Swytch - apparent tiny battery capacity?

[hemo]

I wouldn't touch one of those liitokala with the preverbial, cheap china junk using crap cells and electronics.

[OzWaz]

I am not sure how Swytch measures the range available from their batteries. Maybe you only get 15 or 30km if use a high power setting, and have power on all the time.

Our experience is that we get much more than their stated 'default' range. But we only use the battery as a 'boost' when we need the extra energy on a hill or into a string headwind.

On regular rides between 30 and 60 km we barely use any battery, albeit on relatively flat rides. Even with the motor set on Level 1 constantly for a 40km ride we still had 2 bars of battery capacity remaining after the ride (Max battery). And it only takes an hour or so to recharge.

I reckon that used as a boost accessory (rather than full-time power) we will get around a 60 km range from a Swytch MAX battery.

For those who may be interested, I have written up some details of our experiences at….

https://bit.ly/3LEVrtt (Scroll down the page for info about our battery range.)

OzWaz

[cliffords]

There is a lot of nonsense expressed about range (often from the manufacturers' own marketing). When talking about range, the answer is always that it depends on a number of factors such as:

• What power setting you have
• How much effort you put into peddling
• Terrain you are travelling over
• Prevailing wind
• Total weight (bike, rider, cargo)
• Tyre tread
• Tyre pressure

However when talking about run time it is a very simple and unambiguous equation:

> runtime = Capacity/Power

So for example for the Swytch AIR 90Wh battery, running at full permitted power of 250W, the runtime is 90/250 = 0.36 hours (~22 minutes). For the MAX (180Wh) that would be ~43 minutes.

So the answer to range is however far you can get in that time, and it is that that is dependent on all the above conditions. That is the time is fixed, the conditions are variable. Heavily loaded or up hill, you would not expect to get so far in the same time - whether you had a motor or not.

Of course by running at half power, you can double the time. That may not result in quite doubling the range because unless you peddle harder, the bike will accelerate faster and be slower up hills. It will still assist you up until 15mph, so on a flat continuous run, you will likely get close to double the range.

Note that sometimes battery capacity is expressed in Ampere Hours (Ah) rather than Watt Hours (Wh). For the above equation, you need to use Watt Hours and Watts to get hours.

To determine Wh form Ah: Watt Hours = Battery Voltage x Ampere Hours

Unlike many manufacturers' marketing, Swytch are remarkably clear on this "time constant" aspect:

The battery capacity of the AIR is 98 Watt-Hours (Wh) and will last for about 40 minutes at constant power in the default power mode

(https://support.swytchbike.com/hc/en-gb ... -capacity-)
I am guessing that "default" is half power. I have a Gen 2 Swytch kit. It remembers the power level you set, so I am not sure there really is a "default". The default they use for calculation purposes is how I would read that.

[Jdsk]

To determine Wh form Ah: Watt Hours = Battery Voltage/Ampere Hours

Should that be multiply rather than divide?

Thanks

Jonathan

[cliffords]

Should that be multiply rather than divide?

Yes, fixed it.

[stodd]

However when talking about run time it is a very simple and unambiguous equation:

That's true (to a first level of approximation) for speed controllers, or for each level of current controllers, but not really for torque sensor controllers.

[cliffords]

@stod - fair point, although specifically for Swytch which has a cadence sensor (a pretty crude one, that I have since replaced) it holds (more or less), and runtime is subject to fewer variables than range, and far less variable.

Clearly if you pedal hard enough (remarkably difficult as when the assist cuts out it feels suddenly very heavy going after the easy ride to 15mph) or are going down hill coasting or at soeed, you get that for free, but on a round trip, there will be as much ascent as descent, and it tends to even out.

My point is that when you emphasise range, you will get very variable experience, with some stating they get more than the manufacturer claims, and others less. While they are likely all getting the same run time. At least using the technology used by Swytch.

[Bonzo Banana]

There is a lot of nonsense expressed about range (often from the manufacturers' own marketing). When talking about range, the answer is always that it depends on a number of factors such as:

• What power setting you have
• How much effort you put into peddling
• Terrain you are travelling over
• Prevailing wind
• Total weight (bike, rider, cargo)
• Tyre tread
• Tyre pressure

However when talking about run time it is a very simple and unambiguous equation:

> runtime = Capacity/Power

So for example for the Swytch AIR 90Wh battery, running at full permitted power of 250W, the runtime is 90/250 = 0.36 hours (~22 minutes). For the MAX (180Wh) that would be ~43 minutes.

So the answer to range is however far you can get in that time, and it is that that is dependent on all the above conditions. That is the time is fixed, the conditions are variable. Heavily loaded or up hill, you would not expect to get so far in the same time - whether you had a motor or not.

Of course by running at half power, you can double the time. That may not result in quite doubling the range because unless you peddle harder, the bike will accelerate faster and be slower up hills. It will still assist you up until 15mph, so on a flat continuous run, you will likely get close to double the range.

Note that sometimes battery capacity is expressed in Ampere Hours (Ah) rather than Watt Hours (Wh). For the above equation, you need to use Watt Hours and Watts to get hours.

To determine Wh form Ah: Watt Hours = Battery Voltage x Ampere Hours

Unlike many manufacturers' marketing, Swytch are remarkably clear on this "time constant" aspect:

The battery capacity of the AIR is 98 Watt-Hours (Wh) and will last for about 40 minutes at constant power in the default power mode

(https://support.swytchbike.com/hc/en-gb ... -capacity-)
I am guessing that "default" is half power. I have a Gen 2 Swytch kit. It remembers the power level you set, so I am not sure there really is a "default". The default they use for calculation purposes is how I would read that.

Ebikes aren't 250W though. They are all over the place from about 100W motors (crappy little 24V motors with less than 15Nm torque up to mid-drive ebikes with Bosch motors for example which are discharging the battery at about 900W when giving their full torque of 90Nm approx, something like 23-26A at 36V. The 250W rating is just pure nonsense that is meaningless really. That only allows 5A at 48V or about 7A at 36V. Need to know how much the controller will feed the motor at different times and from what I understand the certification incredibly doesn't care about the controller that dictates power it's only cares about whether the motor can handle 250W or not and that motor could be really 500W or 750W or even 1000W as long as it still handles 250W which of course it would if it can handle much more. So that Swytch motor gets 150W or about 4A at 36V (98Wh for 40min) in its default power mode which isn't that far off half 250W really.

I wish Swytch well but I certainly will never be buying one of their products.

[NickJP]

I converted my wife's old commute bike using the Swytch kit with 180Wh battery. When she takes that out on a 60km ride that we do every Friday, that has about 500m of climbing along the way, she usually has about 40% battery remaining at the end of the ride. However, as an experienced cyclist, she really only uses the battery assist when climbing, and rarely uses anything more than the lowest power assist level when she has it on.