Battery goes from 18% to 31% without charging

flaxseedoil1000

New Member
Region
USA
Greetings,

This is my first EV anything and am wondering if this is normal or not.

Shut the bike down last night after a ride, 18% remaining. Did not hook up the charger.
This morning it reads 31%.

I notice this all the time, sometimes during a ride if I turn it off then right back on the % remaining increases a fair amount. These two pics show that, off then right back on and an 8% increase.

Hard to tell when to head back home without an accurate reading.

tia

PXL_20211101_220005385small.jpg

PXL_20211101_220040260small.jpg
 

tomjasz

Well-Known Member
Region
USA
City
Minnesnowta
Yikes! I hate to see that much of a sag. How old is the battery? Is this display reading confirmed with a multimeter? Do you have a display manual?

Magicycle Ebike Blog

I always run my new battery to the LVC low voltage cutout. I note the mileage and back off 10% less than my calculated mileage. But 18% is a bit concerning. What is the battery voltage? Is there a voltage reading that displays while riding?
 
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Gionnirocket

Well-Known Member
Region
USA
City
Y. O.
Percentage readouts are notoriously poorly calibrated. Does your display have the option to read volts?
What size is your battery?
A battery will regain a bit after resting... especially after a heavy load and/or change in temperature.
 

flaxseedoil1000

New Member
Region
USA
Yikes! I hate to see that much of a sag. How old is the battery? Is this display reading confirmed with a multimeter? Do you have a display manual?

Magicycle Ebike Blog

I always run my new battery to the LVC low voltage cutout. I note the mileage and back off 10% less than my calculated mileage. But 18% is a bit concerning. What is the battery voltage? Is there a voltage reading that displays while riding?
Thanks, 2 months old, 200 miles.
Yep I can switch from % to V, I assume % is based off the max and min volts.
 

flaxseedoil1000

New Member
Region
USA
If you are riding throttle only, in the cold, and you have a smaller battery with a big motor, it could be normal when the battery warms a bit.
Thanks, battery is 52V 15Ah, 22 amp controller.
Does it consistently regardless of ambient temperature.
Am curious if going from 22 amps to zero is affecting the reading from the voltage sensor.
I gather from the responses this is not normal.
 

flaxseedoil1000

New Member
Region
USA
Percentage readouts are notoriously poorly calibrated. Does your display have the option to read volts?
What size is your battery?
A battery will regain a bit after resting... especially after a heavy load and/or change in temperature.
Thanks, yeah I can switch to voltage but I assumed % was just doing the math for me.
I have PAS max at 70% = 800 watts, throttle is 1,144 watts which I try to use sparingly.
Next ride I am going to do a cool down lap before I shut it down and see if there is a difference.
 

Gionnirocket

Well-Known Member
Region
USA
City
Y. O.
Thanks, yeah I can switch to voltage but I assumed % was just doing the math for me.
I have PAS max at 70% = 800 watts, throttle is 1,144 watts which I try to use sparingly.
Next ride I am going to do a cool down lap before I shut it down and see if there is a difference.
Well now that you have it set to voltage... See what your full charge is and your spread.
With my ride it reads 100% at just above 50.0v but my battery full charge voltage is 54.6v
On the other end it reads 0% at about 40.0v which really should be closer to 35v...but this is a good thing as running a battery to actual 0% is destructive
 
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flaxseedoil1000

New Member
Region
USA
Well now that you have it set to voltage... See what your full charge is and your spread.
With my ride it reads 100% at just above 50.0v but my battery full charge voltage is 54.6v
On the other end it reads 0% at about 40.0v which really should be closer to 35v...but this is a good thing as running a battery to actual 0% is destructive
Thanks, I will give it a try. I'm just an old fart trying to wrap my head around these and figure out what is normal or not.
I you need help jetting your carb or setting your points I am your guy. :)
 

JRA

Well-Known Member
"battery is 52V 15Ah,"

Full charge is 58.8v, 43v LVC for a 52v battery, the above numbers are for a 48v one but the same theory applies.

What you are experiencing is voltage sag which is common on all battery operated devices while under load. At rest they will spring back some however dependent on the Ah and quality of the cells in use.

As indicated the displays on eBikes seem to be having a hard time actually providing reliable information in regards to battery level. Best thing to do is to get to know your system and what it is capable of and abiding by that.
 

flaxseedoil1000

New Member
Region
USA
"battery is 52V 15Ah,"

Full charge is 58.8v, 43v LVC for a 52v battery, the above numbers are for a 48v one but the same theory applies.

What you are experiencing is voltage sag which is common on all battery operated devices while under load. At rest they will spring back some however dependent on the Ah and quality of the cells in use.

As indicated the displays on eBikes seem to be having a hard time actually providing reliable information in regards to battery level. Best thing to do is to get to know your system and what it is capable of and abiding by that.
Holy cow you guys weren't kidding when you said percentage is not accurate.

Charged to 100% last night, checked this morning, still 100%, switched to volts and it was at 55.6.
Thanks to JRA pointing out 58.8v I put it back on the charger and this time let it charge until it shut off and got to 58.6.
I'm used to a gas gauge in a car, these are so different but thanks to you all I am figuring it out.
btw is there a time to turn around and head home voltage you look for?

Thanks again everyone!
PXL_20220117_185645179.PORTRAIT.jpgPXL_20220117_204727181.PORTRAIT.jpg
 

JRA

Well-Known Member
Without knowing your exact LVC the best you can do is run the battery down close to home and see where it cuts out. If you do it purposely using a high mode of assist it won't take as long and be fun at the same time.....when it cuts out/shuts down take note of the voltage. You should be able to continue on by off/onning the display and lowering the assist level that should get you closer to the LVC until at level 1 it finally won't provide any assist at all. That way you can gauge when you should head home in the future and at what level of assist it will take to get there given the terrain you have to travel. Each bike is different I have found and there is no standard voltage for all.
 

fauconnier

Active Member
Region
Canada
Load voltage vs open cells voltage...
 

flaxseedoil1000

New Member
Region
USA
Thx all, it's my first EV anything and there is a learning curve coming from ic engines.

I have since learned that this rise and drop in voltage is completely normal, just takes some getting used to.