SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Yesterday, 04:00 PM
aka JetMan Joe
MCSGUY's Avatar
Joined Feb 2010
2,535 Posts
The rain is back in Seattle so I'm turning back to battery testing, specifically the life cycle testing. I'm trying to settle on a simple method of determining and showing if a pack is actually delivering on the capacity it claims and also to determine when to call it depleted. I've also posed the question to Waynes IR thread as those guys have done alot of life testing on the smaller packs

I'm really not comfortable taking a pack down to 3v/cell or there abouts as part of the testing process. I've always tried to model my testing on our real life use patterns and I think I've come up with a way that would be easy to manage and tell us what we need to know. It may not be the "best" way but I don't want to complicate the process.

It's simply to calculate 80% of a packs stated capacity, pull it out and evaluate what's left. So after fully charging a 5000mah pack I would pull out 4000mah. The voltage level remaining is the metric by which we can judge the pack.

Using the voltage/capacity table we can determine that a new "5000mah" pack should have an average cell voltage level no less then 3.73v or 20% left after 4000 mah is pulled out of it. If it does then we have a rightous brand. Proceeding on to the life cycle testing the pack is subjected to 25 charge/4000mah discharge cycles and then tested again to determine if 3.73v/20% still remains. This process will repeat until the pack is depleted. At what value would you consider one of your packs "dead"? If it were mine I would say that 3.61v/5% is pretty definitive but I'm open to other opinions

Joe
MCSGUY is offline Find More Posts by MCSGUY
Reply With Quote
Sign up now
to remove ads between posts
Old Yesterday, 05:24 PM
chuck
santa barbara, CA
Joined May 2009
4,026 Posts
i think you are wise not to take the packs down to 3v / cell ........ we try never to do that in normal use .

maybe i should already know this from following the thread but what c rate will u use to draw off 80%? seems to me any decent load for realist cycle testing will result in less than 80% of the rated capacity being available w/o getting to a dangerously low voltage. i do 1c discharges on new packs and rarely see more than 80% of the label capacity when resting is at 3.7 v/ cell. i think your method is the best to simulate our use but may have to be to a lesser % discharge? i have been under the impression the the label capacity is at somewhere around 1c or less and at high discharge levels to expect considerably less . agreed, 3.6v is done imo.

chuck.
chas650r is online now Find More Posts by chas650r
Reply With Quote
Old Yesterday, 05:44 PM
aka JetMan Joe
MCSGUY's Avatar
Joined Feb 2010
2,535 Posts
Looks like I'm really going to have to bite the bullet on the MAH quantity measurement: http://www.rcgroups.com/forums/showt...0#post29315050 Report 599

I will be discharging at 135A to start with a constant resistance load. That's about 27C and I figure it's reasonable as most of us never really draw higher then that and it does put the pack under a good workout that should not be abusive (to a good pack)

Joe
MCSGUY is offline Find More Posts by MCSGUY
Reply With Quote
Old Yesterday, 06:04 PM
chuck
santa barbara, CA
Joined May 2009
4,026 Posts
very good and thanks again.
chas650r is online now Find More Posts by chas650r
Reply With Quote
Reply


Thread Tools