Top off or not to top off that is the question...

[cliffdawg]

Hello,

Just wondering if you guys top your lipos off before a run if they have been sitting for a week or two with a full charge. Or do most lipos maintain a full charge within that period of time.

Ryan

[ultimate_monkey]

lipos dont drop voltage like the nimh cells, over a week they normally dont drop tho they do have a "natural discharge" but its insanly slow, i lost a lipo found it a few months later and it had drop like .1 of a volt. that being said i dont store lipos at full charge, i store at around 3.3v per cell, then chrage up to 4.2v per cell when im ready to use.

lipos arnt like the old NiCd cells, they dont have that "memory" so topping them up at any givin time isnt goin to decrease the capacity of the cell

[Sharkey]

lipos shouldnt be stored fully charged for more than a day. lipos should be stored at around 60% charged, somewhere around 3.7-3.8 volts.

[cliffdawg]

What should I do If I have a bunch of charged lipos?

[Jkelley]

run'm

[lidebt2]

Originally Posted by cliffdawg

What should I do If I have a bunch of charged lipos?

Depending on your charger, you might be able to discrage them a little. If not, run them a little bit to bring the charge down.

[Jkelley]

I found it hard to get the 60% charge from running down pack. Its almost impossible. I normally just run mine dead. Then calculate 60% of the capacity and set my charger to stop on that number, then charge them UP too 60% instead of running them DOWN to 60%. Works good.

[nathanschmoekel]

I have used LIPO's for 8+ years starting with airplanes and now in trucks,boats, and transmitters. If you are using it within 30-60 days of the day you last charged it- it's still at full capacity (or so close it's not worth mentioning)

As to storing them at full charge....I usually do, I like to be ready at a moments notice. My airplane transmitter is always fully charged and ready....had that pack for going on 5 years now and the pack still tests to 90% capacity. I cycle it once a year to check capacity, cause crashing sucks. Keeping it at full charge is not hurting it a bit.

For long term storage it's better for them to read close to nominal voltage (7.4, 11.1,etc) check them with a volt meter. I do this if I know I'm not going to use the battery for a few months.

To discharge for storage set your charger to the lowest amp value possable, and set the stop voltage to nominal (what's printed on the pack)....for discharging it is OK to set the charger to a nicad/nimh setting....most chargers have more stop point voltage options in those modes.

[lidebt2]

A real good article on lipos: http://www.rchelicopterfun.com/rc-lipo-batteries.html

[Jkelley]

I cant speak for all packs but I've seen some maxamps swell from being stored at full capacity. A friend of mine has about 15 lipo batterys and he does the exact same thing with all of them. Runs them in the same cars, airplanes, and heli's and the only ones to swell are the Maxamps. He contacted them and they said it was due to him storing them at 100% charge. He runs all of his packs at least once a week on various Rc's and usually more than once. But according to them He ruined them by storing them at 100%. Who knows they may have just not wanted to replace them.

[Sharkey]

ive heard of other brands having that issue as well, however its not usually low capacity packs, its usually the high capacity race quality packs that swell when stored charged.

[nathanschmoekel]

Are you "swell" guys checking the balance of the batteries when they come off the charger? If you have a cell over 4.2 volts it's going to swell.

My suspicion is that those max amps (cheep asian) batteries don't have well matched cells in them. When poorly matched cells are charged together, one or more cells can take the charge faster and the voltage in those cells will be too high. Unless you use a balancing charger, the charger only reads the total voltage of the pack and is oblivious to the over charged cells.

Hooking a cell balancer up to the pack when it comes off the charger will deplete any over charged cells down to a safe level. I use on from common scense RC....link.... http://www.commonsenserc.com/product...roducts_id=184

More good general battery info here also.... http://www.commonsenserc.com/page.ph...3l10njku47fj92

[Jkelley]

I cant speak for the other guys, but the above batterys I said were swelling on my friend have never been charged any way but balanced. I'm the same way. I only balance charge mine. I run cheap packs (turnigy & Rhino) on my crawler, scaler, slash, Helicopter, and 3 planes and I've never had a swelling problem. But I've never let mine sit 100% charged for more than a day either.

[cliffdawg]

So what would be worse, a fully charge lipo sitting or a after use to the safe cutoff sitting???