Tuesday, January 10, 2006

LiPo balancing -- Andre Kilian

You have probably not picked up much on the subject on the internet, as it has not been much of an issue at the charge/discharge rates used. One of the reasons for the limitation on the charge rate of 1C on lipos was to ensure that they stay balanced - you will note that some of the manufacturers are using higher charge rates possible with lipo balancers as a "selling point" - I have seen charging times advertised as 20 mins! I have personally checked the voltage on idividual cells on an old Kokam 1500 3S pack that has more than 100 charge/discharge cycles, and cells were within a few milli volts of each other.

The problem comes in with the new 20C packs (20C continous rating - 30C peak), as at these high discharge rates the cells tend to become unbalanced. I have noted that the problem also arises when running a number of cells next to each other, e.g. 5S packs. I suspect that the imbalance arises from the different internal resistance of the inner cells that are running at higher temperatures.

You also need a seperate lipo balancer that normally works with any lipo charger. These monitor the voltages on each individual cell - that is why the tags are used. An added advantage is the safety feature - the better ones cut off before overcharging the batteries if you have chosen the incorrect settings!

My advice is not to worry about lipo balancing unless you are using the 15 - 20C rated cells and are pushing them to their limits! As a precautionary measure I have soldered tags on all my batteries and only charge through the tags - accidents are bound to happen, as I am charging 2S, 3S, 4S and 5S packs! At about R10 a tag I view it as a worthwhile investment, as i have enough "fat packs"!



No comments:

Blog Archive

Total Pageviews


Web site terms and conditions

Copyright of material on all the pages of this site is vested in the SAMAA or the original authors. You may use the material in terms of the Creative Commons license for non-commercial purposes on the condition that you acknowledge its origin.

This work is licensed under a Creative Commons License

The views expressed on this web site, or on any directly or indirectly linked site, are not necessarily those of the SAMAA Committee, or the web editor. The information provided on this site is provided for recreational purposes only. The SAMAA and the authors of presented content assume no liability whatsoever on the use of information contained in this site. The information on this site is provided on an "as-is" basis, without warrantee of any kind. Links provided on this site will let you leave the SAMAA web site. The linked sites are not under the control of the SAMAA, and the SAMAA is not responsible for the contents of any linked site, or any link contained within a linked site, or updates to such sites.