Tiny hub motor sucking the life out of my batteries.

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utsi   1 W

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Tiny hub motor sucking the life out of my batteries.

Post by utsi » Nov 11 2018 8:51am

So I have a 500W 48V brushless hub motor I bought from aliexpress. It's been working OKish for a couple of winters now, but it has always been a bit noisy and the range has been much shorter than that of my summer bike. At first I thought it was because of a weak battery, but after switching to a bigger, triangle-pack that has been very reliable powering my summer bike for years it still exibits the sambe behaviour. Stopping, mostly when going uphill only after a couple of kilometres.

The is no noise when the wheel is spinning with no load, and when there is, it sounds like I'm making it myself pretending to be a moped. A little embarrasing, considering the pathetic performance.

I've tried 3 different controllers, both self study and manual, so I think it must be the motor. And the connections must be right as I have smooth movement without noise when wheel spins without load.

1) Could this be caused by a half busted hall sensor?

2) Also, this seems to be getting worse. Today I went for a short ride with a fully charged battery and the bike stopped on my way home. Measuring the battery the voltmeter said 29V and it took quite some time before it would charge. Could the motor kill my battery?

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neptronix   100 GW

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Re: Tiny hub motor sucking the life out of my batteries.

Post by neptronix » Nov 11 2018 10:05am

Would be helpful to know what motor you're talking about... and in what size wheel?
My first major build: 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w on a Turner O2 full suspension.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB

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utsi   1 W

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Re: Tiny hub motor sucking the life out of my batteries.

Post by utsi » Nov 11 2018 10:14am

neptronix wrote:
Nov 11 2018 10:05am
Would be helpful to know what motor you're talking about... and in what size wheel?
Very similar to this https://www.aliexpress.com/item/Electri ... 89404343f9. Pretty standard unbranded kind.

The wheel size is 28".

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Re: Tiny hub motor sucking the life out of my batteries.

Post by neptronix » Nov 11 2018 11:17am

Hmm.. no power graph.. no efficiency figure.. power ratings are particularly low.. no idea what winding/kv we're talking about or what voltage/amperage combination is appropriate per speed for the motor per the description.

My guess is that it's an oldschool 0.5mm lam 9C that operates in the low 80% efficiency range. These are relatively noisy designs.

You've tried several controllers and hall/phase combinations, so i think we can rule that out.

So.. let's take a peek at the load..
1) what kind of wattage are you seeing and at what speed?
2) how many volts and amp hours are your battery?
3) What's the maximum amperage on the controller?
My first major build: 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w on a Turner O2 full suspension.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB

"The best time to plant a tree was 20 years ago. The second best time is now."- Chinese Proverb

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Re: Tiny hub motor sucking the life out of my batteries.

Post by utsi » Nov 11 2018 12:07pm

1) Unfortunately I don't have a CA or anything with a display so I would have to go oldschool with a wattmeter and a long wire to measure that. But what I don't understand is that the neither the wires, controller or motor feel hot.

2) The battery is a 48V 20Ah one, als bought from aliexpress.

3) Right now I'm using a controller similar to this https://www.aliexpress.com/item/Electri ... fc10945634. It's for up to 1500W motors but I'm using the lowest speed which should be fine.

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Re: Tiny hub motor sucking the life out of my batteries.

Post by MadRhino » Nov 11 2018 12:34pm

You need to have a mean to measure your power draw and battery capacity.

In the meantime, have you tried the new battery on your other bike?

You say nothing gets hot. Does that include battery temp nonitoring? When there is a power loss, there is some heat produced. That is the first thing to look for.
Make it fool-proof, and I will make a better fool.
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Re: Tiny hub motor sucking the life out of my batteries.

Post by utsi » Nov 11 2018 5:10pm

MadRhino wrote:
Nov 11 2018 12:34pm
You need to have a mean to measure your power draw and battery capacity.

In the meantime, have you tried the new battery on your other bike?

You say nothing gets hot. Does that include battery temp nonitoring? When there is a power loss, there is some heat produced. That is the first thing to look for.
OK, so I went ahead and ordered a power meter from Hobby King https://hobbyking.com/en_us/turnigy-180 ... lyzer.html.

I will try the battery on my other bike as per your suggestion. Will try both bikes on the same route, starting fully charged and measure the voltage afterwards.

I'm running a really cheap setup with no monitoring of anything. Have only been checking with my hand and maybe not at the right times.

Thanks for your input!

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Re: Tiny hub motor sucking the life out of my batteries.

Post by neptronix » Nov 12 2018 12:33am

Yup watt metering is essential. You will also find out the truth about the battery with it.
My first major build: 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w on a Turner O2 full suspension.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB

"The best time to plant a tree was 20 years ago. The second best time is now."- Chinese Proverb

utsi   1 W

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Re: Tiny hub motor sucking the life out of my batteries.

Post by utsi » Nov 12 2018 2:24am

neptronix wrote:
Nov 12 2018 12:33am
Yup watt metering is essential. You will also find out the truth about the battery with it.
I get it:) Do you have any recommendations for my 72V system?

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Re: Tiny hub motor sucking the life out of my batteries.

Post by neptronix » Nov 12 2018 5:20pm

cycle analyst v2 standalone is pretty popular and will work with anything that has voltage running through it.

If your controller has a CA connector, the regular cycle analyst is good stuff too.
My first major build: 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w on a Turner O2 full suspension.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB

"The best time to plant a tree was 20 years ago. The second best time is now."- Chinese Proverb

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Re: Tiny hub motor sucking the life out of my batteries.

Post by dogman dan » Nov 14 2018 8:58am

Well, all we can do it guess some shit. One,, your battery will die faster in winter, even new. And its not new at all. Its about when you expect it to die.

So guess one is that the battery is more than half your problem. Yeah, it was perky last summer, that was then. this is now. I suspect that when you get that watt meter, you will see your 1000 watt hour battery is now putting out less than 500 watt hours. That's still functioning, but its a zombie battery now. It can still pull 200w maybe, but not 1000w.

Second, that could be a 30 amps controller, meaning a normal motor can still pull lots of power up a hill, like 1500w. That could run down your battery fairly quick, when it was newer, and it was summer. Pull 1500w from a zombie, its dies out fast.

Third, don't take it personal, but do you weigh a lot? If so, your hubmotor could be pulling a ton of power up those hills, but making only heat with it. If you are bogging down, below 25 kph up that hill, its making heat with as much as half your power. that would make climbing that hill bad even with a good battery, if the hill is just too steep for your weight. under 100 kilos no problem, but if you are 250 kilos, that's part of the issue.


Lastly, comparing the two bikes is comparing apples to oranges, but you have only described the apple so far.

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Re: Tiny hub motor sucking the life out of my batteries.

Post by utsi » Nov 14 2018 1:13pm

neptronix wrote:
Nov 12 2018 5:20pm
cycle analyst v2 standalone is pretty popular and will work with anything that has voltage running through it.

If your controller has a CA connector, the regular cycle analyst is good stuff too.
I'm sure that's the best there is, but I am looking for something cheaper. Not because I'm cheap but because the bike is kind of illegal and could be confiscated by the cops at any time.
dogman dan wrote:
Nov 14 2018 8:58am
Well, all we can do it guess some shit. One,, your battery will die faster in winter, even new. And its not new at all. Its about when you expect it to die.

So guess one is that the battery is more than half your problem. Yeah, it was perky last summer, that was then. this is now. I suspect that when you get that watt meter, you will see your 1000 watt hour battery is now putting out less than 500 watt hours. That's still functioning, but its a zombie battery now. It can still pull 200w maybe, but not 1000w.

Second, that could be a 30 amps controller, meaning a normal motor can still pull lots of power up a hill, like 1500w. That could run down your battery fairly quick, when it was newer, and it was summer. Pull 1500w from a zombie, its dies out fast.

Third, don't take it personal, but do you weigh a lot? If so, your hubmotor could be pulling a ton of power up those hills, but making only heat with it. If you are bogging down, below 25 kph up that hill, its making heat with as much as half your power. that would make climbing that hill bad even with a good battery, if the hill is just too steep for your weight. under 100 kilos no problem, but if you are 250 kilos, that's part of the issue.


Lastly, comparing the two bikes is comparing apples to oranges, but you have only described the apple so far.
Interesting zombie theory - I think I may have been abusing the battery a little bit with the 30 amps controller, always pushing it to the max before I got my new battery. As for the winter temperatures, it's not really that cold yet, it's hardly been below 0 Celsius.

My wight isn't that bad, I'm only 85 kilos, but I'm driving my kid to school and we're both wearing backpacks with laptops + gym bags and stuff. That puts me in the same boat as a person on the heavy side, I guess. Could this have been contributing to a premature battery death?

The orange is very similar to the apple, only with a 1000W (gearless brushless) rear motor and a controller like this https://www.ebay.com/itm/36v-48v-60v-72 ... :rk:3:pf:0. The battery is a chinese 72V 20Ah triangle pack from Aliexpress.

Is a bigger 48V battery, let's say 30Ah better suited for heavy loads? I've ordered a 1000W motor for my winter bike now, 500 is just too sluggish.

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Re: Tiny hub motor sucking the life out of my batteries.

Post by utsi » Dec 13 2018 2:10am

So I got the wattmeter from from hobbyking and a new motor from aliexpress. It turns out that you were right @dogman dan, the battery seems to be getting tired. I also read about your battery fire now, so sorry to hear about it. My battery is very similar and bought around the same time. Thank you for the warning!

I've ordered a new battery from em3ev, hopefully it will last longer.

What do people do with "zombie-batteries" that are not strong enough anymore, is there a marked for them?

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Re: Tiny hub motor sucking the life out of my batteries.

Post by MadRhino » Dec 13 2018 6:31pm

utsi wrote:
Dec 13 2018 2:10am
...

What do people do with "zombie-batteries" that are not strong enough anymore, is there a marked for them?
Slowly drain them to 0v, then you can put them in the recycling bin or drop them to specific battery recycling, depending on the facilities where you live.
Make it fool-proof, and I will make a better fool.
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Re: Tiny hub motor sucking the life out of my batteries.

Post by amberwolf » Dec 13 2018 10:46pm

utsi wrote:
Dec 13 2018 2:10am
What do people do with "zombie-batteries" that are not strong enough anymore, is there a marked for them?
There's a market for anything someone will pay you for. ;)

But realistically, used batteries (especially with problems) won't get you much, if anything, from most people.

However, you can always parallel it with the new battery, if they are the same voltage and chemistry, to get a little more range and a little less total voltage sag under load. Since the new battery will be providing most of the current, the old one won't sag as badly as when used alone, so it will actually be able to provide some useful capacity.

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Re: Tiny hub motor sucking the life out of my batteries.

Post by utsi » Dec 14 2018 6:31am

amberwolf wrote:
Dec 13 2018 10:46pm
However, you can always parallel it with the new battery, if they are the same voltage and chemistry, to get a little more range and a little less total voltage sag under load. Since the new battery will be providing most of the current, the old one won't sag as badly as when used alone, so it will actually be able to provide some useful capacity.
That's interesting! I won't be able to use the em3ev battery because it's 52V, but I do have an old li ion battery with the same problem as this one, but it's a different size, 12Ah instead of 20-ish. Could it still work?

I may have to get a little creative in regards of placement since I don't have room for both inside the triangle..

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Re: Tiny hub motor sucking the life out of my batteries.

Post by Philaphlous » Dec 14 2018 7:58am

MadRhino wrote:
Dec 13 2018 6:31pm
utsi wrote:
Dec 13 2018 2:10am
...

What do people do with "zombie-batteries" that are not strong enough anymore, is there a marked for them?
Slowly drain them to 0v, then you can put them in the recycling bin or drop them to specific battery recycling, depending on the facilities where you live.

Holy scheit...thats by far the worse advise I've ever heard besides elon taking Tesla private for $420 a share...no offense. You do that and you're basically begging and praying and sacrificing your first born for a battery fire. Don't ever do that! The reason why batteries become unstable and cause fires/failure is from having them at a state not in normal range. Meaning if you drain cells below 2.5V your asking for trouble or if your overcharging cells to like 4.5v per cell. Just because there's no voltage doesn't mean the chemicals in the battery can't react. You take a 0v battery to a recycler and they're going to ask you to keep the battery outside away from the building.

I would say make sure the battery is at nominal voltage before doing anything with it. That is essentially the safest state the battery can be in.

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Re: Tiny hub motor sucking the life out of my batteries.

Post by MadRhino » Dec 14 2018 5:16pm

Sorry, but draining them to 0v is the only way to dispose them safely. And, no matter what you had been said, draining them won’t start a fire. Either leaving them plugged on a low power light or any other resistance, or sinking them in salt water, until they are completely drained.

LiCo chemistry is very dangerous to dispose when it is active, because a short or puncture would start a fire. After they are at 0v, your cells are inert.

That, mind you, is the ONLY good advise for proper disposal of lico chemistry batteries.
Make it fool-proof, and I will make a better fool.
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Re: Tiny hub motor sucking the life out of my batteries.

Post by neptronix » Dec 14 2018 5:28pm

Draining a lithium cell to 0v makes it inert.
It's internal structure is forever changed then, and it can no longer functions as a battery.

Dangerous things only start happening when you do the really stupid thing and try to recharge it.
My first major build: 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w on a Turner O2 full suspension.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB

"The best time to plant a tree was 20 years ago. The second best time is now."- Chinese Proverb

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