when to charge pack ?

[Doug Smock]

http://uterc.org/files/LipoStorageTips.pdf

[rol243]

thanks for all the great info guys, much appreciated.

[madmikepags]

I used to charge all my batteries the night or even during the week before a race. I typically run 4-5 classes and my 2 daughters run 3 or 4 each, and most of my boats run 2 packs and some 4, and I would have all my batteries charged for 3 full heats, So I would routinely have 60+ packs ready for each race. This would be a chore even with 4 chargers going. In the past 2 years I have come to a conclusion that I don't need this many packs and with higher c rate charging its very easy and quick to charge during a race. Most boaters do not use their packs often enough to disqualify using higher c rate charging. I typically charge my 4,5, and 6000 packs now at 15 amps. "they say" It will degrade cycle life by 15-20% but when cycle life is typically 350-400 cycles, I have never put my boat batteries through 200 cycles, probably closer to 70-80 before newer technology comes out and I replace them. And batteries always perform better when they are freshly charged, and warm by the way! Also there is no need to let your batteries cool down before recharging, unless they are over 150' and then you should probably rethink your setup. When charging high capacity packs (4000-6000mah) at 1-2c it is not an issue with recharging when they are warm. On a side note I race rc cars and we, (car racers) typically charge at 40 amps, on a 4000mah pack that is 10c!!! and we charge, run, cycle and charge again all in a row without letting anything cool down. I have 3 year old car packs with probably close to 400 cycles on them and they are still running well. While it is OK to charge the night and even a couple of days before, I have found I no longer need to do this, Higher C rate charging is safe and effective (if you have a good balancing charger). I also have 4 chargers at a race so that makes it easier also. Invest in good chargers, it makes a big difference! I recommend looking at the FMa chargers either the powerlab or GT series of chargers are great investments.

[CraigP]

That's good stuff... I'm going to start pushing C rates higher on charge. Tell me, when you charge at a race, how do you power your charger? Off a car or do you have a small generator? Just curious...

[R2315]

madmikepags, are you parallel charging at those c rates or all individual chargers?

[madmikepags]

I use a honda 2000 generator. You can use your car, but make sure your car is running or you will kill the car battery. Really I have seen no degradation in cells with higher c rate charging. But again use a quality balancing charger.

[madmikepags]

I parallel charge at 10 amps, I have one multi board, over that is individual charging.

[R2315]

I got my Powerlab not long ago and haven't done anything but the first preset for accurate charge on auto 1C for my 5000mah's and storage/discharge at 5 amp mostly because of paranoid reading of horror stories about destroying packs and lipo fires, its encouraging to hear some positive feedback about higher C rates and faster charge times. It would be nice to utilize the capabilities of modern technology and not have to wait so long for each charge cycle.

[madmikepags]

The powerlab is the safest and easiest charger on the market, using the high power mode I charge my packs to the 4.22 voltage setting at 15 amps. (and when racing cars I do 40 amps) The charger will shut down and go into "safe charge mode" when it deems that voltage of one or more cells are out of balance or when the resistance is out of whack. The reason why most lipo fires occur is because one or more cells are not in balance, most chargers would read only the total voltage of the pack, if one cell is very low the rest of the cells will charge until the charger "thinks" the pack is charged. So in a 4 cell pack if one cell is at 3.0 when you start and the others are at 4.0 then by the time the pack is at 16.8 the 3 cells will be over 4.5 volts!!! "BOOM". even some balance chargers only display the individual voltage but don't necessarily "balance" the packs.

[NativePaul]

Yup, check the ballance current of your charger, most can burn off 300mA, but some only 100, and some like some of the FMAs and the Shultze charge each cell individually so are unlimited.

The issue is if the battery is more than 300mA out of ballance (on one with a 300 mA ballancer) when charging at 1c it wont be ballanced by the hour it takes to charge, and a cell can be overcharged. At 2c it only has half the time to burn off the extra unballance at the same 300mA so it can only handle cells that are 150mA out. At 10c it only has 6 mins to burn off excess at 300mA, so can only cope with 30mA inballance.

[rol243]

so is it safer to charge at 2c rather than 1c ?

[fweasel]

so is it safer to charge at 2c rather than 1c ?

No, safer at lower C rate, but that's not to say anything over 1C is unsafe.

[madmikepags]

It really depends on your charger, your batts, your leads, and connections. Charging any high C rated Charge and D/C 4000-6000mah Lipo is safe anywhere between 1-15 amps, as long as your charger (and poweer supply) can handle it. Now just because your charger says it can charge up to 15 amps doesn't mean it can charge a 6S 5000mah pack. Remember POWER is watts. (Amps x Volts = Watts) 6S=25.2volts x 15amps = 378watts so your charger and power supply better be at least 400 watts and 20amps.

[rol243]

i have a 450 watt power supply and my chargers are 350 watts. would it be safe to 2c charge a 5800 / 65c / 4s pack ? or stay with the normal 1c charge rate ? my main issue is waite time as i now have 6 packs to charge.

[fweasel]

At 2C for a 4S 5800mAh lipo, that charger will pull close to 200W so the power supply should be rated at a minimum of 250W, i.e. no problem. However, you said "my chargers" so I wouldn't try to run to multiple chargers off the same power supply given that battery spec.