Nick Posted February 28, 2014 Share Posted February 28, 2014 I've been helping someone with choosing a battery/brushless setup but they've been getting very confusing e-mails from Castle regarding the Castle Sidewinder SV3 ESC. I realize brushless systems depend on a battery C rating but Castle say it must be ABOVE a certain mAh This is what e-mail they got when they contacted Castle asking what battery they recommend: We recommend running batteries with a minimum of 5000mAh or higher, and a minimum discharge rating of 30c continuous or higher. Running a 7.4 LiPo with only a 3700mAh is going to cause the ESC to fail. The inadequate battery that you were running is what caused the failure. When asked why it would fail they replied with... If the mAh rating and discharge rating are not high enough to properly power the ESC it will cause what is called ripple voltage. Ripple causes stress on the input capacitors which can lead to a catastrophic failure. Is this nonsense like I believe it to be? Why would a 2000mAh 30C Lipo fail but a 5000mAh 30C Lipo wouldn't? Quote Link to comment Share on other sites More sharing options...
53HRA Posted February 28, 2014 Share Posted February 28, 2014 (edited) If they can confuse the owner of MSUK forum as well as a staff member of the Modelsport shop ,i think there is a good chance of them speaking poop Besides if the rating is the same,it wouldnt have a reason to fail? Just because the mah is less,doesn't mean the power isnt? Edit: Garry get online and solve the mystery! Edited February 28, 2014 by 53HRA Quote Link to comment Share on other sites More sharing options...
jayuk022002 Posted February 28, 2014 Share Posted February 28, 2014 Maybe if the motor was drawing more than the battery could supply then I wonder if the esc might struggle a bit Quote Link to comment Share on other sites More sharing options...
hebby Posted February 28, 2014 Share Posted February 28, 2014 Smells like plop to me Quote Link to comment Share on other sites More sharing options...
Vr5fx Posted February 28, 2014 Share Posted February 28, 2014 Is this nonsense like I believe it to be? Why would a 2000mAh 30C Lipo fail but a 5000mAh 30C Lipo wouldn't? 2000mAh 30c = 60amp output, 5000mAh 30c = 150amp output. As far as I know. I might be wrong. I may have read some balls somewhere. 2 Quote Link to comment Share on other sites More sharing options...
DannyP Posted February 28, 2014 Share Posted February 28, 2014 This is correct2000mAh 30c = 60amp output, 5000mAh 30c = 150amp output. 1 Quote Link to comment Share on other sites More sharing options...
-BEZ- Posted February 28, 2014 Share Posted February 28, 2014 From what it sounds like to me they are saying that the ESC needs lipos that can provide a constant discharge of 150A minimum So it shouldn't matter what the mAh or C is as long as the total discharge is >150A ie 4000mAh 40c (4A x 40) = 160A Discharge 3000mAh 60c (3 x 60) = 180A That aside though, 150A available power is quite a reserve for a ESC that can only channel about 80A to the motor. I know Castle products can be quite prone to ripple current but that is one heck of a safety margin lol EDIT: But to be fair there is no harm in fitting a overkill battery to any RC. I always fit over spec'd lipos it doesn't do the RC any harm. Better to be safe than sorry Quote Link to comment Share on other sites More sharing options...
Tug Posted February 28, 2014 Share Posted February 28, 2014 Makes perfect sense to me, a 3000mah 30C pack won't maintain voltage under load like a 5000mah 30C pack would. This is load dependent of course, that's why it's crucial to select the right battery for your intended set-up, using as much effort and Information as you would when choosing your combo. Hence cap-packs on the XL2 and the XO1 ESC. They're there to protect the ESC from volt-sag. Quote Link to comment Share on other sites More sharing options...
Nick Posted February 28, 2014 Author Share Posted February 28, 2014 That is correct, however, they don't say you can run 3000mAh 60C for example, which would be 180amps... So saying there is a mAh minimum is irrelevant as it still depends on the C rating of the battery. I guess they are just saying it to cover their backs from newbies. But yeah, 150a minimum is still loads for a SV3 system. Cheers guys. Quote Link to comment Share on other sites More sharing options...
Tug Posted February 28, 2014 Share Posted February 28, 2014 Yeah, the milliamp minimum is a bit of a misnomer. It does sound like a get out clause. Perhaps it's time Castle actually took a leaf from the HW book? Prior to having my cap-pack fitted, I drove the Baja and checked for volt-sag on the data log, it showed 3 volts. Once the cap-pack had been fitted it dropped to 0.3 of a volt. Just thought I'd mention. Quote Link to comment Share on other sites More sharing options...
Tug Posted February 28, 2014 Share Posted February 28, 2014 Just another thought, could Castle be being wary of exaggerated C rating claims? Therefore, if they ask you to use a higher capacity pack there's less chance of ripple? Quote Link to comment Share on other sites More sharing options...
Shudson Posted February 28, 2014 Share Posted February 28, 2014 Whilst I am not an expert on brushless setups, I do have a basic understanding of electrical theory and, unless there is further information that is not mentioned, all those e-mails say to me is avoid Castle! It is not the ESC in isolation that "demands" a certain level of power, but the motor. Assuming the battery rating is sufficient for the motor being used (i.e. it does not draw more than 60A peak) then what they are saying would also be true of a half discharged 5000mah battery (effective capacity at that point 2500mah) or that their units should not be "under-run" - i.e used with motors demanding less than 150A. If you are running a motor with higher demands than the 3700mah battery is rated (110A, assuming 30C) you are going to wreck your battery anyway. You are also going to get the same effect even with a 5000mah battery as it nears the end of its useful life and performance starts to fall off. I can only draw two conclusions from the e-mails. Either its a load of bovine excrement to avoid responsibility for a defective unit or, if true, there is a significant design fault with a high chance of failure in normal use. Quote Link to comment Share on other sites More sharing options...
atom3624 Posted February 28, 2014 Share Posted February 28, 2014 I've had similar and confusing communications with CC over the last year. I've had a few XL2 failures, which in fairness, they have replaced free of charge - this is definitely not a complaint! I did get a telephone call from a Castle Technician, which surprised me as it was early evening and I was on 'baby restraining duties' to avoid significant colour changes to the carpet ... so had absolutely no idea what he was talking about ... Said I had over-geared the XL2 which caused excessive loading hence why it failed ... but this was only on a (largish) 1/8 geared for 50 mph and not a 1/5 weighing 12+ kg geared for 70 mph as we've seen in many videos. I'm guessing they realise that they're getting a lot more failures lately, so are trying to clamp down on repairs / replacements. If the battery doesn't have adequate capacity to permit full power running, surely, despite not ideal, it will mean there's little chance in over-powering the ESC? Al. Quote Link to comment Share on other sites More sharing options...
Joe Bailey Posted February 28, 2014 Share Posted February 28, 2014 The issue is voltage ripple on the supply pack. The Fets used in all esc' are susceptible to heat and voltage sag. This directly affects the gate shut off speed of the FET. Heat is fairly easy to compensate for, if the esc is this hot the gate close signal needs to start this much earlier in the cycle. Voltage sag is much harder to match and predict. Seeing as how a poor lipo will sag so much more then a good one and the esc has no idea how good the lipo is. It becomes impossible to write a firmware algorithm to compensate the the gate timing. Even with compensation there will be a point when the FET driver can no longer close the gate any sooner and you reach critical point. The + gate of one phase will still be wide open at the same time as the - phase causing a direct short failure across the FETs and as a result you get flames and smoke. The comment on mah does make sense but a better wording along the lines, use the best quality, largest capacity possible with your esc to ensure the best operation and life cycle of your esc. Quote Link to comment Share on other sites More sharing options...
Tug Posted February 28, 2014 Share Posted February 28, 2014 Loving this thread, some top info getting banded about. Quote Link to comment Share on other sites More sharing options...
tonysmini Posted February 28, 2014 Share Posted February 28, 2014 I always go for the biggest battery with the highest C rating I can on any rig. I can't see the logic in building a kit up then running it from a battery that will end up getting massively stressed when you nail it, potentially causing it to fail and everything goes up in smoke or a fireball. If I fit something that needs 80amps, then the battery I get must cover at least double that (160amps+), so far this has never failed me. Quote Link to comment Share on other sites More sharing options...
Si Coe Posted February 28, 2014 Share Posted February 28, 2014 If Castle were correct the whole idea of Shorty packs which are becoming popular in 1/10th racing wouldn't work. You can get small capacity extremely high discharge rate packs that demanding racers ate using. Quote Link to comment Share on other sites More sharing options...
Nitroholic Posted February 28, 2014 Share Posted February 28, 2014 I can understand the voltage sag issue, and the implications for the FETs...But I think Castle have confused the issue by using Mah as the measure to be careful of. If they were talking about the battery not being able to maintain the current, then that would make sense to the hobbyist in the know. What they have done, I suspect, is to pick something simple and written large on a battery pack, that any user will be able to read and Castle's warranty people would be able to check.A 5000Mah LiPo will almost certainly have enough power, so they cover the issue without having to get too technical.Where they have gone wrong, IMHO, is in assuming that the sort of people who buy and run their kit wouldn't understand a slightly more involved explanation.If HPI and Traxxas are still using Castle gear, I wonder if the same sort of warnings will appear in their manuals..... Quote Link to comment Share on other sites More sharing options...
tonysmini Posted February 28, 2014 Share Posted February 28, 2014 I can understand the voltage sag issue, and the implications for the FETs... But I think Castle have confused the issue by using Mah as the measure to be careful of. If they were talking about the battery not being able to maintain the current, then that would make sense to the hobbyist in the know. What they have done, I suspect, is to pick something simple and written large on a battery pack, that any user will be able to read and Castle's warranty people would be able to check. A 5000Mah LiPo will almost certainly have enough power, so they cover the issue without having to get too technical. Where they have gone wrong, IMHO, is in assuming that the sort of people who buy and run their kit wouldn't understand a slightly more involved explanation. If HPI and Traxxas are still using Castle gear, I wonder if the same sort of warnings will appear in their manuals..... Thinking about it, I've not seen a 5000mah battery of less than 30c so their quote actually makes a lot of sense for those who maybe don't know how to calculate the current draw their batts can handle. Quote Link to comment Share on other sites More sharing options...
suicideneil Posted March 1, 2014 Share Posted March 1, 2014 This advice ( from Castle ) has been in place for many years, surprized that it's confusing people now suddenly.Consider this- what do you think will happen if you fit a 1000mah 150C ( continuous- hypothetical ) lipo into your 1:8 'uggy or truck, considering that it could in principle still supply 150amps continuously? I'll let you guys & girls dwell on that one... Quote Link to comment Share on other sites More sharing options...
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