update on > 45mph ebike after 4500 miles

[Hillhater]

Guys,
I came across this vid of checking & monitoring the IR of lipo packs ( can do individual cells also).
I think it is a good way to monitor and asses pack life.
Note also in the last test , the effect of temperature.
http://www.youtube.com/watch?feature=endscreen&v=usRE3gLFnOc&NR=1

 

[chroot]

iChargers has the IR testing feature built-in (Not 100% accuracy but maybe 90% accuracy) and it's pretty good one. That's how i caught my old 5s LiPo pack started dying and my iCharger showed over 200 IR ohms.

If someone wants more accuracy IR testing then get this http://www.rcgroups.com/forums/showpost.php?p=20038311&postcount=249

Guys,
I came across this vid of checking & monitoring the IR of lipo packs ( can do individual cells also).
I think it is a good way to monitor and asses pack life.
Note also in the last test , the effect of temperature.

http://www.youtube.com/watch?feature=en ... LFnOc&NR=1

 

[chroot]

@mvly BINGO, You got all good information write up.

 

[Hillhater]

iChargers has the IR testing feature built-in (Not 100% accuracy but maybe 90% accuracy) and it's pretty good one. That's how i caught my old 5s LiPo pack started dying and my iCharger showed over 200 IR ohms.

If someone wants more accuracy IR testing then get this http://www.rcgroups.com/forums/showpost.php?p=20038311&postcount=249

Agree , but i like the way the YouTube vid measures the IR on a discharge load that is similar to that seen by the cells when in real use

 

[mvly]

Just checked the ir of the cells and all are < 10mohms. Again this is done when it is fully charged. I did not do one when fully discharged, but I suspect it would be around 20-30mohms. So I say the cells are still good. I still stand by my recommendation of NOT using lipo if you want to get into this hobby for the long run.

 

[Hillhater]

Originally ,(when new) you had 3volt sag at 50amps, which would imply a total pack IR of 60 mohm.
Or, on a per cell basis , an IR of 6 mohm .

you are now seeing 6 volt sag at the same 50 amps, implying a full pack IR of 120 mohm... double the original !

But If you have measured the individual cells IR at <10mohm now.. ( but was that at 50amp discharge ?) ... then maybe you have some suspect contacts in the pack ?
Or maybe that one "weak cell" is the problem ?
Or..possibly it was just the low temperature ?

 

[mvly]

Well I measured it using the I charger. It is not as good, but it should give me an idea. One thing people keep telling me is the voltage sag due to the temperature. What I am saying is temperature constant, the voltage sag is 2x compared to when it was new. Therefore cold weather should NOT be the reason. Maybe it is a a few bad cells causing the voltage sag, but it just means the battery pack is not any good anymore. Hence my battery conclusion. I just want to point this out to other user who thinks they can get 600 or more cycles if they treat it well. I mean sure if you are drawing less than 1C out of the pack. But remember the reason for running lipo is so you don't have to run it at 1C. Maybe I won't have this problem if I had thunder power lipo. But that is cost prohibited. I think it is best if you plan to swap out the battery often is to run regular turnigy and swap out like madrhino does: every year.

 

[jkbrigman]

Here is my update on > 45mph ebike after 4700 miles. ~4500 on the image with CA below This will be a long post, but I think it is warranted for all those who want to get into this hobby for the long run. Here is the original build link and It has since then change quite a bit. http://endless-sphere.com/forums/viewtopic.php?f=4&t=33528&hilit=temperature+K2

Thanks mvly, for posting your "4700 mile update". Experience like that is invaluable to share with the rest of us!