SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Aug 11, 2012, 05:14 AM
Registered User
Joined Aug 2012
11 Posts
Discussion
How to test individual cells battery won't charge

Hi
My 8.4v batts won't charge.. Have tried everything but they must be crap cells
I want to break down the 2 packs and maybe make one good one
How can I see which are the good ones?
Please bare in mind there not holding much of a charge
Cheers
Beersmith1000 is offline Find More Posts by Beersmith1000
Reply With Quote
Sign up now
to remove ads between posts
Old Aug 11, 2012, 09:54 AM
Registered User
flydiver's Avatar
United States, WA, Seattle
Joined Jan 2007
5,264 Posts
In my experience if you have an older used pack with individual cells not functioning properly the rest aren't far behind. If you already don't know how to do cell surgery I'm not sure it's worth the risk. They are cheap now and the process is a bit touchy. I used to do it and don't bother anymore.
flydiver is offline Find More Posts by flydiver
Reply With Quote
Old Aug 11, 2012, 10:17 AM
Registered User
So. Cal.
Joined Oct 2004
8,151 Posts
More specifics on your packs... Are they NiCd, NiMH, or Lipoly packs?

The easiest way to fix the sort of issue that you're experiencing is with a credit card.
mrforsyth is online now Find More Posts by mrforsyth
RCG Plus Member
Reply With Quote
Old Aug 11, 2012, 10:19 AM
Registered User
Joined Aug 2012
11 Posts
Sorry there nimh and there new but gotta a refund as there faulty . Just thinking might be able to salvage a good batt out of two
Beersmith1000 is offline Find More Posts by Beersmith1000
Reply With Quote
Old Aug 11, 2012, 11:15 AM
Registered User
flydiver's Avatar
United States, WA, Seattle
Joined Jan 2007
5,264 Posts
NiMh is even MORE of a problem. If you can isolate a single bad cell in a pack you might be able to replace it...but it's a hassle and outcome is dubious.

Cut the shrink off...they are all soldered together. Voltage alone is not necessarily a good indicator of cell quality in NiXX so finding the bad one(s) is problematic. Best way is unsolder them all, test each cell individually with a decent charge/discharge charger and go from there......see the problem.
flydiver is offline Find More Posts by flydiver
Reply With Quote
Old Aug 11, 2012, 11:25 AM
Registered User
Joined Aug 2012
11 Posts
How do I do the testing when there individual ?
Beersmith1000 is offline Find More Posts by Beersmith1000
Reply With Quote
Old Aug 11, 2012, 11:58 AM
Registered User
So. Cal.
Joined Oct 2004
8,151 Posts
The easiest way is with a battery analyzer such as the CBA IV.
mrforsyth is online now Find More Posts by mrforsyth
RCG Plus Member
Reply With Quote
Old Aug 11, 2012, 07:19 PM
Registered User
ggcrandall1's Avatar
USA, GA, Marietta
Joined Aug 2005
5,693 Posts
Why has no one asked what charger you are using?

Does your charger provide you with individual cell information? If not your first order of business should be to get a quality charger. Also you should have a good wattmeter.

With a quality charger which has discharge capability you can test individual cells. You will have to make up some special test cables to allow you to connect to individual cells via the balance connector.

See here for typical wiring connections:
http://scriptasylum.com/rc_speed/lipo.html

Also here is some excellent reading concerning LiPo batteries:
https://sites.google.com/site/tjingu...arging-how-tos

However the cost of a 2S LiPo is so reasonable as to make it not worthwhile to expend much energy on trying to rebuild a bad pack. But you still need a good charger and a wattmeter.

Glen
ggcrandall1 is online now Find More Posts by ggcrandall1
Reply With Quote
Old Aug 12, 2012, 12:18 AM
Registered User
So. Cal.
Joined Oct 2004
8,151 Posts
I'm with Glen.

Since NiMH do not have taps that allow easy diagnostics / troubleshooting for bad cells, you would be much better served by upgrading to Lipolys, especially given the fact that Lipolys are so cheap these days and offer significant performance improvement and runtime vs. NiMH or NiCd.

Mark
mrforsyth is online now Find More Posts by mrforsyth
RCG Plus Member
Reply With Quote
Old Aug 12, 2012, 03:04 AM
Registered User
Joined Aug 2012
11 Posts
Ok guys but my budget is very limited .. What's the cost of a lipo charger that's good enough for the job? And will my s controller take it

I have a slash with an x5
Beersmith1000 is offline Find More Posts by Beersmith1000
Reply With Quote
Old Aug 12, 2012, 03:06 AM
Registered User
Joined Aug 2012
11 Posts
It's a vector nx85 charger
Beersmith1000 is offline Find More Posts by Beersmith1000
Reply With Quote
Old Aug 12, 2012, 05:11 AM
Registered User
ggcrandall1's Avatar
USA, GA, Marietta
Joined Aug 2005
5,693 Posts
Quote:
Originally Posted by Beersmith1000 View Post
Ok guys but my budget is very limited .. What's the cost of a lipo charger that's good enough for the job? And will my s controller take it

I have a slash with an x5
My mistake. I failed to note that you had NiMH batteries not LiPo's. The charger you have is a NiMH charger and is probably OK.

Glen
ggcrandall1 is online now Find More Posts by ggcrandall1
Reply With Quote
Old Aug 12, 2012, 05:45 AM
Canadian Bacon
flypaper 2's Avatar
Kingston, Canada
Joined Jun 2004
12,888 Posts
When I was playing with nicads and nimhs I stuck a straight pin through the covering to check the voltage of the individual cells with a VOM.

Gord.
flypaper 2 is online now Find More Posts by flypaper 2
Reply With Quote
Old Aug 12, 2012, 03:53 PM
Registered User
Joined Aug 2012
11 Posts
Ok will try that should there be an obvious voltage difference on the bad cells as there probably not very charged
Beersmith1000 is offline Find More Posts by Beersmith1000
Reply With Quote
Old Aug 13, 2012, 05:46 AM
Registered User
Florida
Joined Aug 2004
4,134 Posts
Before you do anything else, put the battery on a slow charge (charge at 0.1C for 15 to 16 hours) and then test it. As mentioned above, you can use a pin to poke through the insulation to measure the voltage of each cell.
Rodney is offline Find More Posts by Rodney
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion 8.4v battery packs won't charge Beersmith1000 Car Talk 6 Aug 13, 2012 02:31 PM
Discussion PowerLab 8 won't auto discharge after charge (won't cycle) martinwinlow FMA Direct 6 Apr 08, 2012 05:26 AM
Help! Li-Fe Battery Won't Charge? DJO Batteries and Chargers 31 Mar 04, 2012 02:10 PM
Help! Lipo battery charge connector question. How to read individual cell voltage? Scott C Batteries and Chargers 2 Oct 04, 2011 08:30 PM
Discussion parkzone T28 trojan 3 cell battery won't charge up. Dale Sawchuk Batteries and Chargers 1 Jul 05, 2011 12:50 AM