ST5 owners - Can you maintain 28mph for whole battery?

[mike156]

Question for ST5 owners - can you maintain 28 mph for the whole battery? I have an ST2, and it's great, but I notice assist tapers as my 814 battery depletes from 100%. I tend to ride in level 3. It's very eager and fun for the first 5 or so miles, but that eagerness fades over time until I'm pushing to maintain 24 mph for the last 20% of the battery. I've attributed this to the lithium battery voltage curve.

Perhaps the ST5's power remains consistent from 100% battery down towards 0%?

I'm curious about your experiences as they will influence whether I upgrade.

 

[opimax]

I have had an st2 and currently a st2s , I have not noticed much power drop off as the battery depleted, 1 of Stromers good points to me. i can’t say Iive at 28 but but I do leave it in highest power level as I go through batteries on a ride.

how old is your battery? Do you have a 2nd battery to compare?

 

[bluecat]

Perhaps the ST5's power remains consistent from 100% battery down towards 0%?

Yes, you can go down to 0% battery without remarkable loss of power. But on low battery, the (S) - mode is disabled. Riding with "all in" settings up to 45km/h, the range will be 50 to 60km. The decreasing voltage is compensated by higher amperage.

 

[mike156]

I have had an st2 and currently a st2s , I have not noticed much power drop off as the battery depleted, 1 of Stromers good points to me. i can’t say Iive at 28 but but I do leave it in highest power level as I go through batteries on a ride.

how old is your battery? Do you have a 2nd battery to compare?

That's a really good point. I got my bike with the 814 battery in June 2016, and we got an ST2 with 814 for my girlfriend June 2018.

I just rode my bike with her battery from 100% to under 10%, and it was a very fun ride. Then I had some dinner and rode the same route my bike with my battery 100% to under 10%, and it got a little tough to keep speed at 30% and then it got harder and harder under 20%.

The condition of both batteries is 'Very Good,' and they both lasted the same number of miles, but there seems to be a difference between what they can do.

 

[mike156]

Yes, you can go down to 0% battery without remarkable loss of power. But on low battery, the (S) - mode is disabled. Riding with "all in" settings up to 45km/h, the range will be 50 to 60km. The decreasing voltage is compensated by higher amperage.

That's really interesting, thanks for the insight. That's a great feature of the ST5 that it compensates for decreasing voltage with higher amperage. Does the ST2 also do this or only the ST5?

 

[Ravi Kempaiah]

From my experience, Stromer is one of the few bikes that maintains excellent acceleration and top speed up until the last 2% of battery.
I had to run the battery down to zero on several occasions and the bike always performed excellent.

 

[mike156]

From my experience, Stromer is one of the few bikes that maintains excellent acceleration and top speed up until the last 2% of battery.
I had to run the battery down to zero on several occasions and the bike always performed excellent.

Thanks so much Ravi. In your experience, what are the signs a rectangular ST2 battery needs to be replaced? And, do you have a rough idea how long they tend to last?

 

[mrc3]

Mike, that one is hard to make generic statements as there are many personal variables. The ST1 batteries were made of high quality Samsung 18650 Lithium cells. Admittedly these are not the same as the ST2's... but much of the same theory applies.

The indications it needs to be replaced is significant decrease in range from previous uses under similar conditions. (Boost settings, weather, temperature, speed, tire pressure, rider, etc).

How long they last also depends on many factors:
- Discharging a Lithium battery to zero is hard on the battery so usually the battery management systems shuts off the bike when the battery reaches a lower limit above zero. (usually 3.3V/cell or 33V for 36V 10S ST1 stromer pack.) If you keep the charge level on the battery above 30% the packs will last longer (just picking a number out of a hat that is larger than empty).
- Storage of the battery for extended periods of time should be done with battery between 50 and 60 percent charge.
- Number of cycles on the battery is more important than time.
- Ideally one would charge the battery, right before use, ride, storage charge to 50% on return. But that is not realistic work flow for most people and the chargers do not support storage charge. But the quality cells used are fairly robust to abuse and this ideal behavior does not buy you much additional life. I only worry about storage charge when I store for winter.

Mike

 

[bluecat]

- Number of cycles on the battery is more important than time.

Indeed, in the early years of e-bikes, this was an important number. Until some brands offering batteries up to 1'000 full charging cycles. As we talk about a ST5 battery with a typical range around 100km, this would be 100'000km...

beyond the Stromer warranty for their batteries (read their website), I recommend:

• charge only at ambient / room temperature - never charge a cold battery
• avoid deep discharge, better charge at 30% than at 5% after the next ride
• only use original Stromer charger with the well configured charging protocol
• if feasible, don't let the battery outside during the cold winter (while at work)
• use a time / clock switch to charge (starting the day with a warm, freshly charged battery is best)

 

[mrc3]

1000 cycles sounds like a lot... but what about commuting to work daily for 5 years and charging it daily... Seems more feasible than 100,000km

But then again you are probably right though the cycle count will probably not factor in to battery life as much as the various ways we abuse the batteries such as leaving it fully discharged or for that matter fully charged, for an extended length of time., letting it self discharge down to zero over winter (I think the BMS in the battery is always powered and drawing from the battery even when out of bicycle... but that is an assumption on my part.

Also you are absolutely correct about charging at room temperatures... If you charge a battery to 100% at near freezing temperatures, it will be over charged at room temperatures or in operation once it heats up while in discharge. Lithium batteries REALLY dislike being charged to higher voltage than 4.2

Mike

 

[bluecat]

1000 cycles sounds like a lot... but what about commuting to work daily for 5 years and charging it daily... Seems more feasible than 100,000km

This will will charge your budget with about 0.025 CHf per day for the new battery. You're able to afford this - as you were able to buy the ST5.

Lithium batteries REALLY dislike being charged to higher voltage than 4.2

At the time, I see no way to overcharge a Stromer battery. If you have found one, please let me know - to tell the people what not to do.

 

[mrc3]

If you fully charge (to 4.2V) a lithium battery at freezing, then raise battery to room temperature, the voltage of the cell will rise to an overcharge voltage.

Mike

 

[bluecat]

If you fully charge (to 4.2V) a lithium battery at freezing

You forget, a Stromer battery's BMS works with temperature sensors. At deep temperatures, all charging (internal and external) is disabled.

 

[mrc3]

Perhaps I misspoke. The voltage of a fully charged cell decreases with temperature. I know of no temperature compensated chargers. So if you charge a low temperature cell to 4.2V you are overcharging it.

Mike

 

[bluecat]

I know of no temperature compensated chargers.

Stromer works with a public CAN bus protocol. Stromer was the first major company in 2014 which implemented this heigh industrial standard protocol. Meanwhile, the logo has changed, but in the list of members you'll find the major players in the e-bike battery area.

 

[Insider]

I think your question is rather abstract.

The short answer is yes, but I don't think it is the answer you are really looking for.
I think, much of the lower voltage experience has to do with voltage sag.

If you use max assist settings you are just going to hit battery cut off sooner. The bike will reduce performance to avoid voltage sag dip to auto cut off.

Keep in mind that the ST5 is not a twist-n-go ebike.
Depends on your fitness, you could maintain 28mph even if the bike automatically dials back the assist due to lower voltages.
Some above comment mentions the notice of performance reduction at 30%, but maybe it could be different for you.
I've done a 50 miles ride (charged to 100% over night) and still left with 75% when I got home.

This is probably true with all modern ebikes.

I'm curious to see what the programming does to manage performance vs state of change.

 

[mike156]

Thanks for the thoughts. All the comments are really interesting and enlightening.

In case some folks find my post abstract or unclear, I'd like to know if ST-5 owners find the assist remains consistent from 100% down to near 0% when riding in level 3 or S for the entire ride.

 

[bluecat]

The bike will reduce performance to avoid voltage sag dip to auto cut off.

the bike automatically dials back the assist due to lower voltages.

Some above comment mentions the notice of performance reduction at 30%,

This is exactly the opposite of the observations of ST5 owners in Switzerland!

And in addition, it also does not fit with my personal experience with the ST5 and ST3.

 

[Insider]

This is exactly the opposite of the observations of ST5 owners in Switzerland!

And in addition, it also does not fit with my personal experience with the ST5 and ST3.

So battery voltage sag is a known fact no matter what kind of load is drawing from the battery

Perhaps Stromer has raised the battery gauge so even at lower have of the gauge the rider is not experiencing performance degradation?

I'vc done 85 miles and taken the battery to 9%

 

[bluecat]

So battery voltage sag is a known fact no matter what kind of load is drawing from the battery

There is a huge misunderstanding!

I'm talking about power and performance of the ST5 - which is completely independent from the SOC.

The SOC - State Of Charge, AKA voltage - is important for the range of the bike. Coming back to the entrance question: Yes, I have to emphasize, you can ride the ST5 at top speed until the battery is empty. As stated above, you'll only lose the (S) mode on low battery.