat above a light base with a tiny light battery means very high CG position. That cannot be safe in extreme angles such as we get crossing rough ground, if a tyre sinks in muddy feild, or up a steep ramp.
Those lift up arms will likely not be strong enough to allow a 20 stone guy to pressure lift on, or stable enough (wobbles side to side) to drive the chair properly once I reprogram it so it goes and steers correctly! They must be rigid like in a vice. I never saw any lift up hinged ones that came close.
I am a touch lighter than you (only 18 stones or 115kg) and I assure you I can put my weight on them without hesitation. And I already programmed it to steer correctly ( Thank you Lenny)
I will take your word for it. Can you move the end where the controller sits, side to side more than say 5mm by pushing? If so its no good once programmed to go and steer how I like. E.G.
http://www.wheelchairdriver.com/gopro/control.mp4And its imperative that I can get access to at LEAST the equivelent programming tools as you. At least manufacturing level. When I buy a chair, the very first box to tick is the OEM or factory programmer availability. Not available? Legally or otherwise? Then that chair is automatically removed from my list as a matter of course. Its that important to daily use. I never drove any powerchair yet that I didnt consider gutless, slow to respond, lacking in torque and dangerous because of it. And need to fine tune many things. I doubt any built in programming with a tiny screen can do this OEM level stuff adequately. If it cant then its as pointless as the one built in to the r-net controllers.
Which brings me to the next issue. Range. That chair uses 48V which is commendable for various reasons. But 20Ah? Thats about 1/3 of what is actually required. My own 26 kmh capable chair has 45V lithium ion phosphate (safe) lithium battery of 3.5x that capacity. Its about enough for a good days use at 45V and 72Ah. Or 3.24kwh. Compared to yours at just 20Ah x 48V = 0.96kwh. So 3.4x greater capacity. And then theres the stability issues. With such a small battery the CofG must be very high. So the chair must be either lacking stability or extra long and wide. Theser no option.
In reality chair is running on 52V. Use of geared brushless motors gives 10-15% advantage in efficiency and weight reduction. I agree that more capacity would be beneficial if you do not like to charge your chair every day. Batteries we use have 3000 cycle lifespan.
So far, I did not witness lack of stability. Doing 90 degree turn at maximum speed is a standard ISO test. Don't forget, the seat of this chair is 14" from the ground in a lowest position. We are testing it half way up.
1. you will only get 3000 cycles if you discharge it at low C rates. Typically (well) below 1C. That means max current 20A on your battery... So your battery is way too small for that. It will degrade faster.
2. you will only get max cycles if the battery never sees above 3.600v oper cell or less. Or discharged deeply regularly. I charge at an exact 3.550V per cell plus or minus 0.003v. A typical BMS balances both too soon during the charge and some do it all the time, at too low voltage and with a feeble balance current. And allows too high voltage on charge before repeatedly cutting off charge as it tries to balance with too small current, and so bounces the high cells repeatedly over the ideal voltage limit. So again the battery CELLS charged and used properly may offer 3000 cycles but your BMS and charge setup will limit that to a much lower figure. Or fail. As most BMS setups inevitably do.
3. since the battery offeres only an ISO test 30 miles (50kms) and a real world figure of around half this, is typical. So 15 miles usable in the real world. Thats what you get if you run till its empty. Since we cant do that for fear of getting back home we can go 'away' 6 miles, and back 6 miles leaving a small bit in reserve only. Its called range anxiety, and it limits what we attempt subconciously and affects our lives. . I do more than double that 1kwh most days if I am busy, and going out again in an evening.
The whole point of fitting lithium is so that you can fit typoically 1.6 to 2x the Ah in the same volume as the lead bricks you removed. Failing to do this misses the entyre poiunt of lithium and loses its big advantaages.
Which are RANGE. Which you havent really capitalised on, and fitted a small sub 1kwh pack. (mine are 3.24kwh, over 3x bigger but still lighter than lead.)
And LONGEVITY. By fitting a small pack with a BMS you are running the battery low, daily, and topping up to a too high BMS controlled voltage daaily, and drawing far too many Amps per Ah of battery (high C rate draw). These 3 things mean you will get a far lower number of cycles than you would if you fitted a bigger pack! So losing this advantaage too.
Weight with batteries
290 Lbs / 130kg
Too heavy. And top heavy. Did you get it through all the regulations yet? Esp as it includes a small lightweight lithium battery causing a higher CofG.
Agreed completely. This is just a prototype. Once we get closer to production it will not exceed 100kg. Please keep in mind this chair has full compliment of power seating. What is the weight of BM3?
Its not really about max weight (unless hill climbing) but of the centre of mass. CG position. With a 3.24kwh pack, and a simple frame seat the CG is kept within limits. Even so stability is compronmised compared to a lead battery setup, requiring longer wheelbase, and a slightly wider track. Or we suffer caster shake issues, and tip over the back on steep ramps etc. Longer anti tip bars are a no no because they get hung up on stuff in the real world.
Range
50 km
ISO mileage test? You will get half of that in actual real world use at best. Why? Brushless hub motors have a huge stall current, or when trying to make a lot of torque for turns in place etc compared to geared motors. While having extremely low high speed current draw. So a few minutes indoor use or turning left/right requires a massive amount of battery power compared to the iso test procedure. Which is basically mostly fast running where a brushless hub motor excels. In other words they are at a large advantage on the ISO test procedure compared to geared brushed motor.
My own 26kph chair has 45 to 50 miles REAL WORLD measured range (75 to 80km). Not the unrealistic result from the iso test.
Motors we are using are geared. We use chair indoor and outdoor and battery easily lasts though the day.
Not a chance that a 1kwh battery would last me a day! I use my chairs. 1kwh (yours is 960watt hours) is around the same as you get from a set of group24 lead. Its nowhere near enough for a days use if you are heavy.
Also we suffer from a leaned thing called range anxiety. Its a subconcious thing that stops us getting out there and enjoying life! So even if we know its got an ISO 30 miles as yours has, we can only do half that in reality. The ISO test is not realistic. So you will actually run out of power around half this. That means I cant get through a busy day since its 2pm now, and I already did 14 miles. I am going into town later, to the pub. Thats another 6 miles return, plus all the power used moving around in the pub etc. Would I gt back? I cant know... Indoors shuffling about actually eats more Ah than traveling the streets. So under 1kwh is not adequate. And of course lithium batteries wears out faster with deeper discharges, and recharging daily uses up cycles. And heavy currents per cell mean less cycles. So a bigger battery makes way more sense all around. Thats why my chairs use 3kwh plus packs, with proper charging and balancing, and no BMS I get 45 REAL miles on the fast chair (55 REAL miles on the slower chair) as well as a much greater life expectancy.
Maximum Speed
15 km/h
Not enough! Thats 9mph. Well it is enough for some maybe, but its far too slow for me!
http://www.wheelchairdriver.com/BM-MK3- ... rchair.htm does 16mph or 26kph.
I love the speed too.
In Canada we are limited to 15 km/h by law and most people we spoke to do not want to go faster. In some cases we can unlock more speed if desired.
Great. But remamber that if YOU can unlock the speed via programmiung then I should be able to do this too. This thing where manufacturers lock away the tools must stop! This is why I will not buy any chair that I cannot get FULL programming capability for.
Speed Settings
10 settings
Why? Mines on max 24/7. If the programming is good, then you only require 1 speed setting or rather 1 profile. If its not and likely it wont be then we also need real full "OEM level" programming access or its basically unusable by me and many on this forum.
Some people do not have good driving skills and prefer to limit speed when they are indoors. Some don't. All programming access is done from the same display. No need for external programmer.
See above. this should be the USERS choice! But yes, some cant use proportional linear control.
Max Weight Capacity
300lb / 136 kg
Inadequate. For eg I am already on its max limit. Why is it this low? Let me guess. Inadequate motor stall torque?
This is Canadian standard capacity for non bariatric chair. In real world this chair can lift much more. Each leg can lift 200kg.
Maybe, what does it do for stability, programming, stall torque adequate?
Charger
7A Charger
Too small and its dumb. And you are likely to be using a generic BMS too... See: viewtopic.php?f=2&t=1813 see first couple of posts.
I am using a PC controlled and fully programable charge and discharge graphing, cell balancing 40A 1344 watt charger. And it works in my van too.
I like your setup, you probably can charge you battery in 2 hours. It takes us 3.5 hours. Compared to mass produced chairs this is probably acceptable.
Its not about speed. If you fit a sensible sized lithium battery to take advantage of the extra range, extra reliability, extra longevity that lithium can give us, as you surely must, then a 7A charger will take an age.
E.G. My BM2 chair has a 120Ah pack. I charge this at 7A and it will take almost 20 hours!!!
A 40A charger still takes 3.5 hours because the batterystores a useful amount of power.
More importantly, it charges PROPERLY where a dumb charger and BMS does not. And measures Ah in, and can measure capacity, IR, display cell balance and graph this as you charge etc. And it works as I drive in my van!