SparkFun Forums

[SingleMalt]

Hey, guys.

I have a question regarding the sparkfun product "Polymer Lithium Ion Battery - 400mAh". I searched the forum already for similar questions but there are none.

Does anybody have the discharge characteristic as the typical non-linear discharge curve "voltage over capacity"?

The background is that I am using this battery for a project. I also use a Pololu 3.3V Step-Up/Step-Down voltage regulator to get a constant 3.3 V for my curcuit.
Even though the battery shall have a discharge protection, I recently noticed during capacity measurements that the voltage dropped to below 3.0 V, which shouldn't have happened. After checking the data sheet http://dlnmh9ip6v2uc.cloudfront.net/dat ... ection.pdf I noticed that the minimum value of the over discharge protection is 2.827 V. So, according to my knowledge of LiPo batteries, that voltage would already cause a permanent and significant damage to the capacity of the battery. Is that correct?? If so, what is this protection circuit of the battery for?

If drained below this value, is there an increased danger of explosion if charged again?

I hope somebody can help me with that.

Thanks

[SingleMalt]

Damn, it seems that I always ask the difficult questions

[jremington]

Google "lipo discharge curve" for lots of informative hits, including, of course, many examples of discharge curves. It is very simple to generate a discharge curve for your own battery.

Since different lipo protection PCBs have different cutoffs, it seems unlikely that the exact value of the cutoff voltage is absolutely critical. Furthermore, batteries from different manufacturers seem to be of greatly differing quality and with apparently little honesty in the industry, you are pretty much on your own.

[SingleMalt]

Ok, I understand. Thank you. I measured the discharge curve and I drained the battery until the protection kicked in, which was below 3,0 V. I am building an additional voltage monitor and cut off all power by software if 3,5 V are reached.

Thanks