battery charging

[bundydeity]

hi all,

im currently using 2200mah 35c hyperion batteries in my b400 - im using the swallow charger and have it set to 2200mah 11.1v
this can take 40 mins to an hour to charge at that setting, but have noticed the hyperion batteries can be charged at 5c speed charging (according to their website)

should i want to speed charge my batteries, what is the safe speed to charge them at while still prolonging their life? i currently only have 2 and dont want to give them an early grave.
if i do speed charge them, how do i set the charger to do that? if im charging it at 2x speed would i set it to 4400mah but still 11.1v??

[gryffin2007]

Someone else correct me if I am wrong:

For a 2200mah battery, your standard charge input would be 2.2 amps or 1C. To achieve 2C, your charge input would be 4.4 amps and at 5C that would be 11amps. I personally wouldn't go past 2C. Increasing the amps does increase the heat generated when the battery charges. If you do charge it at a faster/higher rate, be certain to sit by and watch it, just in case.

[Stormbringer]

sounds right to me

[jabu32]

you keep it at 11.1V and just change the current. 1c 2.2, 2c 4.4, 3c 6.6.... like gryffin said 2c is probably the max you want to go.

[Harbormaster]

Check the Hyperion website. It says right there that you can charge at 5C without diminishing life. I have a couple of those same batteries that I charge with 6 to 10 amps and they're doing fine after 100 cycles. You bought premium batteries that you can flog pretty hard, so flog 'em and get back to flying!

Here it is:

...they can be safely charged at up to 6C rates with absolutely no negative impact on lifespan - for charge times as low as 10 to 12 minutes - is just icing on a very tasty cake. (G3 have been certified for 6C without cycle decrease. However, charge time difference between 6C and 5C is negligible (or often zero) due to CC/CV curves, so we believe 5C to be the ideal fast-charge setting for quality Lipo).

http://media.hyperion.hk/dn/g3lipo/default.htm

What kills lipos is overdischarging them and storing them fully charged.

I'm guessing that the 11.1 volt setting is a nominal voltage setting. You know that a fully charged 3-cell lipo is 3x4.2=12.6 volts, right?

[bundydeity]

Originally Posted by Harbormaster

What kills lipos is overdischarging them and storing them fully charged.

I'm guessing that the 11.1 volt setting is a nominal voltage setting. You know that a fully charged 3-cell lipo is 3x4.2=12.6 volts, right?

yeah i had seen that on their website but have seen lots of different views on it. i dont want to regularly charge them so fast however it would be handy to do it out in the field get back up in the air quicker.

i've also read this about overdischarging or storing them fully charged. im wondering however what is classified as storage? i always leave my packs charged so whenever i have a chance to fly can just get out and do it not wait for charging. sometimes for a week or more.

[gryffin2007]

I think most folks store their lipo's at 50% charge. That's about 3.85v per cell or 11.55v (fully charged is 12.6v). I keep mine about 3.8v +/-; so far so good.

[wulfrun]

Originally Posted by bundydeity

yeah i had seen that on their website but have seen lots of different views on it. i dont want to regularly charge them so fast however it would be handy to do it out in the field get back up in the air quicker.

i've also read this about overdischarging or storing them fully charged. im wondering however what is classified as storage? i always leave my packs charged so whenever i have a chance to fly can just get out and do it not wait for charging. sometimes for a week or more.

There are probably as many opinions as LiPo owners and scientifically acquired data isn't easy to come by. Based on what data I can find, optimum charge for storage is stated at 46% (ok, I'm sure "half" is close enough). If you fly your pack and charge it straight back up, that means it spends virtually all of its life at full charge - that's exactly the scenario that's meant to do harm. Once again, plenty of folks do this and report no problems but it does go against the advice.

LiPos do not have a linear discharge curve, voltage-wise, so you really can't place too much faith in the numbers being quoted. If you want to know they're half charged then a known load for a known time is about the best (or a charger that can discharge to a known state). However, it's probably fair to say that 3.8-3.9V per cell will be close enough.

Personally I keep mine at about half-charge and just charge them if they are going to be used or are highly likely to be used (UK weather can mess with your plans!). If the weather screws things up, I'll discharge them halfway if they've sat for a couple of days. Even at half-charge, a decent charger can get them ready in half an hour at the outside. I'm rarely impatient enough for less!

[bundydeity]

so for a 2200ma 11.1v battery, to discharge to half should i set the charger to discharge at 1100ma 11,1v??

[wulfrun]

Originally Posted by bundydeity

so for a 2200ma 11.1v battery, to discharge to half should i set the charger to discharge at 1100ma 11,1v??

Check your charger manual how to do it. At that rate it would take an hour. I think you're getting confused by the LiPo numbers, let's try and get the basics sorted:

LiPos are (nominally) 3.7V per cell. In reality it varies with the state of charge, 3V is about as low as you can go without permanent damage (and still that's not a wise level) and above 4.2v you risk bursting the cell. However, stick with the 3.7V number. That means 2 cells in series is 7.4V, 3 cells is 11.1V and so on.

The next number for a cell it its capacity, usually given in mAh (milliampere-hours). The milliampere-hour figure is determined at the optimum rate for the cell, since it varies according to how fast you run the cell down. In theory, a 1000mAh cell can deliver 1000mA for an hour or 100mA for 10 hours or 10,000mA for 6 minutes (i.e. 1/10 hour). In other words, any combination of mA and hours which multiplies to 1000. In reality you'd be very lucky to get 10,000mA for only 3 minutes but 100mA for 10 hours is quite likely. At high discharge rates the capacity has to be "de-rated".

The next couple of numbers are the C-ratings (confusing since you might be thinking "capacity" and be wrong). They relate to how much current the cell can safely handle. If you multiply the 'C' figure by the capacity you'll arrive at this current. There is a 'C' figure for charging and another for discharging and they are generally very, very different numbers. Often, only the discharge one is quoted and then it's only safe to assume the charging 'C' is ONE unless you know otherwise.

Ok, so, for a typical battery for your Blade 400 you might have a 3S 11.1V 2200mAh 40C cell. 3S tells you it's 3 cells (you know that anyway because it also says 11.1V and 11.1/3.7=3). 2200mAh means it can deliver (maybe!) 2200mA for one hour. 40C means it can safely deliver 40 x 2200=88000mA maximum (that's 80A). With no information otherwise, it can safely be charged at 1 x 2200mA = 2200mA maximum, which takes, theoretically, one hour.

[Harbormaster]

Originally Posted by bundydeity

yeah i had seen that on their website but have seen lots of different views on it. i dont want to regularly charge them so fast however it would be handy to do it out in the field get back up in the air quicker.

i've also read this about overdischarging or storing them fully charged. im wondering however what is classified as storage? i always leave my packs charged so whenever i have a chance to fly can just get out and do it not wait for charging. sometimes for a week or more.

Corporations seldom seem to want to come out and say, "You can do X," because it makes them legally liable, but Hyperion comes right out on their website and says that you can not only charge at 6C but that it does no harm and that their batteries are even *certified* for 6C charging. There's no legal wiggle room there so they must really mean it! As I said, I have 100 cycles on mine at 3-4C charge rate with no deterioration.

I can't quote a corporate website on this one, but my reading says that leaving batteries at 100% charge is hard on them--that somewhere around 50% charge is best. My fancy Hyperion charger takes my fancy Hyperion batteries to 70% charge for storage.

Better to store half charged and then rapid charge to 100% than to slow charge to 100% and leave it on the shelf. In any case, at about 70% charge or so, charging voltage hits 12.6 volts and then you get current limiting. That is, the last part of the charge--going from storage level to full charge--is at lower and lower charge rates at the battery approaches 100% charge--well below the maximum charge rate. (If you get a Hyperion charger, you can watch the charge curve on your computer, which is worth the price of the charger in entertainment value if you're a battery geek.)

Batteries have dropped in price enough now so that buying a replacement battery for a 400-class bird isn't that big a deal. I still say flog 'em hard and fly!

[JasonRP_7743]

Here's a question: if you charge at more than 1c rate, should you do so through the output wires, using a "blinky" for balancing? Seems otherwise that is a lot of current through those tiny balance wires.