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Model Forum / Radio Controlled / Air Models / October 2006Batteries, old and new
Hi, I have an idea. I am presently using 3 battery packs of 3S, Li Polies. Each was used separately to fly small planes (about 20 oz.) for about 25 - 30 minutes. The idea is to connect the 3 packs in parallel to make a pack that results in 6300 mAh (3 x 2100 Mah) This will extend my flight time in my larger aircraft. The question is, can an older battery be connected to newer batteries without harm? (1 battery is over 3 years, the newest one is about a year, while the 3rd one is about 2 years old) The batteries are of the older generation Thunderpower. Any opinions or suggestions? Wan As long as they are the same number of cells and all fully charged, they can be connected in parallel for flight. They should be charged separately however.  SignatureRed S. Red's R/C Battery Clinic http://www.rcbatteryclinic.com Check us out for "revolting" information. > Hi, > [quoted text clipped - 15 lines] > > Wan I would say that if they all test out at the same capacity, go for it. SignaturePaul McIntosh RC-Bearings.com "when steel just isn't enough" > Hi, > [quoted text clipped - 15 lines] > > Wan Thanks to both Red and Paul. I will fly when the weather here is better. I hope to get an increase in flight time by about 40% from my previous 18 min. to about 25 min., If my math is correct. There is one question. Once the batteries are balanced, would they need to be charged separately? Wan As Red said, yes. SignaturePaul McIntosh RC-Bearings.com "when steel just isn't enough" > Thanks to both Red and Paul. I will fly when the weather here is > better. I hope to get an increase in flight time by about 40% from my [quoted text clipped - 3 lines] > > Wan | Thanks to both Red and Paul. I will fly when the weather here is | better. I hope to get an increase in flight time by about 40% from my | previous 18 min. to about 25 min., If my math is correct. It's probably close. With the additional weight, you'll need more power and so your flight times will decrease, but the difference is likely to be small. | There is one question. Once the batteries are balanced, would they | need to be charged separately? Red did already say yes ... With all three packs in parallel, if you charge them, you'll be charging all three at once and it should work just as expected. (With NiMH/NiCd cells this isn't right, but with LiPo and Pb cells it should.) But the danger is that some packs will have a lower internal resistance than the others and so a larger percentage of the total charge current will go into those packs, and if the difference is large enough, you could charge that pack at a rate that's too high and damage it. It's relatively unlikely, but possible. You'd probably be just fine if you charged your three pack combination at a rate that is acceptable for the smallest pack -- i.e. if you have a 900 mAh, 1000 mAh and 1100 mAh pack in parallel, charging at 900 mA should be fine. Of course, it'll also take a little over three hours for a full charge ... SignatureDoug McLaren, dougmc@frenzy.com There's no need to fear, UNDERDOG is here! (snip)You'd probably be just fine if you charged your three pack combination at a rate that is acceptable for the smallest pack -- i.e. if you have a 900 mAh, 1000 mAh and 1100 mAh pack in parallel, charging at 900 mA should be fine. Of course, it'll also take a little over three hours for a full charge ...(snip) The 3 batteries are of the same voltage and capacity (3S3P Thunderpower, 11.1 V and 2100 mAh) Three hours a long time. That's the reason I would like to charge the whole pack at the same time as I've done many times before with my Kokam batteries. They are also nine celled, 3S3P and it took about an hour to recharge. Of course the Kokams have only 4500 mAh per pack while the Thunderpower will have 6300 mAh. I know Red said to charge the 3S packs separately. But it would be great if I could charge the whole pack once they are balanced. | I know Red said to charge the 3S packs separately. But it would be | great if I could charge the whole pack once they are balanced. You probably could. 99% of the time, it would work just fine. But that other 1% ... if something happens to one of the packs (like a wire breaks) then suddenly the other two are now being charged at 50% too high of a rate ... You know, my Lacross BC-900 charger just screwed up. It was charging 4 AA 2500 mAh NiMH cells at 500 mA like it always does, but then I heard a sizzling, and all four cells are at like 300 degrees. I was thinking that I had a hot steamer, and peeled them all out of the charger, but the charger still says it's charging at 500 mA even with no batteries. Not sure what happened, but since it happened to all four cells at once, it's pretty obvious that the charger malfunctioned somehow (as opposed to the cells suddenly shorting -- that might happen to one, but not to all four at once.) Which sucks, because I paid like $50 for this charger! (Because it can peak charge four cells individually.) I'm not sure what would have happend if I wasn't around ... I guess it would have kept cooking the cells ... My point? You need to watch your charging batteries, even the NiCd and NiMH ones ... SignatureDoug McLaren, dougmc@frenzy.com Honk if you hate bumper stickers that say "Honk if ..." > You know, my Lacross BC-900 charger just screwed up. It was charging > 4 AA 2500 mAh NiMH cells at 500 mA like it always does, but then I > heard a sizzling, and all four cells are at like 300 degrees. I was > thinking that I had a hot steamer, and peeled them all out of the > charger, but the charger still says it's charging at 500 mA even with > no batteries. I had a similar incident with a Panasonic charger. One cell swelled and the charger was melted/destroyed. Panasonic later recalled the chargers..... I had purchased the Panansonic unit as a cheaper partner to my Maha charger. Now, I have two Mahas. Good flying, desmobob How does the Maha compare to an Orbit? >> You know, my Lacross BC-900 charger just screwed up. It was charging >> 4 AA 2500 mAh NiMH cells at 500 mA like it always does, but then I [quoted text clipped - 12 lines] > Good flying, > desmobob I think you should use 3 battery pack cause u r comparing something. And< Alcso you would need those Batteries,Anyway >Hi, > [quoted text clipped - 15 lines] > >Wan I think you should use 3 battery pack cause u r comparing something. And< Alcso you would need those Batteries,Anyway >Hi, > [quoted text clipped - 15 lines] > >Wan |
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