I purchased a Hobbico LiFe 3200 Mah battery pack and loved it. After sailing one Sunday with my club, I forgot to turn off the receiver in the boat. I did not sail for a couple of weeks after that. When I opened the boat and pulled the battery out of the bilge, the first thing I noticed was if felt "puffy". I didn't remember it feeling like that before, but I plugged into the charger and the balancing board and turned it on. Beep Beep Beep! Error message. HMMM. I charged up another NiMh and whent sailing. I spoke with some of my fellow members at the pond and I was told that LiFe batterys are ruined if totaly discharged. Man O Man - I was pretty bummed that I ruined an expensive battery after only a couple of uses.
Not to be beat, I looked and looked on the web for any information about "resurecting" a LiFe battery. I could not find any definative information except that my freiends were right. I thought about what to do. Two ideas came to mind: make a lead to connect a NiMh to the LiFe or use a standard NiMh/NiCd charger. My thinking was that the LiFe charger needs to receive some feedback that there is some voltage in the pack before it will charge. So the battery to battery would balance voltage between the two and the NiMh charger wouldn't care. So, I decided to try charging it with a battery charger not specified for LiFe Batteries. I put the charging leads on the puffy pack and set the charge rate at .08amps on a trickle mode. I did not get the error message this time, but nothing was happening. OK what next? Turn the Amps up and hit it with the fast charge.....drum role.....voila! The battery began taking the charge, stayed cool and did not blow up. I left it on that charger for less than 3 minutes and the moved it to the balanced charger. Amazingly it charged. As it was on the charger, I closely monitored the rate, the voltage balance between the cells and the temperature. Almost immediately the puffiness went down. When the battery had charged to 2100MaH, the charger "stopped". It took about 45 minutes at 1.5amps. The battery was still cool so I let the charger rest a bit and then upped the charging voltage up to the manufacturer's recommendation of 3.0 Volts. The charger stayed on and the battery topped out at around 3200 total MaH. The charge signaled that the charge "ended" rather than just "stopped". I sailed with it all morning yesterday and it worked like a charm. Whew!! I am not sure if I was just lucky, but who cares, it seemed to work well and I hope that this information might help someone else who drained the battery below its threshhold voltage.
Lessoned learned: Unplug your LiFe batteries after use to insure this does not happen.
By the way, does anyone know of a usage meter that can be installed between the battery and the receiver which would measure the nuber of MaH's used? I have read that it is critical to not let the battery be over discharged(obviously), but but because the voltage on these does not drop measurably until it reaches that low voltage threshold ( about 2.5 volts) and then drops dramatically to the "dead zone" (Read Dick Hedderick's excellent article on the buid page). So, a load tester really does not help and a volt meter does not really help either.
Flyers measure the number of MaH used by measuring how many it took to bring th battery back up to full charge after use. So they measure "time" not volts. Usually, this battery burns about 450MaH for 2 hours of sailing in light/medium conditions so about 3.75Mah/hour. I suppose if my math is right I should be able to sail safely all day. Hope this helps.