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FES BATTERY PACK GEN2 14S, Version 1.23
6. Maintenance
With proper and carefull use of FES battery packs, there is practically no maintenance
required. FES battery packs are built from the most suitable cells available, so that they can
provide high power and good endurance and will serve you for many years and charging
cycles.
Note: Unfortunately, some capacity deterioration will occur due to aging of
the cells whether the battery packs are in use or not. The useful life of a lithium
cells is based on several factors which can prevent the battery from providing
sufficient current draw due to increased internal resistance.
Suitable uses and treatment that will reduce deterioration include:
1. During powered flight, use low power settings as much as possible and practical.
2. Do not discharge cells below 3,4V (total voltage at 95V), if it is not really neccessary.
3. Store battery packs at suitable temperatures when they are not in use (review next
chapter 7. Storage)
4. Store battery packs at suitable charge levels (around 50% SOC, see next chapter 7.
Storage)
Good indication of the battery packs condition is SOH – State of Health % parameter,
which can be read in lower right corner of BMS control software. It is calculated from
average internal resistance of the cells, measured during charging, and number of charging
cycles.
With poor treatment of the battery packs, their cells internal resistance will be rising
faster, and so calculated SOH % level will become lower. When it will be as low as 50%, it
would be time to think about replacement of the battery packs (at least the cells, BMS
electronic could be reused).
Poor condition of the cells can be recognizable also during powered flight:
- much deeper voltage drops at max power settings,
- much reduced maximum achievable power (with fully charged packs),
- much reduced usable capacity – altitude gain and range of level flight,
- temperature rise gradient of the battery pack will become much faster.
Note: We suggest replacing FES battery packs, when maximum available
range of level flight (to reach 90V or 55°C, whatever first), is reduced to one
third of the range experienced when they were new. Probbably there would
be not much sense to utilize them further on in such conditions.
Please handle FES battery packs very carefully to avoid mechanical damage of
housing. Only if battery packs are free of any damages it is allowed to charge them and
then install them into the glider. They must be always visually inpected before each charging
and before installation to the glider. This is even more important when glider is used by a
syndicate of pilots or in aeroclubs. If the housing is found to be damaged, somethimes also
cells inside might be damaged, which could be dangerous. In such case please contact
manufacturer, for evaluation of damage and further steps.
Page 19 of 26
September 2019
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