current draw with external BEC but Tx off?

[mrklaw]

Hi

Just fitted a castle BEC, and am running a rooster crawler ESC and a spektrum SR300 DSM receiver. Wired up as per the castle diagram with the BEC going into the Rx, and the servos coming out of the Rx, and the red lead from the ESC disconnected.

Am I right in thinking that my BEC is now powering the Rx, and the ESC is only controlling the power to the motor? In which case, what does the switch on the ESC do? Assuming the Tx is off, the receiver won't be sending anything to the esc anyway right? Can I just leave the esc switch 'on'? if it isn't doing anything meaningful in this setup.

Also, does this mean that my Rx is on whenever my battery is connected? anyone know the current draw of a spektrum receiver? Will it be less because the Tx isn't on, or will it be constantly looking for a connection as its DSM? And will the servos be drawing any current if the Tx is off? Seems a bit odd as instructions always tell you to power up the Tx first then the Rx, but that isn't practical if I have to pull the battery between sessions.

I'm trying to figure out how long I can leave it in 'dormant' mode, with the esc switched off, but the battery still connected (because I have to remove the body to get to the battery). I'd like to be able to drive to/from a crawling place with the body on, and also leave it between sessions.

alternatively, can I fit a switch to the BEC? If so, would it be best to put it between BEC and battery, or BEC and receiver (figure the latter would be best).

[allgm1]

99.999999% of the peaple using the castle bec leave the switch for the esc on and unplug the batteries to shut off the rx/ speedcontrol. I don't think its a real good idea to leave your battery plugged in while the tx is off, your supposed to turn the tx on first then the rx, and reverse for turning things off. The rx/speedcontrol get turned off first then the tx, doing it this way makes sure you will avoid any run aways. I suppose you could intall a switch before the bec, but you only opening up another spot in the wiring which could potentially fail.

[mrklaw]

so Tx on, connect battery, mount body - run. Then unmount body, battery off, Tx off?

Doesn't sound fun if I'm doing several short runs with breaks inbetween.

[constantmotion]

Originally Posted by mrklaw

so Tx on, connect battery, mount body - run. Then unmount body, battery off, Tx off?

Doesn't sound fun if I'm doing several short runs with breaks inbetween.

Reach underneath body and unplug your battery. I wire my crawlers so that I can plug/unplug my batteries without taking off the body.

[Robbob]

Guess its a good thing you didnt race Oval in the Nicd/Nimh time .... unscrew body - tape battery - solder battery - screw body on - race for 4 minutes and repeat

But like Costantmotion said, just leave the wires in an area you can reach easily. I prefer to turn the ESC off before disconnecting the battery though. With using the Castle I hate taking the chance of spikeing the battery when plugging it in and screwing up my profiles.

And yes if the battery stays plugged in the BEC will draw off of it with the ESC off so its not a good thing to do. Always unplug the battery.

[mrklaw]

Originally Posted by constantmotion

Reach underneath body and unplug your battery. I wire my crawlers so that I can plug/unplug my batteries without taking off the body.

thanks.

any suggestions as to where? Its a CR01 so don't know where safe locations will be that won't get caught up.

[clockworks]

If you are using a Spektrum Tx, it isn't a problem to leave the battery connected for short periods with the Tx off.
I'd never dream of doing this with an AM or FM radio, but you don't get interference or frequency sharing problems with 2.4GHz radios. There's still the slight risk of the ESC failing and causing a drive-away, so it's best to get the wheels off the ground.

The Spektrum Rx draws very little current. I accidentally left mine powered overnight on my bench - not in a model, just an Rx and some servos while I was testing a Tx mod. Battery was still fine in the morning.
However, with a BEC fitted, you'll be drawing more current (powering the BEC as well as the servos), so don't leave the battery connected for more than, say, 30 minutes, especially at the end of a run when the pack is low on charge.

On my Venom Creeper, with the pack mounted on the axle, I've tied the ESC power cables to a top link. Makes it reasonably easy to connect the pack with the body on if I turn the steering. If your pack is on the top deck, it's harder to do safely. Like you say, if the cables hang down outside the chassis, there's a danger they'll get caught.

BTW, where did you find a Castle BEC? Everywhere in the UK seems to be out of stock while Castle switch to a new distributor.

[mrklaw]

I ordered from holmes hobbies. They were mentioned on here and can preset the BEC to any voltage, which is handy as I wanted 6v and don't have a castle link cable

[clockworks]

Originally Posted by mrklaw

I ordered from holmes hobbies. They were mentioned on here and can preset the BEC to any voltage, which is handy as I wanted 6v and don't have a castle link cable

Did you get stung for import duty?

[mrklaw]

nope. I think the envelope was marked pretty cheaply. Isn't it under the import duty threshold anyway?

[Biscuit]

How do you have your body mounted that makes it such a pain in the butt to take off? Most people are running three or four mount post. (sometimes only one or two) I run three myself and it takes me maybe 15 seconds to remove all three clips and unplug my battery...... Never thought it was that big of a deal honestly.

[clockworks]

Originally Posted by mrklaw

nope. I think the envelope was marked pretty cheaply. Isn't it under the import duty threshold anyway?

UK duty-free limit is £18, but that includes the shipping cost. When I looked at buying from HH, the total price was $39.50. That's over the limit. If the package gets stopped at customs, you'd be liable for VAT, import tax, and an £8 handling charge. Takes the total price to around £36, if you get caught for the duty.

That put me off, as UK sellers were advertising the BEC plus the Link kit for around £40. I placed an order, but I'm still waiting for stock.

Thinking about it, you may have just scraped in under the limit, because customs would look at the declared value of the goods, plus the actual shipping cost, not the shipping charged by HH. If the postage only cost $5, not the $15 charged by HH, the total would be just under £18 as far as customs were concerned.

Importing goods from outside the EU is a gamble. I bought a secondhand watch on eBay from a seller in Jersey, Channel Islands. For some reason, although Jersey is a effectively a British territory, it's not part of the EU.
The seller grossly over-declared the value for insurance reasons, in case it got lost in transit. The duty ended up costing me as much as the sale price of the watch.

[69CrazyHorse]

Originally Posted by constantmotion

Reach underneath body and unplug your battery. I wire my crawlers so that I can plug/unplug my batteries without taking off the body.

X2 to this

[mrklaw]

Originally Posted by clockworks

UK duty-free limit is £18, but that includes the shipping cost. When I looked at buying from HH, the total price was $39.50. That's over the limit. If the package gets stopped at customs, you'd be liable for VAT, import tax, and an £8 handling charge. Takes the total price to around £36, if you get caught for the duty.

That put me off, as UK sellers were advertising the BEC plus the Link kit for around £40. I placed an order, but I'm still waiting for stock.

Thinking about it, you may have just scraped in under the limit, because customs would look at the declared value of the goods, plus the actual shipping cost, not the shipping charged by HH. If the postage only cost $5, not the $15 charged by HH, the total would be just under £18 as far as customs were concerned.

Importing goods from outside the EU is a gamble. I bought a secondhand watch on eBay from a seller in Jersey, Channel Islands. For some reason, although Jersey is a effectively a British territory, it's not part of the EU.
The seller grossly over-declared the value for insurance reasons, in case it got lost in transit. The duty ended up costing me as much as the sale price of the watch.

you sure about the shipping charge? I think in the past I've successfully got my customs/handling charges dropped by DHL when they included the shipping charges in their calculations (the item itself was below the threshold)

but yeah, it is a bit hit and miss.

[clockworks]

Originally Posted by mrklaw

you sure about the shipping charge? I think in the past I've successfully got my customs/handling charges dropped by DHL when they included the shipping charges in their calculations (the item itself was below the threshold)

but yeah, it is a bit hit and miss.

Yes, the actual postage cost (from the stamp or frank) is included in the tax limit, at least it is when the parcel is handled by Royal Mail or Parcelforce, as they stick rigidly to the rules.

Other couriers may turn a blind eye to avoid the paperwork.