Extend service life?!

Is that possible? The simple answer is YES...but

In connection with the care of Li-ion batteries, the term "battery voodoo" is sometimes used. This refers to excessive maintenance in order to increase the service life. In principle, it can be assumed that batteries with a Battery Management System (BMS) are designed to get the optimum performance and service life out of the battery. The Stromer BMS also does this. Nevertheless, there are ways of giving the BMS a helping hand and increasing the battery's service life:

> ‚Care: Mechanical, in operation / storage / safety'
> 'Aging - SoH loss'

In addition to the points described in the two topics, the user can also do the following:

1) Charging at... °C

Outside temperature > 10 °C In midsummer, the Stromer should not be left out in the blazing sun for long periods. After a ride in midsummer with maximum assistance, the battery temperature can rise above 40 °C. You should allow the battery to cool down before charging it.

Outside temperature < 10 °C A distinction must be made here as to whether one:
a.) has been driven longer and the battery has developed 'intrinsic heat' or
b.) wants to make a cold start

If the battery has cooled down (b), it should first be warmed up in a temperature-controlled room, then charged and only inserted shortly before the journey.

For safety reasons, the Stromer BMS prevents charging of the battery and recuperation below 0 °C and above 40 °C.

The battery temperature can be read on the start page of the Omni app.

2) Limit the loading stroke

If you charge a battery from 0 to 100%, this is referred to as a full charge cycle. Standard NMC cells can go through around 350-500 such charging cycles until they reach the end of life (EoL). Depending on the definition, EoL is 60-80% of the nominal capacity. At Stromer it is defined as 75%.

If the depth of discharge (DoD) is limited, it is possible to double (or even increase) the charging cycles and therefore the service life. More on this topic can be found here or here read/watch.

If a battery is regularly run down to 0% SoC and then recharged to 100%, this will shorten its service life. The following applies:

• If the battery is charged to 100% and driven straight away, this is not ideal but is harmless. Leaving it at 100% for longer will shorten its service life in the long term.
• If the battery is completely discharged and you leave it lying around for a long time without recharging it, there is a risk of deep discharge. This causes lasting damage to the battery.

If you can afford a partial discharge/charge due to the required daily mileage, it is advisable to limit the charging stroke. In practice, this means using an SoC range of 10 - 80 (max. 90%). The battery should therefore not be driven completely empty, but should not be fully charged either.

Many battery manufacturers use the BMS to limit the amount of energy effectively available from the outset in favor of the service life and create a buffer at the top and bottom. The display of 0% capacity therefore does not necessarily mean an empty battery and 100% a full battery.

With the Stromer BQ983 battery, only around 90% of the nominal capacity can be used. Of the 983 Wh of a new battery, around 890 Wh remain for effective riding. The legal light reserve at the lower end is also responsible for this.

Is it possible to set the charging stroke or upper charging limit on the Stromer?

Stromer does not offer a charging stroke limit or SoC upper limit setting. The battery is always fully charged. To achieve a partial charge, you have to use a timer, a smart socket or DIY.

• Timer: An empty battery is charged approximately with 22% (BQ983) or 33% (BQ814) per hour
• DIY solution: Patrick Doyle (Arduino)
• SmartPlug from bikechef.at
• Smart socket with home assistant: stromerforum.ch - from 'berghamster'
• Charging calculator: stromerforum.ch
• Limit 'battery charge' - Thread in the stromerforum.ch

Every few charging processes it is necessary to charge the battery to 100% to enable balancing of the cells.

3) Use additional battery (extender)

A sustainable way to extend the service life is to use an additional battery (extender) in parallel with the main battery. This has the following advantages:

a.) The maximum peak discharge current per cell is reduced b.) When using maximum recuperation, the cells are not overloaded. (See here too) c.) Regular charging is gentler because the charging current/cell is reduced again.

Stromer does not offer the option of integrating an extender into the on-board electrical system. How such an extender can still be operated is described, for example, in the Stromerforum.ch to read. See also main menu: PIMP mySTROMER - 'Battery - Extender'.

Lifetime calculator

Stephan Klapszus has a Online calculator This allows you to set various parameters such as the SoC (State of Charge), the DoD (Depth of Discharge), the number of charging cycles/week, the charging speed, etc. The result is the number of possible charging cycles and an estimate of the service life in hours. The result is the number of possible charging cycles and an estimate of the service life in years. SK emphasizes that these values are an approximation based on a mix of different Li-ion batteries. For more precise results, a separate calculator would have to be implemented for each battery type.