Battery do i expect to much

[Hixyhicks]

I have a Bafang HD with a 52v 17ah jumbo shark battery.At the moment i get the train to work,cycle to the station and then cycle home.I use the bike for approximately 18-20 mile at anything between pas 2 and pas 6.By the time im home the battery is 3/4 used.Does that seem normal.At the moment im 90-100 kg and the bike is over 25 kg.


Mick

 

[Gavin]

the battery is 3/4 used

Is that based on the bars on the display? Have you taken a voltage reading from the battery with a multimeter to determine how much is left?

 

[Hixyhicks]

I'm going by the green bar on the screen.It does show voltage but i cant remember the Reading, will take a note tonight.when i put the battery on the charger 1 light is illuminated before i plug the charger in.

 

[Gavin]

So forgetting what the display is showing, does the bike actually feel slower?

The display may be giving an innacurate status. You only really know how much range you've got once you've hit the LVC a few times. When you hit the LVC, take a note of the voltage

 

[sjpt]

Even riding at 2 on that may be close to riding on turbo on 'standard' e-bikes. You don't mention how hilly it is which makes a huge difference to battery consumption. Or how much pedalling effort you put in, or speed you ride, or type of tyres. If you ride fast without much effort and there are any significant hills that doesn't seem a surprising range even allowing for the very substantial battery capacity.

 

[Hixyhicks]

Thank you both.Its very hilly 377 metres of climbing according to Strava.The bike doesn't lose any power toward the end of the ride.I was just wondering I'm glad i didn't listen to the fella at the bike shop.The figures he was giving for a 400wh battery were way over the top.

 

[wheeliepete]

As already suggested, use voltage reading to gauge battery usage. With your pack, 51v is approx. 50% capacity.

 

[vfr400]

It depends on how hard you're pedalling and how fast you're going. I used to use 480 watt-hours to travel 14.4 miles at a modal speed of 18 mph, and climbing about 100 meters, so 19 miles would take 633 Wh. Your battery has 884 Wh, so what you're getting sounds about right, especially with three times as much climbing. My motor was 1080W max, though I rarely used max power. Yours is 1300W.

 

[Hixyhicks]

I peddle all the way and hard .its great exercise.

 

[trevor brooker]

I'm going by the green bar on the screen.It does show voltage but i cant remember the Reading, will take a note tonight.when i put the battery on the charger 1 light is illuminated before i plug the charger in.

Adjust your screen to show voltage, rather than bars

 

[Hixyhicks]

I thought i had.I have the 850cv2 it shows the voltage now next to the green bar.Ill check it at the end of my ride home.

 

[vfr400]

Adjust your screen to show voltage, rather than bars

View attachment 36550View attachment 36550

That chart isn't right. It shows linear reduction in voltage with capacity, but the rate of fall in the voltage isn't constant. The battery goes down fast for the first volt, then it steadies off until about 2/3 discharged, then it accelerated downwards. The higher the current, the sooner and the more the chart bends downwards. Here's a typical discharge chart:

Also, the watt-hours in the battery is the area under the curve. If you use watt-hours at a constant rate, the 50% of the area wouldn't be half-way across. It would be closer to 1/3 of the way across. Counting the squares on that graph above 3.1v, it would be round about 3.7v, which would be closer to your 60%

Lastly, the 0% is at 42v. Most batteries cut off at 3.1v, per cell (43.4v) and even then, voltage sag will cut them much sooner than that.

Considering everything, I'd use 46.2v as empty and 52v as 50%, 53.8v as 75% and 49.7v as 25%. That's all if you're using around 2.5 amps per cell.

 

[Hixyhicks]

Is this what you mean.Voltage is showing.I dont know how to remove the green bar.

 

[Nealh]

No need to remove the green battery gauge, use the voltage reading along with the battery gauge to give you an idea of the gauges reading at 75%, 50% & 25%.

 

[Hixyhicks]

i got back with 52 volts left Didnt use as much as yesterday

 

[Nealh]

i got back with 52 volts left Didnt use as much as yesterday

Maybe there was more wind today, you rode faster, used more higher assistance today or had an extra slice of toast for breakfast and an extra sandwich at lunch time.

 

[Hixyhicks]

I tried harder.Used pas 2 most of the way.

 

[Nealh]

I tried harder.Used pas 2 most of the way.

Beg pardon, I totally misread your post .
Yes working harder and using lower assist will use less battery capacity, ideal for longer rides.

 

[trevor brooker]

That chart isn't right. It shows linear reduction in voltage with capacity, but the rate of fall in the voltage isn't constant. The battery goes down fast for the first volt, then it steadies off until about 2/3 discharged, then it accelerated downwards. The higher the current, the sooner and the more the chart bends downwards. Here's a typical discharge chart:

Also, the watt-hours in the battery is the area under the curve. If you use watt-hours at a constant rate, the 50% of the area wouldn't be half-way across. It would be closer to 1/3 of the way across. Counting the squares on that graph above 3.1v, it would be round about 3.7v, which would be closer to your 60%

Lastly, the 0% is at 42v. Most batteries cut off at 3.1v, per cell (43.4v) and even then, voltage sag will cut them much sooner than that.

Considering everything, I'd use 46.2v as empty and 52v as 50%, 53.8v as 75% and 49.7v as 25%. That's all if you're using around 2.5 amps per cell.

Yes - you are correct. I copied that chart from another website, as the DPC 14 (850c) display I use correctly shows the battery voltage, but the percentage option only works if your battery has a smart BMS that is specifically designed to communicate with it (as per the User Manual). So I wanted a way of estimating the battery remaining. Based upon the discharge graph I will update my chart & see how it works. Many thanks for highlighting my error.

 

[vfr400]

There was exactly what you wanted in that linked ES thread about testing 28650s yesterday. It night have been in the thread about a Woosh bike,where the guy wanted to go faster up hills. Maybe whoever linked it will link it here.