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03-24-2015 10:07 PM 6 years ago
 McKrackin
rrProfessor Lucasville,Ohio |
How do you figure wattage on charging? How many watts does it take to charge two 6S packs at 25 amps?I literally never use the word literally right. |
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03-24-2015 10:23 PM 6 years ago
 Eury
rrProfessor Dover NH USA |
Whatever the final voltage of your pack is x desired charge rate will give you your max. It won't be exact, but close. I cheat and just start charging and my charger says what it's pulling from the PS.Nick Crego
Citizen #0168 |
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03-24-2015 10:23 PM 6 years ago
 ssmith512
rrKey Veteran Indianapolis, IN USA |
Watts = Volts x Amps.Steve |
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03-24-2015 10:27 PM 6 years ago
 Fauropitotto
rrApprentice Tampa, FL |
Watts = Amps * VoltageSo say you have a single 6S 2200 mAH pack. Each cell is 3.7V, so 3.7*6 = 22.2 V at nominal charge. However, fully charged it will be 4.2V per cell, so 25.2V when fully charged.Next, we need to know the charge rate. C= AH * amp, so 1C on a 2200mAH pack is 2.2 amps. 3C is 6.6 amps and so on.So a single 6S 2200mAh pack charging at 3C will require 6.6 Amps.
A pair of 6S 2200mAh packs charging in parallel at 3C will require 13.2 amps.Watts = Amps * VoltageFor a single 6S 2200 mAH pack charging at 3C:Watts = 6.6A * 25.2VWatts = 166.3For a pair of 6S 2200 mAH packs charging at 3C in parallelWatts = 13.2A * 25.2VWatts = 332.64If you need help calculating what sort of power supply you need, let me know. |
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03-24-2015 10:50 PM 6 years ago
| michael88997
rrElite Veteran Lewisville,Tx |
I charger duo... it will tell you how many watts your using  |
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03-24-2015 10:55 PM 6 years ago
| McKrackin
rrProfessor Lucasville,Ohio |
I charger duo... it will tell you how many watts your using  I literally never use the word literally right. |
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03-24-2015 10:57 PM 6 years ago
| McKrackin
rrProfessor Lucasville,Ohio |
I was just wondering if I could get more than 40 amps worth of charging going on if I used two chargers at a time.My power supply can only do 1200W though.I literally never use the word literally right. |
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03-24-2015 11:10 PM 6 years ago
| Aaron29
rrProfessor USA |
I've also heard use a fudge factor for inefficiencies in power supply / charger design. Expect about 2/3rd the watts at the battery for every watt of power supply, when all is said and done, due to power supply inefficiency and charger inefficiency.So for your situation, 1200W power supply, losses between PS and battery I'd assume you have about 800W to give the battery. 800W/25.2V (for a 6S, it'd be 25.2V, don't use nominal, use end charge voltage to determine max amps). I get about 30amps.I'm not seeing 40 AMPS unless you get a better PS. Don't push it. |
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03-24-2015 11:21 PM 6 years ago
| michael88997
rrElite Veteran Lewisville,Tx |
I have HP 1200 power supplies in series and I have pulled 40 amps at 24v without any issue from them... might depend on the psu and how efficient they are. |
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03-24-2015 11:25 PM 6 years ago
| Aaron29
rrProfessor USA |
It may push that, but the charger has inefficiencies as well. They are listed in specs, but if you assume 80% PS efficiency and 80% charger you can't go wrong with specs. They will do better than 80% and you will have a little headroom for component longevity. I see no reason to push for 40A to get 4C when 30A will do a 3C charge. It won't save but a few minutes.Edit: a 1200 PS that no kidding does 1200 W probably sucks 1500 from the wall. The efficiency factors in at some point. I like to play it safe. |
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03-24-2015 11:28 PM 6 years ago
| McKrackin
rrProfessor Lucasville,Ohio |
30 amps is not 3C with four 6S 5000mA packs but I see what you mean.I literally never use the word literally right. |
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03-24-2015 11:30 PM 6 years ago
| McKrackin
rrProfessor Lucasville,Ohio |
I have HP 1200 power supplies in series and I have pulled 40 amps at 24v |
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03-24-2015 11:30 PM 6 years ago
| Aaron29
rrProfessor USA |
Yeah I was saying a pair. If you are doing 4 expect 1.5C.I only charge one pair at a time, the other is in the bird! I pop the battery on charge, while it's charging, I load the new battery in the heli, power up, servo checks and beepy noises check, fly, shootthesh1t, and the charger's done before I'm even ready to go back up. Wash rinse repeat.Edit: Mine's a 10S bird. Logo 600. I charge a pair of 5S 4500's at 2-3C using 26A max and it's done in 15 minutes. I can't fly fast enough to outfly the charger. I need more rest. |
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03-24-2015 11:40 PM 6 years ago
| Aaron29
rrProfessor USA |
Short answer to your OP is 1260W.2 x 25.2 x 25=1260W
2 batteries, 25.2V end charge, 25AI wouldn't try it. Because that's 1260W going into the battery. The charger will need a bit more than that from the power supply to account for losses. So, a 1200W PS will be overtasked. |
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03-24-2015 11:47 PM 6 years ago
| McKrackin
rrProfessor Lucasville,Ohio |
My supply wouldn't be over worked. It would just limit the charger.I'll just have to try and see what it does with two packs at 25 amps.
I wouldn't be too disappointed with a 33 amp charge I guess.
I usually charge the evening before anyway.Typical day would be two flights with the 700 and a dozen or so with a micro.
I might sometimes fly a bit more with the 700 if I'm feeling it but not that often.I literally never use the word literally right. |
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03-25-2015 01:17 PM 6 years ago
| ssmith512
rrKey Veteran Indianapolis, IN USA |
Short answer to your OP is 1260W.
2 x 25.2 x 25=1260W
2 batteries, 25.2V end charge, 25A |
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03-25-2015 01:51 PM 6 years ago
 ICUR1-2
rrElite Veteran Ottawa, Ontario |
In most cases if your charger tries to draw to much from the power supply the charger will go into error mode "most times"If you continually max out the power supply it will have a short life expectancy. Try to get a supply of 20% more that what you need.Another to keep in mind is the wattage needed decreases as the battery charges up. |
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03-25-2015 02:00 PM 6 years ago
| ICUR1-2
rrElite Veteran Ottawa, Ontario |
To determine how long it takes to charge a battery the formula is
60 minutes divided by the C rate60/1=60, 60/2=30, 60/3=20, 60/4=15, 60/5=12As you can see you get diminishing returns after 4Csince we only take out 80% of the battery, you use 80% of the batteries MAH rating so a 5000mah is actually 4000mah X the C charge rate to get the amps required to charge |
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03-25-2015 03:11 PM 6 years ago
| ssmith512
rrKey Veteran Indianapolis, IN USA |
Also, just as a point of reference; if you aint chargin' at 1.21 gigawatts, then you aint chargin'.Steve |
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03-25-2015 03:35 PM 6 years ago
| Aaron29
rrProfessor USA |
Ssmith, If he means 25a split between any number of batteries I would think stating the number of batteries would be pointless from a PS consumption perspective. I just assumed he stated two because the information was pertinent. There are duos that will do over 25a per side so it isn't a stretch to assume 25a per 6s.Plus McK never used the word parallel. Looks like folks have different ideas what he's trying to do.Maybe he can enlighten us?Edit.nm. He stated he wants to hook up two chargers to one power supply. I stand by my math. |
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