Battery/Charger issue

[rhyno]

So I think I did something really dumb and ruined four batteries. I just need my stupidity confirmed. Charged up four mSR batteries, unplugged the charger but left the batteries attached to the charger for about a month. Today I decided to fly the heli and none of the four batteries will fire up the mSR, plugged in the charger to the wall and LED's don't turn on to show they are charging.

My guess is leaving batteries plugged into charger completely drained them to the point of being useless...any comments or suggestions??

[Turner]

If you have a volt meter check each pack for voltage. Be careful not to create a short circuit.

[kyleservicetech]

Originally Posted by rhyno

So I think I did something really dumb and ruined four batteries. I just need my stupidity confirmed. Charged up four mSR batteries, unplugged the charger but left the batteries attached to the charger for about a month. Today I decided to fly the heli and none of the four batteries will fire up the mSR, plugged in the charger to the wall and LED's don't turn on to show they are charging.

My guess is leaving batteries plugged into charger completely drained them to the point of being useless...any comments or suggestions??

Do you have access to a wattmeter or similar? If so, connect it between the charger and a "Good" LiPo battery and measure the charge rate. Then disconnect power to your charger, and see if the wattmeter shows a discharge. You may have to reverse the wires on your wattmeter, since the current is now flowing backwards, into the charger.

If you measure any current from the battery to the charger, then you've got your answer. I've checked this reverse current issue on a few chargers. The few I've checked do not allow reverse current to flow without power on the charger. Unfortunately it looks like your results might vary.

If you don't have access to a wattmeter, this thread shows how to use a common digital multimeter for a similar purpose, by modifying a standard servo extension cable. This will allow measuring current more accurately. Those digital meters can be purchased from Harbor Freight, Walmart, just about any place now days. Harbor Freight has some for under $5.00.

http://www.wattflyer.com/forums/showthread.php?t=52821

Pages 6-8 describes how to make an adaptor for measuring battery current. It takes more time to read this than actually do it. FYI, if you connect this adaptor to your charger, you might need to reverse the banana plugs to show a positive charge rate. That way, when you power down the charger input power, that meter will reverse and show a minus in front of the current display. Note that these meters have a fuse on the 200 milliampere range. If you hit that meter with a one ampere charge rate, it'll blow the fuse. You might want to start off on the 10 amp range.

[rhyno]

Thank you, I will give it a try!

[rhyno]

I'm running Thunder Power 25C 125mAH 1-cell 3.7V batteries. Tested all four and had voltage readings from 0.99V-1.14V.

[Turner]

Voltage much below 3 volts/cell for any length of time will damage LiPo cells. Most would say to toss them.