Battery Display Settings

[PedalUma]

Often on bikes the highest bar on the display showing remaining battery power takes you the most miles. The last bar takes you the fewest miles. What if each bar took you the same number of miles? How would you program that? I am programing a bike right now. It has a 48V nominal battery. The charge goes from 54.6V max to 36V low. Zero =36, Max = 54.6V.
20% = 41.1V, 40% = 45.5, 60% = 49.1, 80% =52.2. Below are the voltage gaps.
5.1, 4.4, 3.6, 3.6, 2.4V. It is shaped like a whale with a big head and a long tail.

 

[Gionnirocket]

36v is too low for 0.
Though it is close to actual battery voltage range, taking it that low is harmful and can possibly cause irreversible damage so most BMS/Controllers shut down around 40v or 25%.
As far as the bars... Never cared to care.

 

[PedalUma]

I agree. Most go down to 40V as the low limit. The batteries I use I think are different than most and it works just fine this way. Good point. Other systems might be different in the details but the concept of the chi square shaped distribution curve is still there.

 

[Gionnirocket]

I agree. Most go down to 40V as the low limit. The batteries I use I think are different than most and it works just fine this way. Good point. Other systems might be different in the details but the concept of the chi square shaped distribution curve is still there.

View attachment 209479

How are they different?
I assume they are using standard name brand cells and this is a function of a typical cell. Allowing the end user to take them down to <5% is not recommended at all.

 

[Chazmo]

Folks have a lot of different ideas as to what the power meter should show. What makes sense to me, doesn’t seem to make sense to the industry.

I’d like each bar to represent a linear amount down to a (programmable) minimum (which is the zero). That means each 20% (linear) interval — five bars — varies based on the defined bottom/minimum. I don’t know if most controllers have a flexible “bottom charge” capability, but mine offers a programmable minimum where the battery turns off. The intervals have to be debounced though. You can’t use instantaneous voltages (most controllers already know this) because when the battery is being used there is a voltage drop… Some sort of averaging scheme (like one minute or so) would do. I think most manufacturers have figured that out too.

 

[PedalUma]

How are they different?
I assume they are using standard name brand cells and this is a function of a typical cell. Allowing the end user to take them down to <5% is not recommended at all.

This is why we have peer review. They have Samsung 35e cells with super premium BMS. Never run it all the way into the ground. And never, never leave it like that. The display shows half-bars.

 

[Gionnirocket]

I'd be surprised if even a double super ultra premium BMS will allow a lower output voltage of 39v.
ymmv

 

[PCeBiker]

36v is too low for 0.

I agree. Most go down to 40V as the low limit.

All three of my 48V batteries are Fricken Useless below 42 Volts.

The voltage sag keeps shutting them down even with as low as 150W draw.

I consider "Zero" battery as 42V and use it like an emergency "Reserve" like on a motorcycle.


So here's my math,..
Full range 42V-54V.
A 12V spread.

Power at 42V=V×A
Power at 54V=V×A

Say 500 Watts, for Canada,..


11.9 Amp Draw at 42 Volts.
9.2 Amp Draw at 54 Volts.


So,..
As the battery becomes the weakest, and most drained, it is then required to put out its maximum amps.

It's a disproportionate relationship between power, voltage, and capacity.



My LVC is adjustable using my controller and I set it as high as I could.

There's No Damn Way I'm gunna wait for the BMS on my battery to shut me down.
39V is not a healthy choice.




Ohh, and BTW,..
If you wait for your battery's BMS to shut you down, That's It. You're Dun.

I've had my controller shut me down over and over, and I could shut down my display, and restart it while coasting, and restart my ebike.

At the very end, I had to pedal my Ass up to speed before I'd touch the throttle, to keep the output under 150 Watts.

 

[Gionnirocket]

All three of my 48V batteries are Fricken Useless below 42 Volts.

The voltage sag keeps shutting them down even with as low as 150W draw.

I consider "Zero" battery as 42V and use it like an emergency "Reserve" like on a motorcycle.


So here's my math,..
Full range 42V-54V.
A 12V spread.

Power at 42V=V×A
Power at 54V=V×A

Say 500 Watts, for Canada,..


11.9 Amp Draw at 42 Volts.
9.2 Amp Draw at 54 Volts.


So,..
As the battery becomes the weakest, and most drained, it is then required to put out its maximum amps.

It's a disproportionate relationship between power, voltage, and capacity.



My LVC is adjustable using my controller and I set it as high as I could.

There's No Damn Way I'm gunna wait for the BMS on my battery to shut me down.
39V is not a healthy choice.


Ohh, and BTW,..
If you wait for your battery's BMS to shut you down, That's It. You're Dun.

I've had my controller shut me down over and over, and I could shut down my display, and restart it while coasting, and restart my ebike.

At the very end, I had to pedal my Ass up to speed before I'd touch the throttle, to keep the output under 150 Watts.

Using the Samsung cell as an example... 39v is approximately 22%, which is fine as a LV shut down.
That's what I have my controller set to. I have no idea what my BMS's are set to.
You have a much bigger problem with sag then most because..... You don't f'n pedal!

 

[PCeBiker]

You have a much bigger problem with sag then most because..... You don't f'n pedal!

It not my battery sagging.

It's my personal sag in the saddle that's going to find me walking home.

 

[6zfshdb]

Programming a bar gauge to represent remaining useable wattage instead of current voltage seems reasonably simple to do, yet few if any manufacturers of low & mid level bikes do it. I find the bar gauges on my mid priced bikes to be all but useless. By the time the first of the 5 bars disappears, there is actually 50% charge remaining.

Since I'm a data freak, I use two other gauges to measure remaining charge. One is a simple analog voltmeter that reads like a gas gauge, and the other a bar gauge that measures actual watts consumed. Between the three gauges, I can estimate remaining range within 5 miles or so.

The displays on many of the more expensive bikes are quite sophisticated and provide all the battery / range information at a glance. How much extra would it actually cost to put these displays on all bikes instead of these crappy bar gauges?

 

[Gionnirocket]

Programming a bar gauge to represent remaining useable wattage instead of current voltage seems reasonably simple to do, yet few if any manufacturers of low & mid level bikes do it. I find the bar gauges on my mid priced bikes to be all but useless. By the time the first of the 5 bars disappears, there is actually 50% charge remaining.

Since I'm a data freak, I use two other gauges to measure remaining charge. One is a simple analog voltmeter that reads like a gas gauge, and the other a bar gauge that measures actual watts consumed. Between the three gauges, I can estimate remaining range within 5 miles or so.

The displays on many of the more expensive bikes are quite sophisticated and provide all the battery / range information at a glance. How much extra would it actually cost to put these displays on all bikes instead of these crappy bar gauges?

With experience they could probably calibrate one more accurately with just the voltage and knowing the battery capacity.
With the higher end bikes I believe things get a bit more sophisticated by using CANbus to keep in constant communication with the battery taking into consideration things like temperature and average load.
That said, I'm pretty accurate just knowing the voltage and which battery I'm using. 10Ah or 21Ah.
Maybe I'm more cerebral when it comes to these things... but it didn't take long to figure it out and it doesn't bother me in the least.
Bar indicators I've always found pretty much useless no matter the device.
ymmv

 

[BlackHand]

Yeah, not a fan of bar indicators either - you never know how accurate they are. Glad my bikes have a remaining range display. It's really quite accurate as long as the terrain and riding are consistent.

I'd imagine most people get used to whatever measurement is available to them.