Which indicates distance you can travel
- Thread starter Saracen
- Start date
Wh (which is Ah * V) is indeed the measure of capacity that controls range. Of course there are lots of other variables. Also, if the battery doesn't have very good ability to deliver current then it will suffer voltage sag under load (eg up hills), that might mean even though there is capacity left it will cut out to save killing the battery. That could limit the effective range, especially if there is a big up hill fairly close to your destination; quite likely that the battery gets tired exactly as you need it most when you are tired; uphill at the end of a ride.
They're both the same thing. 36v x 20Ah = 720wh.
If you want the most accurate measurement of range, usage and capacity, you should get a wattmeter, which will not only show you the watt-hours used and remaining, but it'll give you a good understanding of how your bike works and how much battery you use in different circumstances.
One can roughly estimate range by dividing the wh by wh usage and how you ride.
If one rides often above the speed cut off then usage can be in 5 -7wh per mile range, if one rides in low power mode a lot ( ie a current control controller) then one can expect to use 8 - 12 wh per mile . If using a higher assist then anything up to 20wh per mile may be used also applies to riding with a high assist cut off.
If one rides often above the speed cut off then usage can be in 5 -7wh per mile range, if one rides in low power mode a lot ( ie a current control controller) then one can expect to use 8 - 12 wh per mile . If using a higher assist then anything up to 20wh per mile may be used also applies to riding with a high assist cut off.
So potentially that is another advantage of using a controller with power based assist levels rather than speed based assist levels ? They are more efficient, if you are adding quite a bit of pedalling effort ?
Yes .
Most crappy speed controllers give max current more of the time until the speed threshold for the power level is reached , the power based current controllers can be more efficient depending on the power it supplies . The KT's for instance put out approx. 13% of the max power in PAS1, others like woosh set this to 40% in the lishui's. More importantly though is riding above the cut off to increase range just as riding with the battery switched off.
My long rides are 160km on a nice sunny, using a 36v battery and 48v one used independently of each other. 36v PF in the triangle and a homemade 13s 7p PF in a rear bag /rack top pannier, mostly all the journey in PAS 1 except for some PAS4/5 climbing up out of Ovingdean on the way home . I usually still arrive back at home with 30 - 40% of total wh available.
@Saracen - in the longer term if you had some means of measuring how many watt hours you used/consume for your different rides then you will over time get to know how much power you are using for your different riding scenarios.
Once you know this and the capacity of your battery, you'll become quite good at working out your range.
I don't have a watt meter on my bike but back in the bike shed I have a home built rig that;
(a) measures how many watt hours I have to put back into the battery to get back to the fully charged state (having started with a fully charged battery of course) and then log the miles done, type of terrain etc. to obtain the watt hours per mile figure mentioned by Neal in post #6
(b) I can also discharge the battery into a dummy load to measure the capacity in watt hours.
These measurements aren't overly accurate but over time have been enough for me to be confident in what range I'll get for any particular ride - so no range anxiety for me lol.
Once you know this and the capacity of your battery, you'll become quite good at working out your range.
I don't have a watt meter on my bike but back in the bike shed I have a home built rig that;
(a) measures how many watt hours I have to put back into the battery to get back to the fully charged state (having started with a fully charged battery of course) and then log the miles done, type of terrain etc. to obtain the watt hours per mile figure mentioned by Neal in post #6
(b) I can also discharge the battery into a dummy load to measure the capacity in watt hours.
These measurements aren't overly accurate but over time have been enough for me to be confident in what range I'll get for any particular ride - so no range anxiety for me lol.
The watt meter /gauge shows simply how much power (watts) the controller is out putting it won't tell you how many wh is being use or has been used for that one needs an anmeter type watt gauge that uses a shunt on the main power feeds.
d8veh's handy little watt meter mod.
Latest Cheap Wattmeter | Pedelecs - Electric Bike Community
d8veh's handy little watt meter mod.
Latest Cheap Wattmeter | Pedelecs - Electric Bike Community
It's a meter that shows watts rather than a wattmeter. A wattmeter shows present watts, cumulative watt-hours, current, max current, amp-hours and things like that, so you can measure the capacity of your battery for each type of ride you do, then during those rides you can see how much of the battery you've used and calculate or estimate how much further you can go.
I see it's been a while since you've posted, but I just wanted to ask—has anyone noticed if your estimated range changes much depending on cold weather or wind? I’ve been tracking mine and it seems to drop way more than I expected when the temperature drops or there’s a strong headwind. Wondering what kind of difference others are seeing in real-world riding compared to what the display says.
This phenomenon of loss of range in cold weather, is a feature of pretty much all battery systems. A lithium battery is a chemically driven device ,and the reactions inside the cells in which lithium ions move across the electrically insulating separator depend on temperature for efficient movement of ions. When temperatures are low, the process works more slowly.
When you connect the battery terminals to a load, lithium ions move across the battery from anode to cathode. They change the electric charge on the anode and cathode and this makes electrons flow through the terminals from the anode (the negative terminal) to the other side passing through the motor load.
This is what we want when we use a battery and electric motor. The rate of flow changes according to the temperature, and the total amount of flow changes too, so all electric vehicles with batteries see a loss of maximum power and range in colder weather. A cold battery will see voltage sag on a hill climb which probably would not happen in warmer weather.
My smaller bike, which has a nominal 8.5 Ahr battery (about 300 watt hours) showed a noticeable drop off in range during the winter, even though it was quite new. When summer came around again, and the temperature was about twenty centigrade, I noticed that the first voltage led out of four on the simple display unit, went out after 9.5 miles, on upward slopes, whereas in winter it went out at about 7 miles.
This is a rough and ready test, but it shows the tendency which affects all of our batteries. Range is affected in the same way, because the battery system is working less well at lower temperatures. Like most chemical processes, temperature variations affect performance.
As for wind - a solely human powered cyclist will notice head winds. It is simple physics, you are pushing against a strong air flow. This will obviously influence top speed and battery range too.
Cold temperatures also affect the rate at which a battery can be charged.
The internal resistance of the battery rises in low temperatures making it resistant to the charge.
You should not attempt to charge a battery that is at low temperatures around zero. Bring it inside and let it warm up slowly to room temperature.
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Wind is a big factor to overcome esp a head wind , so yes it can reduce range quite a bit.
Cold will also not help range .
Cold will also not help range .
That's a very good question. There are 3 parts to the answer:
Your battery
It's generally accepted the batteries don't give so much capacity in the winter, but I think that the effect is much less than what most people think, though that does depend on individual circumstances. The reason I say that is because batteries have their own central heating system. You can feel some get noticeably warm both when charging and discharging. The inner cells are surrounded by other cells that are also warming up, so they won't be able to lose their heat, and even the ones on the outside are well insulated by the still air around them and the plastic case and often foam rubber. When they do a test of a single cell in the lab, the metal case is directly in contact with the cold air, but it's nothing like that for the cells inside a battery.
You.
It's very well know amongst athletes that your body becomes much less efficient when cold. There have been all sorts of tests done to try to quantify that, but I'd be surprised if you could make a definitive rule. Imagine if you're only pedalling half as hard in the winter as you do in the summer. That would make a profound effect on your range.
Wind
That's simple physics. Wind resistance increases with the cube of its relative velocity. Depending on the wind speed and direction, it can sap anywhere from zero to all the power you and the bike make. Winds are generally stronger in the winter than the summer, so that would make an overall difference in range. Also, the heavier clothing you wear in the winter increases your coefficient of drag. Also, the extra mass of winter clothing also affects your range, assuming that your ride is not 100% flat. The hillier it is, the more the affect of mass.
To summarise, my gut feeling is that the effect of winter temperatures on your own efficiency, along with your heavier mass and larger coefficient of drag have a more substantial effect on range than the affect of temperature on the battery. Ultimately, it makes little difference why, as long as you understand that you can't go as far in the winter as summer.
If you look at https://www.bosch-ebike.com/en/service/range-assistant you get a very good idea of how range changes with conditions. It's for Bosch bikes, but the differences are similar whatever the system. If you interpret things like the motor type carefully you can even get a reasonable idea of range on non-Bosch bikes,
You'll also see how quickly changing from perfect conditions (the 'up to' quoted by so many adverts) to even reasonably OK normal conditions easily drops the range to 1/2, or even 1/3.
You'll also see how quickly changing from perfect conditions (the 'up to' quoted by so many adverts) to even reasonably OK normal conditions easily drops the range to 1/2, or even 1/3.
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