I have a question regarding lithium ion batteries and long term storage, say anything greater than one month. Having read some comments on this over the past year, it seems the general consensus is that batteries stored long term should be kept around a 30-50% charge capacity and not stored at full charge long term. In fact my recent acquisition of a few EGO yard tools reflects this thinking. In reading the literature that came with my most recent purchase, it states:
*Store lithium-ion battery packs in a 30-50% charged condition.
*Every six months of storage, fully charge the battery pack.
*This battery pack is equipped with an advanced self-maintenance function. It can maintain 30% of its charge capacity automatically after it is stored over one month.
While some their statements are a little contradictory, it seems to imply that if you store a battery at 100% capacity, after 30 days the “self-maintenance function” will kick in and reduce/maintain the charge to the optimum 30-50% range.
Sounds like a good design but it begs the question, do my Dewalt and Milwaukee batteries do the same thing? Do they self maintain at the optimal 30-50% charge capacity during prolonged storage and do any other tools manufactures do this?
I’d be curious as to how they would maintain the charge on the battery if it wasn’t plugged up to anything. Ie the battery sitting still would draw down from 100% - if so what’s the mechanism.
Meanwhile most of that logic is considered to be good practice for LI cells. you will see hobbyist doing similar.
I wish more tool companies would offer a MX charge cycle on the charger or at least give you a 70% holding charge option. Simple terms if you are going to set a LI battery unused for say 3 months or more it would be best to charge it to 70% and leave it alone.
I believe most tool company battery systems don’t do this because they plan on the user using them constantly.
Worst case even if you don’t follow those guidelines the battery will most likely last to useable capacity for some 2 years or more. In other words - roughly speaking you have 1000 charge cycles on a li battery - by cycle 600 you’ve most likely knocked down the overall capacity by 30%. SO if you charge up your battery once per week - you still have a few years before the capacity was noticeably short. If you’re using a 3ah battery pack on your drill you might not even notice the degradation. And in 3 years a replacement battery isn’t that expensive - easy to replace - and often even more capacity than what you replaced.
In addition to charge level, it is best to store the batteries in cold place. So a basement is better than a garage for example.