Topping off a battery.


Active Member
I tried posting this in "Parts and Accessories" but only got one answer. Though I'd try it here. I'm looking for some knowledgable input on topping up a battery just prior to riding. "I have been reading up on battery care and for the most part I don't think I want to spend too much time worrying about it. I do however want to do what I can, within reason, to help prolong the life of my battery. I do a few things now that are fairly simple, like not leaving it out in the garage when it's freezing, never letting it get completely drained, always having less than a full charge when storing. These things are easy for me to do. What I'm wondering is if it is less damaging if it is only fully charged momentarily, just prior to a ride, or is just the act of fully charging it, for what ever the length of time, that does the harm? I'm always having "low battery anxiety" and will often topp off just prior to a ride." What I've heard is that fully charging a battery is hard on it.

Ravi Kempaiah

Well-Known Member
like not leaving it out in the garage when it's freezing
Your battery can sit in the cold. NO problem. Just make sure it is back to room temperature before you use it again or charge it.
Freezing temps make the electrolyte into a hard viscous material and this creates more resistance for the flow of Li-ions. So, as long as you bring it back up to the room temperature, you're good.

I don't think I want to spend too much time worrying about it.
Perfectly reasonable.
Our battery BMS does all the important job, so we don't have to worry about it.
Whether you use the battery or not, there is something called "calendar aging"... the chemistry degrades very slowly irrespective of the use.

  1. If there is one thing that you need to worry about: "The amount of time battery spends at the highest voltage and temperature accelerates the chemical wear. "
So, please DO CHARGE the battery fully so you can your E-bike to the fullest. Just don't make it a habit of leaving the battery at 100% for extended lengths of time.
If you just pay attention to this one thing: "amount of time spent at highest voltage and high temperature is not good for the battery".... rest all you can ignore or your BMS will take care of it.
I believe you have a Cannondale Contra-E. This is a Bosch powered bike and the system is well designed. There is nothing to worry about!
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Reactions: JRA


Active Member
A little off topic....

I posted this question a couple of time previously but never got an definite answer:

Purchased a new Bosch 500w battery recently and it seems when I charge it I get the same less then 100% charge indication (on my Nyon controller). Usually around 96-97%.
I thought on my old battery that was an indication of usage over the last two years, but this new battery shows the same thing.
Could this be a malfunction of my Bosch charger?
Anyone else experiencing this? Any input appreciated!

I did have the LBS run diagnostics and updates when I got the battery and everything came up ok.