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Recommended Charge Rates LiPO

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Old 02-15-2012, 08:47 AM
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rowekmr
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Default Recommended Charge Rates LiPO

Hello
Iordered the NexStar EP and will be buying a 5s 3300mah 20 or 25C battery and have been looking at Lipo Peak Detector balance chargers. Many charge up to 5 or 6amps then others charge up to 10 amps but of course they cost more. What is the approximate range of charging rates so I can find which charger would work better for me. Isee some recommend 4C or 5C, what is C the amp/hr rating of the battery pack?

Thanks

Joe
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Old 02-15-2012, 03:22 PM
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Default RE: Recommended Charge Rates LiPO

"C" means capacity , and the number in front of it is a multiplier. 1C on the pack is of course 3.3 amps and 5C is going to be 16.5 amps.

There's charger currents and powers all up and down the range. Many 50,80,100,120,200,250,400 wattt models. I think you'd be happy with either a 10 amp and 200 watt charger or a 20 amp and 400 watt charger. At the least you should get one of the cheap chinese 50 watt chargers , but it will be very slow compare to something bigger.

ps. I've followed your questions and you are well on your way to being an expert. You're asking all the right questions.
ps. Inspired me to take a look at that plane too. Hmm, 68 inch wingspan and electric power. It looks good.
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Old 02-26-2012, 07:45 AM
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Default RE: Recommended Charge Rates LiPO

ORIGINAL: rowekmr

Hello,

... what is C the amp/hr rating of the battery pack ... (5s 3300mah 20 or 25C battery)?
A 20C-25C continuous discharge rating for your 3300mAh pack would be 3.3amps x 20C = 66 amps or 3.3 x 25C = 82amps. Most/all 25C packs (even more so those rated at 40C-50C) aren't really intended to be drained at a continuous discharge rating of 25C if you expect to get at least 100 performance charge/discharge cycles. The ESC/motor may only pull half the discharge rating in order to extend the performance life of your pack. A parkflyer using a 3300mAh 25C pack will more likely than not have an ESC/motor that doesn't pull over 40 amps, or 48% of the continuous discharge rating. This is a general suggestion as the maximum amps pulled and duration depends on the type of plane you're flying and your throttle management. The Nexstar EP ARF comes with a 50amp ESC, so motor/prop pulling 40amps bursts at full throttle should give your EP good performance for many performance cycles using a 5S 3300mah 25C GensAce.

Unless you need to quickly recharge your pack there isn't the need to use a charge rate higher than 2C; especially if you have another pack charged and ready to GO. A 10amp or even a 5 amp charger should be good enough for most LiPo Parkflyers.
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Old 03-10-2012, 03:07 PM
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Default RE: Recommended Charge Rates LiPO

LiPo batteries have a recommended charge rate.
Some will show a maximum rate as well.
1C charge rate is quite common, and up to 5C not unusual.
3300mah, 1C =3.3A, 5C=16.5A
The number of series cells has little effect, other than some heating on the inner cells.
This can be a limiting factor at higher than 1C charge rates.
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Old 05-11-2012, 05:59 AM
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Default RE: Recommended Charge Rates LiPO

Joe,

NexStar EP - that wil be interesting of you could write a line or two later what You think about that plane, if it is as good as it has a potentional to be for a beginner. On paper is is very close to ideal beginner plane in my view.

Anyway, it can be nice to have at least two battery packs but You will be OK with only one if you are in no hurry. But with two packs you can charge one when using the other pack. Little more flow in flying, at least when one can fly.

Charging at 1 C can all LiPo cope with, almost all can cope with 2C charging current also.
At the field I usually charge at 2C (from a marine battery, 12 volt 80 Ah) and at home where I use power supply as power source for the charger I also charge at2C usually unless I'm in a hurry (thenit can can be 4-5C charge current since all my LiPo I have can handle 5C charging current).

If You plan to use the LiPo Youwilluse in the NexStar EP plane also in other planes later that might require more then 20-25C it can be wise to buy already now LiPo that can deliver lets say 45C. If You take care of the LiPo while charging, storing and using them they should last a couple of years (how many charge/discharge cycles a LiPo battery will cope is hard to say but some manufacturer claim up to 500 cycles).

For modest use the cheaper Hobby King LiPo can be OK, but the more demands You may have on the LiPoYou may want to use more higher end LiPo (ThunderPower, Hyperion to name a few brands). ThunderPower LiPo for example are expensive but good. I use myself Hyperion, ThunderPower and DesirePower Lipo.

And some suggestions to help longer LiPo life:
1. Store them at about 60% capacity, for example a 3300 mAh LiPo pack should have about 1980 mAh (that accurate is not needed but about that mAh) left in battery when You do not use them (let say within a week or longer). many charge has a storage charge selection to make this easy, use it.
2. Charging at lower C used to be little friendlier to the LiPo so unless You really need to charge at 4-5C or higher use the higher C charge when really needed and perhaps not at every charge.
3. Do not run down the LiPo below 20% capacity. So when You fly You do not fly until the battery is drained completely.
How quick You will drain the battery down to 20% capacity left will depend how much power (throttle) you use when flying. You can start flying little more moderate flying times in beginning and at next charge You will see how much capacity (mAh) You can charge into the LiPo pack. Lets say You fly 5 minutes on a fully charged 3300 mAh LiPo battery and after landing charge it and can get2000 mAh into it. Then You had 1300 mAh left in it before You charged it. 20% of 3300 mAh is 660 mAh - that is how much You at least want to to have left in battery after a flight.So if Youused 2000 mAh in 5 minutes it mean about 400 mAh per minute. You had 1300 mAh left by then and can go down to about 660 mAh leftso You canconsume 640 mAh more (1300-660)and that is in flight time about 1.65 min = 1 min and 40 sec, lets say 1,5 minute to be conservative. So You should be able to fly 4 + 1.5 min = 5.5 min and still have about 20% left in battery after landing. Use count down timer in transmitter to get warning when for example 30 sek remain and You should prepare for landing. And do not forget to start the timer before each flight (easy to forget - I have done that many times...). There are battery checker that You can plug into a LiPo to see how much mAh is left in the pack (Hyperion have such, Futaba also for example).
4. Be careful with any soldering You do on ESC and battery connectors, any solderingmust be well done so it will be good connections. And keep battery cable lenght short or at least do not extend any battery cables much since ESC may dislike that.
5. Get some LiPo safety bags and have the Lipo in there while charging. At home You can store the LiPo packs in a pottery or similar container that can handle an unlikely LiPo fire. It is also special LiPo safety boxes one can buy but they are usually expensive.

I'm no expert in electric planes but above rules is what I follow as a big picture and it has worked fine so far.

Good luck,
Bo
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Old 06-09-2012, 05:06 PM
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Default RE: Recommended Charge Rates LiPO

I just saw this post sorry I didn't respond earlier. I have only flown the sim and although Ican take off, land and do aerobatics on there realize that powered planes are not for me. I started on powered gliders back in the 80's and prefer to slow graceful flying compared to this type even those these are considered "trainers". I am looking to sell what Ihave and/or trade for a 99" or larger electric powered glider or something like the Dyna flight Butterfly.

ORIGINAL: bem

Joe,

NexStar EP - that wil be interesting of you could write a line or two later what You think about that plane, if it is as good as it has a potentional to be for a beginner. On paper is is very close to ideal beginner plane in my view.

Anyway, it can be nice to have at least two battery packs but You will be OK with only one if you are in no hurry. But with two packs you can charge one when using the other pack. Little more flow in flying, at least when one can fly.

Charging at 1 C can all LiPo cope with, almost all can cope with 2C charging current also.
At the field I usually charge at 2C (from a marine battery, 12 volt 80 Ah) and at home where I use power supply as power source for the charger I also charge at2C usually unless I'm in a hurry (thenit can can be 4-5C charge current since all my LiPo I have can handle 5C charging current).

If You plan to use the LiPo Youwilluse in the NexStar EP plane also in other planes later that might require more then 20-25C it can be wise to buy already now LiPo that can deliver lets say 45C. If You take care of the LiPo while charging, storing and using them they should last a couple of years (how many charge/discharge cycles a LiPo battery will cope is hard to say but some manufacturer claim up to 500 cycles).

For modest use the cheaper Hobby King LiPo can be OK, but the more demands You may have on the LiPoYou may want to use more higher end LiPo (ThunderPower, Hyperion to name a few brands). ThunderPower LiPo for example are expensive but good. I use myself Hyperion, ThunderPower and DesirePower Lipo.

And some suggestions to help longer LiPo life:
1. Store them at about 60% capacity, for example a 3300 mAh LiPo pack should have about 1980 mAh (that accurate is not needed but about that mAh) left in battery when You do not use them (let say within a week or longer). many charge has a storage charge selection to make this easy, use it.
2. Charging at lower C used to be little friendlier to the LiPo so unless You really need to charge at 4-5C or higher use the higher C charge when really needed and perhaps not at every charge.
3. Do not run down the LiPo below 20% capacity. So when You fly You do not fly until the battery is drained completely.
How quick You will drain the battery down to 20% capacity left will depend how much power (throttle) you use when flying. You can start flying little more moderate flying times in beginning and at next charge You will see how much capacity (mAh) You can charge into the LiPo pack. Lets say You fly 5 minutes on a fully charged 3300 mAh LiPo battery and after landing charge it and can get2000 mAh into it. Then You had 1300 mAh left in it before You charged it. 20% of 3300 mAh is 660 mAh - that is how much You at least want to to have left in battery after a flight.So if Youused 2000 mAh in 5 minutes it mean about 400 mAh per minute. You had 1300 mAh left by then and can go down to about 660 mAh leftso You canconsume 640 mAh more (1300-660)and that is in flight time about 1.65 min = 1 min and 40 sec, lets say 1,5 minute to be conservative. So You should be able to fly 4 + 1.5 min = 5.5 min and still have about 20% left in battery after landing. Use count down timer in transmitter to get warning when for example 30 sek remain and You should prepare for landing. And do not forget to start the timer before each flight (easy to forget - I have done that many times...). There are battery checker that You can plug into a LiPo to see how much mAh is left in the pack (Hyperion have such, Futaba also for example).
4. Be careful with any soldering You do on ESC and battery connectors, any solderingmust be well done so it will be good connections. And keep battery cable lenght short or at least do not extend any battery cables much since ESC may dislike that.
5. Get some LiPo safety bags and have the Lipo in there while charging. At home You can store the LiPo packs in a pottery or similar container that can handle an unlikely LiPo fire. It is also special LiPo safety boxes one can buy but they are usually expensive.

I'm no expert in electric planes but above rules is what I follow as a big picture and it has worked fine so far.

Good luck,
Bo
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Old 06-09-2012, 06:22 PM
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Default RE: Recommended Charge Rates LiPO

Put it on the market here at RCU ? perhaps. I still haven't gotten one.
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Old 06-22-2012, 11:14 PM
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Default RE: Recommended Charge Rates LiPO

I have several 3 and 4 cell 3300mah Lipos. Some are rated for up to a 7C charge rate, others at 1 to 2 C rates.
That aside, as the charge percentage increases, the charge current decreases, in order to not apply a voltage greater than 4.2Vdc per cell.
Naturally, the higher applied current, the faster the charger must change from current limit mode (CC) to voltage limit mode (CV).
My chargers are capable of up to 6A into a 4C lipo. They typically only supply max current for a few minutes, then start folding back into
CV mode. Given a choice, and the money, I'd likely buy a Lipo charger that can charge multiple batteries at the same time.
As it is, I have two chargers, on on the bench, and one in the field case, along with the necessary leads to attach to an auto or truck electrical system.
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