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Battery temperature: How hot is too hot for LMR sailplanes
I'm trying to decide on a power system for my XL3200. I have a thread in the sailplanes forum for this. I'm wondering what the highest acceptable battery temperature allowable is for a 10-cell CP-2400SCR pack is. I'll be using it for limited motor runs of about 30-45 seconds. With the desired power system (Hacker B509S w/6.7:1 reduction and 17x10 prop) MotoCalc warns that "the steady-state battery temperature of 241 degress F exceeds the suggested maximum temperature of 140 degress for this cell type". Sean (Shaun?) at Aero-Model suggested a setup along these lines but I'm concerned about the battery temperature. Maybe this isn't so much of a concern for LMR type of flying.
So the question is how hot is too hot when flying LMR sailplanes and using 10-cell CP-2400SCR and CP-1300SCR battery packs??? Jim |
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Motorcalc is not taking into account the limited motor runs you will be using, I get a similar opinion when I input the details of my F5B setup (AveoxF12, 10 Cells, Aveox L160C with an Aeronaut Cam Carbon 15 x 13 prop)
however I am only using 10 - 15 second runs. My batteries get pretty warm (around 140 - 150 deg) but nothing like the 226 predicted by Motocalc. Brian |
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What is the predicted current draw?
For F5B, @ close to 100A static, I am only using 3-5 seconds, perhaps 7 or so on the launch (10-15?? must be because you're only on 10 cells with a lower pitch prop that setup - my Falcon, with a Jeti 30/3 direct needs runs almost that long).. Anyhow, for LMR, your current levels are much lower than F5B - typically in the 60-70A range - you can push zapped 1250SCR's and larger (that means CP1700's, RC cells, etc.) to those levels for 30-45 seconds no problem. It helps for sport flying if you have some air thru the fuse to help them cool after the run, but for competition, this is usally not desired. I would personally not push unzapped cells quite as hard.. ..a |
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Andy, what motor / props are you using please?.
Static current draw with my Aveox F12 / Aeronaut 15 x 13 and 10 matched and zapped cells is c85A, Ive tried an RFM 15 x 15 and 17 x 13 but current draw is similar (90A with the 15 x 15) however the climb is better with the 15 x 13. I was guessing at the run times I gave as I don't actually time them but they are about right. I can certainly get a good flight out of a 6 - 8 second climb but I like to get way up there. Brian |
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