Diagnosis help please ( recent change to very poor mileage per charge)

[Bike me]

I have a store-bought ebike 3 yrs old with Bafang 500 watt hub motor and I have 2 batteries, the 2nd battery was purchased from a different company and was in indoor storage and kept at medium % full, charged some more periodically to not allow to go to low voltage. Both batteries are 48V 17 Ah. I have 8000 miles on the bike.
Recently my mileage on same regular routes has gone way down and seems to be getting worse quickly. It's about half what I was getting before. It's not the weather.
I suspected it was the battery so I changed to the spare battery and that made no difference.
The motor is not making anything like the noise I've heard on videos of mashed planetary gears, so not lot of noise, but it is slightly louder than before.
The wheels are free to turn and nothing is rubbing, neither brakes nor tires.


Any guesses? I've got a spare set of planetary gears for expected eventual replacement.

Thank you for any guidance you might offer.

 

[DaLanMan]

Batteries are like Pizza, great when ya get em, not bad at all for a while, then you find a slice that is 3 years old and it just not the same.

On a more serious note, Lithium batteries of all sorts do age out. If you have been using these regularly (duty cycles) you are towards the end of the expected life of a battery from 3 years ago. I keep being told by vendors that it is not so much of a problem anymore, but I keep mine on a cycle, and I test them yearly...

Hey, I know I am new to the whole e-bike thing... I am *not* new to electronics...

 

[Bike me]

Batteries are like Pizza, great when ya get em, not bad at all for a while, then you find a slice that is 3 years old and it just not the same.

On a more serious note, Lithium batteries of all sorts do age out. If you have been using these regularly (duty cycles) you are towards the end of the expected life of a battery from 3 years ago. I keep being told by vendors that it is not so much of a problem anymore, but I keep mine on a cycle, and I test them yearly...

Hey, I know I am new to the whole e-bike thing... I am *not* new to electronics...

Thank you, DaLanMan.
Only one of them was in use, the other was used only once or twice mostly just well stored. So one of them was used almost every day, the other basically unused.
That difference makes me think it's not the battery(s).

 

[Bike me]

I'm completely ignorant about the controller and I wonder if it could cause the symptom.

 

[DaLanMan]

Well, most likely culprit of slow decline to the best of my knowledge would e the battery, it might be your BMS ... not with two units...

Can you pull data from your unit? (the joys of modern tech, it *is* possible to do such a thing, but does the vendor *want* you to?)

 

[amberwolf]

What happened just before the problem started? Any incidents? Any changes?

Was the problem sudden, or gradual over time? (how much time?)


Almost always a problem like you're seeing is a battery issue, but it could be that settings were changed on your system to use more power, or the assist level has been changed to one that's much higher. But this would not cause a problem that would keep getting worse, it would only cause it to change once, at the time the settings or level changed.

So, it still sounds like a battery issue:

Does the spare have it's own charger? (or is the same charger as the other? what voltage does it charge to, as measured with a voltmeter?) If the charger isn't fully charging the battery, you won't get as much range.


Regarding power usage of the bike changing due to settings/etc., it's hard to know that for sure unless you have a wattmeter on the system, and know what the watts were under the various conditions of your ride before the problem happened, and can see that they are higher now.


If you've eliminated brakes and any other source of friction, that leaves bearings inside the motor, or water intrusion causing corrosion or other damage...but that doesn't usually keep getting significantly worse and worse without other signs like rough running or other audible or human-detectable symptoms. You'd probably notice this serious a problem just hand-spinning the wheel offground.

 

[Bike me]

What happened just before the problem started? Any incidents? Any changes?

Was the problem sudden, or gradual over time? (how much time?)


Almost always a problem like you're seeing is a battery issue, but it could be that settings were changed on your system to use more power, or the assist level has been changed to one that's much higher. But this would not cause a problem that would keep getting worse, it would only cause it to change once, at the time the settings or level changed.

So, it still sounds like a battery issue:

Does the spare have it's own charger? (or is the same charger as the other? what voltage does it charge to, as measured with a voltmeter?) If the charger isn't fully charging the battery, you won't get as much range.


Regarding power usage of the bike changing due to settings/etc., it's hard to know that for sure unless you have a wattmeter on the system, and know what the watts were under the various conditions of your ride before the problem happened, and can see that they are higher now.


If you've eliminated brakes and any other source of friction, that leaves bearings inside the motor, or water intrusion causing corrosion or other damage...but that doesn't usually keep getting significantly worse and worse without other signs like rough running or other audible or human-detectable symptoms. You'd probably notice this serious a problem just hand-spinning the wheel offground.

What happened just before the problem started? Any incidents? Any changes?

Nothing, that I can think of.

Was the problem sudden, or gradual over time? (how much time?)

I'd say that it was more likely sudden and I only discovered how bad it was after I began watching it , fully charging, watching it again.

Almost always a problem like you're seeing is a battery issue, but it could be that settings were changed on your system to use more power, or the assist level has been changed to one that's much higher. But this would not cause a problem that would keep getting worse, it would only cause it to change once, at the time the settings or level changed.

So, it still sounds like a battery issue:

Does the spare have it's own charger? (or is the same charger as the other? what voltage does it charge to, as measured with a voltmeter?)

I have only the one charger and my well-used battery never came to fullest charge possible, but close when measured with meter, after leaving it for a long charge overnight. I did not do that habitually, just to test. From showing 100% on bike screen it would always lose 2% on the first hundred yards, then behave more normally and I could get 50 miles per charge riding at high assist levels. Now it can lose 6% right away. Today's travel of 5 miles took it from 84% to 56%.I am going to fully charge it and measure with meter, will report back. Thank you!

 

[docw009]

You should get an accurate voltmeter and measure the voltage of
1. charger with no battery connected
2. each battery after they are fully charged
3. each battery when you think they're half used up,

 

[amberwolf]

Note that the battery bars on controller displays can be (wildly) inaccurate...sometimes a pack that's at some low voltage when the system is turned on can cause the meter to switch to thinking it's watching a lower voltage pack than ti really is, so it will show a full pack when it isn't.

The opposite can also happen, and cause the system to shutdown early, when a pack is still nearly full.

These usually happen with 36v/48v controllers that autodetect voltage, and 36v / 48v packs.

 

[Bike me]

Note that the battery bars on controller displays can be (wildly) inaccurate...sometimes a pack that's at some low voltage when the system is turned on can cause the meter to switch to thinking it's watching a lower voltage pack than ti really is, so it will show a full pack when it isn't.

The opposite can also happen, and cause the system to shutdown early, when a pack is still nearly full.

These usually happen with 36v/48v controllers that autodetect voltage, and 36v / 48v packs.

I just finished charging the battery I use every day. The charger shut off at 99% on my bike screen and I left it plugged in for another hour and it then showed 100%. This battery had the charger charging light turn off at 98% on the bike screen once last week.
The battery is now showing 100% on the bike, and by meter it shows voltage 54.1 to 54.2, flipping back and forth.
I'll go for a short ride and then meter test again.

 

[Bike me]

You should get an accurate voltmeter and measure the voltage of
1. charger with no battery connected
2. each battery after they are fully charged
3. each battery when you think they're half used up,

The charger is a SANS charger, label says 48 V 3.0 Amps meter reading is 54.2 Volts.

 

[Bike me]

After letting the battery sit for 1/2 hr or so, the meter reads voltage as between 54.0 and 54.1.
That is usual for the battery to do.

 

[Bike me]

I rode 2.2 mi, with one small hill involved, as usual. Temperature is 43F. Wind 4mph. Now reading 88% on the bike screen, and that will probably rebound to 89%. Showing 53.2 V on the meter.
Rebounded to 89% still showing 53.2V on meter
I'll report the V when bike screen is reading 50%, then 20%.
Then I'll test the spare battery.

 

[Bike me]

Reading 48% on bike screen meter says 50.2 volts, 16.5 miles
Later on, reading 34% meter says 49.1 volts 20.5 miles.
On the last trip I rode harder and used the throttle more. Weather and wind conditions the same as the previous trip.

 

[Chalo]

49V resting voltage is over 50% state of charge, if you're using a 13S lithium ion pack. Have you checked your bike's voltage display against a multimeter for accuracy?

 

[DaLanMan]

Sounds like a cel is collapsing and sucking it up. I have seen them pull down the amperage, but not without effecting voltage, and hey, I have been playing with these for like 6 months! I must be smurt

 

[Bike me]

49V resting voltage is over 50% state of charge, if you're using a 13S lithium ion pack. Have you checked your bike's voltage display against a multimeter for accuracy?

The battery is 13s 5p using LG M36 cells

 

[Bike me]

Have you checked your bike's voltage display against a multimeter for accuracy?

From the instruction manual, there is nothing about a voltage display, only the 5 bar graph. But now that you mention it, I think I found a voltage reading or setting they didn't tell us about. The manual says the other settings are presets only. That setting says "52". It does not change with different battery voltage level.

 

[99t4]

From the instruction manual, there is nothing about a voltage display, only the 5 bar graph. But now that you mention it, I think I found a voltage reading or setting they didn't tell us about. The manual says the other settings are presets only. That setting says "52". It does not change with different battery voltage level.

That is a very important clue. That 52 might indicate that the controller is set up for a 52V battery. If that is the case, your symptoms might stem from the controller shutting off when the voltage reaches its LVC for a 52V battery (which higher than for your 48V battery)(So it is shutting down while there is still safely usable energy in your 48V battery).

Can you set the controller for a 48V battery? If not, it may have an auto-sensing feature. Try disconnecting the controller from the battery when the battery is in the low 40s if possible. That way the controller wouldn't mistakenly autosense that the battery is a 52V 14s when you reconnect it.

 

[Bike me]

That is a very important clue. That 52 might indicate that the controller is set up for a 52V battery. If that is the case, your symptoms might stem from the controller shutting off when the voltage reaches its LVC for a 52V battery (which higher than for your 48V battery)(So it is shutting down while there is still safely usable energy in your 48V battery).

Can you set the controller for a 48V battery? If not, it may have an auto-sensing feature. Try disconnecting the controller from the battery when the battery is in the low 40s if possible. That way the controller wouldn't mistakenly autosense that the battery is a 52V 14s when you reconnect it.

Thank you! The heading on that setting on my bike display says "BV" and the number is 52. Your guess seems to be correct. I have no idea about the controller, never even seen it, it's in the downtube.

 

[Bike me]

That is a very important clue. That 52 might indicate that the controller is set up for a 52V battery. If that is the case, your symptoms might stem from the controller shutting off when the voltage reaches its LVC for a 52V battery (which higher than for your 48V battery)(So it is shutting down while there is still safely usable energy in your 48V battery).

Can you set the controller for a 48V battery? If not, it may have an auto-sensing feature. Try disconnecting the controller from the battery when the battery is in the low 40s if possible. That way the controller wouldn't mistakenly autosense that the battery is a 52V 14s when you reconnect it.

Would the voltage reading when charger shuts off (slightly more than 54 V) indicate that it does sense what the battery is?

 

[99t4]

Would the voltage reading when charger shuts off (slightly more than 54 V) indicate that it does sense what the battery is?

Insufficient information to correctly infer. Where are you seeing this voltage readout? What is the lowest voltage you have seen?

We haven't ruled out the possibility that the controller may have incorrectly guessed the battery was a 52V battery instead of a 48V (if the controller is indeed a auto voltage-sensing controller).

 

[Bike me]

Reading 48% on bike screen meter says 50.2 volts, 16.5 miles
Later on, reading 34% meter says 49.1 volts 20.5 miles.
On the last trip I rode harder and used the throttle more. Weather and wind conditions the same as the previous trip.

To compare with the spare battery, which is almost unused, the meter says 50.3 volts for the spare when at 50% on the bike display. Travel was 14.5 miles.
So the 2 batteries are close at that point. The particular low output the LG M36 batteries do attain a high number of recharges in their life life so that isn't very surprising.
Cold does really affect the performance of them, for sure.
I noticed meanwhile that the rear tire has a small slow leak so I'm going to be making sure it is the same 45 lb each ride now. the wind during my regular routes rides has been fairly low. Now there is going to be more variance in temperatures ahead.

 

[Bike me]

Insufficient information to correctly infer. Where are you seeing this voltage readout? What is the lowest voltage you have seen?

We haven't ruled out the possibility that the controller may have incorrectly guessed the battery was a 52V battery instead of a 48V (if the controller is indeed a auto voltage-sensing controller).

I'm using a meter for voltage and the bike display for % full. I will take the batteries down to 20% to see voltage there. I've only once ridden to shutoff and did not meter test then.

 

[Bike me]

I used my spare battery yesterday down to about 30% then charged it to 100%. It sat for 12 hours and voltage had reduced to 53.8 on meter. I just topped it up to 100% and will do my regular route once or twice and recheck.