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500 Class Electric Helicopters 500 Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar. |
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10-27-2010, 10:16 AM | #1 (permalink) |
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Parallel charging help please!
I'm trying to decide what charger and power supply to buy for 6cell packs. I've found out quickly that my Thunder AC6 is not up to the challenge (and barely up to the 11.1 2200 charging for that matter )
I know this is a tedious read-through but could one of you lipo guru's please double check my math and make sure I'm not screwing this up.... I've taken the example from this post from jdacal (thanks) : https://www.helifreak.com/showpost.p...65&postcount=8 and come up with the following: Volts x Charge Rate in Amps = Watts needed 2S (7.4V) 5000mah @ 1C 7.4V x 5amps = 37 watts 6S (22.2v) 2650mah @ 1C 22.2 x 2.65amps = 58.83 watts Watts / PS output voltage = Amperage needed 37 watts / 13.8v (protek super pro 40 output voltage) = 2.68 amps PS needs 2.68 amps to charge 2s 5000mah @ 1c 58.83 watts / 13.8 = 4.26 amps PS needs 4.26 amps to charge 6s 2650mah @ 1c Full equation: PS amperage = (batt volts x charge rate)/PS voltage for 2C, you double the amps, (ie. 3000mah @ 2C = 6amps) when charging in parallel, you combine amps of all batts (3x6s 3000mah packs would = 9000mah or 9amps) So using the above equations for my batts: Parallel charging TWO 6cell 2650mah packs at 1C: 22.2 x 5.3amps = 117.66 watts 117.66 / 13.8 (protek) = 8.52 amps Same batts at 2C: 22.2 x 10.6 amps = 235.32 watts 235.32 / 13.8 = 17.05 amps Parallel charging THREE 6cell 2650mah packs at 1C: 22.2 x 7.95amps = 176.49 watts 176.49 / 13.8 (protek) = 12.78 amps Same batts at 2C: 22.2 x 15.9amps = 352.98 watts 352.98 / 13.8 = 25.57 amps So if I'm looking at this charger: iCharger 208B Maximum charge power capacity : 350W (@ input voltage > 17V) Charge current range : 0.05–20.0A With 2650mah 6cell packs, I could charge 3 packs at 2C (352.98 watts, 17.649 amps) - or is this pushing the limit of this charger? Thanks for your time and help!
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10-27-2010, 11:10 AM | #2 (permalink) |
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Join Date: Feb 2008
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Hi
Even if you could from an electrical point of view charge 3 6S packs on one charger, then I wouldn't do it for the following reasons: - Does the charger has a balancer for 18 cells - if not there is a huge risk that you'll end up over-charging some of the cells, thus destroying the cell. - It will take a long time to charge the 18 cells, as the balancer would have a huge task to make sure that all cells are at the same level, and it the lipo's are not completly identical, then they would behave differently while being charged. Regards Jens |
10-27-2010, 11:16 AM | #3 (permalink) |
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Yes, the balancing is done via a Y adapter such as this
Here is a pretty good write up and video at the bottom: http://www.rchelicopterfun.com/paral...-charging.html From what I've read, most people say this is a very efficient way of charging, and just as safe as series charging. It may look sort of scary but if the charger/PS is up to the task, it makes much more sense when charging multiple lipo's.
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Synergy e7, Vbar, HeliJive 120, Hacker 12L, JR 8917 HV, BLS251 Logo 400, Vbar, Jive 60+lv, S9650, BLS251, Pyro 600-09 TRex 450 Sport, MiniVbar, 5065MG, DS420, 450MX |
10-27-2010, 11:52 AM | #4 (permalink) | |
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Quote:
Bill
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10-27-2010, 12:03 PM | #5 (permalink) |
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Assuming you have a power supply capable of putting out sufficient voltage to sustain the charger, with 3 packs your going to be charging slightly under 2c max output with that charger. You won't damage the charger, you'll simply be putting out its max output. No big deal. Ichargers will limit their current output depending on what voltage is being fed to them, and their max rate.
I have a 206b and am very happy with it. I routinely charge 6 of my 3s 2200 packs at full output 20a in parallel and have no problems. Bill
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The most used last words of males ages 16 to 30 "Hey watch this" To be old and wise, you must first be young and dumb. |
10-27-2010, 12:11 PM | #6 (permalink) |
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Thanks Bill, after researching I'm leaning toward the trusty 206B+P350 combo. I'm actually fine w/charging at 1C I just get that warm fuzzy feeling when thinking of 2-5c parallel capability
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Synergy e7, Vbar, HeliJive 120, Hacker 12L, JR 8917 HV, BLS251 Logo 400, Vbar, Jive 60+lv, S9650, BLS251, Pyro 600-09 TRex 450 Sport, MiniVbar, 5065MG, DS420, 450MX |
10-27-2010, 02:26 PM | #7 (permalink) |
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Join Date: Jan 2010
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math
I think your math is ok, although the equation:
Full equation: PS amperage = (batt volts x charge rate)/PS voltage Should read: Full equation: PS amperage = (batt volts x charge rate / efficiency )/PS voltage Where efficiency is about 0.85 or 0.9 I have an iCharger 208B with a cheap ebay 350 W 25 V charger and LOVE it. I routinely charge 3 6S packs at 15 amps in parallel at the field (we have AC). I don't use the full 350 W: I don't want to find out what happens if you push the limit. A little chatting, a flight, and I've got three packs ready to go! Recently got an Outrage 550 and a Trex 600, so am considering upgrading to a full kW charger. I'll prolly go iCharger if I upgrade. |
10-27-2010, 02:45 PM | #8 (permalink) |
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Running a iCharger 206-B Love it, max output is 12.5 amps. I use the P-350 Power supply with this set up. I does all I could ask for. Some times I even charge {3} 3300 mAh 6s packs at one with the 12.5 amp output. But doing 2 at once is even better if your looking for a fast charge rate.
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10-27-2010, 02:48 PM | #9 (permalink) |
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Thanks guys, after speaking with David at ProgressiveRC and also being anxious to get my new (used) 500 in the air, I ordered the 206B+P350 along with supporting balance/charge cables. I was tempted to go 1000w with it to go nuts w/higher C rating batteries (4 6S @ 2C would be no problem), but honestly most of my batteries will not charge over 2 C anyways. Plus I can test out my lone Hyperion at 5C, just for grins,
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Synergy e7, Vbar, HeliJive 120, Hacker 12L, JR 8917 HV, BLS251 Logo 400, Vbar, Jive 60+lv, S9650, BLS251, Pyro 600-09 TRex 450 Sport, MiniVbar, 5065MG, DS420, 450MX |
10-27-2010, 03:02 PM | #10 (permalink) |
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Join Date: Jan 2010
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c ratings
When you charge at high c-ratings, you reach the "constant voltage" portion of the charge cycle faster. This part of the charge process is a function of the battery not the charger, so high c-ratings don't mean much after about 2.5 C.
Congratulations on your new charger; it's an excellent investment. Last edited by freewheel510; 10-27-2010 at 03:02 PM.. Reason: typo |
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