9C Hubmotor: Parallel/Series Switch (Star/Star)

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Re: 9C Hubmotor: Parallel/Series Switch (Star/Star)

Post by Ferreira » Sep 24 2014 9:56pm

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Re: 9C Hubmotor: Parallel/Series Switch (Star/Star)

Post by Ferreira » Sep 25 2014 7:15am

In my previous comment I do not at all answer your question concerning the battery current limit. Apologies.
John in CR wrote:What is it that you believe changing current limits to something lower during normal riding will accomplish.
The idea is, to keep the input of electrical power that is fed to the motor at 72V the same that it originally was at 48V during normal riding.

John in CR wrote:As long as you ride the same top speed It will have only negligible effect on efficiency, because it requires the same amount of work to accelerate to a given speed. Yes you use higher power to accelerate quicker, but it is shorter in duration. The difference only comes about because accelerating more quickly puts you a cruising speed for longer and therefore a higher average speed, which gives more back to the wind. As long as aren't pushing the motor into saturation at the higher current, then you aren't creating more heat. As long as you're not talking about extreme acceleration, being able to get up to cruise more quickly is safer and more fun. Once you set your bike up to climb that hill without heat problems, you're good to go for all riding. Zippy acceleration at no cost is one of the great things about electrics. :mrgreen:
That's right. Comparing one and the same trip at one and the same top speed, energy consumption should be virtually independent of acceleration and battery current limit. On the other hand, the batteries will live longer and provide more energy when discharged more slowly. The datasheet of my SLAs says that by reducing current to 2/3 of 22A, the time span I can draw that current nearly doubles.

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Re: 9C Hubmotor: Parallel/Series Switch (Star/Star)

Post by dnmun » Sep 25 2014 10:40am

does it really matter? they are lead and have a short cycle life and since the lead is now more expensive than lithium it is the worst of all worlds.

if you are determined to use SLA then you need to reorient the batteries so that the electrodes are laying horizontally (like pancakes) when charging and discharging to extend the cycle life of the SLA.

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Re: 9C Hubmotor: Parallel/Series Switch (Star/Star)

Post by Ferreira » Sep 25 2014 4:51pm

dnmun wrote:does it really matter? they are lead and have a short cycle life and since the lead is now more expensive than lithium it is the worst of all worlds.

if you are determined to use SLA then you need to reorient the batteries so that the electrodes are laying horizontally (like pancakes) when charging and discharging to extend the cycle life of the SLA.
After I found out that there are Lithium batteries which don't need a battery management system and can be soldered not welded I decided to do that. I plan to order them soon, I have asked for a quote from keeppower.com.cn for Sony US18650V3 today.

Why is it that the lifespan of SLAs depends on the orientation? On my bike I could not easily change it.

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Re: 9C Hubmotor: Parallel/Series Switch (Star/Star)

Post by Ferreira » Sep 27 2014 5:35pm

Today I increased the battery current limit from 22A to 33A. I know that this can be done by uploading some parameters to the controller. But I would have to have built or imported an appropriate USB connector first, installed additional wires to my controller, installed software, read lots of manuals, and carried the bike from the basement up to the second floor or carried the computer downstairs. I do not have only a 50m height difference up to my house but also 15m within the estate and more than 6 within the house. I grow tobacco where others might grow wine. So I decided to use a voltage divider parallel to the shunts such that the microcontroller is tricked to read two thirds of the real voltage at the shunts. Also I connected two unused wires (maybe they were designated to connect a Cycle Analyst, I don't know), which allow me to externally shorten the upper resistor of the voltage divider and thus make the controller again read the full voltage at the shunts.

Originally I had planned to use an operational amplifier to also be able to increase the voltage read at the shunts and thus lower the battery current limit, but then, for laziness, I decided that the simple voltage divider is more easy and more robust.

My first impression was, that the idle speed now is reached faster than before. It was raining, but some half an hour after rain had stopped, I tried the last 25m height difference of the road up to the house, which include the steepest part, and I made it in the 3rd gear. Before today, I couldn't dare to use anything but the 1st gear. Then I made it again in 2nd gear. I only have subjective results, but this is the first time in my life (or in the 15 months I own this bike) that I felt like going down again and make it again. And I had only 60V. I had to remove the 6th battery for reasons mentioned in some post above.

The motor felt less warm than my hand after the second try. So I am now convinced, that with 72V and batteries that can deliver continous 40A or 50A, my problem will be solved. Not that no assistance at all will be required to make my 50m/200m grade, but that maybe I can make it without even having to stub out my cigarette.
Last edited by Ferreira on Sep 28 2014 8:54pm, edited 1 time in total.

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Re: 9C Hubmotor: Parallel/Series Switch (Star/Star)

Post by Ferreira » Sep 27 2014 6:13pm

Concerning new batteries: KeepPower said that they currently have no US18650V3 available and also no other Konions. Evva said they don't deliver to Brazil because of the problems with the customs. Having moved here some 15 years ago, shipping a huge box full of stuff, and all my further experience tell me that I can't blame Evva.

Inbetween I already ordered a Greentime 72V charger, an order which was cancelled, due to financial security problems. I now sent lot's of copies of documents to solve these problems to aliexpress, and in the meantime I ordered the same charger again using a different payment method which they offer especially for Brazil.

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Re: 9C Hubmotor: Parallel/Series Switch (Star/Star)

Post by Ferreira » Oct 02 2014 9:25pm

I hope to receive more SLAs which I ordered this week or at the beginning of the coming week (US$20 for 12V 9Ah "deep cycle"), to be able to have my first real 72V test. At the same time I am trying to get Sony US18650V3 Konions from Hongkong (fasttech.com). But they have currently some national holiday (surely freemason stuff) and they ask for patiences concerning tickets.

My 60V/33A test showed that I can climb much faster, but on the other hand additional power is not used to climb with much less human assistance. I can climb faster with more power, but I'd rather climb slower with less assistance. Also, the simulator shows, that at 60V/33A/12km/h the current limit of 33A isn't even reached. In fixed serial star mode the controller's battery current limit is undercut at less than 10km/h already. Following the simulator the situation does not change at 72V. So currently at 60V I have few more than 500W on the road while more than 1300W are used to better the cold southern brazilian winter climate. At 72V I will have well more than 700W on the road while more than 1500W are used to help the summer arrive more early.

The SLAs are able to deliver the 30A. But capacity is significantly decreased drawing such amounts of current. I hope I won't wreck them too soon, before I the US18650V3 will reach Brazil with will take months if not ages. I will cut one of the shunts and change the parallel voltage divider, to be able to limit the current to 10A for normal operation to increase range.

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Re: 9C Hubmotor: Parallel/Series Switch (Star/Star)

Post by Ferreira » Oct 04 2014 5:12pm

This afternoon I was able to make the upper half of the steep road up here three times in a row while my butt didn't even lose contact to the saddle. Afterwards I wasn't out of puff at all, or let's say a little acceptable bit. It still takes some effort, but not too much for a guy who might wear a hat for protection against the sun and might smoke while bicycling. This was at nominal 72V/31A.

Batteries were half empty, I had made a longer test tour in the morning at 72V/11A and had climbed at 72V/13.2A. I didn't want 72V/13.2A, I wanted >30A, but in my modification I errouneously had used nominal 18Ω in the place of 180Ω. I had managed to climb at 72V/13.2A all but the worst part. But it was more or less as laborious as the original configuration. The tour showed that 72V/11A are excellent for normal cruising. The bike makes an estimated maximum of 30-35km/h. Most of the time I go at or near to this topspeed, so efficiency is excellent most of the time, and acceleration is only slightly lower than in the original configuration.

I now use 6 pieces of 12V SLA (CSB "deep cycle", datasheet linked somewhere above) and a controller limit of about 31A to climb. The motor is in series mode, the original nine strand coils modified to three strand coils with three times the number of turns and nine times resistance as well as nine times inductance.

I doubled the voltage the microcontroller reads at the shunt by removing one of two parallel 5mΩ shunts. Thus my original 22A battery current limit is reduced to 11A. For the climbing mode I installed an additional voltage divider (nominal 180Ω / 100Ω, measured 184Ω / 100Ω) parallel to the remaining shunt, which makes the microcontroller interpret about 31A as 22A. To switch between the two current limits I can short the 100Ω by means of a switch, to make the controller read 11A as 22A.

The next thing I plan to do is to build a Konion pack, but it apparently will take more like 3-4 month to get these, and only if I am lucky enough to manage to get some at all.

I want to thank all posters on this thread, amberwolf for his comments with respect to switches and rigid copper in the axle, esselius for pointing out that "different windings won't give you another gearing", which I had believed. I am a "conspiracy theorist", I know that soft science is BS, I don't have any health insurance, or any other insurance, I know that the universe is centered around the earth and revolves around the earth, but I had still thought that hard science was somewhat reliable. Thanks, esselius. I want to thank John in CR for his many comments. I'd like to mention as most important for me his descriptions of how it is possible and necessary to make a steep grade at some reasonable speed, but that is not to say, that all the other various explanations of his were and are less useful for me. Thank you very much. Thank God, that I didn't damage the controller, the motor or anything else in the course of these modifications.

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Re: 9C Hubmotor: Parallel/Series Switch (Star/Star)

Post by Ferreira » Oct 15 2014 10:07pm

I finally managed to wreck some hardware. Charging two of the six VRLAs with a lab power supply I connected the batteries with polarity mixed up. Luckily, the batteries were full enough to take me to the electronics store to buy two 2N3055 transistors. These, a diode, and one more low signal transistor, as well as connecting a relay to always on, made the power supply work again for the purpose.

A new charger for nominal 72V is on the way from Greentime, China.

I also ordered Sony US18350V3 cells, for 20s4p plus some spare cells from fasttech.com for $3.85 per cell, free shipping. A week ago they shipped three packages and I hope the cells will make it through the customs without causing additional costs.

I have seen that there has been some dispute in some threads, whether it is better to hook up paralleled cells in series or series strings in parallel. As far as I understand the problem, paralleling four 20s1p strings should be better than hooking twenty 1s4p blocks in series. On the other hand, I can't really say "I understand the problem". Any suggestions are welcome.

In the meantime I found out, that it does not seem to be a very good idea, to short the upper resistor of the voltage divider parallel to the shunt via 40cm wires by a switch outside of the controller. It works fine at WOT, but the motor sometimes emits strange sounds at less wide open throttle. Not really a problem for me, as I go at WOT only after I switched to higher current, but maybe I will replace the voltage divider by resistors of 10 times less Ω, or think of an entirely different solution. I don't really know what the reason is, but I assume, that it is not a good idea to have a signal of less than 1mA being led out ouf the controller in a bunch of wires including the phase wires.

The overall result of my changes is: It is now easier to climb this hill up to my house, but a good part of the additional power is used to climb faster, and only the resting part releaves me. Climbing faster is a relief too, but I still hope for more relief.

Hopefully sooner than later I will have Sony batteries which can continously deliver 40A. But following the simulator my 3-fold serial star motor won't draw more than 30A at nominal 72V and some slow but reasonable speed. The 9 times higher resistance and 9 times higher inductance cry for 144V instead of the original 48V. So I think about a 3-fold serial delta configuration or a 2-fold serial star configuration. I couldn't find out so far, whether the former requires a modification of the positions of the Halls sensors. Does a delta configuration on a 9C 2805 Hubmotor require any modification of the Halls sensors? The latter would imply that originally 9 parallel wires would be split in half (4/5) to be connected in series. Thus one half of each coil will have slightly higher resistance while the other has slightly lower. This will make the motor slightly more prone to heat problems.

I am also still considering an electronic switch inside the motor to be able to switch the configuration of the windings. Using a NE555 to produce a rectangular signal of some 10mA sent to one of two micro-transformers wound on small ferrit cores from cannibalized "eye cancer light-bulbs". Both transformers having several secondary windings and simple half wave rectifiers to provide several potential-free 12V signals to switch a number of IRFB4110 MOSFETs without common ground. Each MOSFET would burn less than 100mW. This would allow to verify in reality what the simulator says.

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Re: 9C Hubmotor: Parallel/Series Switch (Star/Star)

Post by Ferreira » Jan 04 2019 8:47pm

My last post is of Oct 16 2014. The Sony Konion V3 cells I ordered then, arrived maybe 6 months later, due to brazilian bureaucracy. I neglected my bike since then, but now finally installed the new cells. They had been shipped with some medium voltage and I had charged them to 3.9V. Voltage stayed virtually constant in the past 4 years. Finally I found time for and interest in my bike again:

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I use a 40W soldering iron to apply solder to the Konion cells and a 140W soldering iron to connect them with stranded wire. To apply the solder I first put solder paste (as it is used to solder copper hot water tubes) and have it etching the metal for like three minutes before using the 40W iron and add tin-solder. The stranded wire later tinned and added is standard stuff used to electrify houses, flattened with a hammer or a vise.

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I unnecessarily managed to wreck two cells out of 80 (20s/4p). With some experience and patience, one would never wreck a cell. In case of any problem just stop heating and try again later after some minutes.

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I used cigarilho boxes. Talvis from St. Felix on the other side of the river where Dannemann started to produce more than 100 years ago. Four boxes with 18 cells each and a fifth box with four times two more cells for 20s/4p.

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Re: 9C Hubmotor: Parallel/Series Switch (Star/Star)

Post by Ferreira » Jan 04 2019 9:03pm

My first try making the grade of an average 25% and possibly 30% max, was not successful. I had adapted the controller to limit current at 40A, having now 4p of Sony Konion V3 ready to supply 40A. But I still had to not only assist pedalling but I had to lift my ass standing up pedalling to make it up to my house. Then I put the controller's input destined to sensing current at the shunt to GND, and finally, I could made it up the grade without lifting my ass off the saddle.

Hooray!

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