www.robowars.org

RoboWars Australia Forum Index -> Technical Chat

Annoying A123s
Goto page Previous  1, 2, 3, 4, 5, 6, 7

Post new topic   Reply to topic
  Author    Thread
Glen
Experienced Roboteer


Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect


 Reply with quote  

just take the pack apart and attach each cell to the charger, you can see the voltage that way + see if they take any actual charge.

sometimes the dead ones can show similar voltage as the good cells on a multimeter as well, but under charge or discharge the voltage goes way up or way down compared to the rest, pretty easy to see which ones do it if you can get the charger to run in the first place

Post Mon Jul 12, 2010 10:49 am 
 View user's profile Send private message Send e-mail Visit poster's website MSN Messenger
Daniel
Experienced Roboteer


Joined: 30 Aug 2005
Posts: 2729
Location: Gold Coast


 Reply with quote  

ok, I'll do that tonight
The other annoying thing about my eBay cells was it looks like the tabs weren't cut apart, but rather torn off the next cell. So some cells have tabs on both ends, some on one end and some with no tabs. This made soldering them together really hard and I've had a few failures that way too. Its tempting just to rebuild one good 6-cell pack with as many good tabbed cells as I've got and donate the rest to my brother.

Next time I'll pay a bit more for batteries. I'm sure I lose 50% of fights due to battery failures. If you include batteries falling out of the robot too.

Post Mon Jul 12, 2010 11:54 am 
 View user's profile Send private message Send e-mail
Jaemus
Experienced Roboteer


Joined: 01 Apr 2009
Posts: 2674
Location: NSW


 Reply with quote  

Get a multimeter as well Smile

Strangely you're not alone in this; ive talked to countless car nuts who carry out complex electrical work on their complicated modern japanese sports cars, post up electrical questions and when told to buy a multimeter they seem to be somewhat actively against the idea???

Post Mon Jul 12, 2010 1:49 pm 
 View user's profile Send private message Send e-mail MSN Messenger
Valen
Experienced Roboteer


Joined: 07 Jul 2004
Posts: 4436
Location: Sydney


 Reply with quote  

$40? the $10 ones are good enough ;->
(and when you measure the amps of your A123 pack you wont be too cut over the smoke)
_________________
Mechanical engineers build weapons, civil engineers build targets

Post Mon Jul 12, 2010 4:21 pm 
 View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger ICQ Number
Nick
Experienced Roboteer


Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW


 Reply with quote  

Spend a bit more and get good current measurement. I bought an older model of this meter and couldn't be happier: http://www.jaycar.com.au/productView.asp?ID=QM1563&CATID=12&form=CAT&SUBCATID=300

After 5 years, its still going strong and does everything you are likely to need for robots. Many shops rebadge this meter, so there may be ebay and O/S bargains to be had.

Post Mon Jul 12, 2010 4:30 pm 
 View user's profile Send private message
dyrodium
Experienced Roboteer


Joined: 24 Aug 2004
Posts: 6476
Location: Sydney


 Reply with quote  

I compared a $10 jaycar meter to a ~$500 fluke meter at my old work and the differences were negligible for low current, resistance and voltage measurements, for what we do, the high priced meters are unnessisary. The ones that can measure 20A instead of 10A are handy but no one in robotics needs to measure inductance or capacitance... Laughing
EDIT: A current measurement tool like Nick linked is probably more handy than a multimeter, just make sure its DC capable... Smile
_________________
( •_•)

( •_•)>⌐■-■

(⌐■_■)

YEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAH

Post Mon Jul 12, 2010 6:09 pm 
 View user's profile Send private message Visit poster's website MSN Messenger
Valen
Experienced Roboteer


Joined: 07 Jul 2004
Posts: 4436
Location: Sydney


 Reply with quote  

I reckon buy a number of $10 meters until you don't blow them up anymore ;->
I have about 5 meters, a couple of cheapies and a $40 one.
I use the cheap ones as a semi expendible and keep the good one for situations that warrant some accuracy.
the clamp meter would be handy though, currently we use a precision current shunt for measuring currents in the 10-50A range
_________________
Mechanical engineers build weapons, civil engineers build targets

Post Mon Jul 12, 2010 6:26 pm 
 View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger ICQ Number
Nick
Experienced Roboteer


Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW


 Reply with quote  

Not having to break the circuit to take a current reading is magic! Its so simple that I actually do it rather than take a guess. Other than that. I mainly use DC voltage and resistance. Auto-ranging is another convenience factor that is well worth having That one I linked to is also handy as it is quite small and light.

Post Mon Jul 12, 2010 6:45 pm 
 View user's profile Send private message
Spockie-Tech
Site Admin


Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia


 Reply with quote  

One of the ~$40 Jaycar meters comes with a serial cable and a program that lets you log data on your PC and graph it.

Admittedly Ive only used that function once, since I have a E-station battery charger with logging that does it per cell,

but assuming you didnt have one of those, the PC logging of voltage on a battery pack, with a discharge load like a globe or something could be quite useful to check a packs capacity.

Ditto on the Fluke's accuracy. I've compared my Fluke-87 (I forgot what it cost, but it was in the high hundreds range back in the 90s when I bought it) and the cheapy Jaycar is witin a few % of it..

The main advantage to Fluke's is if you're using them in application that needs *certification* or other documented accuracy, they *can* be calibrated and adjusted by a calibration lab ($$$) - not that I know anyone (except the place I worked for that made aviation altimeter transponders) that has actually *done it*, but it *can be* if you wanted to.. They'd probably turn their noses up if you sent a jaycar meter in for calibration/certifcation..

For Roboteers - who tend to make more magic smoke than most electronic hobbyists (we play with higher power stuff, your average hobbyist couldnt find anything on their bench to supply 200amps even if they tried) - a cheapy meter *would* make more sense. The smoke they use is cheaper so you dont cry so much when it escapes Wink
_________________
Great minds discuss ideas. Average minds discuss events. Small minds discuss people

Post Mon Jul 12, 2010 7:11 pm 
 View user's profile Send private message Send e-mail Visit poster's website MSN Messenger
Jaemus
Experienced Roboteer


Joined: 01 Apr 2009
Posts: 2674
Location: NSW


 Reply with quote  

My company has a calibration lab calibrate their Fluke-11's and various other devices including cheapie insulation testers but other more expensive gear such as temperature dataloggers and microwave leakage detectors, on a regular basis.

I beleive it's actually legally mandatory for using them for field service.

Post Mon Jul 12, 2010 7:37 pm 
 View user's profile Send private message Send e-mail MSN Messenger
seanet1310



Joined: 08 Nov 2006
Posts: 1265
Location: Adelaide


 Reply with quote  

legality would be different between each state anyway.
_________________
Remember to trust me, I am an Engineer.

http://www.youtube.com/watch?v=rp8hvyjZWHs

Post Mon Jul 12, 2010 8:38 pm 
 View user's profile Send private message Send e-mail Yahoo Messenger MSN Messenger
DumHed
Experienced Roboteer


Joined: 29 Jun 2004
Posts: 1219
Location: Sydney


 Reply with quote  

I have some million dollar fluke meter whose leads went dodgy and occasionally just flattens its battery for no reason.

I replaced it with a $20 Jaycar one that does all the same stuff but is smaller and easier to carry Smile
_________________
The Engine Whisperer - fixer of things

Post Mon Jul 12, 2010 9:10 pm 
 View user's profile Send private message Visit poster's website MSN Messenger ICQ Number
  Display posts from previous:      

Forum Jump:
Jump to:  

Post new topic   Reply to topic
Page 7 of 7

Goto page Previous  1, 2, 3, 4, 5, 6, 7

Forum Rules:
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

 

Last Thread | Next Thread  >
Powered by phpBB: © 2001 phpBB Group
millenniumFalcon Template By Vereor.