I've just converted by recumbent using the BBSDH motor with a Bafang 52V 20ah battery. I've only ridden it about 20 miles outside so far. I now have it setup in my basement on a bike stand (too cold outside for me). The range indicator in the DPC18 display seems completely ridiculous. The voltage display shows about 50 volts after about 40 total miles (inside and out) since charging it (it began at 58.4v). I'm trying to figure out how to determine range. So I wonder what the minimum voltage is for the BBSHD is.
BBSHD minimum operating voltage
- Thread starter plummpj
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tomjasz
Well-Known Member
- Region
- USA
- City
- Minnesnowta
Range on a stand is not possible. If you had used your multimeter to read beginning and ending voltages you'd have some data points. However the best method for me is to take what would be a typical ride and use the multimeter to record and get some mileage ranges.
Minimum voltage? Typically around 42V for the Low Voltage Cutoff, LVC. Right now it's 30F in Minnesnowta and my range and speed is reduced by 20-30% with a battery that was in the bike all night without any heat.
I'm trying to extrapolate a range estimate from voltage. I would like to be able to look at voltage indicator to see how much range I have left. It shouldn't matter if on a bike stand or on the road, either way I'm depleting the battery. The DPC18 voltage display is reasonably accurate. After fully charging the battery my multimeter showed 58.0 volts whereas the DPC18 display showed 58.4.
So I could ride it down to 42 volts with no loss of performance?
tomjasz
Well-Known Member
- Region
- USA
- City
- Minnesnowta
Well here's an 11 year rider, user, and reseller of BBSxx series motors telling you that it's a waste of time. Any accurate numbers will come from actual rides and data.
It DOES make a difference. On a stand there's no wind, road resistance, fat lump rider, and other mitigating factors affecting power use.
No, as power is used performance is reduced.
il Munduato
Well-Known Member
- Region
- USA
I concur.. Range on a stand isn't going to be anywhere near accurate.
The battery performance isn't straight line either. It'll be more efficient at full charge and less near empty.
Without loading the motor with real world conditions you are wasting your time.
Then there's more than a few variables. Gearing, tires, wind, weight, hills, temperature... etc... etc... etc...
But to answer your initial question.... 42v on a 52v battery is a safe minimum voltage. 3v/cell
The battery performance isn't straight line either. It'll be more efficient at full charge and less near empty.
Without loading the motor with real world conditions you are wasting your time.
Then there's more than a few variables. Gearing, tires, wind, weight, hills, temperature... etc... etc... etc...
But to answer your initial question.... 42v on a 52v battery is a safe minimum voltage. 3v/cell
m@Robertson
Well-Known Member
- Region
- USA
As noted above, running the bike on a stand is a waste of time. I ended up deleting most of my post because I read what @il Munduato said and he did it more succinctly than I did.
Watching the voltage is a smart move, but trying to derive range from that given all the variables isn't going to happen, either. What you need to do instead is have an understanding of what the voltage numbers mean as if they were fuel tank gauge marks. Use those numbers to figure out how worried you should be about making it back home, and couple that to riding experience. Thats how you guesstimate range.
Look here for a 52v chart. You can make a cutout using the shortcut chart and at some point you will become familiar enough to just know what the number means.
talesontwowheels.com
LVC on a BBSHD is typically 42v, but I'll disagree with the comments above and say that is a BAD number on your 52v pack. 42.0v on a 14S/52v battery is a 3.0v/0% charge. Depth of Discharge is every bit as bad for a Li-NMC battery as charging it to 100% and letting it sit. On the link below scroll down to Table 2 and read the supporting info.
Its not unlikely your BMS will save your bacon and cut off at a higher number, bypassing the motor cutoff. But even if it does not, voltage sag will cause you to touch 42.0v long before the pack is really down that far which will shut the motor off just as cold. I personally set the cut off at 43v and I know people who do it at 44v, which - given the bad things that happen when you drain down a Li-NMC battery like that - is probably the smarter move.
Go here to see what tools you would use to be able to access your LVC on your BBSHD, and also see a lot of other things you can do to change how the motor behaves and increase its range rather significantly over the factory settings.
talesontwowheels.com
Watching the voltage is a smart move, but trying to derive range from that given all the variables isn't going to happen, either. What you need to do instead is have an understanding of what the voltage numbers mean as if they were fuel tank gauge marks. Use those numbers to figure out how worried you should be about making it back home, and couple that to riding experience. Thats how you guesstimate range.
Look here for a 52v chart. You can make a cutout using the shortcut chart and at some point you will become familiar enough to just know what the number means.
Li-Ion Ebike Battery Charge Charts
Whats an 80% charge on a 48v battery? These charts give answers to questions like this on common ebike battery voltages: 36v, 48v, 52v, 60v and 72v.
talesontwowheels.com
LVC on a BBSHD is typically 42v, but I'll disagree with the comments above and say that is a BAD number on your 52v pack. 42.0v on a 14S/52v battery is a 3.0v/0% charge. Depth of Discharge is every bit as bad for a Li-NMC battery as charging it to 100% and letting it sit. On the link below scroll down to Table 2 and read the supporting info.
Its not unlikely your BMS will save your bacon and cut off at a higher number, bypassing the motor cutoff. But even if it does not, voltage sag will cause you to touch 42.0v long before the pack is really down that far which will shut the motor off just as cold. I personally set the cut off at 43v and I know people who do it at 44v, which - given the bad things that happen when you drain down a Li-NMC battery like that - is probably the smarter move.
Go here to see what tools you would use to be able to access your LVC on your BBSHD, and also see a lot of other things you can do to change how the motor behaves and increase its range rather significantly over the factory settings.
BBSHD Programming For The Pedaling Cyclist (2023 Update)
Explore enhanced BBSHD programming for pedal assist settings that don't let the bike run away from you, and throttle settings gentle on the drivetrain.
talesontwowheels.com
harryS
Well-Known Member
The battery has a low voltage cutoff (LVC) for redundacy and safety, Typically around 39V for a 48V battery and 42V for a 52V battery,
All ebike controllers also have an LVC. My BBS02B is factory set to 42V. BBSHD is probably the same. Either the battery or the controller will trip around 42V. While perfectly safe, in a perfect world, I'd want the BBSHD to trip around 45V for a 52V pack. If you have a programming cable, that can be adjusted.
Your 20AH battery is rated 1040 watt hours, probably about 800-850 useable. WHy? BEcause the AH rating is based on discharging the cells to 2.5V, not 3V. ALso, the test is run at low current, compared to ebike currents, Result is you get less watt hoursin real life, at least 10% less.
At 12-14 mph, my BBS02B uses 10 WH/mile. I would expect 80 miles with your battery. I tend to run a low WH/mile number. Some of my other ebikes only use 6-7WH/mile. But the most common number I see is 15WH/mile. Divide 900 by 15 which predicts around 60 mile range for your battery, Depends on your speed, and how much you pedal.
All ebike controllers also have an LVC. My BBS02B is factory set to 42V. BBSHD is probably the same. Either the battery or the controller will trip around 42V. While perfectly safe, in a perfect world, I'd want the BBSHD to trip around 45V for a 52V pack. If you have a programming cable, that can be adjusted.
Your 20AH battery is rated 1040 watt hours, probably about 800-850 useable. WHy? BEcause the AH rating is based on discharging the cells to 2.5V, not 3V. ALso, the test is run at low current, compared to ebike currents, Result is you get less watt hoursin real life, at least 10% less.
At 12-14 mph, my BBS02B uses 10 WH/mile. I would expect 80 miles with your battery. I tend to run a low WH/mile number. Some of my other ebikes only use 6-7WH/mile. But the most common number I see is 15WH/mile. Divide 900 by 15 which predicts around 60 mile range for your battery, Depends on your speed, and how much you pedal.
Thanks everybody for your comments. The battery chart is particularly useful. It tells me that at 50 volts I have approximately 50% charge looking at it optimistically. I don't think how I get to 50 volts matters, whether I'm at PAS 9, 1, in a head wind, or on a bike stand. If I continue to ride with the same conditions, I'm at the half way point in my ride if I want to continue with E assist.
I would think the Bafang algorithm could be written to reflect this, but instead it's completely ridiculous.
il Munduato
Well-Known Member
- Region
- USA
I once knew a guy that walked to school... up hill, both ways.
Seems you have it all figured out... Good luck.
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il Munduato
Well-Known Member
- Region
- USA
I'll add that setting a LVC at 3v/cell or 42v in this case is to have capacity available if the need arises.. not that you should take it that low on every ride. But I like to determine that for myself on each ride, just as I determine my SoC before each rideAs noted above, running the bike on a stand is a waste of time. I ended up deleting most of my post because I read what @il Munduato said and he did it more succinctly than I did.
Watching the voltage is a smart move, but trying to derive range from that given all the variables isn't going to happen, either. What you need to do instead is have an understanding of what the voltage numbers mean as if they were fuel tank gauge marks. Use those numbers to figure out how worried you should be about making it back home, and couple that to riding experience. Thats how you guesstimate range.
Look here for a 52v chart. You can make a cutout using the shortcut chart and at some point you will become familiar enough to just know what the number means.
Li-Ion Ebike Battery Charge Charts
Whats an 80% charge on a 48v battery? These charts give answers to questions like this on common ebike battery voltages: 36v, 48v, 52v, 60v and 72v.
LVC on a BBSHD is typically 42v, but I'll disagree with the comments above and say that is a BAD number on your 52v pack. 42.0v on a 14S/52v battery is a 3.0v/0% charge. Depth of Discharge is every bit as bad for a Li-NMC battery as charging it to 100% and letting it sit. On the link below scroll down to Table 2 and read the supporting info.
Its not unlikely your BMS will save your bacon and cut off at a higher number, bypassing the motor cutoff. But even if it does not, voltage sag will cause you to touch 42.0v long before the pack is really down that far which will shut the motor off just as cold. I personally set the cut off at 43v and I know people who do it at 44v, which - given the bad things that happen when you drain down a Li-NMC battery like that - is probably the smarter move.
Go here to see what tools you would use to be able to access your LVC on your BBSHD, and also see a lot of other things you can do to change how the motor behaves and increase its range rather significantly over the factory settings.
BBSHD Programming For The Pedaling Cyclist (2023 Update)
Explore enhanced BBSHD programming for pedal assist settings that don't let the bike run away from you, and throttle settings gentle on the drivetrain.
Sure a battery will cycle an extremely long time if kept between 40% - 60%, but how practical is that for average use? The wider that gap, the more stress on the battery... but after all you did buy it to use.
Personality I operate starting at 80% and run down to 60% on most of my +/-20 mi rides. This works for me as I sometimes end up riding longer than initially planned and still have plenty of DoD room. But if something unforeseen happens and I end up taking it way down, I want the DoD to be available and decide at that time if I want to stress the battery or my legs.
Set the LVC too high and you lose the option....
Well unless you bring a programing cable and use the SPEEED app on your phone. But then you're still making the decision in real time, but just with more annoyance added to the situation.
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PCeBiker
Well-Known Member
- Region
- Canada
That's not quite accurate.
50 volts is the middle of your voltage range, but it's not the mid point of the capacity.
If your ride is using say, a constant 100 Watts of assistance, your fully charged battery is putting out (100÷58) ~1.72 amps.
When the battery is at the Low Voltage Cutoff, the same 100 Watts needs (100÷42) ~2.38 amps.
So as the battery drains, it starts draining faster.
I have a 48 volt fuel gauge (voltmeter) on my ebike that shows this,..
At 54 volts, the needle is just into the red.
48 volts is the F and 39 volts is the E.
The scale is skewed with a bigger green sweep than white sweep but the needle still travels through the green area faster than the white area.
My midpoint of actual range is closer to 50 volts or so, but that's really hard to measure without hooking up a Watt hour meter.
There is a simple math equation that can calculate the midpoint voltage at half capacity but I forgot all my Gr. 13 Math.
What I did to avoid all the math and staring at the gauges was to to carry a second battery.
Now I just make sure that I'm already heading home before my first battery dies.
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