SN 91F5 Battery, Canada Li-ion Rechargeable 20.9Wh, 2.9Ah IBM SN 91F5 Batteries

Question about SN 91F5 laptop battery ( From internet ):

If a laptop is always plugged in and charging, what is the effect on the SN 91F5 battery?

It will not damage your SN 91F5 battery.

It will shorten its life though, but there is nothing practical you can do about it.

Lithium Ion batteries age in two ways, one is through what is termed "Calendar Life" and the other is Cycle life. Here is what you need to understand about both:

Calendar life - the time spent at a given state of charge (SOC) and a given temperature causes a loss of capacity and increase in internal resistance that is proportional to the square root of the time. Higher SOC imparts greater degradation. Higher temperature imparts greater degradation. Keeping your computer plugged in all the time with the battery ensures that the battery stays hot and charged as much as is possible. If nothing else, turn down the performance of the laptop when you don't need it to overperform so that it runs cooler.

Cycle life - while you might think that it makes sense to fully discharge the batteries, rather than put lots of little cycles into it, the opposite is true. Lots of little cycles do virtually nothing to the cells. 100% discharges are the bane of their existance.

So, the reality is, you could optimize battery life by keeping the battery about 50% charged, letting it discharge a bit and then recharging it, and if chargers allowed for it, floating them at a SOC that was not 100%. However, it is much much easier to just get on with life and use your laptop and not worry too much about this. Assume your battery costs you $1 a day. Put that much away for its replacement. When it is fine on the day you buy your next computer, you have now paid for that new computer, or a good size chunk of it.

If you take the SN 91F5 battery out, it will not be stable and will likely get more dust inside.

What should you do if your old SN 91F5 laptop battery is plugged in but not charging?

1. Remove the power supply from the notebook.
2. Remove the battery from the notebook.
3. Inspect the battery for sign of possible damage to the battery, if there is any damage to the battery like a cracked casing o0r swelling replace the battery.
4. Also inspect the contacts on the battery for signs of dirt or corrosion. If any dirt or corrosion is detected, use a cotton swab with alcohol to clean the contacts. Or, if the contacts are exposed and accessible, use s pencil eraser to clean the contacts. Use compressed air to clean any eraser particles. Do the same for the contacts for the battery in the notebook itself.
5. Re-install the battery, then re-attach the power supply and see if the battery is charging now.

If the battery is charging, you may want to check the manufacturers support site and see if they have a utility to check your battery. (Not all manufactures may have them, I know that HP does for at least some for their notebooks.)

If you want a long life SN 91F5 Battery, just to buy a new original SN 91F5 Battery or higher capacity SN 91F5 Battery. Beacuse genuine battery have original battery cells, higher capacity battery can work longer and reduce annual charge times.