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Ken Wilton
Moderator
455 Posts |
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WiggleSticks
Veteran Member
313 Posts |
 Posted - 05 Aug 2008 : 6:37:44 PM
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| Very good method, thanks. |
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piker
Administrator
1268 Posts |
Posted - 06 Aug 2008 : 09:30:40 AM
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Very good idea. Thanks for sharing. I may incorporate that technique one day.
Robert |
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Peter Mar
Veteran Member
54 Posts |
Posted - 07 Aug 2008 : 7:48:47 PM
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Ugh.
I have Deans.
I have sparks.
I installed extra caps on some ESCs. Now I have extra sparks.
Anyone have a solution that does not involve two sets of Deans for every hi power battery and ESC I own? And, no Anderson power pole recommendations please. I already know that suggestion and who will make it... |
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Ken Wilton
Moderator
455 Posts |
Posted - 08 Aug 2008 : 10:06:28 AM
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Maybe I've got this wrong but . . .
I think you should have a resistor not a cap. I gathered that the idea was to slow the current rather than catch it on connection.
Ken |
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DEdwards
Veteran Member
194 Posts |
Posted - 09 Aug 2008 : 10:55:15 AM
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My Castle Creations 80 died exactly when I connected a 6S pack (with the sparks). Expensive downtime and expensive repair. I had been thinking of using a resistor and this article confirms it. You should be able to use any inexpensive low power connector for the resistor as the current with a 50 ohm resistor will be only an amp for a second with a 50v pack!
EDIT: Oops As Nick points out in the next post, 1 amp x 50v = 50W (if only for a second) so his recommendations as to the size and type of resistor are very important. In my case, its a 6S pack = 25v. Yes the surge is damaging the connectors.
The key question in my case is why my CC 80 blew and all I can think of is it was being operated close to its maximum rated voltage and the surge of charging the capacitors resulted in transient that exceeded its max voltage, possibly by a small amount of inductance in the circuit.
The more you add capacitors, the more you need this solution.
I'm adding some capacitors to a 90amp plane where the existing capacitors are getting very hot due to the very large currents flowing in and out at say 50% power as the controller rapidly turns the current full on (90a), then full off at 50% duty cycle. |
Edited by - DEdwards on 14 Aug 2008 2:47:39 PM |
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njones
Veteran Member
255 Posts |
Posted - 09 Aug 2008 : 12:37:42 PM
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It's not specifically caused by high voltage. The sparks you see are caused by extremely high current (can be hundreds of amps) that flows into the (un-charged) ESC input filter capacitor when you first connect the battery. If the connector makes a perfect connection there will be no sparks, but still a large inrush of current. Unfortunately slight vibrations almost always cause the battery connector to "bounce" and make and break the connection numerous times - resulting in the sparks you see. As soon as the capacitor reaches the battery voltage, the inrush current stops. The sparks caused by the inrush current can pit the connector surfaces, and the high current can be harmful to the capacitor.
The problem is more noticable with higher voltage batteries because the peak inrush current is equal to the battery voltage divided by the combined battery, wire and capacitor resistance. Higher voltage, or lower resistance = higher inrush current and more sparks. The larger the capacitor, the longer it takes to charge up and the longer the high inrush current - hence more sparks.
The solution shown in a previous post, is to charge up the capacitor slowly through a resistance, then remove the resitance. The 2-connector solution has a dual (+) battery lead, one has a resistor and small wire/connector, the other has a high current main wire/connector. When you connect the smaller (+) connector a much lower current flows into the ESC filter capacitor, after a second or two (depending on the capacitor size, battery voltage and resistor), the ESC input capacitor is charged up and you can connect the main (+) connector without high inrush current or sparks.
To avoid the dual connectors you could add a (50 ohm, 2 watt wire-wound resistor or ceramic composition) resistor in-line with your (+) ESC lead and a high current switch to bypass the resistor for normal operation. The switch should be in the "resistor" position when connecting the battery, then moved to the "bypass" position for operation. The switch may introduce some slight voltage drop, but a good high current switch should have the same effect as a few extra inches of wire. The weight of the switch may be of concern.
P.S. I'd avoid carbon film resistors since with a 50V pack, the resistor has a peak power of 50W. Film resistors can't typically tolerate peak power pulses as well as wire-wound or ceramic composition. The worst-thing that happens is your resistor becomes an open circuit and you start getting sparks again.
The dual (+) connector solution looks a little inelegant, but is probably the lightest option - but it requires you to modify all of your battery packs. The ESC switch option requires modifications to only your ESC but may introduce a small voltage drop and adds the weight of the switch.
Nick Jones
Kitchener, Ontario
EMFSO #780 |
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DEdwards
Veteran Member
194 Posts |
Posted - 14 Aug 2008 : 2:50:06 PM
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A lot of good points Nick. I forgot about the power. I updated my previous post to make sure people don't miss that critical piece of info.
Yes my connectors were getting damaged by the spike. |
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DEdwards
Veteran Member
194 Posts |
Posted - 18 Jun 2010 : 7:41:32 PM
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| Just added a bypass for my 6S pack. Works great. No more massive spark (and potential risk to ESC). |
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ededge2002
Veteran Member
66 Posts |
Posted - 12 Jul 2010 : 10:59:43 PM
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Castle recomends not doing this as it faults the low voltage cell counting voltage detecting system. the voltage is read right off and an error can be made in the cell count measurment.
Member#2003 |
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MarcVenis
Veteran Member
78 Posts |
Posted - 13 Jul 2010 : 12:25:01 PM
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> Castle recommends not doing this...
Well that's easy to fix, just program the cell count or the cut off voltage into the ESC. That way the ESC won't have to guess the number of cells at power up.
Marc |
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DEdwards
Veteran Member
194 Posts |
Posted - 17 Jul 2010 : 3:35:39 PM
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The last time I connected the castle esc with 6s, there was the usual massive spark, and a phoenix 80 that is now dead. The esc was essentially brand new but more than a year old and hence out of warranty and cost something like an $80 repair bill from castle and no flying of that plane for close to 2 months.
I believe one possible explanation is the ESC is rated at 6S max. The very large current spike of connecting the 6S battery directly to the esc capacitors could result in a resonate on the power line if there is any inductance at all (in strands of power wire) yielding a ring voltage higher than 6S trashing the esc.
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byrocat
Veteran Member
465 Posts |
Posted - 20 Jul 2010 : 4:22:16 PM
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I'd suggest that you talk to the CC people anyways. I had my old CC 45 Phoenix melt all the soldering on the components while trying some slow-flight at the AMAC field. Net results was the shrink-wrap exploded like a BBQ'ed hot dog and everythign died.
Sent it back with a letter of explanation. Got a reply in the form of a repaired and upgraded ESC and a bill reading "Warranty Repair -- no charge".
EMFSO Formosa Racing #00 |
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DEdwards
Veteran Member
194 Posts |
Posted - 22 Jul 2010 : 5:15:05 PM
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| I did talk to CC. Told them the Phoenix had not even flown. I couldn't find the bill but I knew it was more than one year. No go from them. I get the impression CC is much "harder" on warranty repairs now than they were the past. |
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DEdwards
Veteran Member
194 Posts |
Posted - 28 Aug 2010 : 12:44:10 PM
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| I noticed some high voltage ESCs from Hobby City now come with a spark reduction connector! |
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Topic |
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High voltage spark reduction
