Does torque normally change with battery voltage?

[Alan B]

OK no time now, will parse later see if specific answers are there to see if my understanding is better.

You have to model your actual data to get specific useful predictions. Generalizations don't get you there, even if they are all correct for some situations.

Well when choosing and sourcing the components. . .

> Or mid drives with variable gearing...

I thought just not available big enough to push 400-500lbs up long steep mountain climbs

And yes I know, figure out the simulator

It is certainly available. It is called motorcycle (or scooter) parts.

The 3000 watt hubmotors weren't made for bicycles. They have been adapted to them. But trying to push a lot of weight up a steep grade takes power, and the motor needs to have low enough losses to handle it. Or it takes gearing. If you don't care about speed but want a lot of torque and mid drive parts are not strong enough then use a left hand chain for the motor.

Some mid drives like the BBSHD will handle enough power to handle more weight at low speed. Just be prepared to do more than average maintenance.

 

[john61ct]

I could simply charge my battery every ride, but I am reading frequently that you might get up to 3 times more charges out of your battery if you only charge it for 80 - 85%
So, if possible, I would like to avoid charging it to 100% every day

Definitely best to stop at 4.1Vpc rather than 4.2, but you really are not sacrificing more than low single digits range, if that.

But no harm charging before each ride.

Less time between end of charge and starting your ride the better.

Damage comes not only pushing too high but letting the battery sit there full.

 

[Alan B]

Working with closed systems is so frustrating. Hence one reason most folks on ES use DIY or modified setups.

I think undercharging the battery to make it last longer is silly. Use it. After several years of use replace it. Hobbling an already marginal system is not worthwhile, in my opinion. The only time I would not fully charge it is when parking it for extended periods. That's the real issue, not charging and discharging shortly thereafter. This is a bike, not an electric car where you want 10+ years of battery life.

It begins to sound like this bike may have deeper problems, but I'm not going to analyze that. Hope you can work that out. If there's a repair that's painted over, and the seller did not tell you the story, doesn't sound like full disclosure. Dangers of buying used from an unknown party.

Best of luck with it,

My weight is approx 230 pounds or 105 kg.
The only difference between going uphill with ease and going uphill with tough peddeling is the condition of the battery.
Obvious, the motor torque is hard to measure. Wind conditions make a difference as well. Also, one ride to work and home again is only draining the battery a little so the difference is hard to notice every ride.
I could simply charge my battery every ride, but I am reading frequently that you might get up to 3 times more charges out of your battery if you only charge it for 80 - 85%
So, if possible, I would like to avoid charging it to 100% every day. (Altough it's an option I haven't considered much yet.)
I was not going to feed my motor / controller 8V extra. I intended to give it 41V which it should handle just fine as it's what a fully charged battery is giving it as well.
Today, I tested the system in eco mode, and to my suprise, it was giving nearly the same assistance as in normal.
A closer inspection showed a fracture in the frame near the position of the torque sensor.
The frame had been welded at that position and the welding was nicely painted over to hide the repair. It's possible that the torque sensor became 2 sensitive due to the fracture. Likely the seller and maybe his service center knew about the problem and might have lowered the assistant settings a little to hide the issue.
It's a lot of conspiracy theory, I know.
Maybe the welding broke after I got the bike into my possession, and previous owner rode it happily with the welding repair and without issues. However, I don't have the impression the bike behaves any different now compared to when I first bought it.
It's a lot of questions. I might see first if the frame can be repaired and maybe fabricate something to measure my battery current.

I assume you get used to the "push in the back" real fast and simply go for the next step.

It's just a pitty you need the dealer software to check and adjust settings.

I'll post it over here if there is any progress.

 

[obcd]

A bit off topic.

When I bought the bike, it came with 2 batteries. It was the main reason why I had chosen it. I did a test drive with one of the batteries. Looked fine as far as I could tell. (Hadn't ridden much e-bikes yet). So we removed the battery and placed the bike in the trunk of the car. Coming home, I decided to test it out on the trip to work. I inserted a battery and was greeted with a couple of errors on the display. Big question marks.. I installed the other battery and could happily ride to work.
It appeared one of the batteries wasn't working. I know I should have tested it when I bought the bike, but who expects a seller trying to sell you a bad battery as being good? There is also a 0.01% chanche that the battery was good and broke during transport or during insertion while being on and fully charged.
When I saw the welded fracture, I am even more convinced that I had dealed with a dishonest seller.

I have learned my lesson. I just want to post it here to warn others to be real carefull if they buy something second hand without knowing the seller. There is a reason why people sell their stuff. My seller told me he had equilibrity issues and couldn't ride it anymore from his doctor. Who am I to call him a lyer.

I managed to repair the second battery. They have an intelligent BMS that communicates with the motor. A protection diode in the linbus data line had become shorted so the battery couldn't communicate with the motor anymore.
I hope the frame fracture can be fixed as well. I am unsure if it's related to my climbing issues, but when it's fixed I can remove it from the possible causes.
In order to fix that second battery, I bought myself a broken one to have a spare BMS board. It looks like some of the cells in it are still working which gave me the idea to use them in serie with the existing battery. No idea if the battery indicator will still work. If the motor is measuring the voltage, it will always show full. If the battery is sending it's voltage to the motor over the communication linbus, it should still work as expected.
I don't want this to cost me an arm and a leg. It's also for fun and education I am messing with this.

Back on topic.

The difference in torque is most noticed when I recharge the battery as it goes from low to high again at that moment.
I usually recharge when I have 1 block left on my display (1/5)
When I measure my battery voltage at that moment (unloaded) I still have 36V. No idea what I should make of that.

 

[DrkAngel]

.
... Yes, torque, and attainable speed, are directly relatable to voltage.

Everything else being equal ... 41V vs 31V

 

[dogman dan]

Ok, now we know how simple your solution is. Charge full before each days use. You are heavy, but not that bad. I did wonder if you weighed over 300.

Yes, it could last longer if it was set up to be full, and the bms balanced the battery at 80%. But then you'd need it to be a 48v system to have decent volts to run up that hill, and its not. Its not likely to work if you increase the voltage. You could take one of the batteries, and add 4v, to make it a 40v battery then charge it to the same voltage as the 36v battery when full. Same charger in other words. But then you need a special charger, and you are dedicated to manually being a human bms.

But here's the happy part of your solution. Your bike runs fine up that hill if you just charge it. Battery damage is very small by charging full. It gets a lot worse, if you store it in a hot garage full for days. But if you hop on and ride it within a few hours of it got charged, there is very minimal wear on the battery. The thing about full charge is not as much that it got full, as it is time with it full.

So what some do is just put it on the charger when you wake up. Once you get shaved and dressed, eat, etc, the battery is full, or nearly full. Then you ride it immediately and get very little wear. When I started doing it this way more, my batteries went at least an extra year. Sitting full all the time, I'd get about 2 years from batteries. So just shorten the time from charging to riding, and charge it full each ride. That is easy, practical, and extends your battery life.

Another thing about battery life. They talk number of cycles. This is number of cycles from full to empty. But if you just discharge 25% and then charge, that's not a full cycle. You will get 4 times as many cycles when you discharge shallow like that, possibly more. So charging full each time doesn't burn a full cycle. Charging each time is actually better than running it to near empty. If your bike runs fine charging every other day, then you can do that. But its NOT beneficial at all to ride it to empty before you charge. But you can ride it to near empty without causing extra wear, as you have been doing. But if its not getting up the hill when 70% empty, just charge sooner. Easy.

Lastly, since you are new, don't trust charging overnight inside your house or garage. If you have a battery bunker in the yard, you can put it in there with a timer, and it will start charging in the night for you. Don't sleep with a battery charging in your house. EVER. Chances of disaster are actually incredibly small, but if you really want to economize, don't go and burn your house down like I did.