Battery calibration?

[Homet]

After riding 21ish miles, I return home with 1 to 2 bars (out of 5) on the battery indicator on the lcd display. I suspect it’s nearer 1 bar as the second bar only just came back on after I stopped. This has happened after every single ride since I got the bike and I’ve always been a bit miffed that a 10.5aH battery is only lasting 20 miles. Today, for some reason, I pushed the battery charge indicator on the battery just before I plugged the charger in and I was shocked that it said I had 2 bars (out of 3) charge left!

I started thinking about this and was wondering if bike batteries needed to be calibrated in the way that laptop batteries sometimes need to. How else could it be that my display says I have 1 bar (maybe 20%) battery left but the actual battery says I have significantly more - maybe upto 66% ?

What do you guys think!

 

[tomjasz]

Comparing actual voltages with a multimeter or wattmeter can verify just what the bars represent for power left.

 

[Gionnirocket]

After riding 21ish miles, I return home with 1 to 2 bars on the battery indicator on the lcd display. I suspect it’s nearer 1 bar as the second bar only just came back on after I stopped. This has happened after every single ride since I got the bike and I’ve always been a bit miffed that a 10.5aH battery is only lasting 20 miles. Today, for some reason, I pushed the battery charge indicator on the battery just before I plugged the charger in and I was shocked that it said I had 2 bars (out of 3) charge left!

I started thinking about this and was wondering if bike batteries needed to be calibrated in the way that laptop batteries sometimes need to. How else could it be that my display says I have 1 bar (maybe 20%) battery left but the actual battery says I have significantly more - maybe upto 66% ?

What do you guys think!

I never use the bars as they are akin to idiot lights. But it seems the two sets of bar lights are calibrated differently
See if your display can show voltage as an option... Much more accurate.
Also a batteries voltage can increase a bit after resting for a short while after riding.

 

[AHicks]

And 21ish miles on a 10.5ah battery pack is not that bad. SO MUCH depends on factors like speed, wind, surfaces, and what YOU are putting into it. That sounds cliche, but what you may find, like a lot of us have, is that our battery range does much better when we really learn how to ride the bike - starting out as far as a couple hundred miles. Most of us suck in the beginning as e-bike rookies. Coordinating the proper gear to be in, with the right assist level, and how much effort we're supplying is not something you are born into. It takes some time! I've been riding 4 years now, and STILL challenge myself to manage those options in a manner to max out my battery mileage. My thought anyway. -Al

 

[Homet]

Re what I’m putting into it, I have the bike on Eco mode and pedal my ass off!

The display does show voltage - it starts off when fully charged at 41.4v and by the time I’ve come back home, it’s around 36.5 to 37v. I don’t know how to interpret that!

 

[Gionnirocket]

I'm assuming it is a 36v battery... Your full charge voltage seems to be a bit low.
Do you know the brand of cells you have?

 

[AHicks]

I'm 70, 6'2"/315 lbs, and pedal from the time I leave until the time I get back. That means nothing in the grand scheme of things. It's way more about how you are managing things like speed....

 

[Gionnirocket]

Re what I’m putting into it, I have the bike on Eco mode and pedal my ass off!

The display does show voltage - it starts off when fully charged at 41.4v and by the time I’ve come back home, it’s around 36.5 to 37v. I don’t know how to interpret that!

I'd also add that pedaling your ass off is good as your reducing weight as you go.... But you should probably go back out and get it as you'll probably need it in the morning

 

[Homet]

Re the cells, sorry I’ve no idea. Is your table saying that at 36v, I still have 50% left?! Does that not mean that the BMS needs to be calibrated?

 

[Gionnirocket]

No... I'm assuming that you have a 36v because of your full charge voltage. You should get the spec sheet on the battery if possible

edit: but yes with a 36v battery the voltage range is as the chart shows... so at 36v you are at 50%. Keep in mind that it's not a good idea to run the battery below 40% if you can help it. 40% is an ideal point to recharge.

 

[Homet]

It is a 36v battery. 36v, 10.5aH

 

[Gionnirocket]

Ok.. Look back as I edited my previous reply. There is no calibration for the BMS.. Like I said, watch voltage and use the chart. The bar lights are only for a general reference.
Maybe Thomas, your original reply'r can help shed a little bit more light as I know he rides a 36v system as well.

But as others have stated... They're a are many variables in battery life. But starting with a quality battery is also a major factor

edit: Also include some details about your ebike. Motor location, wattage, make/model... etc

 

[Homet]

350w motor on the rear hub. Generic fat tyre Chinese bike with a battery between the seat and the rear wheel. Display is a Yose Power C500. Not sure if any of this helps.

 

[Gionnirocket]

350w motor on the rear hub. Generic fat tyre Chinese bike with a battery between the seat and the rear wheel. Display is a Yose Power C500. Not sure if any of this helps.

Well understand that you didn't purchase state of the art so things may be a bit off as far as capacity and abilities.
To start the full charge voltage seems to be a little low. I would cycle the battery a few times between 40 to 100% a few times and see if things improve any. Rest the battery for at least an hour after riding and before charging. Try to charge to 100% so that you ride soon after. They don't like to be hot and they don't like to stay at 100% charge.

 

[legsofbeer]

It is a 36v battery. 36v, 10.5aH

That's a 378 watt-hour battery, not very substantial by current standards. For instance, a 2019 radrover (another lower cost fat tire bike) came with a 672 watt-hour battery. I get the advertised 25 miles using full power, and 35-55 miles using half-power or less settings. So I'd say your battery is performing pretty close to what you can expect. You can milk a little more out of it by applying a little brake lever to stop the motor from activating (but not enough to engage the brakes) when you're coasting to a stop and spinning the pedals to gear down.

In my experience, the bar output on the display, and the battery's built-in led meter, are largely useless, and hugely biased to the optimistic side. The best way to gauge your battery is to check its voltage (unloaded) with a multimeter under various scenarios, and correlate that with the miles and hills you've put on it since the last full charge. After that you can use your odometer as a realistic measure of remaining range. Be very fucking careful with the multimeter leads because if you accidentally touch them together while measuring battery voltage you can cook off the battery.

The above tips about charging the battery at room temp and giving it an hour to cool down after a ride will extend your battery's useful life, but will not increase its capacity.

ETA: if you're riding your fatty on "squishy" tire pressure, you'll get better speed (which means more range when at cruising speed) by pumping them up to higher pressure. Check what the tire sidewall says and work with that.

 

[Homet]

Many thanks guys! I was told that the BMS would cut the power to the bike if the voltage drops below 36v (as this is the minimum that the motor needs to work). When this happens, can I leave it for a while and ride it again to get home?

 

[Gionnirocket]

Your low voltage cut off should be a little lower than that. On my 48v system the motor controller is set to cut power when the battery reaches around 20%. On my BMS it is set really low, at the point the battery is just about fully drained. I would not go there as you really start to stress the battery.
As far as getting home after it cuts off, if from the controller say around 20% you may be able to... but I doubt it as it can't recover that much from resting... especially at the lower voltage. And you probably don't want to take that chance with a lower quality battery as it will be stressful and it could damage it if it doesn't further protect itself adequately.

 

[AHicks]

Many thanks guys! I was told that the BMS would cut the power to the bike if the voltage drops below 36v (as this is the minimum that the motor needs to work). When this happens, can I leave it for a while and ride it again to get home?

It depends. If the power loss happened under a big load, the result of a big voltage sag, you may be able to get it home by cooling it at lower throttle settings.

That said, riding until it quits, then nursing it to get home is hard on your battery. Not something you want to make a practice of doing.

 

[Homet]

Ok, just an update. Went pure electric today (I just had to see for myself) and the bike cut out after 25.5 miles. Quite a few hills in there and a couple nasty ones that I assisted on. The rest was all battery. The bike went to 1 bar at 17 miles but stayed on for another 8 miles after that! It cut out at around 33v.
At least now I know that there’s still a fair bit left at 1 bar and I don’t need to rush home immediately!

 

[Homet]

Hmmm... battery now plugged in after letting it cool down for 2 hrs ( it wasn’t hot anyway) and nothing is coming on, even the leds on the battery seem dead! The bike control panel is also dead! Is there a reset button or something somewhere?