Comment by jacquesm
4 years ago
If you can charge your batteries up to 60% when you store them for a longer time rather than 100%, then charge to 100% just before you need them. That will keep them around that much longer. Better still if you can avoid discharging them below 15% soc.
Makes sense for seasonal and recreational riders. We both ride year round though almost daily for transportation.
As for discharging below 15%, Bosch's firmware is pretty smart about this. It keeps a reserve that's used for powering lights for a few hours after the assist cuts off.
Yes, that's at 5% state-of-charge, which is a bit low. If you charge up to 100% and discharge to that cut-off point you will get 300 to 400 cycles out of your battery. If you go from 80% state-of-charge down to 20% then you can get thousands of cycles out of your batteries. That's one of the reasons I designed that pack as large as it is: to stay within the 80-to-20 range on a 100 km trip.
The “charge to 80%” advice isnt generally useful to PEV riders in 2021
It is true that a lithium _cell_ lasts longer when charged to 80%, but a _battery of cells_ must be “balanced” and PEV BMSes only do that balancing in the constant voltage stage of charging in the hours after the charger indicates the battery has been fully recharged.
For anyone just learning about this, an unbalanced cell is usually the cause of a battery going “dead” and can even be the cause of a fire. Very few batteries die because they have outlived their charge cycle count.
This is different than your cell phone which has at most two cells (but usually one) in the battery. In that case, the BMS can monitor and charge individual cells. In a PEV the BMS usually monitors several groups of cells, and can not charge individual cells.
This can change in the future! I believe electric car BMSes generally do it. But its an added expense and PEV manufacturers have not started spending the money. Ill be happy if another commenter can correct me and show that there is some manufacturer who is ahead of the curve.
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Interesting! I've only gotten that low a handful of times. Definitely a bigger battery would be good if you're going that low on a regular basis.