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View Full Version : [Question(s)] Monitoring LiPo battery while it's in use.



Stobs
10-03-2011, 06:52 PM
I've twice run down my LiPo while connected to my arbotiX to below recharging threshold. I obviously need to re-think my procedures here. Both times I had the arbotiX connected to my laptop via the USB AVR Programmer, and was using a DMM to check the voltage across the battery terminals occasionally - it was only after I powered down the laptop/removed the USB AVR that the readings dropped down drastically.

I'm wondering how I should go about monitoring the battery's voltage itself, short of disconnecting the AVR periodically - unless that is the preferred budget-conscious method?

Recommendations and suggestions greatly appreciated. I think I've got the "observations" part down myself but, if you must...


***
For those who want details...I'd say "and a chuckle" but, it'll probably be few months before I can laugh at myself on this one. :/

The first time I did it I drained it down to about 2.0V per cell and had to use the charger on the NiMH setting to get it back to about 2.9V to 3.2V/cell before I could use the charger on the LiPo setting; the battery charged successfully from there.

The second time I did it, idiotically enough, I drained it down to about 0.1V. Words just fail me. I had a lot more difficulty in charging the battery this time on the NiMH setting but, after about three hours, I finally got it to where it was charging steadily. Not wanting to leave it unattended while charging I stopped the cycle for the duration and restarted on my return. BTW, I periodically held the battery tightly to ensure that it wasn't getting warm to the touch. After having checked the battery in this manner, not more than ten minutes latter from my first and only post-lunch temperature check, I glanced at the charger/battery set-up and saw that the battery was considerably bloated. Hmmmm, not so good. I immediately stopped the charging cycle and unplugged the A/C brick from the charger. Not familiar with the battery's packaging bursting point, I did not touch the battery but, I'm surmising, that it was beyond warm. I waited about 20 minutes and, even though it did not return to it's normal size, I felt it and it was room temperature. I disconnected it from the charger, removed the banana connectors and taped the bare ends with electrical tape. Not sure what I'm going to do with it but I can't bring myself to just throw out a $70 battery that I barely even used, puffed or not, but a 40p galvanized spike would nail it to my forehead pretty nicely. :/

Gertlex
10-03-2011, 08:38 PM
All I can say is: *shakes head*

Get the <$10 MaxPro battery monitor corresponding to the number of Lipo cells you're using.... And never touch that battery with + and - terminals again. Probably want an expert to take that off you're hands, but I'm guessing on that point.

cire
10-03-2011, 08:53 PM
http://rcvehicles.about.com/gi/o.htm?zi=1/XJ&zTi=1&sdn=rcvehicles&cdn=hobbies&tm=12&f=10&su=p504.3.336.ip_&tt=3&bt=1&bts=1&zu=http%3A//www.rctoys.com/pr/2007/07/06/safely-dispose-of-lithium-polymer-lipo-lipoly-battery-packs/

I did the same thing you did, more or less.

SK.
10-04-2011, 06:11 AM
I have positive experience with LiPo warners like this from Dealextreme:
http://www.dealextreme.com/p/1s-6s-lipo-battery-voltage-checker-tester-with-dual-speaker-low-voltage-buzzer-alarm-72381

You just plug the warner into the balancer plug of your battery. The warners are cheap and delivery takes 2-3 weeks, but they work as advertised for me so far (and the alarm is hard to overhear ;) )

Stobs
10-04-2011, 10:01 AM
Hi cire, SK,

Thank you both very much for your timely and helpful replies. I hadn't as yet researched how to properly dispose of the battery and that warner/monitor looks like it will work perfectly, so your replies are just what was needed and are very much appreciated.

Regards