Question about New LiPo's

[Steve108]

I ordered an E-Tech 2 cell 300mAh battery about 2 months ago but I don't have a charger yet. I am going to be modifying a cell phone charger but anyway... How long will the battery last at the factory charge level before it dips below that voltage X that destroys it? I'm not using it or anything, it's just laying around.

Thanks,

Steve

[Marion]

It will not discharge just laying around... LiPos are like that -- they do not discharge by themselves

[flunki]

It will very slowly discharge. They are ship most times with 50% charge and could be empty in around 1,5 - 2years. Anyhow, after about 3 years they will only deliver around 50% or a bit more of capacity their nominal capacity. The time starts when the cell is built, check the spec sheets.

[deh6]

I got a 350 mah and a 1500 mah LiPo 2 cell Electrifly packs from Tower several months ago. I checked the voltage when they arrived and they were well above 3.0v, around 3.5 v as I remember. Two days ago I was getting ready to install them and I checked the voltage, expecting them to be "up there." Much to my surprise the 350 mah pack was down to 2.7v! Both cells were the same so it wasn't a case of one bad cell. The 1500 mah looked like it hadn't changed, i.e. still up around 3.5 v.

Somewhere I read that when the voltage drops below about 2.9 v the charging should initially be at less than a C/10 rate; charging at a C rate will damage the cell. Somewhere else it talked about charging with just a few millamps until the voltage comes up. My homemade charger (has a micro in it) charges at 35ma until it hits 3.1 v, then switches to regular rate, etc. The cell voltage came up fast, hitting 3.0 v in a minute or two.

If you haven't got your LiPo charger yet, you could charge the pack for a short time with just about any charger that is within the current rating, monitoring the voltage. When it gets up to say, 3.9 v take it off charge. Just don't forget it and let it go over 4.2 v.

LiPo cells do self-discharge and the mfg'er specs which may be worse-case show figures that suggest the cell could be down in a matter of months, not years. I got 10 surplus LiIon cells a year ago and 9 of them are in the 3.5-3.7 v range, but one had dropped to 2.7v. For what these things cost it's worth taking a little time to check their voltage once a month.

[markmi]

I would not use a cell phone charger as the voltage sensor is in the cell phone.
I use a L200 adjustable regulator with a large heatsink connected to a switch mode power supply 12V similar to that of a computer. I adjust the regulator to 4.220V. Absolute voltage is 4.235V.
Please use a 4 ½ digit multimeter, do not leave unattended and check voltage levels every 10 – 20min. until you have calibrated the regulator correctly. Charging time is 2 hours.

markmi

[spinfree]

It will very slowly discharge. They are ship most times with 50% charge and could be empty in around 1,5 - 2years. Anyhow, after about 3 years they will only deliver around 50% or a bit more of capacity their nominal capacity. The time starts when the cell is built, check the spec sheets.

I have etech 3s1200 cells that are over 3 1/2 years old and still put out 1000mah according to my triton discharge at 1amp to 9v

on the same note I have 3s700 purchased the same time used maybe 5 times that has less than 100mah discharge at 1amp to 9v

my experience is some last longer than others out of 6 3s1200 packs 3 are over 1000mah after 3years and 3 are around 800mah I don't track useage but I think the ones that are around 1000 have many more cycles on them as the others are mounted to helis that don't see much action.

Only pack I've ever puffed was charged for about 5 mins on my triton set to Nimh. glad I turned around when I did. it got big fast.

Thor