Urgent advice needed: 4 pole or 2 pole motors?

[Burgerman]

Yes. But slower on a hill. Its about impedance/torque.

[faico_26]

I’m afraid I don’t have R-Net but VR2. R-Net was about 700€ more expensive.

[faico_26]

Specs say all. A few rpm and 12.5" to 14" is a big difference.

I'm not surprised 2-poles outrun 4-poles at light load, eg flat ground.

165 RPM vs 163 RPM should not make a noticeable difference, should it?
I mean, on flat ground, 2 pole 165 RPM vs 4 pole 163 RPM should result in the same speed. But if I’m using 12,5” tyres instead of 14” then there is the difference.

[faico_26]

So if I want to get maximum possible speed should I change to 14” tyres or should I change to 165RPM 2 pole motors?

[Burgerman]

Well the tyres may make a tiny difference. But it wont be anything significant. And 2 pole motors are definitely a bad idea.

If the speed thing really matters swap to 13kph/8mph motors. Again you will lose torque. But at least the difference will be noticible.

[faico_26]

Well the tyres may make a tiny difference. But it wont be anything significant. And 2 pole motors are definitely a bad idea.

If the speed thing really matters swap to 13kph/8mph motors. Again you will lose torque. But at least the difference will be noticible.

Swapping to 13kph motors does not seem easy, because I don’t think I could find a motor which fits in the motor mount and also then it should be programmed, and you know the shops don’t want to do these adaptations.
Following your calculations, 165 vs 163 RPM is really not noticeable. So the only thing I could do is go for 14” tyres instead of 12,5” to gain a little more speed.

[Burgerman]

8mph 4 pole linix looks the same as 6mph 4 pole linix pretty much. Should be easy to swap. I have a set here in a box...

But the real answer is to order a different chair that has an 8mph option.

[faico_26]

8mph 4 pole linix looks the same as 6mph 4 pole linix pretty much. Should be easy to swap. I have a set here in a box...

But the real answer is to order a different chair that has an 8mph option.

I’m afraid I cannot choose another chair now. Apart from speed there were many other things which made decide for the Q300R.

[LROBBINS]

Do get a programming dongle and check the programming yourself. It's quite possible that the factory or the seller may have limited the top speed, but few dealers will be willing or able to change this. Indeed, you may need OEM access, but OEM dongles are hard to get. However, Burgerman can tell you how to use a dealer dongle to retrieve your current program, get to see all the OEM-only settings, change them and then write the modified program back to the chair using a dealer dongle. RNET dongles are not cheap, but is something well worth buying or borrowing.

[Burgerman]

Absoutely. A chair with no programmer is pretty much useless. Although I doubt you will be able to increase speed. It will very likely already be set to max.

[faico_26]

I have new information! The 2 pole motors that I could have ordered for the q300r is 175RPM!!!
That means that, according to the calculation that Burgerman taught me, the chair has 11,75 km/h with 14” inches.

[Burgerman]

No. That is an unloaded RPM. In realty you get less. That tells us that they know a 2 pole motor has a higher impedance and less torque. So that it needs to have a free unloaded speed that is higher than the chairs target speed. Because the higher the impedance the greater the rpm drop under any given load all else being equal. In other words they will slow down more than a 4 pole motor would, pushing the same chair along. So your question now is: Will that still allow them to be faster with your specific chair, mass, surface gradient etc?

We cant answer that.

And remember that the larger the tyre the greater the load. Same thing as happens no matter how you change the gearing/speed relationship.
So a 4 pole motor will slow down less than a 2 pole one, as a percentage, with a larger tyre diameter used. Other things will also show a greater rpm loss on a 2 pole motor, such as a heavier user, chair or a slope, or with solid tyres etc.

So the real answer to your questions are only answerable by testing!

Look at the grapghs above. They aim to have the best efficiency peak, in use when pushing the chair at max speed. As they know that the load drops the RPM down to this point.

[Burgerman]

So that best efficiency (best range) happens around 80 to 90% maximum speed.

They arrange this max efficiency point to coincide with the motors max speed in use (under load).

[shirley_hkg]

Pneumatic tyre will be faster than the flat free one.

[faico_26]

I see, yes I will have to test. Anyways, I chose 4 pole and despite is less RPM I’m confident now it was the best decision to buy 4 pole instead of 2 pole.
Another thing that surprised me is that the Q300R comes with 64amp AGM battery. I thought GEL was better. What are your thoughts on this?

[Burgerman]

Gel can be better.
Define "better"?

A battery in a physical fixed maximum volume has 3 competing things to maximize.
1. capacity.
2. impedance.
3. cycle life.

Increase any of these, and one of the other two must get worse.

So if cycle life is your goal, gel usually wins. With around 500 x 80% deep cycle capability. At the expense of capacity or impedance or both.
If ultimate low impedance, (means more of that Ah is actually accessible at high discharge rates) and better torque is prefered, then nothing beats say the Odyssey batteries. Those are high quality AGM. But they have less Ah. And less cycle life.

Some grp24's are even rated at 100Ah! But because they are low impedance you cant pull wheelies (voltage collapses) and they "die" at around 40Ah taken out and you stop so that 100Ah is only any use if you discharge them at a slow constant rate for 20 hours. Useless in a chair.

So dont get too hung up on Ah. Impedance is more important. And cycle life, in a chair.

Etc.

WORST of all are cheaply made AGMs from china. These are normally 350 cycles, high impedance and impressive sounding Ah ratings because thats why most people buy a battery because they dont understand the rest. These are generally crap at everything! But very cheap non brand name batteries. I can buy those trade with "my own" brand on them for around £40 each and resell them as deep cycle batteries... Many people do.

For MOST average people, if charged correctly, a GEL battery like MK, MOVE, Sonnenschein, Haze gel EV, etc are best.
For fast charge, heavy use, a "programmed to go" chair, off road, overweight users, 190kg rehab chairs, and a combination of that then the Odyssey low impedance battery will work better, and give at least as good range even though they have smaller Ah. But a little less cycle life.
And so far everything else is worse.
Except LiFePO4 done properly!

[faico_26]

I can replace batteries every year with Spanish health system, so no problem I guess with AGM.
By the way with my current invacare Mirage I used a pair of MK gel 40ah batteries for 6 years and really nice, but I recently changed to a new pair of the same MK batteries and the performance is terrible. Less torque, less acceleration and much less duration. How can it be possible? The model I bought is exactly the same as the model I used for 6 years, the only difference is that the original MK were made in USA and the new ones are made in china: MK M4012SLD-G 12 Volts 40 Amp.

[Burgerman]

The model I bought is exactly the same as the model I used for 6 years, the only difference is that the original MK were made in USA and the new ones are made in china: MK M4012SLD-G 12 Volts 40 Amp.

Its not possible. They are made in factories oveseas to mk's exact same standards and certification and measure exactly the same impedance and capacity. So theres literally no difference.

When you have tools to measure Ah to a couple of decimal places, (PL8v2 and software) and accurate 1000hz impedance tester (as shown in my Lithium cell pinned thread), its trivial to actually MEASURE this stuff. Then all the internet nonsense about US/China made MKs goes away!

It a story I keep on hearing for years. And I have tested and measured them. Exactly the same results.

What has really happened is this:
Cheap crappy generic one size fits all AGM,/Gel univesal chargers are now supplied for 5 to 10 years, and rehab chairs got much heavier and more common to have heavy powered functions. And generally have faster motors and more equipment today. And many chairs got narrower meaning smaller battery Ah.

So net result is deeper average DoD, higher current draw, which has a drastic effect on cycle life. Weight means less range as well as high daily discharge levels. And crappy "modern" chargers that charge at AGM voltages which damages gel, CV charge end too soon mean sulfation on top. So 3 things conspiring to kill gel batteries even if they were not smaller to begin with...

So horror stories appear on the internet looking for "reasons"... Its possible you had a bad one, one that wasnt actually new, or a pair that were not balanced and charged equally before installation. So over the next month of charges one got over, the other got undercharged. Causing permanant issues.

For what its worth the 40Ah ones at the 2 hour rate (6mph for 2 hours = 12 miles and dead batts) are around 25Ah batteries in reality. But because the voltage drops due to peukert you wont even get that before the chair stops moving. So maybe 18 to 22Ah usable. So it doesent take much to make you think they are defective! Way too small for a powerchair to begin with. And this soon means no range.

[faico_26]

I still have the old pair of MK batteries. I will test them again. But honestly the the chair has lost quite performance with this new pair of MK’s. I bought them last July and I’ve using them since then. With a quite limited use (from home to the van, from the van to the office, and back home) I barely have 1 day and a half of decent performance, then it drops.
When I bought them I had to replace 1 of them because it was defective. Bad start.

[Burgerman]

OK.
First of all you cannot just fit 2 new batteries and use them. You must use a 12V charger and charge each FULLY. First. Or you must at very least connect both together in parallel for 24 hours or longer to be sure both are at the same exact state of charge. Or on the very first charge, and the following dozen or so? You will overcharge one, and undercharge the other. That results is one battery becoming slightly sulfated, and the other becoming overcharged with shrinkage of gel, positive grid corrosion, and other issues.
The net result being that you have no range and a defective battery!

Then you cannot replace ONE battery to match the existing one. You must replace the pair or the same crap will happen all over again.

So I am not surprised at all!

You MUST ensure all batteries that are run in series are the same batch, same age, same state of charge, same number of and depth of cycles or they will likely die very soon.

And you must ensure that they are charged CORRECTLY! That does not normally include a mbility charger...

[Raro]

I don't know the reason, but everyone I've spoken to who has changed batteries complains about the same thing: the original ones last longer than any other, even though they're from the same brand.

[Burgerman]

And you say 1 day and a half. Wrong!!!
Even with bigger 80Ah batteries you must charge them at LEAST overnight even if you only went 10 feet.
Charging every 2nd day leaves them partially discharged and gradually sulfating for 48 hours at a time. All the time... They will die faster.

[Burgerman]

I don't know the reason, but everyone I've spoken to who has changed batteries complains about the same thing: the original ones last longer than any other, even though they're from the same brand.

They read it on the internet. Like they think that the batteries need to be fully discharged...
Rose tinted spectacles.
Measuring tools do not lie.

There can be 100 ways to hurt them. But they are exactly the same as always.

[Burgerman]

Look at it like this.
I order a set of MK gel batteries.
These in my case are GRP24 and the manufacturer has a spec sheet.
There are only a few specs that matter on a battery.

It says on the tin that they are 2.5mOhm, 3.5mOhm, 5mOhm etc. And so to measure this I cycle these new batteries (in accordance with the spec sheet by fully charging, 24h on float as well. Then at 25C in my room (as per spec sheet) I discharge at the 20H rate. (1/20th of its 68Ah rated capacity or 3.40 Amps). On the Oddysey for e.g. that is 62Ah when discharged to 10.80V or 68Ah discharged to 10.20V.

So I set the PL8 to discharge at 3.40A, expect it to take approx 20 hours, and it is programmed to keep discharging until it reaches 10.20V. At this point it stops, after drawing a discharge curve. If its as good as the manufacturer claims it will read 68,000mAh.

So its EASY to test a battery to very accurate levels.
Its also easy to compare this to the manufacturer claims.

I used to sell batteries, odyssey, optima, and the odd MK for years. So have tested hundreds.

You can even test them in series, in a powerchair via the XLR connector.

Heres one on a discharge test.
This was a 75Ah AGM battery. Its about 6? month old.
Its got about 10 mins to go, before it reaches the 10.8V per battery cut off point as determined by the manufactuere. That reached almost exactly the rated 75Ah at that time. So 100% as per spec.
So far its given back 74,023mAh or 74Ah.

[Burgerman]

To measure and check the manufacturers claimed impedance figure you need a 4 wire 1000hz impedance tester!

This one is currently checking that my lithium cells were as advertised! And not used etc.

In this case these cells are supremely low impedance at a rediculously low 0.22 mOhm!

[Burgerman]

If these two measurements are as per spec, then the battery or cell is exactly what it claims to be. And the MK GRP24 from china, and the older ones from the US measure EXACTLY the same!

Internet nonsense, seat of pants measurements, uncontrolled tests, rose tinted memories, and so on mean nothing. Evidence and measurement is everything.

But I can tell you this.
The best lead bricks are truly crap and about 30% better than the cheapest lead bricks.
Lithium is at least 1000% better is every respect as long as the pack is big enough.

Here are the manufacturer specs for EACH INDIVIDUAL cell that I recieved.

When tested, every one was within 1 % of the cell spec in capacity, and within 0.005mOhm. of the factory spec. And thats basically within measurement error.

All were around 0.21 to 0.23 of a mOhm...
All measured 244Ah Which is pretty good for a set of 230Ah cells!

[faico_26]

The shop where I bought the 2 MK rejected to replace the 2 batteries and after me complaining they accepted to replace only 1 (the one that was clearly damaged).
With the 64amp AGM of the new Q300R is there any specific recommendation of charging/discharging or it is the same as with the Gel batteries?

[Burgerman]

Gel vary depending on design, But 29.0V CV, same 10 or 12A, 300mA termination point and 27.2V Float for 4 to 6 hours.

[Raro]

It's not that they read it on the internet, it's that with the same usage and the same mobility charger, they last less time. Like in the case of faico_26, for whatever reason, one of them got damaged even though it was new. Why?

[faico_26]

Thinking in NO damaging the AGM batteries of the new Q300R, making a full charge of 12 hours or so and then charging them every day would be enough?
Think that I’m just an average user, with only some knowledge of Rc cars and Rc planes but I have no clue about how to make a charge/discharge cycle in the wheelchair batteries.