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12v battery power g 4.5v servos

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12v battery power g 4.5v servos

Old 07-03-2015, 06:13 PM
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X1AaronW
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Default 12v battery to 4.5v servos

I'm trying to figure out how to step both the voltage and the amperage down from 12v 660cca to 4.5v 200mah I'm stumped please help

Last edited by X1AaronW; 07-03-2015 at 09:52 PM.
Old 07-04-2015, 01:34 AM
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mfr02
 
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A BEC (Battery Eliminator Circuit) will step the voltage down to 5 volts (thats fairly standard for RC items rather than 4.5 volts which I suspect is a minimum figure for your servos). Being presented with the right voltage, the items so powered will take what current they need. UBEC units are tiny, cheap and, working by switching rather than acting as self adjusting resistors, produce their regulated voltage without creating heat. The source determines the maximum current that can be supplied, the load determines what is actually taken. As long as the load wants less than the source can supply, everything works.
Despite being in the industry for a lot of years, I've never come across a reference to "cca" with regard to a battery. Usually they get referred to by their nominal charged voltage, their capacity in "AH" or "mAH" and in some cases a "C" rating to indicate a maximum discharge rate.
Old 07-05-2015, 06:19 AM
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X1AaronW
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ill be including a BEC in the near future. To be honest i was stumped on what to do so thank you for replying. Cold Cranking Amps is what CCA means. I just did the conversion and it comes up to 33AH.
Old 07-07-2015, 05:27 AM
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33AH?? Thats BIG. What is it going in?
Old 07-07-2015, 06:05 AM
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X1AaronW
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A 4.5 ft long 1.5 ft wide anchor handling tugboat. It will be powered by a12v deep cycle Marine battery. It will have about 10 servos and will use a 40lb trolling motor. Is still early in the build but I'm trying to work on it every chance I get.
Old 07-07-2015, 01:20 PM
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Is the battery sealed? If not, the compartment where is sits will need good ventilation if the fumes are not to dissolve everything metal inside the boat. That's why SLA (and NiMH etc) are preferred, even then, there have been instances of 2H2 and O2 recombining inside models where charging has resulted in vapour release.
With all those servos, and possibly a few other items, look for the higher power UBECs, possibly think of using a few and distributing the power, but, to misquote the Ghostbusters, never let the positives meet.
Old 07-07-2015, 02:09 PM
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Lol nice. I plan to ventilate the battery space with 2 cooling fans. 1 pulling air in and 1 blowing air out. The battery will be removable. Now let me ask you this. I have a 6ch transmitter and this is my plan with the servos. Ch1,2,3,and 4 will have a 2 servos connected to the channel but power will only be going to 1 set. When I flip ch6 that servo will flip a switch and divert power from 1 set to the other. Basically making set for basic operation like throttle, rudder, bow thruster, and tail winch. The second set will be for port anchor, starboard anchor, anchor lock, and maybe lights. My question is does that sound possible?
Old 07-08-2015, 01:37 AM
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Should work, but remember that servos tend to twitch a bit as power comes on, then settle to whatever signal they are receiving. If the signal leads are intercepted, normally the un-signalled servos will stay put until they get a new valid signal. Switching power just needs one change over contact, switching the signal leads would need one contact per servo, or the use of some ICs like the CD4066 quad bilateral switch - http://www.ti.com/lit/ds/symlink/cd4066b.pdf - for 4 pairs of servos, two of them worked by the contact of the relay.

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