polymer li-ion battery monitoring and under-voltage protection

Hi - I recently found out that li-ions can be overly discharged to the point where they get damaged. Does anybody know at what point this normally happens at? I was told 2.7V, but then when I've been looking for a 3 cell under-voltage protection chip I stumbled upon the max1665

formatting link
that has a cutoff voltage of 2.5V. So what is the proper cut off voltage? Also, does anybody know of any chips similar to the 1665 but that have a higher cutoff voltage (if that voltage is too low). It looked perfect for my needs besides the low cutoff. If it matters, I plan on using three of these:
formatting link

On a related note - is there a good way to monitor the voltage of a set of 3 li-ion cells in series? They will be powering a dc/dc converter that will be powering a ARM microcontroller. I thought about just using a resistive voltage divider, but is there anything better out there?

Thanks,

-M. Noone

Reply to
M. Noone
Loading thread data ...

There are a number of manufacturers out there producing porotection chips for 1 through 4 cell stacks, but thye were VERY hard for us to locate two years back.

One of the key roles of the protection module in multi-cell configurations is to guard against differences in cell voltage. When these differences appear, the result of a voltage divider approach is that the lower voltage cells discharge further than the "average" represented by the divider. Similarly, on charge the CC->CV transition and termination conditions will be met with (at least) one cell at a higher than desired potential. Both are potentially dangerous situations. Use a 3-cell protection chip for a 3-cell string.

Reply to
budgie

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.